240 research outputs found
Kinematics of galaxies from [CII] line emission
We study the kinematical properties of galaxies in the Epoch of Reionization
via the [CII] 158m line emission. The line profile provides information on
the kinematics as well as structural properties such as the presence of a disk
and satellites. To understand how these properties are encoded in the line
profile, first we develop analytical models from which we identify disk
inclination and gas turbulent motions as the key parameters affecting the line
profile. To gain further insights, we use "Althaea", a highly-resolved () simulated prototypical Lyman Break Galaxy, in the redshift range , when the galaxy is in a very active assembling phase. Based on
morphology, we select three main dynamical stages: I) Merger , II) Spiral Disk,
and III) Disturbed Disk. We identify spectral signatures of merger events,
spiral arms, and extra-planar flows in I), II), and III), respectively. We
derive a generalised dynamical mass vs. [CII]-line FWHM relation. If precise
information on the galaxy inclination is (not) available, the returned mass
estimate is accurate within a factor (). A Tully-Fisher relation is
found for the observed high- galaxies, i.e. for which we provide a simple, physically-based
interpretation. Finally, we perform mock ALMA simulations to check the
detectability of [CII]. When seen face-on, Althaea is always detected at ; in the edge-on case it remains undetected because the larger
intrinsic FWHM pushes the line peak flux below detection limit. This suggests
that some of the reported non-detections might be due to inclination effects.Comment: 14 pages, 12 figures, accepted for publication in MNRA
Evidence of extended cold molecular gas and dust haloes around z ∼ 2.3 extremely red quasars with ALMA
Large-scale outflows are believed to be an important mechanism in the evolution of galaxies. We can determine the impact of these outflows by studying either current galaxy outflows and their effect in the galaxy or by studying the effect of past outflows on the gas surrounding the galaxy. In this work, we examine the CO(7-6), [C I] (3P1→ 3P0), H2O 211-202, and dust continuum emission of 15 extremely red quasars at z ∼2.3 using ALMA. By investigating the radial surface brightness profiles of both the individual sources and the stacked emission, we detect extended cold gas and dust emission on scales of ∼14 kpc in CO(7-6), [C I](2-1), and dust continuum. This is the first time that the presence of a large amount of molecular gas was detected on large, circumgalactic medium scales around quasar host galaxies using [C i] extended emission. We estimate the dust and molecular gas mass of these haloes to be 107.6 and 1010.6 M⊙, indicating significant dust and molecular gas reservoirs around these extreme quasars. By estimating the time-scale at which this gas can reach these distances by molecular gas outflows (7-32 Myr), we conclude that these haloes are a relic of past AGN or starburst activity, rather than an effect of the current episode of extreme quasar activity
Deep into the structure of the first galaxies: SERRA views
We study the formation and evolution of a sample of Lyman Break Galaxies in
the Epoch of Reionization by using high-resolution (),
cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow
the interstellar medium (ISM) thermo-chemical non-equilibrium evolution, and
perform on-the-fly radiative transfer of the interstellar radiation field
(ISRF). The simulation outputs are post-processed to compute the emission of
far infrared lines ([CII], [NII], and [OIII]). At , the most massive
galaxy, `Freesia', has an age , stellar mass
, and a star formation rate
, due to a recent burst.
Freesia has two stellar components (A and B) separated by ; other 11 galaxies are found within . The
mean ISRF in the Habing band is and is spatially uniform; in
contrast, the ionisation parameter is , and
has a patchy distribution peaked at the location of star-forming sites. The
resulting ionising escape fraction from Freesia is .
While [CII] emission is extended (radius 1.54 kpc), [OIII] is concentrated in
Freesia-A (0.85 kpc), where the ratio . As many high- galaxies, Freesia lies below the local [CII]-SFR
relation. We show that this is the general consequence of a starburst phase
(pushing the galaxy above the Kennicutt-Schmidt relation) which
disrupts/photodissociates the emitting molecular clouds around star-forming
sites. Metallicity has a sub-dominant impact on the amplitude of [CII]-SFR
deviations.Comment: 22 pages, 14 figures, accepted by MNRA
The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow
We present the best sensitivity and angular resolution maps of the molecular
disk and outflow of Mrk 231, as traced by CO observations obtained with
IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We
constrain the physical properties of both the molecular disk and outflow, the
presence of a highly-ionized ultra-fast nuclear wind, and their connection. The
molecular outflow has a size of ~1 kpc, and extends in all directions around
the nucleus, being more prominent along the south-west to north-east direction,
suggesting a wide-angle biconical geometry. The maximum projected velocity of
the outflow is nearly constant out to ~1 kpc, thus implying that the density of
the outflowing material decreases from the nucleus outwards as . This
suggests that either a large part of the gas leaves the flow during its
expansion or that the bulk of the outflow has not yet reached out to ~1 kpc,
thus implying a limit on its age of ~1 Myr. We find and erg s.
Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow
(UFO) with velocity -20000 km s, , and momentum load .We find as predicted for outflows undergoing an energy
conserving expansion. This suggests that most of the UFO kinetic energy is
transferred to mechanical energy of the kpc-scale outflow, strongly supporting
that the energy released during accretion of matter onto super-massive black
holes is the ultimate driver of giant massive outflows. We estimate a momentum
boost . The ratios and agree
with the requirements of the most popular models of AGN feedback.Comment: 16 pages, 17 figures. Accepted for publication in A&
An investigation of the circumgalactic medium around z~2.2 AGN with ACA and ALMA
While observations of molecular gas at cosmic noon and beyond have focused on
the gas within galaxies (i.e., the interstellar medium; ISM), it is also
crucial to study the molecular gas reservoirs surrounding each galaxy (i.e., in
the circumgalactic medium; CGM). Recent observations of galaxies and quasars
hosts at high redshift (z>2) have revealed evidence for cold gaseous halos of
scale r_CGM~10kpc, with one discovery of a molecular halo with r_CGM~200kpc and
a molecular gas mass one order of magnitude larger than the ISM of the central
galaxy. As a follow-up, we present deep ACA and ALMA observations of CO(3-2)
from this source and two other quasar host galaxies at z~2.2. While we find
evidence for CO emission on scales of r~10kpc, we do not find evidence for
molecular gas on scales larger than r>20 kpc. Therefore, our deep data do not
confirm the existence of massive molecular halos on scales of ~100 kpc for
these X-ray selected quasars. As an interesting by-product of our deep
observations, we obtain the tentative detection of a negative continuum signal
on scales larger than r>200kpc, which might be tracing the Sunyaev-Zeldovich
effect associated with the halo heated by the active galactic nucleus (AGN). If
confirmed with deeper data, this could be direct evidence of the preventive AGN
feedback process expected by cosmological simulations.Comment: 17 pages, 12 figures. Accepted for publication in MNRA
Early galaxy growth: mergers or gravitational instability?
We investigate the spatially-resolved morphology of galaxies in the early
Universe. We consider a typical redshift z = 6 Lyman Break galaxy, "Althaea"
from the SERRA hydrodynamical simulations. We create mock rest-frame
ultraviolet, optical, and far-infrared observations, and perform a
two-dimensional morphological analysis to de-blend the galaxy disk from
substructures (merging satellites or star-forming regions). We find that the
[CII]158um emitting region has an effective radius 1.5 - 2.5 times larger than
the optical one, consistent with recent observations. This [CII] halo in our
simulated galaxy arises as the joint effect of stellar outflows and carbon
photoionization by the galaxy UV field, rather than from the emission of
unresolved nearby satellites. At the typical angular resolution of current
observations (> 0.15") only merging satellites can be detected; detection of
star-forming regions requires resolutions of < 0.05". The [CII]-detected
satellite has a 2.5 kpc projected distance from the galaxy disk, whereas the
star-forming regions are embedded in the disk itself (distance < 1 kpc). This
suggests that multi-component systems reported in the literature, which have
separations > 2 kpc, are merging satellites, rather than galactic
substructures. Finally, the star-forming regions found in our mock maps follow
the local L[CII] - SFR_UV relation of galaxy disks, although sampling the
low-luminosity, low-SFR tail of the distribution. We show that future JWST
observations, bridging UV and [CII] datasets, will be exceptionally suited to
characterize galaxy substructures thanks to their exquisite spatial resolution
and sensitivity to both low-metallicity and dust-obscured regions that are
bright at infrared wavelengths.Comment: Accepted for publication in MNRAS; 17 pages (plus appendix), 7
figures, 4 table
The dense molecular gas in the QSO SDSS J231038.88+185519.7 resolved by ALMA
We present ALMA observations of the CO(6-5) and [CII] emission lines and the
sub-millimeter continuum of the quasi-stellar object (QSO) SDSS
J231038.88+185519.7. Compared to previous studies, we have analyzed a synthetic
beam that is ten times smaller in angular size, we have achieved ten times
better sensitivity in the CO(6-5) line, and two and half times better
sensitivity in the [CII] line, enabling us to resolve the molecular gas
emission. We obtain a size of the dense molecular gas of kpc, and
of kpc for the 91.5 GHz dust continuum. By assuming that CO(6-5) is
thermalized, and by adopting a CO--to-- conversion factor , we infer a molecular gas mass of
. Assuming that the
observed CO velocity gradient is due to an inclined rotating disk, we derive a
dynamical mass of , which is a factor of approximately two smaller than the previously
reported estimate based on [CII]. Regarding the central black hole, we provide
a new estimate of the black hole mass based on the C~IV emission line detected
in the X-SHOOTER/VLT spectrum: . We find a molecular gas fraction of ,
where . We derive a ratio
suggesting high gas turbulence, outflows/inflows
and/or complex kinematics due to a merger event. We estimate a global Toomre
parameter , indicating likely cloud fragmentation. We compare,
at the same angular resolution, the CO(6-5) and [CII] distributions, finding
that dense molecular gas is more centrally concentrated with respect to [CII].
