We have studied the interrelation of young AGN with their hosts. The objects
of study are the young and powerful GPS and CSS radio sources. Due to their
small size, GPS and CSS sources are excellent probes of this relation.
Furhthermore, their young age allows us to compare them to the larger, old
radio sources and establish a time-line evolution of this relation. Combining
imaging and spectroscopy at UV, optical and radio wavelengths we find evidence
of strong interaction between the host and the radio source. The presence and
expansion of the radio source clearly affects the properties and evolution of
the host. Furthermore, the radio source and host significantly affect each
other's evolution. We describe our results and how these interactions take
place.Comment: 6 pages. To appear in "Highlights of Spanisg astrophysics IV.
  Proceedings of the VII scientific meeting of the Spanish Astronomical
  Society". Editors: F. Figueras, J.M. Girart, M.Hernanz, C. Jordi. Springe

Barthel, P. D.

Labiano, A.

O'Dea, C. P.

Vermeulen, R. C.

English

arXiv

University of Groningen Research Database

  
 University of Groningen
Environment of compact extragalactic radio sources
Labiano, A.; O'Dea, C. P.; Barthel, Pieter; Vermeulen, R. C.
Published in:
Astronomy and Astrophysics
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Labiano, A., O'Dea, C. P., Barthel, P. D., & Vermeulen, R. C. (2006). Environment of compact extragalactic
radio sources. Astronomy and Astrophysics, 447(2).
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Environment of compact extragalactic radio
sources
A. Labiano1, C.P.O’Dea2, P.D. Barthel3 and R.C. Vermeulen4
1 Departamento de Astrof´ısica Molecular e Infrarroja, Instituto de Estructura de
la Materia (CSIC), Madrid, Spain labiano@damir.iem.csic.es
2 Department of Physics, Rochester Institute of Technology, Rochester, NY,
14623, USA odea@cis.rit.edu
3 Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlands
pdb@astro.rug.nl
4 Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990
AA Dwingeloo, The Netherlands rvermeulen@astron.nl
Summary. We have studied the interrelation of young AGN with their hosts. The
objects of study are the young and powerful GPS and CSS radio sources. Due to their
small size, GPS and CSS sources are excellent probes of this relation. Furhthermore,
their young age allows us to compare them to the larger, old radio sources and
establish a time-line evolution of this relation. Combining imaging and spectroscopy
at UV, optical and radio wavelengths we find evidence of strong interaction between
the host and the radio source. The presence and expansion of the radio source clearly
affects the properties and evolution of the host. Furthermore, the radio source and
host significantly affect each other’s evolution. We describe our results and how these
interactions take place.
1 Introduction
GHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio
sources are the most likely candidates for the progenitors of the large scale
powerful classical double (FR) sources (e.g., [40, 22, 20, 50, 49, 39]; for a
review see [38]). The GPS and CSS sources are powerful but compact radio
sources whose spectra are generally simple and convex with peaks near 1 GHz
and 100 MHz respectively. The GPS sources are contained within the extent
of the optical narrow emission line region (< 1 kpc) while the CSS sources are
contained within the host galaxy (< 15 kpc).
Current models for the evolution of powerful radio galaxies suggest that
these sources propagate from the ∼ 10 pc to Mpc scales at roughly constant
velocity through an ambient medium which declines in density as ρ(R) ∝
R−2 while the sources decline in radio luminosity as Lrad ∝ R
−0.5 ([20, 5,
2 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen
49, 16, 30, 29, 52]). Such a scenario is consistent with the observed number
densities of powerful radio sources as a function of linear size (from tens of
parsecs to hundreds of kpc; e.g., [39, 21]). However, the situation must be more
complicated than this simple picture. (1) The GPS and CSS sources must
interact with the host galaxy as they propagate through it. The discovery of
emission line gas aligned with and presumably co-spatial with the CSS radio
sources and the presence of broad and complex integrated emission line profiles
([24]) indicates that the radio source is strongly interacting with the ambient
gas ([14, 13, 3]). Therefore, we would expect shocks to contribute strongly
to the ionization of the gas ([6]). (2) The GPS sources are observed to have
expansion velocities several times higher than the estimated advance speeds of
large scale classical doubles ([1]). This would require the evolving GPS sources
to decelerate as they propagate though the host galaxy and would require the
radio sources to dim faster than the simple models predict. It may be that
the deceleration takes place via interaction with ambient gas (see [15, 7, 8]).
We have carried out a multiwavelength study of how GPS and CSS sources
evolve and relate with their host as the expansion takes place.
2 Emission line gas
The first traces of interaction between GPS/CSS and their hosts were find
in the emission line gas. The properties observed in [O III] λ5007 emission
lines ([24]) suggested that, even though the AGN was partly photoionizing
the nebula, the radio source was dominating the emission-line kinematics. A
few years later, the alignment effect (similar extent for radio and optical wave-
lengths) seen in large radio sources (e.g., [9, 35]) was found in GPS and CSS
([14, 13, 3]). The alignment between the radio source and emission line gas
suggests interaction between them, as the radio source propagates through
the host. The emission line gas was found to be brighter in the center of the
radio lobes and dimmed with distance. Therefore, the hypothesis adopted was
that the gas inside the radio lobe had been shock-ionized while the gas out-
side was photoionized by the precursor gas in the shock. At the same time,
the AGN could contribute to the whole system with photoionization. Cooling
time arguments suggested lobe expansion velocities >1000 km s−1 for most
of the sources. [42] studied the kinematics of the emission line nebulae of CSS
sources, finding that the radio source is accelerating the clouds of gas in the
host.
We have obtained Hubble Space Telescope Imaging Spectrograph long-slit
spectroscopy of the aligned emission line nebulae in three compact steep spec-
trum radio sources: 3C 67, 3C 277.1, and 3C 303.1. Comparing our data with
with shock and photo-ionization models (MAPPINGS [31, 17] and CLOUDY
[23]) and examining the relationships between the ionization diagnostics and
Environment of compact extragalactic radio sources 3
the gas kinematics, we find that:
1.- In general the extended emission lines are consistent with a mixture
of shocked and photo-ionized gas. In 3C 67, the data lie between the MAP-
PINGS models for a contribution to the observed luminosity from shocked
gas ranging from 0 to 50%. In 3C 303.1, the contribution to the luminosity
from shocked gas is between 30 and 70%. In 3C 277.1, the data scatter around
the model for 100% contribution to the luminosity from precursor gas. The
sources tend to lie in the regions for moderate to high shock velocities (500
to 1000 km/s) and we do not obtain any useful constraints on magnetic field
strengths in the MAPPINGS models.
2.- The three sources show a decrease in ionization with distance from the
nucleus (consistent with a decrease in photoionization with distance) a weak
trend for ionization to decrease with increasing FWHM and a strong trend
for ionization to decrease with increasing velocity offset (which is consistent
with shock ionization).
These results are consistent with a picture in which the CSS sources inter-
act with dense clouds as they propagate through their host galaxies, shocking
the clouds thereby ionizing and accelerating them (as suggested by [42]).
3 Cold gas
Many GPS, CSS and larger radio sources are in merging or interacting systems
(e.g., [12, 28]), therefore we expect their hosts to have dense nuclear environ-
ments. Furthermore, most of the radio loud AGN seem to live in elliptical
galaxies (e.g., [18]). [57] found that the presence of gas (and dust) in early
type galaxies is correlated with the occurrence and strength of a central radio
source. This gas is found both in molecular and atomic form (e.g., [32, 44]).
Observations at different wavelengths find central structures of gas in AGN
hosts ([53, 55, 19, 54, 37]). If the gas is centrally concentrated and GPS/CSS
sources are precursors of FR sources, we expect GPS/CSS to show higher
densities in the gas surrounding their radio lobes5. In 2003, using the recently
improved Westerbork Synthesis Radio Telescopes, [56] and [48] presented a
study of the occurrence and properties of atomic gas associated with compact
radio sources. They found that ∼ 50% of GPS and CSS sources showed HI 21
cm absorption, in contrast to normal elliptical galaxies (< 10%, [53]). Further-
more, they found that GPS sources tend to have higher HI column densities
than CSS sources and that these densities were consistent with the young sce-
nario. However, their data lack spatial resolution to accurately locate the HI
absorption. Just a few high resolution HI observations of GPS/CSS sources
5 However, extremely high densities may confine the sources.
4 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen
were available at that time ([11, 45, 47, 46]).
We have used European VLBI Network UHF band spectral line observa-
tions, to localise the redshifted 21cm HI absorption known to occur in the
subgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. The
radio lobes with detected HI absorption (1) are brighter and closer to the
core than the opposite lobes; (2) are more depolarized; and (3) are preferen-
tially associated with optical emission line gas. The association between the
HI absorption and the emission line gas, supports the hypothesis that the HI
absorption is produced in the atomic cores of the emission line clouds. How-
ever, we cannot rule out the existence of HI elsewhere. We suggest that the
asymmetries in the radio and optical emission are due to interaction of the
radio source with an asymmetric distribution of dense clouds in their environ-
ment. Our results are consistent with a picture in which CSS sources interact
with clouds of dense gas as they propagate through their host galaxy.
4 Star formation and AGN - Starburst connection
Mergers and strong interactions can trigger AGN activity in a galaxy (e.g.,
[25, 4, 27]). These events can also produce instabilities in the ISM and trigger
star formation (e.g., [26]). Numerical simulations and models (e.g., [36, 51])
suggest that the advancement of the jets through the host galaxy environment
can also trigger star formation. Imaging studies in ultraviolet (UV) light of the
hosts of large 3CR sources find traces of episodes of star formation around the
time when the radio source was triggered ([33, 2, 10, 43, 41, 34]) suggesting a
possible link between both.
GPS and CSS radio sources are young, smaller versions of the large pow-
erful radio sources, so they are expected to exhibit signs of more recent star
formation. They have not yet completely broken through the host ISM, so
these interactions are expected to be even more important than in the larger
sources. Near-UV observations are very sensitive to the presence of hot young
stars and therefore will trace recent star formation events. We have obtained
high resolution HST - Advanced Camera for Surveys near-UV images of GPS
and CSS sources to study the morphology and the extent of recent star for-
mation.
We find near UV emission consistent with the presence of recent star for-
mation in most of the observed the sources. In the CSS sources 1443+77 and
1814–637 the near UV light is aligned with and is co-spatial with the radio
source. We suggest that in these sources the UV light is produced by star
formation triggered and/or enhanced by the radio source.
Environment of compact extragalactic radio sources 5
The connection between the AGN and the star formation is not yet clear
but our observations suggest that some connection exists. Stellar synthesis
models are consistent with a burst of star formation before the formation of
the radio source. The starburst and AGN activity could have been triggered by
the same event. However, observations at other wavelengths and measurement
of the colors are needed to definitively establish the nature of the observed
UV light.
5 Conclusions
We have used the young and powerful GPS and CSS radio sources to study the
interrelation of AGN with their hosts. We find evidence of strong interaction
between the radio source and the host at all wavelengths studied, suggesting
that the presence and expansion of powerful radio sources clearly affect the
properties and evolution of their hosts.
The radio source and host can significantly affect each others evolution.
However, this influence takes place in different ways. The influence that the
host has on the radio source is somehow indirect, although it can completely
change its destiny: depending of the contents, distribution and density of
the gas, the radio source will die early, expand and grow into the large FR
sources, or remain confined inside its host. In contrast, the influence of the
radio source on its host seems to be more direct and takes place during its
expansion through the host: the radio source will affect the kinematics and
ionization of the emission line gas, and may change the star formation history
of the host.
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Environment of compact extragalactic radio sources

