34 research outputs found
An extended Lyman outflow from a radio galaxy at z=3.7?
Spatially resolved observations of AGN host galaxies undergoing feedback
processes are one of the most relevant avenues through which galactic evolution
can be studied, given the long lasting effects AGN feedback has on gas
reservoirs, star formation, and AGN environments at all scales. Within this
context we report results from VLT/MUSE integral field optical spectroscopy of
TN J1049-1258, one of the most powerful radio sources known, at a redshift of
3.7. We detected extended ( 18 kpc) Lyman emission, spatially
aligned with the radio axis, redshifted by 2250 60 km s with
respect to the host galaxy systemic velocity, and co-spatial with UV continuum
emission. This Lyman emission could arise from a companion galaxy,
although there are arguments against this interpretation. Alternatively, it
might correspond to an outflow of ionized gas stemming from the radio galaxy.
The outflow would be the highest redshift spatially resolved ionized outflow to
date. The enormous amount of energy injected, however, appears to be unable to
quench the host galaxy's prodigious star formation, occurring at a rate of
4500 M, estimated using its far infra-red luminosity.
Within the field we also found two companion galaxies at projected distances of
25 kpc and 60 kpc from the host, which suggests the host galaxy is
harbored within a protocluster.Comment: Pre-proofs version - Accepted for publication in ApJ
Testing the paradigm: First spectroscopic evidence of a quasar-galaxy Mpc-scale association at cosmic dawn
State-of-the-art models of massive black hole formation postulate that quasars at z > 6 reside in extreme peaks of the cosmic density structure in the early universe. Even so, direct observational evidence of these overdensities is elusive, especially on large scales ( 6b1 Mpc) as the spectroscopic follow-up of z > 6 galaxies is observationally expensive. Here we present Keck/DEIMOS optical and IRAM/NOEMA millimeter spectroscopy of a z \u303 6 Lyman-break galaxy candidate originally discovered via broadband selection, at a projected separation of 4.65 physical Mpc (13.94 arcmin) from the luminous z = 6.308 quasar J1030+0524. This well-studied field presents the strongest indication to date of a large-scale overdensity around a z > 6 quasar. The Keck observations suggest a z \u303 6.3 dropout identification of the galaxy. The NOEMA 1.2 mm spectrum shows a 3.5\u3c3 line that, if interpreted as [C II], would place the galaxy at z = 6.318 (i.e., at a line-of-sight separation of 3.9 comoving Mpc assuming that relative proper motion is negligible). The measured [C II] luminosity is 3
7 108 L&09, in line with expectations for a galaxy with a star formation rate \u30315 M&09 yr-1, as inferred from the rest-frame UV photometry. Our combined observations place the galaxy at the same redshift as the quasar, thus strengthening the overdensity scenario for this z > 6 quasar. This pilot experiment demonstrates the power of millimeter-wavelength observations in the characterization of the environment of early quasar
The infrared-dominated jet of 3C401
We present a Hubble Space Telescope image of the FRII radio galaxy 3C 401,
obtained at 1.6 microns with the NICMOS camera in which we identify the
infrared counterpart of the brightest region of the radio jet. The jet has a
complex radio structure and brightens where bending occurs, most likely as a
result of relativistic beaming. We analyze archival data in the radio, optical
and X-ray bands and we derive its spectral energy distribution. Differently
from all of the previously known optical extragalactic jets, the jet in 3C401
is not detected in the X-rays even in a long 48ksec X-ray Chandra exposure and
the infrared emission dominates the overall SED. We propose that the dominant
radiation mechanism of this jet is synchrotron. The low X-ray emission is then
caused by two different effects: i) the lack of any strong external photon
field and ii) the shape of the electron distribution. This affects the location
of the synchrotron peak in the SED, resulting in a sharp cut-off at energies
lower than the X-rays. Thus 3C401 shows a new type of jet which has
intermediate spectral properties between those of FRI, which are dominated by
synchrotron emission up to X-ray energies, and FRII/QSO, which show a strong
high-energy emission due to inverse-Compton scattering of external photons.
