221 research outputs found
The nuclear radio structure of X-ray bright AGN
The physical nature of the X-ray/radio correlation of AGN is still an
unsolved question. High angular resolution observations are necessary to
disentangle the associated energy dynamics into nuclear and stellar components.
We present MERLIN/EVN 18cm observations of 13 X-raying AGN. The sample consists
of Seyfert 1, Narrow Line Seyfert 1, and LINER-like galaxies. We find that for
all objects the radio emission is unresolved and that the radio luminosities
and brightness temperatures are too high for star formation to play an
important role. This indicates that the radio emission in these sources is
closely connected to processes that occur in the vicinity of the central
massive black hole, also where the X-ray emission is believed to originate in.Comment: 5 pages, 3 figures, submitted to "The Universe under the Microscope -
Astrophysics at High Angular Resolution", Bad Honnef, German
Near infrared imaging of the broad absorption line quasar BAL QSO 0134+3253
In this paper we present near infrared (NIR) imaging data of the host galaxy
of the broad absorption line quasar (BALQ) at z=2.169, serendipitously found
close to 3C48. The data were obtained with the ESO-VLT camera ISAAC during
period 67. We find extended, rest-frame optical emission around the BALQ after
subtracting a scaled stellar point spread function from the quasar nucleus in
J, H, and Ks. The extended rest-frame optical emission can be interpreted as an
approximately 2 Gyr old stellar population composing the host galaxy of the
BALQ or a stellar population of similar age associated with an intermediate
(z=1.667) absorption system spectroscopically identified by Canalizo & Stockton
(1998) simultaneously. The rest-frame-UV emission on the other hand is
dominated by a young, 500 Myr old stellar population. The UV/optical colors
resemble a mixture of the two populations, of which the young one accounts for
about 80%. Assuming that the residual emission is located at the BALQ redshift,
we find that the host galaxy has a resolved flux of about 10% of the BALQ flux.
The physical scale is quite compact, typical for radio quiet QSOs or Lyman
break galaxies at these redshifts, indicating that the systems are still in the
process of forming.Comment: 14 pages, referee style, 6 figures, 4 tables, accepted for
publication in A&
The nuclear radio structure of X-ray bright AGN
The physical nature of the X-ray/radio correlation of AGN is still an
unsolved question. High angular resolution observations are necessary to
disentangle the associated energy dynamics into nuclear and stellar components.
We present MERLIN/EVN 18cm observations of 13 X-raying AGN. The sample consists
of Seyfert 1, Narrow Line Seyfert 1, and LINER-like galaxies. We find that for
all objects the radio emission is unresolved and that the radio luminosities
and brightness temperatures are too high for star formation to play an
important role. This indicates that the radio emission in these sources is
closely connected to processes that occur in the vicinity of the central
massive black hole, also where the X-ray emission is believed to originate in.Comment: 5 pages, 3 figures, submitted to "The Universe under the Microscope -
Astrophysics at High Angular Resolution", Bad Honnef, German
The nuclear radio structure of X-ray bright AGN
The physical nature of the X-ray/radio correlation of AGN is still an
unsolved question. High angular resolution observations are necessary to
disentangle the associated energy dynamics into nuclear and stellar components.
We present MERLIN/EVN 18cm observations of 13 X-raying AGN. The sample consists
of Seyfert 1, Narrow Line Seyfert 1, and LINER-like galaxies. We find that for
all objects the radio emission is unresolved and that the radio luminosities
and brightness temperatures are too high for star formation to play an
important role. This indicates that the radio emission in these sources is
closely connected to processes that occur in the vicinity of the central
massive black hole, also where the X-ray emission is believed to originate in.Comment: 5 pages, 3 figures, submitted to "The Universe under the Microscope -
Astrophysics at High Angular Resolution", Bad Honnef, German
Galaxy evolution across the optical emission-line diagnostic diagrams?