Abstract: We have studied the interrelation of young AGN with their hosts. The objects of study are the young and powerful GPS and CSS radio sources. Due to their small size, GPS and CSS sources are excellent probes of this relation. Furhthermore, their young age allows us to compare them to the larger, old radio sources and establish a time-line evolution of this relation. Combining imaging and spectroscopy at UV, optical and radio wavelengths we find evidence of strong interaction between the host and the radio source. The presence and expansion of the radio source clearly affects the properties and evolution of the host. Furthermore, the radio source and host significantly affect each other's evolution. We describe our results and how these interactions take place

ARTS repository - University of Groningen

   University of GroningenEnvironment of compact extragalactic radio sourcesLabiano, A.; O'Dea, C. P.; Barthel, P. D.; Vermeulen, R. C.Published in:Astronomy and astrophysicsIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2006Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Labiano, A., O'Dea, C. P., Barthel, P. D., & Vermeulen, R. C. (2006). Environment of compact extragalacticradio sources. Astronomy and astrophysics, 447(2).CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 09-09-2023arXiv:astro-ph/0611738 v1   23 Nov 2006Environment of compact extragalactic radiosourcesA. Labiano1, C.P.O’Dea2, P.D. Barthel3 and R.C. Vermeulen41 Departamento de Astrof́ısica Molecular e Infrarroja, Instituto de Estructura dela Materia (CSIC), Madrid, Spain labiano@damir.iem.csic.es2 Department of Physics, Rochester Institute of Technology, Rochester, NY,14623, USA odea@cis.rit.edu3 Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlandspdb@astro.rug.nl4 Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990AA Dwingeloo, The Netherlands rvermeulen@astron.nlSummary. We have studied the interrelation of young AGN with their hosts. Theobjects of study are the young and powerful GPS and CSS radio sources. Due to theirsmall size, GPS and CSS sources are excellent probes of this relation. Furhthermore,their young age allows us to compare them to the larger, old radio sources andestablish a time-line evolution of this relation. Combining imaging and spectroscopyat UV, optical and radio wavelengths we find evidence of strong interaction betweenthe host and the radio source. The presence and expansion of the radio source clearlyaffects the properties and evolution of the host. Furthermore, the radio source andhost significantly affect each other’s evolution. We describe our results and how theseinteractions take place.1 IntroductionGHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radiosources are the most likely candidates for the progenitors of the large scalepowerful classical double (FR) sources (e.g., [40, 22, 20, 50, 49, 39]; for areview see [38]). The GPS and CSS sources are powerful but compact radiosources whose spectra are generally simple and convex with peaks near 1 GHzand 100 MHz respectively. The GPS sources are contained within the extentof the optical narrow emission line region (< 1 kpc) while the CSS sources arecontained within the host galaxy (< 15 kpc).Current models for the evolution of powerful radio galaxies suggest thatthese sources propagate from the ∼ 10 pc to Mpc scales at roughly constantvelocity through an ambient medium which declines in density as ρ(R) ∝R−2 while the sources decline in radio luminosity as Lrad ∝ R−0.5 ([20, 5,2 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen49, 16, 30, 29, 52]). Such a scenario is consistent with the observed numberdensities of powerful radio sources as a function of linear size (from tens ofparsecs to hundreds of kpc; e.g., [39, 21]). However, the situation must be morecomplicated than this simple picture. (1) The GPS and CSS sources mustinteract with the host galaxy as they propagate through it. The discovery ofemission line gas aligned with and presumably co-spatial with the CSS radiosources and the presence of broad and complex integrated emission line profiles([24]) indicates that the radio source is strongly interacting with the ambientgas ([14, 13, 3]). Therefore, we would expect shocks to contribute stronglyto the ionization of the gas ([6]). (2) The GPS sources are observed to haveexpansion velocities several times higher than the estimated advance speeds oflarge scale classical doubles ([1]). This would require the evolving GPS sourcesto decelerate as they propagate though the host galaxy and would require theradio sources to dim faster than the simple models predict. It may be thatthe deceleration takes place via interaction with ambient gas (see [15, 7, 8]).We have carried out a multiwavelength study of how GPS and CSS sourcesevolve and relate with their host as the expansion takes place.2 Emission line gasThe first traces of interaction between GPS/CSS and their hosts were findin the emission line gas. The properties observed in [O III] λ5007 emissionlines ([24]) suggested that, even though the AGN was partly photoionizingthe nebula, the radio source was dominating the emission-line kinematics. Afew years later, the alignment effect (similar extent for radio and optical wave-lengths) seen in large radio sources (e.g., [9, 35]) was found in GPS and CSS([14, 13, 3]). The alignment between the radio source and emission line gassuggests interaction between them, as the radio source propagates throughthe host. The emission line gas was found to be brighter in the center of theradio lobes and dimmed with distance. Therefore, the hypothesis adopted wasthat the gas inside the radio lobe had been shock-ionized while the gas out-side was photoionized by the precursor gas in the shock. At the same time,the AGN could contribute to the whole system with photoionization. Coolingtime arguments suggested lobe expansion velocities >1000 km s−1 for mostof the sources. [42] studied the kinematics of the emission line nebulae of CSSsources, finding that the radio source is accelerating the clouds of gas in thehost.We have obtained Hubble Space Telescope Imaging Spectrograph long-slitspectroscopy of the aligned emission line nebulae in three compact steep spec-trum radio sources: 3C 67, 3C 277.1, and 3C 303.1. Comparing our data withwith shock and photo-ionization models (MAPPINGS [31, 17] and CLOUDY[23]) and examining the relationships between the ionization diagnostics andEnvironment of compact extragalactic radio sources 3the gas kinematics, we find that:1.- In general the extended emission lines are consistent with a mixtureof shocked and photo-ionized gas. In 3C 67, the data lie between the MAP-PINGS models for a contribution to the observed luminosity from shockedgas ranging from 0 to 50%. In 3C 303.1, the contribution to the luminosityfrom shocked gas is between 30 and 70%. In 3C 277.1, the data scatter aroundthe model for 100% contribution to the luminosity from precursor gas. Thesources tend to lie in the regions for moderate to high shock velocities (500to 1000 km/s) and we do not obtain any useful constraints on magnetic fieldstrengths in the MAPPINGS models.2.