This might be a clue for the presence of a continuous ``sequence'' in the
properties of large scale jets, in analogy with the ``blazar sequence'' already
proposed for sub-pc scale jets.Comment: 7 pages, 5 figures, accepted for publication in the ApJ. A typo in
the value of the radio to X-ray spectral index (sect. 5, paragraph 2, thanks
to T. Cheung) and other minor corrections have been mad
The MURALES survey. VI. Properties and origin of the extended line emission structures in radio galaxies
This is the sixth paper presenting the results of the MUse RAdio Loud
Emission line Snapshot survey (MURALES). We observed 37 radio sources from the
3C sample with z<0.3 and declination <20 degrees with the MUSE optical integral
field spectrograph at the VLT. We here focus on the properties of the extended
emission line regions (EELRs) that can be studied with unprecedented detail
thanks to the depth of these observations. Line emission in the 10 FRIs is, in
most cases, confined to within 4 kpc) ionized gas
is seen in all but two of the 26 FRIIs. It usually takes the form of elongated
or filamentary structures, typically extending between 10 and 30 kpc, but also
reaching distances of ~80 kpc. We find that 1) the large-scale ionized gas
structures show a tendency to be oriented at large angles from the radio axis,
and 2) the gas on a scale of a few kpc from the nucleus often shows ordered
rotation with a kinematical axis forming a median angle of 65 degrees with the
radio axis. We also discuss the velocity field and ionization properties of the
EELRs. The observed emission line structures appear to be associated with
gaseous "superdisks" formed after a gas rich merger. The different properties
of the EELR can be explained with a combination of the source evolutionary
state and the orientation of the "superdisk" with respect to the radio axis.
The general alignment between the superdisks and radio axis might be produced
by stable and coherent accretion maintained over long timescales.Comment: Pre-proofs version - Accepted for publication in A&
The web of the Giant: spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524
We report on the spectroscopic confirmation of a large scale structure around
the luminous, z=6.31 QSO SDSS~J1030+0524, that is powered by a billion solar
mass black hole. The structure is populated by at least six members, four Lyman
Break Galaxies (LBGs) and two Lyman Alpha Emitters (LAEs). The four LBGs have
been identified among a sample of 21 i-band dropouts with z{AB}<25.5 selected
up to projected separations of 5 physical Mpc (15 arcmin) from the QSO. Their
redshifts have been determined through up to 8hr-long multi-object
spectroscopic observations at 8-10m class telescopes. The two LAEs have been
identified in a 6hr VLT/MUSE observation centered on the QSO. The redshifts of
the six galaxies cover the range 6.129-6.355. Assuming that peculiar velocities
are negligible, this range corresponds to radial separations of +/-5 physical
Mpc from the QSO, that is comparable to the projected scale of the observed LBG
distribution on the sky. We conservatively estimate that this structure is
significant at >3.5 sigma level, and that the level of the galaxy overdensity
is at least 1.5-2 within the large volume sampled (~780 physical Mpc^3). The
spectral properties of the six member galaxies (Lyalpha strength and UV
luminosity) are similar to those of field galaxies at similar redshifts. This
is the first spectroscopic identification of a galaxy overdensity around a
super-massive black hole in the first billion years of the Universe. Our
finding lends support to the idea that the most distant and massive black holes
form and grow within massive (>10^{12} Msun) dark matter halos in large scale
structures, and that the absence of earlier detections of such systems was
likely due to observational limitations.Comment: 8 pages including Appendix, 5 figures, accepted as a letter on
Astronomy & Astrophysics. v2: minor changes in Table 1 caption and Figs. 2 &
3 label
The MURALES survey. IV. Searching for nuclear outflows in 3C radio galaxies at z < 0.3 with MUSE observations
We analyze VLT/MUSE observations of 37 radio galaxies from the Third
Cambridge catalogue (3C) with redshift 0.3 searching for nuclear outflows of
ionized gas. These observations are part of the MURALES project (a MUse RAdio
Loud Emission line Snapshot survey), whose main goal is to explore the feedback
process in the most powerful radio-loud AGN. We applied a nonparametric
analysis to the [O~III] 5007 emission line, whose asymmetries and
high-velocity wings reveal signatures of outflows. We find evidence of nuclear
outflows in 21 sources, with velocities between 400 - 1000 km s,
outflowing masses of M, and a kinetic energy in the
range erg. In addition, evidence for extended outflows
is found in the 2D gas velocity maps of 13 sources of the subclasses of
high-excitation (HEG) and broad-line (BLO) radio galaxies, with sizes between
0.4 and 20 kpc. We estimate a mass outflow rate in the range 0.4 - 30 M
yr and an energy deposition rate of erg s. Comparing the jet power, the nuclear luminosity of the active
galactic nucleus, and the outflow kinetic energy rate, we find that outflows of
HEGs and BLOs are likely radiatively powered, while jets likely only play a
dominant role in galaxies with low excitation. The low loading factors we
measured suggest that these outflows are driven by momentum and not by energy.
