751 research outputs found
The Complex Structure of the Multi-Phase Galactic Wind in a Starburst Merger
Neutral outflows have been detected in many ultraluminous infrared galaxies
(ULIRGs) via the Na I D absorption-line doublet.
For the first time, we have mapped and analyzed the 2-D kinematics of a cool
neutral outflow in a ULIRG, F10565+2448, using the integral field unit (IFU) on
Gemini North to observe the Na I D feature. At the same time we have mapped the
ionized outflow with the [NII] and H emission lines. We find a systemic
rotation curve that is consistent with the rotation of the molecular disk
determined from previous CO observations. The absorption lines show evidence of
a nuclear outflow with a radial extent of at least 3 kpc, consistent with
previous observations. The strength of the Na I D lines have a strong,
spatially resolved correlation with reddening, suggesting that dust is present
in the outflow. Surprisingly, the outflow velocities of the neutral gas show a
strong asymmetry in the form of a major-axis gradient that is opposite in sign
to disk rotation. This is inconsistent with entrained material rotating along
with the galaxy or with a tilted minor-axis outflow. We hypothesize that this
unusual behavior is due to an asymmetry in the distribution of the ambient gas.
We also see evidence of asymmetric ionized outflow in the emission-line
velocity map, which appear to be decoupled from the neutral outflow. Our
results strengthen the hypothesis that ULIRG outflows differ in morphology from
those in more quiescent disk galaxies.Comment: Accepted to Ap
Half-Megasecond Chandra Spectral Imaging of the Hot Circumgalactic Nebula around Quasar Mrk 231
A deep 400-ksec ACIS-S observation of the nearest quasar known, Mrk 231, is
combined with archival 120-ksec data obtained with the same instrument and
setup to carry out the first ever spatially resolved spectral analysis of a hot
X-ray emitting circumgalactic nebula around a quasar. The 65 x 50 kpc X-ray
nebula shares no resemblance with the tidal debris seen at optical wavelengths.
One notable exception is the small tidal arc 3.5 kpc south of the nucleus where
excess soft X-ray continuum emission and Si XIII 1.8 keV line emission are
detected, consistent with star formation and its associated alpha-element
enhancement, respectively. An X-ray shadow is also detected at the location of
the 15-kpc northern tidal tail. The hard X-ray continuum emission within 6 kpc
of the center is consistent with being due entirely to the bright central AGN.
The soft X-ray spectrum of the outer (>6 kpc) portion of the nebula is best
described as the sum of two thermal components with T~3 and ~8 million K and
spatially uniform super-solar alpha element abundances, relative to iron. This
result implies enhanced star formation activity over ~10^8 yrs accompanied with
redistribution of the metals on large scale. The low-temperature thermal
component is not present within 6 kpc of the nucleus, suggesting extra heating
in this region from the circumnuclear starburst, the central quasar, or the
wide-angle quasar-driven outflow identified from optical IFU spectroscopy on a
scale of >3 kpc. Significant azimuthal variations in the soft X-ray intensity
are detected in the inner region where the outflow is present. The soft X-ray
emission is weaker in the western quadrant, coincident with a deficit of Halpha
and some of the largest columns of neutral gas outflowing from the nucleus.
Shocks created by the interaction of the wind with the ambient ISM may heat the
gas to high temperatures at this location. (abridged)Comment: 43 pages, 11 figures, accepted for publication in the Astrophysical
Journa
A Deep HST H-Band Imaging Survey of Massive Gas-Rich Mergers. II. The QUEST PG QSOs
We report the results from a deep HST NICMOS H-band imaging survey of 28 z <
0.3 QSOs from the Palomar-Green (PG) sample. This program is part of QUEST
(Quasar / ULIRG Evolution STudy) and complements a similar set of data on 26
highly-nucleated ULIRGs presented in Paper I. Our analysis indicates that the
fraction of QSOs with elliptical hosts is higher among QSOs with undetected
far-infrared (FIR) emission, small infrared excess, and luminous hosts. The
hosts of FIR-faint QSOs show a tendency to have less pronounced merger-induced
morphological anomalies and larger QSO-to-host luminosity ratios on average
than the hosts of FIR-bright QSOs, consistent with late-merger evolution from
FIR-bright to FIR-faint QSOs. The spheroid sizes and total host luminosities of
the radio-quiet PG QSOs in our sample are statistically indistinguishable from
the ULIRG hosts presented in Paper I, while those of radio-loud PG QSOs are
systematically larger and more luminous. ULIRGs and PG QSOs with elliptical
hosts fall near, but not exactly on, the fundamental plane of inactive
spheroids. We confirm the systematic trend noted in Paper I for objects with
small (< 2 kpc) spheroids to be up to ~1 mag. brighter than inactive spheroids.
The host colors and wavelength dependence of their sizes support the idea that
these deviations are due at least in part to non-nuclear star formation.
However, the amplitudes of these deviations does not depend on host R-H colors.