- The three sources show a decrease in ionization with distance from thenucleus (consistent with a decrease in photoionization with distance) a weaktrend for ionization to decrease with increasing FWHM and a strong trendfor ionization to decrease with increasing velocity offset (which is consistentwith shock ionization).These results are consistent with a picture in which the CSS sources inter-act with dense clouds as they propagate through their host galaxies, shockingthe clouds thereby ionizing and accelerating them (as suggested by [42]).3 Cold gasMany GPS, CSS and larger radio sources are in merging or interacting systems(e.g., [12, 28]), therefore we expect their hosts to have dense nuclear environ-ments. Furthermore, most of the radio loud AGN seem to live in ellipticalgalaxies (e.g., [18]). [57] found that the presence of gas (and dust) in earlytype galaxies is correlated with the occurrence and strength of a central radiosource. This gas is found both in molecular and atomic form (e.g., [32, 44]).Observations at different wavelengths find central structures of gas in AGNhosts ([53, 55, 19, 54, 37]). If the gas is centrally concentrated and GPS/CSSsources are precursors of FR sources, we expect GPS/CSS to show higherdensities in the gas surrounding their radio lobes5. In 2003, using the recentlyimproved Westerbork Synthesis Radio Telescopes, [56] and [48] presented astudy of the occurrence and properties of atomic gas associated with compactradio sources. They found that ∼ 50% of GPS and CSS sources showed HI 21cm absorption, in contrast to normal elliptical galaxies (< 10%, [53]). Further-more, they found that GPS sources tend to have higher HI column densitiesthan CSS sources and that these densities were consistent with the young sce-nario. However, their data lack spatial resolution to accurately locate the HIabsorption. Just a few high resolution HI observations of GPS/CSS sources5 However, extremely high densities may confine the sources.4 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulenwere available at that time ([11, 45, 47, 46]).We have used European VLBI Network UHF band spectral line observa-tions, to localise the redshifted 21cm HI absorption known to occur in thesubgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. Theradio lobes with detected HI absorption (1) are brighter and closer to thecore than the opposite lobes; (2) are more depolarized; and (3) are preferen-tially associated with optical emission line gas. The association between theHI absorption and the emission line gas, supports the hypothesis that the HIabsorption is produced in the atomic cores of the emission line clouds. How-ever, we cannot rule out the existence of HI elsewhere. We suggest that theasymmetries in the radio and optical emission are due to interaction of theradio source with an asymmetric distribution of dense clouds in their environ-ment. Our results are consistent with a picture in which CSS sources interactwith clouds of dense gas as they propagate through their host galaxy.4 Star formation and AGN - Starburst connectionMergers and strong interactions can trigger AGN activity in a galaxy (e.g.,[25, 4, 27]). These events can also produce instabilities in the ISM and triggerstar formation (e.g., [26]). Numerical simulations and models (e.g., [36, 51])suggest that the advancement of the jets through the host galaxy environmentcan also trigger star formation. Imaging studies in ultraviolet (UV) light of thehosts of large 3CR sources find traces of episodes of star formation around thetime when the radio source was triggered ([33, 2, 10, 43, 41, 34]) suggesting apossible link between both.GPS and CSS radio sources are young, smaller versions of the large pow-erful radio sources, so they are expected to exhibit signs of more recent starformation. They have not yet completely broken through the host ISM, sothese interactions are expected to be even more important than in the largersources. Near-UV observations are very sensitive to the presence of hot youngstars and therefore will trace recent star formation events. We have obtainedhigh resolution HST - Advanced Camera for Surveys near-UV images of GPSand CSS sources to study the morphology and the extent of recent star for-mation.We find near UV emission consistent with the presence of recent star for-mation in most of the observed the sources. In the CSS sources 1443+77 and1814–637 the near UV light is aligned with and is co-spatial with the radiosource. We suggest that in these sources the UV light is produced by starformation triggered and/or enhanced by the radio source.Environment of compact extragalactic radio sources 5The connection between the AGN and the star formation is not yet clearbut our observations suggest that some connection exists. Stellar synthesismodels are consistent with a burst of star formation before the formation ofthe radio source. The starburst and AGN activity could have been triggered bythe same event. However, observations at other wavelengths and measurementof the colors are needed to definitively establish the nature of the observedUV light.5 ConclusionsWe have used the young and powerful GPS and CSS radio sources to study theinterrelation of AGN with their hosts. We find evidence of strong interactionbetween the radio source and the host at all wavelengths studied, suggestingthat the presence and expansion of powerful radio sources clearly affect theproperties and evolution of their hosts.The radio source and host can significantly affect each others evolution.However, this influence takes place in different ways. The influence that thehost has on the radio source is somehow indirect, although it can completelychange its destiny: depending of the contents, distribution and density ofthe gas, the radio source will die early, expand and grow into the large FRsources, or remain confined inside its host. In contrast, the influence of theradio source on its host seems to be more direct and takes place during itsexpansion through the host: the radio source will affect the kinematics andionization of the emission line gas, and may change the star formation historyof the host.References1. Alexander, P. et al. MNRAS 225, 1–26 (1987)2. Allen, M.G. et al. ApJS 139, 411–438 (2002).3. Axon, D.J. et al. AJ 120, 2284–2299 (2000)4. Baum, S.A. et al. ApJ 389, 208–222 (1992).5. Begelman, M.C. Baby Cygnus A’s. In: Cygnus A – Study of a Radio Galaxy,p. 209 (1996)6. Bicknell, G.V. et al. ApJ 485, 112 (1997)7. Carvalho, J.C. A&A 292, 392–394 (1994)8. Carvalho, J.C. A&A 329, 845–852 (1998)9. Chambers, K.C.et al. Nature 329, 604–606 (1987).10. Chiaberge, M.et al. ApJ 571, 247–255 (2002).11. Conway, J.E.: In The second workshop on Gigahertz peaked spectrum and com-pact steep spectrum radio sources, Leiden Univ, ed. I. Snellen, R. T. Schilizzi,H. A. J. Rttgering, M. N. Bremer (Leiden: Publ JIVE) p. 198 (1996)6 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen12. de Vries, W.H. et al. AJ 120, 2300–2330 (2000)13. de Vries, W.H. et al. ApJ 526, 27–39 (1999)14. de Vries, W.H. et al. ApJS 110, 191 (1997)15. De Young, D.S. ApJ 402, 95–108 (1993)16. De Young, D.S. ApJ 490, L55 (1997)17. Dopita, M.A., Sutherland, R.S. ApJS 102, 161 (1996)18. Dunlop, J.S. et al. MNRAS 340, 1095–1135 (2003).19. Evans, A.S. et al. ApJ 521, L107–L110 (1999).20. Fanti, C. et al. A&A 302, 317 (1995)21. Fanti, C. et al. A&A 369, 380–420 (2001)22. Fanti, R. et al. A&A 231, 333–346 (1990)23. Ferland, G.J. et al. PASP 110, 761–778 (1998)24. Gelderman, R., Whittle, M. ApJS 91, 491–505 (1994)25. Heckman, T.M. et al. ApJ 311, 526–547 (1986).26. Ho, L.C. ArXiv, astro-ph/0511157 (2005)27. Israel, F.P. A&A Rev. 8, 237–278 (1998)28. Johnston, H.M. et al. MNRAS 356, 515–523 (2005).29. Kaiser, C.R., Alexander, P. MNRAS 286, 215–222 (1997)30. Kaiser, C.R. et al. MNRAS 292, 723 (1997)31. Kewley, L. et al. (2006 in prep.)32. Knapp, G.R., Rupen, M.P. ApJ 460, 271 (1996).33. Koekemoer, A.M. et al. ApJ 525, 621–637 (1999).34. Martel, A.R. et al. AJ 123, 1357–1363 (2002).35. McCarthy, P.J. et al. ApJ 321, L29–L33 (1987).36. Mellema, G. et al. A&A 395, L13–L16 (2002).37. Morganti, R. et al. MNRAS 323, 331–342 (2001).38. O’Dea, C.P. PASP 110, 493–532 (1998)39. O’Dea, C.P., Baum, S.A. AJ 113, 148–161 (1997)40. O’Dea, C.P. et al. ApJ 380, 66–77 (1991)41. O’Dea, C.P. et al. PASA 20, 88–93 (2003)42. O’Dea, C.P. et al. AJ 123, 2333–2351 (2002)43. O’Dea, C.P. et al. AJ 121, 1915–1926 (2001).44. Oosterloo, T. et al. PASA 16, 28–34 (1999)45. Peck, A.B., Taylor, G.B. ApJ 502, L23 (1998)46. Peck, A.B., Taylor, G.B. New A Rev. 46, 295–298 (2002)47. Peck, A.B. et al. ApJ 521, 103–111 (1999)48. Pihlström, Y.M. et al. A&A 404, 871–881 (2003)49. Readhead, A.C.S. et al. ApJ 460, 634 (1996)50. Readhead, A.C.S. et al. ApJ 460, 612 (1996)51. Rees, M.J. MNRAS 239, 1P–4P (1989)52. Snellen, I.A.G. et al. MNRAS 319, 445–456 (2000)53. van Gorkom, J.H. et al. AJ 97, 708–719 (1989)54. van Langevelde, H.J. et al. A&A 354, L45–L48 (2000)55. Verdoes Kleijn, G.A.et al. AJ 118, 2592–2617 (1999).56. Vermeulen, R.C. et al. A&A 404, 861–870 (2003)57. Walsh, D.E.P. et al. ApJ 337, 209–229 (1989).

