247 research outputs found
ALMA Observations of a Candidate Molecular Outflow in an Obscured Quasar
We present Atacama Large Millimeter/Submillimeter Array (ALMA) CO (1-0) and
CO (3-2) observations of SDSS J135646.10+102609.0, an obscured quasar and
ultra-luminous infrared galaxy (ULIRG) with two merging nuclei and a known
20-kpc-scale ionized outflow. The total molecular gas mass is M_{mol} ~
9^{+19}_{-6} x 10^8 Msun, mostly distributed in a compact rotating disk at the
primary nucleus (M_{mol} ~ 3 x 10^8 Msun) and an extended tidal arm (M_{mol} ~
5 x 10^8 Msun). The tidal arm is one of the most massive molecular tidal
features known; we suggest that it is due to the lower chance of shock
dissociation in this elliptical/disk galaxy merger. In the spatially resolved
CO (3-2) data, we find a compact (r ~ 0.3 kpc) high velocity (v ~ 500 km/s)
red-shifted feature in addition to the rotation at the N nucleus. We propose a
molecular outflow as the most likely explanation for the high velocity gas. The
outflowing mass of M_{mol} ~ 7 x 10^7 Msun and the short dynamical time of
t_{dyn} ~ 0.6 Myr yield a very high outflow rate of \dot{M}_{mol} ~ 350 Msun/yr
and can deplete the gas in a million years. We find a low star formation rate
(< 16 Msun/yr from the molecular content and < 21 Msun/yr from the far-infrared
spectral energy distribution decomposition) that is inadequate to supply the
kinetic luminosity of the outflow (\dot{E} ~ 3 x 10^43 erg/s). Therefore, the
active galactic nucleus, with a bolometric luminosity of 10^46 erg/s, likely
powers the outflow. The momentum boost rate of the outflow (\dot{p}/(Lbol/c) ~
3) is lower than typical molecular outflows associated with AGN, which may be
related to its compactness. The molecular and ionized outflows are likely two
distinct bursts induced by episodic AGN activity that varies on a time scale of
10^7 yr.Comment: 16 pages, 7 figures, ApJ accepte
The dynamics of the ionized and molecular ISM in powerful obscured quasars at z>=3.5
We present an analysis of the kinematics and excitation of the warm ionized
gas in two obscured, powerful quasars at z>=3.5 from the SWIRE survey, SWIRE
J022513.90-043419.9 and SWIRE J022550.67-042142, based on imaging spectroscopy
on the VLT. Line ratios in both targets are consistent with luminous
narrow-line regions of AGN. SWIRE J022550.67-042142 has very broad (FWHM=2000
km/s), spatially compact [OIII] line emission. SWIRE J022513.90-043419.9 is
spatially resolved, has complex line profiles of H-beta and [OIII], including
broad wings with blueshifts of up to -1500 km/s relative to the narrow
[OIII]5007 component, and widths of up to FWHM=5000 km/s. Estimating the
systemic redshift from the narrow H-beta line, as is standard for AGN host
galaxies, implies that a significant fraction of the molecular gas is
blueshifted by up to ~ -1000 km/s relative to the systemic velocity. Thus the
molecular gas could be participating in the outflow. Significant fractions of
the ionized and molecular gas reach velocities greater than the escape
velocity. We compare empirical and modeling constraints for different energy
injection mechanisms, such as merging, star formation, and momentum-driven AGN
winds. We argue that the radio source is the most likely culprit, in spite of
the sources rather modest radio power of 10^25 W/Hz. Such a radio power is not
uncommon for intense starburst galaxies at z~2. We discuss these results in
light of the co-evolution of AGN and their host galaxy.Comment: Accepted by MNRA
Observations of Feedback from Radio-Quiet Quasars: I. Extents and Morphologies of Ionized Gas Nebulae
Black hole feedback -- the strong interaction between the energy output of
supermassive black holes and their surrounding environments -- is routinely
invoked to explain the absence of overly luminous galaxies, the black hole vs.
bulge correlations and the similarity of black hole accretion and star
formation histories. Yet direct probes of this process in action are scarce and
limited to small samples of active nuclei. We present Gemini IFU observations
of the distribution of ionized gas around luminous, obscured, radio-quiet (RQ)
quasars at z~0.5. We detect extended ionized gas nebulae via [O III]5007
emission in every case, with a mean diameter of 28 kpc. These nebulae are
nearly perfectly round. The regular morphologies of nebulae around RQ quasars
are in striking contrast with lumpy or elongated nebulae seen around radio
galaxies at low and high redshifts. We present the uniformly measured
size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and
type 2 quasars spanning 6 orders of magnitude in luminosity and confirm the
flat slope of the correlation (R ~ L^{0.25+/-0.02}). We find a universal
behavior of the [O III]/H-beta ratio in our entire RQ quasar sample: it
persists at a constant value (~10) in the central regions, until reaching a
"break" isophotal radius ranging from 4 to 11 kpc where it starts to decrease.