Taken at face value (i.e., no correction for extinction or the presence of a
young stellar population), the H-band spheroid-host luminosities imply BH
masses ~5 -- 200 x 10^7 M_sun and sub-Eddington mass accretion rates for both
QSOs and ULIRGs. These results are compared with published BH mass estimates
derived from other methods. (abridged)Comment: Accepted for publication in the Astrophysical Journal, Vol. 701,
August 20 issue. Paper with high-resolution figures can be downloaded at
http://www.astro.umd.edu/~veilleux/pubs/nicmos2.pd
A Chandra X-Ray Survey of Ultraluminous Infrared Galaxies
We present results from Chandra observations of 14 ultraluminous infrared
galaxies (ULIRGs; log(L_IR/L_Sun) >= 12) with redshifts between 0.04 and 0.16.
The goals of the observations were to investigate any correlation between
infrared color or luminosity and the properties of the X-ray emission and to
attempt to determine whether these objects are powered by starbursts or active
galactic nuclei (AGNs). The sample contains approximately the same number of
high and low luminosity objects and ``warm'' and ``cool'' ULIRGs. All 14
galaxies were detected by Chandra. Our analysis shows that the X-ray emission
of the two Seyfert 1 galaxies in our sample are dominated by AGN. The remaining
12 sources are too faint for conventional spectral fitting to be applicable.
Hardness ratios were used to estimate the spectral properties of these faint
sources. The photon indices for our sample plus the Chandra-observed sample
from Ptak et al.(2003) peak in the range of 1.0-1.5, consistent with
expectations for X-ray binaries in a starburst, an absorbed AGN, or hot
bremsstrahlung from a starburst or AGN. The values of photon index for the
objects in our sample classified as Seyferts (type 1 or 2) are larger than 2,
while those classified as HII regions or LINERs tend to be less than 2. The
hard X-ray to far-infrared ratios for the 12 weak sources are similar to those
of starbursts, but we cannot rule out the possibility of absorbed, possibly
Compton-thick, AGNs in some of these objects. Two of these faint sources were
found to have X-ray counterparts to their double optical and infrared nuclei.Comment: 40 pages, 5 tables, 14 figures, accepted by Ap
A Kinematic Link between Boxy Bulges, Stellar Bars and Nuclear Activity in NGC 3079 and NGC 4388
We present direct kinematic evidence for bar streaming motions in two active galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-Perot Interferometer was used on the Canada-France-Hawaii 3.6-m telescope and the University of Hawaii 2.2-m telescope to derive the two-dimensional velocity field of the line-emitting gas in the disks of the Sc galaxy NGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work based on long-slit data, the detection of the bar potential from the Fabry-Perot data does not rely on the existence of inner Lindblad resonances or strong bar-induced shocks. Simple kinematic models which approximate the intrinsic gas orbits as nonintersecting, inclined elliptical annuli that conserve angular momentum characterize the observed velocity fields. Box-shaped bulges in both NGC 3079 and NGC 4388 are confirmed using new near-infrared images to reduce dust obscuration. Morphological analysis of starlight in these galaxies is combined with the gas kinematics derived from the Fabry-Perot spectra to test evolutionary models of stellar bars that involve transitory boxy bulges, and to quantify the importance of such bars in fueling active nuclei. Our data support the evolutionary bar models, but fail to prove convincingly that the stellar bars in NGC 3079 and NGC 4388 directly trigger or sustain the nuclear activity. (abridged
Quasar Feedback in the Ultraluminous Infrared Galaxy F11119+3257: Connecting the Accretion Disk Wind with the Large-Scale Molecular Outflow
In Tombesi et al. (2015), we reported the first direct evidence for a quasar
accretion disk wind driving a massive molecular outflow. The target was
F11119+3257, an ultraluminous infrared galaxy (ULIRG) with unambiguous type-1
quasar optical broad emission lines. The energetics of the accretion disk wind
and molecular outflow were found to be consistent with the predictions of
quasar feedback models where the molecular outflow is driven by a hot
energy-conserving bubble inflated by the inner quasar accretion disk wind.
However, this conclusion was uncertain because the energetics were estimated
from the optically thick OH 119 um transition profile observed with Herschel.
Here, we independently confirm the presence of the molecular outflow in
F11119+3257, based on the detection of broad wings in the CO(1-0) profile
derived from ALMA observations. The broad CO(1-0) line emission appears to be
spatially extended on a scale of at least ~7 kpc from the center. Mass outflow
rate, momentum flux, and mechanical power of (80-200) R_7^{-1} M_sun/yr,
(1.5-3.0) R_7^{-1} L_AGN/c, and (0.15-0.40)% R_7^{-1} L_AGN are inferred from
these data, assuming a CO-to-H_2 conversion factor appropriate for a ULIRG (R_7
is the radius of the outflow normalized to 7 kpc and L_AGN is the AGN
luminosity). These rates are time-averaged over a flow time scale of 7x10^6
yrs. They are similar to the OH-based rates time-averaged over a flow time
scale of 4x10^5 yrs, but about a factor 4 smaller than the local
("instantaneous"; <10^5 yrs) OH-based estimates cited in Tombesi et al. The
implications of these new results are discussed in the context of time-variable
quasar-mode feedback and galaxy evolution. The need for an energy-conserving
bubble to explain the molecular outflow is also re-examined.Comment: 15 pages, 6 figures, 4 tables, accepted for publication in Ap
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