Based on the gas masses, velocities, and energetics involved, we conclude that
the observed ionized outflows have a limited effect on the gas content or the
star formation in the host. In order to obtain a complete view of the feedback
process, observations exploring the complex multiphase structure of outflows
are required.Comment: 40 pages; accepted for publication on A&A
Optical spectroscopy of local type-1 AGN LINERs
The Balmer emission originated in the broad-line region (BLR) of active galactic nuclei (AGNs) could be either weak and difficult to detect, or even absent, for low-luminosity AGNs, as low-ionization nuclear emission-line regions (LINERs). Our goals in this paper are threefold. First, we want to explore the AGN nature of nearby type-1 LINERs. Secondly, we aim at deriving a reliable interpretation for the different components of emission lines by studying their kinematics and ionization mechanism. Thirdly, we intend to probe the neutral gas in the nuclei of these LINERs. We study the 22 local (z < 0.025) type-1 LINERs from the Palomar survey, on the basis of optical ground- and space-based long-slit spectroscopic observations taken with the TWIN spectrograph at Calar Alto Observatory (CAHA) and ALFOSC/NOT (Andalucia Faint Object Spectrograph and Camera/2.6 m North Optical Telescope). Kinematics and fluxes of a set of emission lines, from Hβ λ4861 to [S II] λλ6716, 6731, and the NaD λλ5890, 5896 doublet in absorption have been modelled and measured, after the subtraction of the underlying starlight. We also use ancillary spectroscopic data from HST/STIS (Hubble Space Telescope/Space Telescope Imaging Spectrograph). We found that the broad H α component is sometimes elusive in our ground-based spectroscopy, whereas it is ubiquitous for space-based data. By combining optical diagnostic diagrams, theoretical models [for AGNs, post-asymptotic giant branch (pAGB) stars, and shocks] and the weak/strong-[O I] classification, we exclude the pAGB star scenario in favour of the AGN as the dominant mechanism of ionization in these LINERs, being shocks however relevant. The kinematical properties of the emission lines may indicate the presence of ionized outflows, preferentially seen in [O I]. However, the neutral gas outflows, diagnosed by NaD, would appear to be less frequent
Blazar Variability with the Vera C. Rubin Legacy Survey of Space and Time
With their emission mainly coming from a relativistic jet pointing toward us, blazars are fundamental sources for studying extragalactic jets and their central engines, consisting of supermassive black holes fed by accretion disks. They are also candidate sources of high-energy neutrinos and cosmic rays. Because of the jet orientation, the nonthermal blazar emission is Doppler beamed; its variability is unpredictable, and it occurs on timescales from less than 1 hr to years. Comprehension of the diverse mechanisms producing the flux and spectral changes requires well-sampled multiband light curves over long time periods. In particular, outbursts are the best test bench for shedding light on the underlying physics, especially when studied in a multiwavelength context. The Vera C. Rubin Legacy Survey of Space and Time (Rubin-LSST) will monitor the southern sky for 10 yr in six photometric bands, offering a formidable tool for studying blazar variability features in a statistical way. The alert system will allow us to trigger follow-up observations of outstanding events, especially at high (keV-to-GeV) and very high (TeV) energies. We here examine the simulated Rubin-LSST survey strategies with the aim of understanding which cadences are more suitable for blazar variability science. Our metrics include light curve and color sampling. We also investigate the problem of saturation, which will affect the brightest and many flaring sources, and will have a detrimental impact on follow-up observations
Bubbles and outflows: the novel JWST/NIRSpec view of the z=1.59 obscured quasar XID2028
Quasar feedback in the form of powerful outflows is invoked as a key
mechanism to quench star formation in galaxies, although direct observational
evidence is still scarce and debated. Here we present Early Release Science
JWST NIRSpec IFU observations of the z=1.59 prototypical obscured quasar
XID2028: this target represents a unique test case to study QSO feedback at the
peak epoch of AGN-galaxy co-evolution thanks to its existing extensive
multi-wavelength coverage and massive and extended outflow detected both in the
ionised and molecular components. With the unprecedented sensitivity and
spatial resolution of JWST, the NIRSpec dataset reveals a wealth of structures
in the ionised gas kinematics and morphology previously hidden in the
seeing-limited ground-based data. In particular, we find evidence of
interaction between the interstellar medium of the galaxy and the QSO-driven
outflow and radio jet, which is producing an expanding bubble from which the
fast and extended wind detected in previous observations is emerging. The new
observations confirm the complex interplay between the AGN jet/wind and the ISM
of the host galaxy, highlighting the role of low luminosity radio jets in AGN
feedback, and showcase the new window opened by NIRSpec on the detailed study
of feedback at high redshift.Comment: 12 pages, 11 figures, submitted to A&A. Comments welcom