The discovery of the M-sigma relation, the local galaxy bimodality, and the
link between black-hole and host-galaxy properties, have raised the question
whether AGN play a role in galaxy evolution. Several theoretical models
implement AGN feedback to explain the observed galaxy luminosity function, and
possibly the color and morphological transformation of spiral galaxies into
passive ellipticals. To understand the importance of AGN feedback, a study of
the AGN populations in the radio-optical domain is crucial. A mass sequence
linking star-forming galaxies and AGN has been already noted in previous works,
and it is now investigated as possible evolutionary sequence. We observed a
sample of 119 intermediate-redshift (0.04<z<0.4) SDSS-FIRST radio emitters with
the Effelsberg 100-m telescope at 4.85 and 10.45 GHz and obtained spectral
indices. We find indications of spectral index flattening in high-metallicity
star-forming galaxies, composite galaxies, and Seyferts. This "flattening
sequence" along the [NII]-based emission-line diagnostic diagram is consistent
with the hardening of galaxy ionizing field, due to nuclear activity. After
combining our data with FIRST measurements at 1.4 GHz, we find that the
three-point radio spectra of Seyferts and LINERs show substantial differences,
attributable to small radio core components and larger (arcsecond sized)
jet/lobe components, respectively. A visual inspection of FIRST images seems to
confirm this hypothesis. Galaxies along this sequence are hypothesized to be
transitioning from the active star-forming galaxies (blue cloud) to the passive
elliptical galaxies (red sequence). This supports the suggestion that AGN play
a role in shutting down star-formation, and allow the transition from one
galaxy class to the other.Comment: 20 pages, 19 figures, accepted for publication in A&
Vocabulary Instruction and Student Participation and Retention
This action research investigated vocabulary retention and participation gain from integrating close reading passages into a Kindergarten and Second Grade public school classroom. The methods incorporated included turn and talk opportunities, student journals, and close reading passages. Thirty-six primary school aged students were included in the study. Sources of data collection include a teacher self-evaluation survey, vocabulary recognition task, observational checklist, and observational rubric. Students displayed an increase in vocabulary retention and participation. Because of the students’ increase in retention and participation during whole group instruction, we will continue to use close reading passages in our classrooms
Using Virtual Observatory techniques to search for Adaptive Optics suitable AGN
Until recently, it has been possible only for nearby galaxies to study the
scaling relations between central black hole and host galaxy in detail. Because
of the small number densities at low redshift, (luminous) AGN are
underrepresented in such detailed studies. The advent of adaptive optics (AO)
at large telescopes helps overcoming this hurdle, allowing to reach small
linear scales over a wide range in redshift. Finding AO-suitable targets, i.e.,
AGN having a nearby reference star, and carrying out an initial multiwavelength
classification is an excellent use case for the Virtual Observatory. We present
our Virtual-Observatory approach to select an AO-suitable catalog of
X-ray-emitting AGN at redshifts 0.1<z<1.Comment: 4 pages, 5 figures, submitted to "EURO-VO AIDA workshop:
Multiwavelength astronomy and Virtual Observatory", ESAC, Spain, 1-3 Dec.
200
A low-luminosity type-1 QSO sample; III. Optical spectroscopic properties and activity classification
We report on the optical spectroscopic analysis of a sample of 99
low-luminosity quasi-stellar objects (LLQSOs) at base the
Hamburg/ESO QSO survey (HES). The LLQSOs presented here offer the possibility
of studying the faint end of the QSO population at smaller cosmological
distances and, therefore, in greater detail. A small number of our LLQSO
present no broad component. Two sources show double broad components, whereas
six comply with the classic NLS1 requirements. As expected in NLR of broad line
AGNs, the [S{\sc{ii}}]based electron density values range between 100 and
1000 N/cm. Using the optical characteristics of Populations A and
B, we find that 50\% of our sources with H broad emission are consistent
with the radio-quiet sources definition. The remaining sources could be
interpreted as low-luminosity radio-loud quasar. The BPT-based classification
renders an AGN/Seyfert activity between 50 to 60\%. For the remaining sources,
the possible star burst contribution might control the LINER and HII
classification. Finally, we discuss the aperture effect as responsible for the
differences found between data sets, although variability in the BLR could play
a significant role as well.Comment: 22 pages; 5 tables; 17 figures; in press with A&
A Sample of X-Ray active extragalactic Sources suitable for NIR Adaptive Optics Observations
Recent X-ray surveys have now resolved most of the X-ray background (XRB)
into discrete sources. While this represents a break- through in the
understanding of the XRB, the astrophysical nature of these sources still
remains mysterious. In this article we present a sample of X-ray/optically
selected extragalactic objects which are suitable for adaptive optics
observations in the near infrared (NIR) at highest angu- lar resolution. The
sample is based on a cross-correlation of the Sloan Digital Sky Survey and the
ROSAT All Sky Survey. The NIR properties can help to disentangle the nature of
the X-ray bright, partially absorbed and spectroscopically passive background
objects and their hosts.Comment: 4 pages with 1 figure, LateX, uses newpasp.sty, to appear in "AGN
Physics with the Sloan Digital Sky Survey", ed. G. T. Richards and P. B. Hall
(San Francisco: ASP), 200
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