NARCIS 

Dissertations of the University of Groningen

   University of GroningenEnvironment of compact extragalactic radio sourcesLabiano, A.; O'Dea, C. P.; Barthel, P. D.; Vermeulen, R. C.Published in:Astronomy and astrophysicsIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2006Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Labiano, A., O'Dea, C. P., Barthel, P. D., & Vermeulen, R. C. (2006). Environment of compact extragalacticradio sources. Astronomy and astrophysics, 447(2).CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 16-07-2023arXiv:astro-ph/0611738 v1   23 Nov 2006Environment of compact extragalactic radiosourcesA. Labiano1, C.P.O’Dea2, P.D. Barthel3 and R.C. Vermeulen41 Departamento de Astrof́ısica Molecular e Infrarroja, Instituto de Estructura dela Materia (CSIC), Madrid, Spain labiano@damir.iem.csic.es2 Department of Physics, Rochester Institute of Technology, Rochester, NY,14623, USA odea@cis.rit.edu3 Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlandspdb@astro.rug.nl4 Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990AA Dwingeloo, The Netherlands rvermeulen@astron.nlSummary. We have studied the interrelation of young AGN with their hosts. Theobjects of study are the young and powerful GPS and CSS radio sources. Due to theirsmall size, GPS and CSS sources are excellent probes of this relation. Furhthermore,their young age allows us to compare them to the larger, old radio sources andestablish a time-line evolution of this relation. Combining imaging and spectroscopyat UV, optical and radio wavelengths we find evidence of strong interaction betweenthe host and the radio source. The presence and expansion of the radio source clearlyaffects the properties and evolution of the host. Furthermore, the radio source andhost significantly affect each other’s evolution. We describe our results and how theseinteractions take place.1 IntroductionGHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radiosources are the most likely candidates for the progenitors of the large scalepowerful classical double (FR) sources (e.g., [40, 22, 20, 50, 49, 39]; for areview see [38]). The GPS and CSS sources are powerful but compact radiosources whose spectra are generally simple and convex with peaks near 1 GHzand 100 MHz respectively. The GPS sources are contained within the extentof the optical narrow emission line region (< 1 kpc) while the CSS sources arecontained within the host galaxy (< 15 kpc).Current models for the evolution of powerful radio galaxies suggest thatthese sources propagate from the ∼ 10 pc to Mpc scales at roughly constantvelocity through an ambient medium which declines in density as ρ(R) ∝R−2 while the sources decline in radio luminosity as Lrad ∝ R−0.5 ([20, 5,2 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen49, 16, 30, 29, 52]). Such a scenario is consistent with the observed numberdensities of powerful radio sources as a function of linear size (from tens ofparsecs to hundreds of kpc; e.g., [39, 21]). However, the situation must be morecomplicated than this simple picture. (1) The GPS and CSS sources mustinteract with the host galaxy as they propagate through it. The discovery ofemission line gas aligned with and presumably co-spatial with the CSS radiosources and the presence of broad and complex integrated emission line profiles([24]) indicates that the radio source is strongly interacting with the ambientgas ([14, 13, 3]). Therefore, we would expect shocks to contribute stronglyto the ionization of the gas ([6]). (2) The GPS sources are observed to haveexpansion velocities several times higher than the estimated advance speeds oflarge scale classical doubles ([1]). This would require the evolving GPS sourcesto decelerate as they propagate though the host galaxy and would require theradio sources to dim faster than the simple models predict. It may be thatthe deceleration takes place via interaction with ambient gas (see [15, 7, 8]).We have carried out a multiwavelength study of how GPS and CSS sourcesevolve and relate with their host as the expansion takes place.2 Emission line gasThe first traces of interaction between GPS/CSS and their hosts were findin the emission line gas. The properties observed in [O III] λ5007 emissionlines ([24]) suggested that, even though the AGN was partly photoionizingthe nebula, the radio source was dominating the emission-line kinematics. Afew years later, the alignment effect (similar extent for radio and optical wave-lengths) seen in large radio sources (e.g., [9, 35]) was found in GPS and CSS([14, 13, 3]). The alignment between the radio source and emission line gassuggests interaction between them, as the radio source propagates throughthe host. The emission line gas was found to be brighter in the center of theradio lobes and dimmed with distance. Therefore, the hypothesis adopted wasthat the gas inside the radio lobe had been shock-ionized while the gas out-side was photoionized by the precursor gas in the shock. At the same time,the AGN could contribute to the whole system with photoionization. Coolingtime arguments suggested lobe expansion velocities >1000 km s−1 for mostof the sources. [42] studied the kinematics of the emission line nebulae of CSSsources, finding that the radio source is accelerating the clouds of gas in thehost.We have obtained Hubble Space Telescope Imaging Spectrograph long-slitspectroscopy of the aligned emission line nebulae in three compact steep spec-trum radio sources: 3C 67, 3C 277.1, and 3C 303.1. Comparing our data withwith shock and photo-ionization models (MAPPINGS [31, 17] and CLOUDY[23]) and examining the relationships between the ionization diagnostics andEnvironment of compact extragalactic radio sources 3the gas kinematics, we find that:1.- In general the extended emission lines are consistent with a mixtureof shocked and photo-ionized gas. In 3C 67, the data lie between the MAP-PINGS models for a contribution to the observed luminosity from shockedgas ranging from 0 to 50%. In 3C 303.1, the contribution to the luminosityfrom shocked gas is between 30 and 70%. In 3C 277.1, the data scatter aroundthe model for 100% contribution to the luminosity from precursor gas. Thesources tend to lie in the regions for moderate to high shock velocities (500to 1000 km/s) and we do not obtain any useful constraints on magnetic fieldstrengths in the MAPPINGS models.2.- The three sources show a decrease in ionization with distance from thenucleus (consistent with a decrease in photoionization with distance) a weaktrend for ionization to decrease with increasing FWHM and a strong trendfor ionization to decrease with increasing velocity offset (which is consistentwith shock ionization).These results are consistent with a picture in which the CSS sources inter-act with dense clouds as they propagate through their host galaxies, shockingthe clouds thereby ionizing and accelerating them (as suggested by [42]).3 Cold gasMany GPS, CSS and larger radio sources are in merging or interacting systems(e.g., [12, 28]), therefore we expect their hosts to have dense nuclear environ-ments. Furthermore, most of the radio loud AGN seem to live in ellipticalgalaxies (e.g., [18]). [57] found that the presence of gas (and dust) in earlytype galaxies is correlated with the occurrence and strength of a central radiosource. This gas is found both in molecular and atomic form (e.g., [32, 44]).Observations at different wavelengths find central structures of gas in AGNhosts ([53, 55, 19, 54, 37]). If the gas is centrally concentrated and GPS/CSSsources are precursors of FR sources, we expect GPS/CSS to show higherdensities in the gas surrounding their radio lobes5. In 2003, using the recentlyimproved Westerbork Synthesis Radio Telescopes, [56] and [48] presented astudy of the occurrence and properties of atomic gas associated with compactradio sources. They found that ∼ 50% of GPS and CSS sources showed HI 21cm absorption, in contrast to normal elliptical galaxies (< 10%, [53]). Further-more, they found that GPS sources tend to have higher HI column densitiesthan CSS sources and that these densities were consistent with the young sce-nario. However, their data lack spatial resolution to accurately locate the HIabsorption. Just a few high resolution HI observations of GPS/CSS sources5 However, extremely high densities may confine the sources.4 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulenwere available at that time ([11, 45, 47, 46]).We have used European VLBI Network UHF band spectral line observa-tions, to localise the redshifted 21cm HI absorption known to occur in thesubgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. Theradio lobes with detected HI absorption (1) are brighter and closer to thecore than the opposite lobes; (2) are more depolarized; and (3) are preferen-tially associated with optical emission line gas. The association between theHI absorption and the emission line gas, supports the hypothesis that the HIabsorption is produced in the atomic cores of the emission line clouds. How-ever, we cannot rule out the existence of HI elsewhere. We suggest that theasymmetries in the radio and optical emission are due to interaction of theradio source with an asymmetric distribution of dense clouds in their environ-ment. Our results are consistent with a picture in which CSS sources interactwith clouds of dense gas as they propagate through their host galaxy.4 Star formation and AGN - Starburst connectionMergers and strong interactions can trigger AGN activity in a galaxy (e.g.,[25, 4, 27]). These events can also produce instabilities in the ISM and triggerstar formation (e.g., [26]). Numerical simulations and models (e.g., [36, 51])suggest that the advancement of the jets through the host galaxy environmentcan also trigger star formation. Imaging studies in ultraviolet (UV) light of thehosts of large 3CR sources find traces of episodes of star formation around thetime when the radio source was triggered ([33, 2, 10, 43, 41, 34]) suggesting apossible link between both.GPS and CSS radio sources are young, smaller versions of the large pow-erful radio sources, so they are expected to exhibit signs of more recent starformation. They have not yet completely broken through the host ISM, sothese interactions are expected to be even more important than in the largersources. Near-UV observations are very sensitive to the presence of hot youngstars and therefore will trace recent star formation events. We have obtainedhigh resolution HST - Advanced Camera for Surveys near-UV images of GPSand CSS sources to study the morphology and the extent of recent star for-mation.We find near UV emission consistent with the presence of recent star for-mation in most of the observed the sources. In the CSS sources 1443+77 and1814–637 the near UV light is aligned with and is co-spatial with the radiosource. We suggest that in these sources the UV light is produced by starformation triggered and/or enhanced by the radio source.Environment of compact extragalactic radio sources 5The connection between the AGN and the star formation is not yet clearbut our observations suggest that some connection exists. Stellar synthesismodels are consistent with a burst of star formation before the formation ofthe radio source. The starburst and AGN activity could have been triggered bythe same event. However, observations at other wavelengths and measurementof the colors are needed to definitively establish the nature of the observedUV light.5 ConclusionsWe have used the young and powerful GPS and CSS radio sources to study theinterrelation of AGN with their hosts. We find evidence of strong interactionbetween the radio source and the host at all wavelengths studied, suggestingthat the presence and expansion of powerful radio sources clearly affect theproperties and evolution of their hosts.The radio source and host can significantly affect each others evolution.However, this influence takes place in different ways. The influence that thehost has on the radio source is somehow indirect, although it can completelychange its destiny: depending of the contents, distribution and density ofthe gas, the radio source will die early, expand and grow into the large FRsources, or remain confined inside its host. In contrast, the influence of theradio source on its host seems to be more direct and takes place during itsexpansion through the host: the radio source will affect the kinematics andionization of the emission line gas, and may change the star formation historyof the host.References1. Alexander, P. et al. MNRAS 225, 1–26 (1987)2. Allen, M.G. et al. ApJS 139, 411–438 (2002).3. Axon, D.J. et al. AJ 120, 2284–2299 (2000)4. Baum, S.A. et al. ApJ 389, 208–222 (1992).5. Begelman, M.C. Baby Cygnus A’s. In: Cygnus A – Study of a Radio Galaxy,p. 209 (1996)6. Bicknell, G.V. et al. ApJ 485, 112 (1997)7. Carvalho, J.C. A&A 292, 392–394 (1994)8. Carvalho, J.C. A&A 329, 845–852 (1998)9. Chambers, K.C.et al. Nature 329, 604–606 (1987).10. Chiaberge, M.et al. ApJ 571, 247–255 (2002).11. Conway, J.E.: In The second workshop on Gigahertz peaked spectrum and com-pact steep spectrum radio sources, Leiden Univ, ed. I. Snellen, R. T. Schilizzi,H. A. J. Rttgering, M. N. Bremer (Leiden: Publ JIVE) p. 198 (1996)6 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen12. de Vries, W.H. et al. AJ 120, 2300–2330 (2000)13. de Vries, W.H. et al. ApJ 526, 27–39 (1999)14. de Vries, W.H. et al. ApJS 110, 191 (1997)15. De Young, D.S. ApJ 402, 95–108 (1993)16. De Young, D.S. ApJ 490, L55 (1997)17. Dopita, M.A., Sutherland, R.S. ApJS 102, 161 (1996)18. Dunlop, J.S. et al. MNRAS 340, 1095–1135 (2003).19. Evans, A.S. et al. ApJ 521, L107–L110 (1999).20. Fanti, C. et al. A&A 302, 317 (1995)21. Fanti, C. et al. A&A 369, 380–420 (2001)22. Fanti, R. et al. A&A 231, 333–346 (1990)23. Ferland, G.J. et al. PASP 110, 761–778 (1998)24. Gelderman, R., Whittle, M. ApJS 91, 491–505 (1994)25. Heckman, T.M. et al. ApJ 311, 526–547 (1986).26. Ho, L.C. ArXiv, astro-ph/0511157 (2005)27. Israel, F.P. A&A Rev. 8, 237–278 (1998)28. Johnston, H.M. et al. MNRAS 356, 515–523 (2005).29. Kaiser, C.R., Alexander, P. MNRAS 286, 215–222 (1997)30. Kaiser, C.R. et al. MNRAS 292, 723 (1997)31. Kewley, L. et al. (2006 in prep.)32. Knapp, G.R., Rupen, M.P. ApJ 460, 271 (1996).33. Koekemoer, A.M. et al. ApJ 525, 621–637 (1999).34. Martel, A.R. et al. AJ 123, 1357–1363 (2002).35. McCarthy, P.J. et al. ApJ 321, L29–L33 (1987).36. Mellema, G. et al. A&A 395, L13–L16 (2002).37. Morganti, R. et al. MNRAS 323, 331–342 (2001).38. O’Dea, C.P. PASP 110, 493–532 (1998)39. O’Dea, C.P., Baum, S.A. AJ 113, 148–161 (1997)40. O’Dea, C.P. et al. ApJ 380, 66–77 (1991)41. O’Dea, C.P. et al. PASA 20, 88–93 (2003)42. O’Dea, C.P. et al. AJ 123, 2333–2351 (2002)43. O’Dea, C.P. et al. AJ 121, 1915–1926 (2001).44. Oosterloo, T. et al. PASA 16, 28–34 (1999)45. Peck, A.B., Taylor, G.B. ApJ 502, L23 (1998)46. Peck, A.B., Taylor, G.B. New A Rev. 46, 295–298 (2002)47. Peck, A.B. et al. ApJ 521, 103–111 (1999)48. Pihlström, Y.M. et al. A&A 404, 871–881 (2003)49. Readhead, A.C.S. et al. ApJ 460, 634 (1996)50. Readhead, A.C.S. et al. ApJ 460, 612 (1996)51. Rees, M.J. MNRAS 239, 1P–4P (1989)52. Snellen, I.A.G. et al. MNRAS 319, 445–456 (2000)53. van Gorkom, J.H. et al. AJ 97, 708–719 (1989)54. van Langevelde, H.J. et al. A&A 354, L45–L48 (2000)55. Verdoes Kleijn, G.A.et al. AJ 118, 2592–2617 (1999).56. Vermeulen, R.C. et al. A&A 404, 861–870 (2003)57. Walsh, D.E.P. et al. ApJ 337, 209–229 (1989).

