arXiv subjects

F. Combes

Publications and source records attributed to F. Combes.

At least 127 records · Page 7Linked to original sources

arXiv2020

ALMA observations of CS in NGC 1068: chemistry and excitation

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 ($\sim14$ Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, $r\sim200$ pc) and a starburst ring (SB ring, $r\sim1.3$ kpc). These high-resolution maps ($\sim0.5$", $\sim35$ pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. Local thermodynamic equilibrium (LTE) analysis of the gas is used to calculate CS densities in each sub-region, followed by non-LTE analysis conducted using the radiative transfer code RADEX to fit observations and constrain gas temperature, CS column density and hydrogen density. Finally, the chemical code UCLCHEM is used to reconstruct the gas, allowing an insight into its origin and chemical history. The density of hydrogen in the CND is found to be $\geq10^5$ cm$^{-2}$, although exact values vary, reaching $10^6$ cm$^{-2}$ at the AGN. The conditions in the two arms of the SB ring appear similar to one another, though the density found ($\sim10^4$ cm$^{-2}$) is lower than in the CND. The temperature in the CND increases from east to west, and is also overall greater than found in the SB ring. These modelling methods indicate the requirement for multi-phase gas components in order to fit the observed emission over the galaxy. A larger number of high resolution transitions across the SLED may allow for further constraining of the conditions, particularly in the SB ring.

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arXiv2020

A molecular absorption line survey toward the AGN of Hydra-A

We present Atacama Large Millimeter/submillimeter Array observations of the brightest cluster galaxy Hydra-A, a nearby ($z=0.054$) giant elliptical galaxy with powerful and extended radio jets. The observations reveal CO(1-0), CO(2-1), $^{13}$CO(2-1), CN(2-1), SiO(5-4), HCO$^{+}$(1-0), HCO$^{+}$(2-1), HCN(1-0), HCN(2-1), HNC(1-0) and H$_{2}$CO(3-2) absorption lines against the galaxy's bright and compact active galactic nucleus. These absorption features are due to at least 12 individual molecular clouds which lie close to the centre of the galaxy and have velocities of approximately $-50$ to $+10$ km/s relative to its recession velocity, where positive values correspond to inward motion. The absorption profiles are evidence of a clumpy interstellar medium within brightest cluster galaxies composed of clouds with similar column densities, velocity dispersions and excitation temperatures to those found at radii of several kpc in the Milky Way. We also show potential variation in a $\sim 10$ km/s wide section of the absorption profile over a two year timescale, most likely caused by relativistic motions in the hot spots of the continuum source which change the background illumination of the absorbing clouds.

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arXiv2020

Cold molecular gas and PAH emission in Seyfert galaxies

We investigate the relation between the detection of the $11.3\,μ$m PAH feature in the nuclear ($\sim 24-230\,$pc) regions of 22 nearby Seyfert galaxies and the properties of the cold molecular gas. For the former we use ground-based (0.3-0.6" resolution) mid-infrared (mid-IR) spectroscopy. The cold molecular gas is traced by ALMA and NOEMA high (0.2-1.1") angular resolution observations of the CO(2-1) transition. Galaxies with a nuclear detection of the $11.3\,μ$m PAH feature contain more cold molecular gas (median $1.6\times 10^7\,M_\odot$) and have higher column densities ($N({\rm H}_2) = 2 \times 10^{23}\,{\rm cm}^{-2}$) over the regions sampled by the mid-IR slits than those without a detection. This suggests that molecular gas plays a role in shielding the PAH molecules in the harsh environments of Seyfert nuclei. Choosing the PAH molecule naphthalene as an illustration, we compute its half-life in the nuclear regions of our sample when exposed to 2.5keV hard X-ray photons. We estimate shorter half-lives for naphthalene in nuclei without a $11.3\,μ$m PAH detection than in those with a detection. The Spitzer/IRS PAH ratios on circumnuclear scales ($\sim$ 4" $\sim$ 0.25-1.3kpc) are in between model predictions for neutral and partly ionized PAHs. However, Seyfert galaxies in our sample with the highest nuclear H$_2$ column densities are not generally closer to the neutral PAH tracks. This is because in the majority of our sample galaxies, the CO(2-1) emission in the inner $\sim$ 4" is not centrally peaked and in some galaxies traces circumnuclear sites of strong star formation activity. Spatially resolved observations with the MIRI medium-resolution spectrograph (MRS) on the James Webb Space Telescope will be able to distinguish the effects of an active galactic nucleus (AGN) and star formation on the PAH emission in nearby AGN.