We propose a model of clumpy nebulae in which clouds that produce line emission
transition from being ionization-bounded at small distances from the quasar to
being matter-bounded in the outer parts of the nebula, which qualitatively
explains the observed line ratio and surface brightness profiles. It is
striking that we see such smooth and round large-scale gas nebulosities in this
sample, which are inconsistent with illuminated merger debris and which we
suggest may be the signature of accretion energy from the nucleus reaching gas
at large scales.Comment: 44 pages, 11 figures, 3 tables. Accepted for publication in MNRA
Observations of Feedback from Radio-Quiet Quasars - II. Kinematics of Ionized Gas Nebulae
The prevalence and energetics of quasar feedback is a major unresolved
problem in galaxy formation theory. In this paper, we present Gemini Integral
Field Unit observations of ionized gas around eleven luminous, obscured,
radio-quiet quasars at z~0.5 out to ~15 kpc from the quasar; specifically, we
measure the kinematics and morphology of [O III]5007 emission. The round
morphologies of the nebulae and the large line-of-sight velocity widths (with
velocities containing 80% of the emission as high as 1000 km/s combined with
relatively small velocity difference across them (from 90 to 520 km/s) point
toward wide-angle quasi-spherical outflows. We use the observed velocity widths
to estimate a median outflow velocity of 760 km/s, similar to or above the
escape velocities from the host galaxies. The line-of-sight velocity dispersion
declines slightly toward outer parts of the nebulae (by 3% per kpc on average).
The majority of nebulae show blueshifted excesses in their line profiles across
most of their extents, signifying gas outflows. For the median outflow
velocity, we find a kinetic energy flow between 4x10^{44} and 3x10^{45} erg/s
and mass outflow rate between 2000 and 20000 Msun/yr. These values are large
enough for the observed quasar winds to have a significant impact on their host
galaxies. The median rate of converting bolometric luminosity to kinetic energy
of ionized gas clouds is ~2%. We report four new candidates for "super-bubbles"
-- outflows that may have broken out of the denser regions of the host galaxy.Comment: 23 pages, 10 figures, 2 tables, accepted for publication in MNRA
The black holes of radio galaxies during the "Quasar Era": Masses, accretion rates, and evolutionary stage
We present an analysis of the AGN broad-line regions of 6 powerful radio
galaxies at z>~2 (HzRGs) with rest-frame optical imaging spectroscopy obtained
at the VLT. All galaxies have luminous (L(H-alpha)=few x 10^44 erg s^-1),
spatially unresolved H-alpha line emission with FWHM>= 10,000 km s^-1 at the
position of the nucleus, suggesting their AGN are powered by supermassive black
holes with masses of few x 10^9 M_sun and accretion luminosities of a few
percent of the Eddington luminosity. In two galaxies we also detect the BLRs in
H-beta, suggesting relatively low extinction of A_V~1 mag, which agrees with
constraints from X-ray observations. By relating black hole and bulge mass, we
find a possible offset towards higher black-hole masses of at most ~0.6 dex
relative to nearby galaxies at a given host mass, although each individual
galaxy is within the scatter of the local relationship. If not entirely from
systematic effects, this would then suggest that the masses of the host
galaxies have increased by at most a factor ~4 since z~2 relative to the
black-hole masses, perhaps through accretion of satellite galaxies or because
of a time lag between star formation in the host galaxy and AGN fueling. We
also compare the radiative and mechanical energy output (from jets) of our
targets with predictions of recent models of "synthesis" or "grand unified" AGN
feedback, which postulate that AGN with similar radiative and mechanical energy
output rates to those found in our HzRGs may be nearing the end of their period
of active growth. We discuss evidence that they may reach this stage at the
same time as their host galaxies.Comment: A&A in pres
CO line emission in the halo of a radio galaxy at z=2.6
We report the detection of luminous CO(3-2) line emission in the halo of the
z=2.6 radio galaxy (HzRG) TXS0828+193, which has no detected counterpart at
optical to mid-infrared wavelengths implying a stellar mass < few x10^9 M_sun
and relatively low star-formation rates. With the IRAM PdBI we find two CO
emission line components at the same position at ~80 kpc distance from the HzRG
along the axis of the radio jet, with different blueshifts of few 100 km s^-1
relative to the HzRG and a total luminosity of ~2x10^10 K km s^-1 pc^2 detected
at 8 sigma significance. HzRGs have significant galaxy overdensities and
extended halos of metal-enriched gas often with embedded clouds or filaments of
denser material, and likely trace very massive dark-matter halos. The CO
emission may be associated with a gas-rich, low-mass satellite galaxy with
little on-going star formation, in contrast to all previous CO detections of
galaxies at similar redshifts. Alternatively, the CO may be related to a gas
cloud or filament and perhaps jet-induced gas cooling in the outer halo,
somewhat in analogy with extended CO emission found in low-redshift galaxy
clusters.Comment: MNRAS Letters, accepte
Defying jet-gas alignment in two radio galaxies at z~2 with extended light profiles: Similarities to brightest cluster galaxies
We report the detection of extended warm ionized gas in two powerful
high-redshift radio galaxies, NVSS J210626-314003 at z=2.10 and TXS 2353-003 at
z=1.49, that does not appear to be associated with the radio jets. This is
contrary to what would be expected from the alignment effect, a characteristic
feature of distant, powerful radio galaxies at z> 0.6. The gas also has smaller
velocity gradients and line widths than most other high-z radio galaxies with
similar data. Both galaxies are part of a systematic study of 50 high-redshift
radio galaxies with SINFONI, and are the only two that are characterized by the
presence of high surface-brightness gas not associated with the jet axis and by
the absence of such gas aligned with the jet. Both galaxies are spatially
resolved with ISAAC broadband imaging covering the rest-frame R band, and have
extended wings that cannot be attributed to line contamination. We argue that
the gas and stellar properties of these galaxies are more akin to gas-rich
brightest cluster galaxies in cool-core clusters than the general population of
high-redshift radio galaxies at z>2. In support of this interpretation, one of
our sources, TXS 2353-003, for which we have H\alpha\ narrowband imaging, is
associated with an overdensity of candidate H\alpha\ emitters by a factor of 8
relative to the field at z=1.5. We discuss possible scenarios of the
evolutionary state of these galaxies and the nature of their emission line gas
within the context of cyclical AGN feedback.Comment: A&A in pres
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