Proceedings - University of Groningen

   University of GroningenEnvironment of compact extragalactic radio sourcesLabiano, A.; O'Dea, C. P.; Barthel, P. D.; Vermeulen, R. C.Published in:Astronomy and astrophysicsIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2006Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Labiano, A., O'Dea, C. P., Barthel, P. D., & Vermeulen, R. C. (2006). Environment of compact extragalacticradio sources. Astronomy and astrophysics, 447(2).CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 28-12-2022arXiv:astro-ph/0611738 v1   23 Nov 2006Environment of compact extragalactic radiosourcesA. Labiano1, C.P.O’Dea2, P.D. Barthel3 and R.C. Vermeulen41 Departamento de Astrof́ısica Molecular e Infrarroja, Instituto de Estructura dela Materia (CSIC), Madrid, Spain labiano@damir.iem.csic.es2 Department of Physics, Rochester Institute of Technology, Rochester, NY,14623, USA odea@cis.rit.edu3 Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlandspdb@astro.rug.nl4 Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990AA Dwingeloo, The Netherlands rvermeulen@astron.nlSummary. We have studied the interrelation of young AGN with their hosts. Theobjects of study are the young and powerful GPS and CSS radio sources. Due to theirsmall size, GPS and CSS sources are excellent probes of this relation. Furhthermore,their young age allows us to compare them to the larger, old radio sources andestablish a time-line evolution of this relation. Combining imaging and spectroscopyat UV, optical and radio wavelengths we find evidence of strong interaction betweenthe host and the radio source. The presence and expansion of the radio source clearlyaffects the properties and evolution of the host. Furthermore, the radio source andhost significantly affect each other’s evolution. We describe our results and how theseinteractions take place.1 IntroductionGHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radiosources are the most likely candidates for the progenitors of the large scalepowerful classical double (FR) sources (e.g., [40, 22, 20, 50, 49, 39]; for areview see [38]). The GPS and CSS sources are powerful but compact radiosources whose spectra are generally simple and convex with peaks near 1 GHzand 100 MHz respectively. The GPS sources are contained within the extentof the optical narrow emission line region (< 1 kpc) while the CSS sources arecontained within the host galaxy (< 15 kpc).Current models for the evolution of powerful radio galaxies suggest thatthese sources propagate from the ∼ 10 pc to Mpc scales at roughly constantvelocity through an ambient medium which declines in density as ρ(R) ∝R−2 while the sources decline in radio luminosity as Lrad ∝ R−0.5 ([20, 5,2 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen49, 16, 30, 29, 52]). Such a scenario is consistent with the observed numberdensities of powerful radio sources as a function of linear size (from tens ofparsecs to hundreds of kpc; e.g., [39, 21]). However, the situation must be morecomplicated than this simple picture. (1) The GPS and CSS sources mustinteract with the host galaxy as they propagate through it. The discovery ofemission line gas aligned with and presumably co-spatial with the CSS radiosources and the presence of broad and complex integrated emission line profiles([24]) indicates that the radio source is strongly interacting with the ambientgas ([14, 13, 3]). Therefore, we would expect shocks to contribute stronglyto the ionization of the gas ([6]). (2) The GPS sources are observed to haveexpansion velocities several times higher than the estimated advance speeds oflarge scale classical doubles ([1]). This would require the evolving GPS sourcesto decelerate as they propagate though the host galaxy and would require theradio sources to dim faster than the simple models predict. It may be thatthe deceleration takes place via interaction with ambient gas (see [15, 7, 8]).We have carried out a multiwavelength study of how GPS and CSS sourcesevolve and relate with their host as the expansion takes place.2 Emission line gasThe first traces of interaction between GPS/CSS and their hosts were findin the emission line gas. The properties observed in [O III] λ5007 emissionlines ([24]) suggested that, even though the AGN was partly photoionizingthe nebula, the radio source was dominating the emission-line kinematics. Afew years later, the alignment effect (similar extent for radio and optical wave-lengths) seen in large radio sources (e.g., [9, 35]) was found in GPS and CSS([14, 13, 3]). The alignment between the radio source and emission line gassuggests interaction between them, as the radio source propagates throughthe host. The emission line gas was found to be brighter in the center of theradio lobes and dimmed with distance. Therefore, the hypothesis adopted wasthat the gas inside the radio lobe had been shock-ionized while the gas out-side was photoionized by the precursor gas in the shock. At the same time,the AGN could contribute to the whole system with photoionization. Coolingtime arguments suggested lobe expansion velocities >1000 km s−1 for mostof the sources. [42] studied the kinematics of the emission line nebulae of CSSsources, finding that the radio source is accelerating the clouds of gas in thehost.We have obtained Hubble Space Telescope Imaging Spectrograph long-slitspectroscopy of the aligned emission line nebulae in three compact steep spec-trum radio sources: 3C 67, 3C 277.1, and 3C 303.1. Comparing our data withwith shock and photo-ionization models (MAPPINGS [31, 17] and CLOUDY[23]) and examining the relationships between the ionization diagnostics andEnvironment of compact extragalactic radio sources 3the gas kinematics, we find that:1.- In general the extended emission lines are consistent with a mixtureof shocked and photo-ionized gas. In 3C 67, the data lie between the MAP-PINGS models for a contribution to the observed luminosity from shockedgas ranging from 0 to 50%. In 3C 303.1, the contribution to the luminosityfrom shocked gas is between 30 and 70%. In 3C 277.1, the data scatter aroundthe model for 100% contribution to the luminosity from precursor gas. Thesources tend to lie in the regions for moderate to high shock velocities (500to 1000 km/s) and we do not obtain any useful constraints on magnetic fieldstrengths in the MAPPINGS models.2.- The three sources show a decrease in ionization with distance from thenucleus (consistent with a decrease in photoionization with distance) a weaktrend for ionization to decrease with increasing FWHM and a strong trendfor ionization to decrease with increasing velocity offset (which is consistentwith shock ionization).These results are consistent with a picture in which the CSS sources inter-act with dense clouds as they propagate through their host galaxies, shockingthe clouds thereby ionizing and accelerating them (as suggested by [42]).3 Cold gasMany GPS, CSS and larger radio sources are in merging or interacting systems(e.g., [12, 28]), therefore we expect their hosts to have dense nuclear environ-ments. Furthermore, most of the radio loud AGN seem to live in ellipticalgalaxies (e.g., [18]). [57] found that the presence of gas (and dust) in earlytype galaxies is correlated with the occurrence and strength of a central radiosource. This gas is found both in molecular and atomic form (e.g., [32, 44]).Observations at different wavelengths find central structures of gas in AGNhosts ([53, 55, 19, 54, 37]). If the gas is centrally concentrated and GPS/CSSsources are precursors of FR sources, we expect GPS/CSS to show higherdensities in the gas surrounding their radio lobes5. In 2003, using the recentlyimproved Westerbork Synthesis Radio Telescopes, [56] and [48] presented astudy of the occurrence and properties of atomic gas associated with compactradio sources. They found that ∼ 50% of GPS and CSS sources showed HI 21cm absorption, in contrast to normal elliptical galaxies (< 10%, [53]). Further-more, they found that GPS sources tend to have higher HI column densitiesthan CSS sources and that these densities were consistent with the young sce-nario. However, their data lack spatial resolution to accurately locate the HIabsorption. Just a few high resolution HI observations of GPS/CSS sources5 However, extremely high densities may confine the sources.4 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulenwere available at that time ([11, 45, 47, 46]).We have used European VLBI Network UHF band spectral line observa-tions, to localise the redshifted 21cm HI absorption known to occur in thesubgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. Theradio lobes with detected HI absorption (1) are brighter and closer to thecore than the opposite lobes; (2) are more depolarized; and (3) are preferen-tially associated with optical emission line gas. The association between theHI absorption and the emission line gas, supports the hypothesis that the HIabsorption is produced in the atomic cores of the emission line clouds. How-ever, we cannot rule out the existence of HI elsewhere. We suggest that theasymmetries in the radio and optical emission are due to interaction of theradio source with an asymmetric distribution of dense clouds in their environ-ment. Our results are consistent with a picture in which CSS sources interactwith clouds of dense gas as they propagate through their host galaxy.4 Star formation and AGN - Starburst connectionMergers and strong interactions can trigger AGN activity in a galaxy (e.g.,[25, 4, 27]). These events can also produce instabilities in the ISM and triggerstar formation (e.g., [26]). Numerical simulations and models (e.g., [36, 51])suggest that the advancement of the jets through the host galaxy environmentcan also trigger star formation. Imaging studies in ultraviolet (UV) light of thehosts of large 3CR sources find traces of episodes of star formation around thetime when the radio source was triggered ([33, 2, 10, 43, 41, 34]) suggesting apossible link between both.GPS and CSS radio sources are young, smaller versions of the large pow-erful radio sources, so they are expected to exhibit signs of more recent starformation. They have not yet completely broken through the host ISM, sothese interactions are expected to be even more important than in the largersources. Near-UV observations are very sensitive to the presence of hot youngstars and therefore will trace recent star formation events. We have obtainedhigh resolution HST - Advanced Camera for Surveys near-UV images of GPSand CSS sources to study the morphology and the extent of recent star for-mation.We find near UV emission consistent with the presence of recent star for-mation in most of the observed the sources. In the CSS sources 1443+77 and1814–637 the near UV light is aligned with and is co-spatial with the radiosource. We suggest that in these sources the UV light is produced by starformation triggered and/or enhanced by the radio source.Environment of compact extragalactic radio sources 5The connection between the AGN and the star formation is not yet clearbut our observations suggest that some connection exists. Stellar synthesismodels are consistent with a burst of star formation before the formation ofthe radio source. The starburst and AGN activity could have been triggered bythe same event. However, observations at other wavelengths and measurementof the colors are needed to definitively establish the nature of the observedUV light.5 ConclusionsWe have used the young and powerful GPS and CSS radio sources to study theinterrelation of AGN with their hosts. We find evidence of strong interactionbetween the radio source and the host at all wavelengths studied, suggestingthat the presence and expansion of powerful radio sources clearly affect theproperties and evolution of their hosts.The radio source and host can significantly affect each others evolution.However, this influence takes place in different ways. The influence that thehost has on the radio source is somehow indirect, although it can completelychange its destiny: depending of the contents, distribution and density ofthe gas, the radio source will die early, expand and grow into the large FRsources, or remain confined inside its host. In contrast, the influence of theradio source on its host seems to be more direct and takes place during itsexpansion through the host: the radio source will affect the kinematics andionization of the emission line gas, and may change the star formation historyof the host.References1. Alexander, P. et al. MNRAS 225, 1–26 (1987)2. Allen, M.G. et al. ApJS 139, 411–438 (2002).3. Axon, D.J. et al. AJ 120, 2284–2299 (2000)4. Baum, S.A. et al. ApJ 389, 208–222 (1992).5. Begelman, M.C. Baby Cygnus A’s. In: Cygnus A – Study of a Radio Galaxy,p. 209 (1996)6. Bicknell, G.V. et al. ApJ 485, 112 (1997)7. Carvalho, J.C. A&A 292, 392–394 (1994)8. Carvalho, J.C. A&A 329, 845–852 (1998)9. Chambers, K.C.et al. Nature 329, 604–606 (1987).10. Chiaberge, M.et al. ApJ 571, 247–255 (2002).11. Conway, J.E.: In The second workshop on Gigahertz peaked spectrum and com-pact steep spectrum radio sources, Leiden Univ, ed. I. Snellen, R. T. Schilizzi,H. A. J. Rttgering, M. N. Bremer (Leiden: Publ JIVE) p. 198 (1996)6 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen12. de Vries, W.H. et al. AJ 120, 2300–2330 (2000)13. de Vries, W.H. et al. ApJ 526, 27–39 (1999)14. de Vries, W.H. et al. ApJS 110, 191 (1997)15. De Young, D.S. ApJ 402, 95–108 (1993)16. De Young, D.S. ApJ 490, L55 (1997)17. Dopita, M.A., Sutherland, R.S. ApJS 102, 161 (1996)18. Dunlop, J.S. et al. MNRAS 340, 1095–1135 (2003).19. Evans, A.S. et al. ApJ 521, L107–L110 (1999).20. Fanti, C. et al. A&A 302, 317 (1995)21. Fanti, C. et al. A&A 369, 380–420 (2001)22. Fanti, R. et al. A&A 231, 333–346 (1990)23. Ferland, G.J. et al. PASP 110, 761–778 (1998)24. Gelderman, R., Whittle, M. ApJS 91, 491–505 (1994)25. Heckman, T.M. et al. ApJ 311, 526–547 (1986).26. Ho, L.C. ArXiv, astro-ph/0511157 (2005)27. Israel, F.P. A&A Rev. 8, 237–278 (1998)28. Johnston, H.M. et al. MNRAS 356, 515–523 (2005).29. Kaiser, C.R., Alexander, P. MNRAS 286, 215–222 (1997)30. Kaiser, C.R. et al. MNRAS 292, 723 (1997)31. Kewley, L. et al. (2006 in prep.)32. Knapp, G.R., Rupen, M.P. ApJ 460, 271 (1996).33. Koekemoer, A.M. et al. ApJ 525, 621–637 (1999).34. Martel, A.R. et al. AJ 123, 1357–1363 (2002).35. McCarthy, P.J. et al. ApJ 321, L29–L33 (1987).36. Mellema, G. et al. A&A 395, L13–L16 (2002).37. Morganti, R. et al. MNRAS 323, 331–342 (2001).38. O’Dea, C.P. PASP 110, 493–532 (1998)39. O’Dea, C.P., Baum, S.A. AJ 113, 148–161 (1997)40. O’Dea, C.P. et al. ApJ 380, 66–77 (1991)41. O’Dea, C.P. et al. PASA 20, 88–93 (2003)42. O’Dea, C.P. et al. AJ 123, 2333–2351 (2002)43. O’Dea, C.P. et al. AJ 121, 1915–1926 (2001).44. Oosterloo, T. et al. PASA 16, 28–34 (1999)45. Peck, A.B., Taylor, G.B. ApJ 502, L23 (1998)46. Peck, A.B., Taylor, G.B. New A Rev. 46, 295–298 (2002)47. Peck, A.B. et al. ApJ 521, 103–111 (1999)48. Pihlström, Y.M. et al. A&A 404, 871–881 (2003)49. Readhead, A.C.S. et al. ApJ 460, 634 (1996)50. Readhead, A.C.S. et al. ApJ 460, 612 (1996)51. Rees, M.J. MNRAS 239, 1P–4P (1989)52. Snellen, I.A.G. et al. MNRAS 319, 445–456 (2000)53. van Gorkom, J.H. et al. AJ 97, 708–719 (1989)54. van Langevelde, H.J. et al. A&A 354, L45–L48 (2000)55. Verdoes Kleijn, G.A.et al. AJ 118, 2592–2617 (1999).56. Vermeulen, R.C. et al. A&A 404, 861–870 (2003)57. Walsh, D.E.P. et al. ApJ 337, 209–229 (1989).