We find that the current BH growth rate is similar to that of its host galaxy.Comment: A&A in pres
The MAGNUM survey: Positive feedback in the nuclear region of NGC 5643 suggested by MUSE
We study the ionization and kinematics of the ionized gas in the nuclear
region of the barred Seyfert 2 galaxy NGC~5643 using MUSE integral field
observations in the framework of the MAGNUM (Measuring Active Galactic Nuclei
Under MUSE Microscope) survey. The data were used to identify regions with
different ionization conditions and to map the gas density and the dust
extinction. We find evidence for a double sided ionization cone, possibly
collimated by a dusty structure surrounding the nucleus. At the center of the
ionization cone, outflowing ionized gas is revealed as a blueshifted,
asymmetric wing of the [OIII] emission line, up to projected velocity
v(10)~-450 km/s. The outflow is also seen as a diffuse, low luminosity radio
and X-ray jet, with similar extension. The outflowing material points in the
direction of two clumps characterized by prominent line emission with spectra
typical of HII regions, located at the edge of the dust lane of the bar. We
propose that the star formation in the clumps is due to `positive feedback'
induced by gas compression by the nuclear outflow, providing the first
candidate for outflow induced star formation in a Seyfert-like radio quiet AGN.
This suggests that positive feedback may be a relevant mechanism in shaping the
black hole-host galaxy coevolution.Comment: 9 pages, 7 figures, accepted for publication in A&
Ionised outflows in z 2.4 quasar host galaxies
AGN-driven outflows are invoked by galaxy evolutionary models to quench star
formation and to explain the origin of the relations observed locally between
super massive black holes and their host galaxies. This work aims to detect the
presence of extended ionised outflows in luminous quasars where we expect the
maximum activity both in star formation and in black hole accretion. Currently,
there are only a few studies based on spatially resolved observations of
outflows at high redshift, . We analyse a sample of six luminous () quasars at , observed in H-band using the
near-IR integral field spectrometer SINFONI at VLT. We perform a kinematic
analysis of the [OIII] emission line at . [OIII] has a
complex gas kinematic, with blue-shifted velocities of a few hundreds of km/s
and line widths up to 1500 km/s. Using the spectroastrometric method we infer
size of the ionised outflows of up to 2 kpc. The properties of the
ionised outflows, mass outflow rate, momentum rate and kinetic power, are
correlated with the AGN luminosity. The increase in outflow rate with
increasing AGN luminosity is consistent with the idea that a luminous AGN
pushes away the surrounding gas through fast outflows driven by radiation
pressure, which depends on the emitted luminosity. We derive mass outflow rates
of about 6-700 M/yr for our sample, which are lower than those
observed in molecular outflows. Indeed physical properties of ionised outflows
show dependences on AGN luminosity which are similar to those of molecular
outflows but indicating that the mass of ionised gas is smaller than that of
the molecular one. Alternatively, this discrepancy between ionised and
molecular outflows could be explained with different acceleration mechanisms.Comment: 13 pages, 11 figures; accepted for publication in A&
Cold molecular outflows in the local Universe and their feedback effect on galaxies
We study molecular outflows in a sample of 45 local galaxies, both star
forming and AGN, primarily by using CO data from the ALMA archive and from the
literature. For a subsample we also compare the molecular outflow with the
ionized and neutral atomic phases. We infer an empirical analytical function
relating the outflow rate simultaneously to the SFR, , and galaxy
stellar mass; this relation is much tighter than the relations with the
individual quantities. The outflow kinetic power shows a larger scatter than in
previous, more biased studies, spanning from 0.1 to 5 per cent of , while the momentum rate ranges from 1 to 30 times ,
indicating that these outflows can be both energy-driven, but with a broad
range of coupling efficiencies with the ISM, and radiation pressure-driven. For
about 10 per cent of the objects the outflow energetics significantly exceed
the maximum theoretical values; we interpret these as 'fossil outflows'
resulting from activity of a past strong AGN, which has now faded. We estimate
that, in the stellar mass range probed here ( 10), less
than 5 per cent of the outflowing gas escapes the galaxy. The molecular gas
depletion time associated with the outflow can be as short as a few million
years in powerful AGN, however, the total gas (H+HI) depletion times are
much longer. Altogether, our findings suggest that even AGN-driven outflows
might be relatively ineffective in clearing galaxies of their entire gas
content, although they are likely capable of clearing and quenching the central
region
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