   University of GroningenEnvironment of compact extragalactic radio sourcesLabiano, A.; O'Dea, C. P.; Barthel, P. D.; Vermeulen, R. C.Published in:Astronomy and astrophysicsIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2006Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Labiano, A., O'Dea, C. P., Barthel, P. D., & Vermeulen, R. C. (2006). Environment of compact extragalacticradio sources. Astronomy and astrophysics, 447(2).CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 28-10-2022arXiv:astro-ph/0611738 v1   23 Nov 2006Environment of compact extragalactic radiosourcesA. Labiano1, C.P.O’Dea2, P.D. Barthel3 and R.C. Vermeulen41 Departamento de Astrof́ısica Molecular e Infrarroja, Instituto de Estructura dela Materia (CSIC), Madrid, Spain labiano@damir.iem.csic.es2 Department of Physics, Rochester Institute of Technology, Rochester, NY,14623, USA odea@cis.rit.edu3 Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlandspdb@astro.rug.nl4 Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990AA Dwingeloo, The Netherlands rvermeulen@astron.nlSummary. We have studied the interrelation of young AGN with their hosts. Theobjects of study are the young and powerful GPS and CSS radio sources. Due to theirsmall size, GPS and CSS sources are excellent probes of this relation. Furhthermore,their young age allows us to compare them to the larger, old radio sources andestablish a time-line evolution of this relation. Combining imaging and spectroscopyat UV, optical and radio wavelengths we find evidence of strong interaction betweenthe host and the radio source. The presence and expansion of the radio source clearlyaffects the properties and evolution of the host. Furthermore, the radio source andhost significantly affect each other’s evolution. We describe our results and how theseinteractions take place.1 IntroductionGHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radiosources are the most likely candidates for the progenitors of the large scalepowerful classical double (FR) sources (e.g., [40, 22, 20, 50, 49, 39]; for areview see [38]). The GPS and CSS sources are powerful but compact radiosources whose spectra are generally simple and convex with peaks near 1 GHzand 100 MHz respectively. The GPS sources are contained within the extentof the optical narrow emission line region (< 1 kpc) while the CSS sources arecontained within the host galaxy (< 15 kpc).Current models for the evolution of powerful radio galaxies suggest thatthese sources propagate from the ∼ 10 pc to Mpc scales at roughly constantvelocity through an ambient medium which declines in density as ρ(R) ∝R−2 while the sources decline in radio luminosity as Lrad ∝ R−0.5 ([20, 5,2 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen49, 16, 30, 29, 52]). Such a scenario is consistent with the observed numberdensities of powerful radio sources as a function of linear size (from tens ofparsecs to hundreds of kpc; e.g., [39, 21]). However, the situation must be morecomplicated than this simple picture. (1) The GPS and CSS sources mustinteract with the host galaxy as they propagate through it. The discovery ofemission line gas aligned with and presumably co-spatial with the CSS radiosources and the presence of broad and complex integrated emission line profiles([24]) indicates that the radio source is strongly interacting with the ambientgas ([14, 13, 3]). Therefore, we would expect shocks to contribute stronglyto the ionization of the gas ([6]). (2) The GPS sources are observed to haveexpansion velocities several times higher than the estimated advance speeds oflarge scale classical doubles ([1]). This would require the evolving GPS sourcesto decelerate as they propagate though the host galaxy and would require theradio sources to dim faster than the simple models predict. It may be thatthe deceleration takes place via interaction with ambient gas (see [15, 7, 8]).We have carried out a multiwavelength study of how GPS and CSS sourcesevolve and relate with their host as the expansion takes place.2 Emission line gasThe first traces of interaction between GPS/CSS and their hosts were findin the emission line gas. The properties observed in [O III] λ5007 emissionlines ([24]) suggested that, even though the AGN was partly photoionizingthe nebula, the radio source was dominating the emission-line kinematics. Afew years later, the alignment effect (similar extent for radio and optical wave-lengths) seen in large radio sources (e.g., [9, 35]) was found in GPS and CSS([14, 13, 3]). The alignment between the radio source and emission line gassuggests interaction between them, as the radio source propagates throughthe host. The emission line gas was found to be brighter in the center of theradio lobes and dimmed with distance. Therefore, the hypothesis adopted wasthat the gas inside the radio lobe had been shock-ionized while the gas out-side was photoionized by the precursor gas in the shock. At the same time,the AGN could contribute to the whole system with photoionization. Coolingtime arguments suggested lobe expansion velocities >1000 km s−1 for mostof the sources. [42] studied the kinematics of the emission line nebulae of CSSsources, finding that the radio source is accelerating the clouds of gas in thehost.We have obtained Hubble Space Telescope Imaging Spectrograph long-slitspectroscopy of the aligned emission line nebulae in three compact steep spec-trum radio sources: 3C 67, 3C 277.1, and 3C 303.1. Comparing our data withwith shock and photo-ionization models (MAPPINGS [31, 17] and CLOUDY[23]) and examining the relationships between the ionization diagnostics andEnvironment of compact extragalactic radio sources 3the gas kinematics, we find that:1.- In general the extended emission lines are consistent with a mixtureof shocked and photo-ionized gas. In 3C 67, the data lie between the MAP-PINGS models for a contribution to the observed luminosity from shockedgas ranging from 0 to 50%. In 3C 303.1, the contribution to the luminosityfrom shocked gas is between 30 and 70%. In 3C 277.1, the data scatter aroundthe model for 100% contribution to the luminosity from precursor gas. Thesources tend to lie in the regions for moderate to high shock velocities (500to 1000 km/s) and we do not obtain any useful constraints on magnetic fieldstrengths in the MAPPINGS models.2.- The three sources show a decrease in ionization with distance from thenucleus (consistent with a decrease in photoionization with distance) a weaktrend for ionization to decrease with increasing FWHM and a strong trendfor ionization to decrease with increasing velocity offset (which is consistentwith shock ionization).These results are consistent with a picture in which the CSS sources inter-act with dense clouds as they propagate through their host galaxies, shockingthe clouds thereby ionizing and accelerating them (as suggested by [42]).3 Cold gasMany GPS, CSS and larger radio sources are in merging or interacting systems(e.g., [12, 28]), therefore we expect their hosts to have dense nuclear environ-ments. Furthermore, most of the radio loud AGN seem to live in ellipticalgalaxies (e.g., [18]). [57] found that the presence of gas (and dust) in earlytype galaxies is correlated with the occurrence and strength of a central radiosource. This gas is found both in molecular and atomic form (e.g., [32, 44]).Observations at different wavelengths find central structures of gas in AGNhosts ([53, 55, 19, 54, 37]). If the gas is centrally concentrated and GPS/CSSsources are precursors of FR sources, we expect GPS/CSS to show higherdensities in the gas surrounding their radio lobes5. In 2003, using the recentlyimproved Westerbork Synthesis Radio Telescopes, [56] and [48] presented astudy of the occurrence and properties of atomic gas associated with compactradio sources. They found that ∼ 50% of GPS and CSS sources showed HI 21cm absorption, in contrast to normal elliptical galaxies (< 10%, [53]). Further-more, they found that GPS sources tend to have higher HI column densitiesthan CSS sources and that these densities were consistent with the young sce-nario. However, their data lack spatial resolution to accurately locate the HIabsorption. Just a few high resolution HI observations of GPS/CSS sources5 However, extremely high densities may confine the sources.4 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulenwere available at that time ([11, 45, 47, 46]).We have used European VLBI Network UHF band spectral line observa-tions, to localise the redshifted 21cm HI absorption known to occur in thesubgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. Theradio lobes with detected HI absorption (1) are brighter and closer to thecore than the opposite lobes; (2) are more depolarized; and (3) are preferen-tially associated with optical emission line gas. The association between theHI absorption and the emission line gas, supports the hypothesis that the HIabsorption is produced in the atomic cores of the emission line clouds. How-ever, we cannot rule out the existence of HI elsewhere. We suggest that theasymmetries in the radio and optical emission are due to interaction of theradio source with an asymmetric distribution of dense clouds in their environ-ment. Our results are consistent with a picture in which CSS sources interactwith clouds of dense gas as they propagate through their host galaxy.4 Star formation and AGN - Starburst connectionMergers and strong interactions can trigger AGN activity in a galaxy (e.g.,[25, 4, 27]). These events can also produce instabilities in the ISM and triggerstar formation (e.g., [26]). Numerical simulations and models (e.g., [36, 51])suggest that the advancement of the jets through the host galaxy environmentcan also trigger star formation. Imaging studies in ultraviolet (UV) light of thehosts of large 3CR sources find traces of episodes of star formation around thetime when the radio source was triggered ([33, 2, 10, 43, 41, 34]) suggesting apossible link between both.GPS and CSS radio sources are young, smaller versions of the large pow-erful radio sources, so they are expected to exhibit signs of more recent starformation. They have not yet completely broken through the host ISM, sothese interactions are expected to be even more important than in the largersources. Near-UV observations are very sensitive to the presence of hot youngstars and therefore will trace recent star formation events. We have obtainedhigh resolution HST - Advanced Camera for Surveys near-UV images of GPSand CSS sources to study the morphology and the extent of recent star for-mation.We find near UV emission consistent with the presence of recent star for-mation in most of the observed the sources. In the CSS sources 1443+77 and1814–637 the near UV light is aligned with and is co-spatial with the radiosource. We suggest that in these sources the UV light is produced by starformation triggered and/or enhanced by the radio source.Environment of compact extragalactic radio sources 5The connection between the AGN and the star formation is not yet clearbut our observations suggest that some connection exists. Stellar synthesismodels are consistent with a burst of star formation before the formation ofthe radio source. The starburst and AGN activity could have been triggered bythe same event. However, observations at other wavelengths and measurementof the colors are needed to definitively establish the nature of the observedUV light.5 ConclusionsWe have used the young and powerful GPS and CSS radio sources to study theinterrelation of AGN with their hosts. We find evidence of strong interactionbetween the radio source and the host at all wavelengths studied, suggestingthat the presence and expansion of powerful radio sources clearly affect theproperties and evolution of their hosts.The radio source and host can significantly affect each others evolution.However, this influence takes place in different ways. The influence that thehost has on the radio source is somehow indirect, although it can completelychange its destiny: depending of the contents, distribution and density ofthe gas, the radio source will die early, expand and grow into the large FRsources, or remain confined inside its host. In contrast, the influence of theradio source on its host seems to be more direct and takes place during itsexpansion through the host: the radio source will affect the kinematics andionization of the emission line gas, and may change the star formation historyof the host.References1. Alexander, P. et al. MNRAS 225, 1–26 (1987)2. Allen, M.G. et al. ApJS 139, 411–438 (2002).3. Axon, D.J. et al. AJ 120, 2284–2299 (2000)4. Baum, S.A. et al. ApJ 389, 208–222 (1992).5. Begelman, M.C. Baby Cygnus A’s. In: Cygnus A – Study of a Radio Galaxy,p. 209 (1996)6. Bicknell, G.V. et al. ApJ 485, 112 (1997)7. Carvalho, J.C. A&A 292, 392–394 (1994)8. Carvalho, J.C. A&A 329, 845–852 (1998)9. Chambers, K.C.et al. Nature 329, 604–606 (1987).10. Chiaberge, M.et al. ApJ 571, 247–255 (2002).11. Conway, J.E.: In The second workshop on Gigahertz peaked spectrum and com-pact steep spectrum radio sources, Leiden Univ, ed. I. Snellen, R. T. Schilizzi,H. A. J. Rttgering, M. N. Bremer (Leiden: Publ JIVE) p. 198 (1996)6 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen12. de Vries, W.H. et al. AJ 120, 2300–2330 (2000)13. de Vries, W.H. et al. ApJ 526, 27–39 (1999)14. de Vries, W.H. et al. ApJS 110, 191 (1997)15. De Young, D.S. ApJ 402, 95–108 (1993)16. De Young, D.S. ApJ 490, L55 (1997)17. Dopita, M.A., Sutherland, R.S. ApJS 102, 161 (1996)18. Dunlop, J.S. et al. MNRAS 340, 1095–1135 (2003).19. Evans, A.S. et al. ApJ 521, L107–L110 (1999).20. Fanti, C. et al. A&A 302, 317 (1995)21. Fanti, C. et al. A&A 369, 380–420 (2001)22. Fanti, R. et al. A&A 231, 333–346 (1990)23. Ferland, G.J. et al. PASP 110, 761–778 (1998)24. Gelderman, R., Whittle, M. ApJS 91, 491–505 (1994)25. Heckman, T.M. et al. ApJ 311, 526–547 (1986).26. Ho, L.C. ArXiv, astro-ph/0511157 (2005)27. Israel, F.P. A&A Rev. 8, 237–278 (1998)28. Johnston, H.M. et al. MNRAS 356, 515–523 (2005).29. Kaiser, C.R., Alexander, P. MNRAS 286, 215–222 (1997)30. Kaiser, C.R. et al. MNRAS 292, 723 (1997)31. Kewley, L. et al. (2006 in prep.)32. Knapp, G.R., Rupen, M.P. ApJ 460, 271 (1996).33. Koekemoer, A.M. et al. ApJ 525, 621–637 (1999).34. Martel, A.R. et al. AJ 123, 1357–1363 (2002).35. McCarthy, P.J. et al. ApJ 321, L29–L33 (1987).36. Mellema, G. et al. A&A 395, L13–L16 (2002).37. Morganti, R. et al. MNRAS 323, 331–342 (2001).38. O’Dea, C.P. PASP 110, 493–532 (1998)39. O’Dea, C.P., Baum, S.A. AJ 113, 148–161 (1997)40. O’Dea, C.P. et al. ApJ 380, 66–77 (1991)41. O’Dea, C.P. et al. PASA 20, 88–93 (2003)42. O’Dea, C.P. et al. AJ 123, 2333–2351 (2002)43. O’Dea, C.P. et al. AJ 121, 1915–1926 (2001).44. Oosterloo, T. et al. PASA 16, 28–34 (1999)45. Peck, A.B., Taylor, G.B. ApJ 502, L23 (1998)46. Peck, A.B., Taylor, G.B. New A Rev. 46, 295–298 (2002)47. Peck, A.B. et al. ApJ 521, 103–111 (1999)48. Pihlström, Y.M. et al. A&A 404, 871–881 (2003)49. Readhead, A.C.S. et al. ApJ 460, 634 (1996)50. Readhead, A.C.S. et al. ApJ 460, 612 (1996)51. Rees, M.J. MNRAS 239, 1P–4P (1989)52. Snellen, I.A.G. et al. MNRAS 319, 445–456 (2000)53. van Gorkom, J.H. et al. AJ 97, 708–719 (1989)54. van Langevelde, H.J. et al. A&A 354, L45–L48 (2000)55. Verdoes Kleijn, G.A.et al. AJ 118, 2592–2617 (1999).56. Vermeulen, R.C. et al. A&A 404, 861–870 (2003)57. Walsh, D.E.P. et al. ApJ 337, 209–229 (1989).

   University of GroningenEnvironment of compact extragalactic radio sourcesLabiano, A.; O'Dea, C. P.; Barthel, P. D.; Vermeulen, R. C.Published in:Astronomy and astrophysicsIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2006Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Labiano, A., O'Dea, C. P., Barthel, P. D., & Vermeulen, R. C. (2006). Environment of compact extragalacticradio sources. Astronomy and astrophysics, 447(2).CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 13-02-2023arXiv:astro-ph/0611738 v1   23 Nov 2006Environment of compact extragalactic radiosourcesA. Labiano1, C.P.O’Dea2, P.D. Barthel3 and R.C. Vermeulen41 Departamento de Astrof́ısica Molecular e Infrarroja, Instituto de Estructura dela Materia (CSIC), Madrid, Spain labiano@damir.iem.csic.es2 Department of Physics, Rochester Institute of Technology, Rochester, NY,14623, USA odea@cis.rit.edu3 Kapteyn Astronomical Institute, Groningen, 9700 AV, The Netherlandspdb@astro.rug.nl4 Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990AA Dwingeloo, The Netherlands rvermeulen@astron.nlSummary. We have studied the interrelation of young AGN with their hosts. Theobjects of study are the young and powerful GPS and CSS radio sources. Due to theirsmall size, GPS and CSS sources are excellent probes of this relation. Furhthermore,their young age allows us to compare them to the larger, old radio sources andestablish a time-line evolution of this relation. Combining imaging and spectroscopyat UV, optical and radio wavelengths we find evidence of strong interaction betweenthe host and the radio source. The presence and expansion of the radio source clearlyaffects the properties and evolution of the host. Furthermore, the radio source andhost significantly affect each other’s evolution. We describe our results and how theseinteractions take place.1 IntroductionGHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radiosources are the most likely candidates for the progenitors of the large scalepowerful classical double (FR) sources (e.g., [40, 22, 20, 50, 49, 39]; for areview see [38]). The GPS and CSS sources are powerful but compact radiosources whose spectra are generally simple and convex with peaks near 1 GHzand 100 MHz respectively. The GPS sources are contained within the extentof the optical narrow emission line region (< 1 kpc) while the CSS sources arecontained within the host galaxy (< 15 kpc).Current models for the evolution of powerful radio galaxies suggest thatthese sources propagate from the ∼ 10 pc to Mpc scales at roughly constantvelocity through an ambient medium which declines in density as ρ(R) ∝R−2 while the sources decline in radio luminosity as Lrad ∝ R−0.5 ([20, 5,2 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulen49, 16, 30, 29, 52]). Such a scenario is consistent with the observed numberdensities of powerful radio sources as a function of linear size (from tens ofparsecs to hundreds of kpc; e.g., [39, 21]). However, the situation must be morecomplicated than this simple picture. (1) The GPS and CSS sources mustinteract with the host galaxy as they propagate through it. The discovery ofemission line gas aligned with and presumably co-spatial with the CSS radiosources and the presence of broad and complex integrated emission line profiles([24]) indicates that the radio source is strongly interacting with the ambientgas ([14, 13, 3]). Therefore, we would expect shocks to contribute stronglyto the ionization of the gas ([6]). (2) The GPS sources are observed to haveexpansion velocities several times higher than the estimated advance speeds oflarge scale classical doubles ([1]). This would require the evolving GPS sourcesto decelerate as they propagate though the host galaxy and would require theradio sources to dim faster than the simple models predict. It may be thatthe deceleration takes place via interaction with ambient gas (see [15, 7, 8]).We have carried out a multiwavelength study of how GPS and CSS sourcesevolve and relate with their host as the expansion takes place.2 Emission line gasThe first traces of interaction between GPS/CSS and their hosts were findin the emission line gas. The properties observed in [O III] λ5007 emissionlines ([24]) suggested that, even though the AGN was partly photoionizingthe nebula, the radio source was dominating the emission-line kinematics. Afew years later, the alignment effect (similar extent for radio and optical wave-lengths) seen in large radio sources (e.g., [9, 35]) was found in GPS and CSS([14, 13, 3]). The alignment between the radio source and emission line gassuggests interaction between them, as the radio source propagates throughthe host. The emission line gas was found to be brighter in the center of theradio lobes and dimmed with distance. Therefore, the hypothesis adopted wasthat the gas inside the radio lobe had been shock-ionized while the gas out-side was photoionized by the precursor gas in the shock. At the same time,the AGN could contribute to the whole system with photoionization. Coolingtime arguments suggested lobe expansion velocities >1000 km s−1 for mostof the sources. [42] studied the kinematics of the emission line nebulae of CSSsources, finding that the radio source is accelerating the clouds of gas in thehost.We have obtained Hubble Space Telescope Imaging Spectrograph long-slitspectroscopy of the aligned emission line nebulae in three compact steep spec-trum radio sources: 3C 67, 3C 277.1, and 3C 303.1. Comparing our data withwith shock and photo-ionization models (MAPPINGS [31, 17] and CLOUDY[23]) and examining the relationships between the ionization diagnostics andEnvironment of compact extragalactic radio sources 3the gas kinematics, we find that:1.- In general the extended emission lines are consistent with a mixtureof shocked and photo-ionized gas. In 3C 67, the data lie between the MAP-PINGS models for a contribution to the observed luminosity from shockedgas ranging from 0 to 50%. In 3C 303.1, the contribution to the luminosityfrom shocked gas is between 30 and 70%. In 3C 277.1, the data scatter aroundthe model for 100% contribution to the luminosity from precursor gas. Thesources tend to lie in the regions for moderate to high shock velocities (500to 1000 km/s) and we do not obtain any useful constraints on magnetic fieldstrengths in the MAPPINGS models.2.- The three sources show a decrease in ionization with distance from thenucleus (consistent with a decrease in photoionization with distance) a weaktrend for ionization to decrease with increasing FWHM and a strong trendfor ionization to decrease with increasing velocity offset (which is consistentwith shock ionization).These results are consistent with a picture in which the CSS sources inter-act with dense clouds as they propagate through their host galaxies, shockingthe clouds thereby ionizing and accelerating them (as suggested by [42]).3 Cold gasMany GPS, CSS and larger radio sources are in merging or interacting systems(e.g., [12, 28]), therefore we expect their hosts to have dense nuclear environ-ments. Furthermore, most of the radio loud AGN seem to live in ellipticalgalaxies (e.g., [18]). [57] found that the presence of gas (and dust) in earlytype galaxies is correlated with the occurrence and strength of a central radiosource. This gas is found both in molecular and atomic form (e.g., [32, 44]).Observations at different wavelengths find central structures of gas in AGNhosts ([53, 55, 19, 54, 37]). If the gas is centrally concentrated and GPS/CSSsources are precursors of FR sources, we expect GPS/CSS to show higherdensities in the gas surrounding their radio lobes5. In 2003, using the recentlyimproved Westerbork Synthesis Radio Telescopes, [56] and [48] presented astudy of the occurrence and properties of atomic gas associated with compactradio sources. They found that ∼ 50% of GPS and CSS sources showed HI 21cm absorption, in contrast to normal elliptical galaxies (< 10%, [53]). Further-more, they found that GPS sources tend to have higher HI column densitiesthan CSS sources and that these densities were consistent with the young sce-nario. However, their data lack spatial resolution to accurately locate the HIabsorption. Just a few high resolution HI observations of GPS/CSS sources5 However, extremely high densities may confine the sources.4 A. Labiano, C.P.O’Dea, P.D. Barthel and R.C. Vermeulenwere available at that time ([11, 45, 47, 46]).We have used European VLBI Network UHF band spectral line observa-tions, to localise the redshifted 21cm HI absorption known to occur in thesubgalactic sized compact steep spectrum galaxies 3C 49 and 3C 268.3. Theradio lobes with detected HI absorption (1) are brighter and closer to thecore than the opposite lobes; (2) are more depolarized; and (3) are preferen-tially associated with optical emission line gas. The association between theHI absorption and the emission line gas, supports the hypothesis that the HIabsorption is produced in the atomic cores of the emission line clouds. How-ever, we cannot rule out the existence of HI elsewhere. We suggest that theasymmetries in the radio and optical emission are due to interaction of theradio source with an asymmetric distribution of dense clouds in their environ-ment. Our results are consistent with a picture in which CSS sources interactwith clouds of dense gas as they propagate through their host galaxy.4 Star formation and AGN - Starburst connectionMergers and strong interactions can trigger AGN activity in a galaxy (e.g.,[25, 4, 27]). These events can also produce instabilities in the ISM and triggerstar formation (e.g., [26]). Numerical simulations and models (e.g., [36, 51])suggest that the advancement of the jets through the host galaxy environmentcan also trigger star formation. Imaging studies in ultraviolet (UV) light of thehosts of large 3CR sources find traces of episodes of star formation around thetime when the radio source was triggered ([33, 2, 10, 43, 41, 34]) suggesting apossible link between both.GPS and CSS radio sources are young, smaller versions of the large pow-erful radio sources, so they are expected to exhibit signs of more recent starformation. They have not yet completely broken through the host ISM, sothese interactions are expected to be even more important than in the largersources. Near-UV observations are very sensitive to the presence of hot youngstars and therefore will trace recent star formation events. We have obtainedhigh resolution HST - Advanced Camera for Surveys near-UV images of GPSand CSS sources to study the morphology and the extent of recent star for-mation.We find near UV emission consistent with the presence of recent star for-mation in most of the observed the sources. In the CSS sources 1443+77 and1814–637 the near UV light is aligned with and is co-spatial with the radiosource. We suggest that in these sources the UV light is produced by starformation triggered and/or enhanced by the radio source.Environment of compact extragalactic radio sources 5The connection between the AGN and the star formation is not yet clearbut our observations suggest that some connection exists. Stellar synthesismodels are consistent with a burst of star formation before the formation ofthe radio source. The starburst and AGN activity could have been triggered bythe same event. However, observations at other wavelengths and measurementof the colors are needed to definitively establish the nature of the observedUV light.5 ConclusionsWe have used the young and powerful GPS and CSS radio sources to study theinterrelation of AGN with their hosts. We find evidence of strong interactionbetween the radio source and the host at all wavelengths studied, suggestingthat the presence and expansion of powerful radio sources clearly affect theproperties and evolution of their hosts.The radio source and host can significantly affect each others evolution.However, this influence takes place in different ways. The influence that thehost has on the radio source is somehow indirect, although it can completelychange its destiny: depending of the contents, distribution and density ofthe gas, the radio source will die early, expand and grow into the large FRsources, or remain confined inside its host. In contrast, the influence of theradio source on its host seems to be more direct and takes place during itsexpansion through the host: the radio source will affect the kinematics andionization of the emission line gas, and may change the star formation historyof the host.References1. Alexander, P. et al. MNRAS 225, 1–26 (1987)2. 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Environment of compact extragalactic radio sources

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