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arXiv2020

Circum-nuclear molecular disks: role in AGN fueling and feedback

Gas inflows fueling AGN are now traceable at high-resolution with ALMA and NOEMA. Dynamical mechanisms are essential to exchange angular momentum and drive the gas to the super-massive black hole. While at 100pc scale, the gas is sometimes stalled in nuclear rings, recent observations reaching 10pc scale (50mas), inside the sphere of influence of the black hole, may bring smoking gun evidence of fueling, within a randomly oriented nuclear molecular disk. AGN feedback is also observed, in the form of narrow and collimated molecular outflows, which point towards the radio mode, or entrainment by a radio jet. Precession has been observed in a molecular outflow, indicating the precession of the radio jet. One of the best candidates for precession is the Bardeen-Petterson effect at small scale, which exerts a torque on the accreting material, and produces an extended disk warp. The misalignment between the inner and large-scale disk, enhances the coupling of the AGN feedback, since the jet sweeps a large part of the molecular disk.

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arXiv2020

Detection of deuterated molecules, but not of lithium hydride, in the z=0.89 absorber toward PKS1830-211

Deuterium and lithium are light elements of high cosmological and astrophysical importance. In this work we report the first detection of deuterated molecules and a search for lithium hydride, 7LiH, at redshift z=0.89 in the spiral galaxy intercepting the line of sight to the quasar PKS1830-211. We used ALMA to observe several submillimeter lines of ND, NH2D, and HDO, and their related isotopomers NH2, NH3, and H2^18O, in absorption against the southwest image of the quasar, allowing us to derive XD/XH abundance ratios. The absorption spectra mainly consist of two distinct narrow velocity components for which we find remarkable differences. One velocity component shows XD/XH abundances that is about 10 times larger than the primordial elemental D/H ratio, and no variability of the absorption profile during the time span of our observations. [...] The second component has XD/XH abundances that are 100 times larger than the primordial D/H ratio, a deepening of the absorption by a factor of two within a few months, and a rich chemical composition, with relative enhancements of N2H+, CH3OH, SO2, and complex organic molecules. We therefore speculate that this component is associated with the analog of a Galactic dark cloud, while the first component is likely more diffuse. Our search for the 7LiH (1--0) line was unsuccessful and we derive an upper limit 7LiH/H2 = 4 x 10^-13 (3sigma) in the z=0.89 absorber toward PKS1830-211. Besides, with ALMA archival data, we could not confirm the previous tentative detections of this line in the z=0.68 absorber toward B0218+357; we derive an upper limit 7LiH/H2 = 5 x 10^-11 (3sigma), although this is less constraining than our limit toward PKS1830-211. We conclude that, as in the Milky Way, only a tiny fraction of lithium nuclei are possibly bound in LiH in these absorbers at intermediate redshift.

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arXiv2020

Environmental processing in cluster core galaxies at z=1.7

Today, the brightest cluster galaxies (BCGs) are passive and very massive galaxies at the center of their clusters, and they still accrete mass through swallowing companions and gas from cooling flows. However their formation history is not well known. We report CO(4$\rightarrow$3) and continuum map observations of the SpARCS1049+56 BCG at $z=1.709$, one of the most distant known BCGs. Our observations yield $M_{{\rm H}_2}<1.1\times10^{10}M_\odot$ for the BCG; while in CO(4$\rightarrow$3), we detect two gas-rich companions at the northeast and southeast of the BCG, within 20 kpc, with ${L^\prime_{\rm CO(4\rightarrow3)}=(5.8\pm0.6)\times10^{9}}$ K km s$^{-1}$ pc$^2$ and $(7.4\pm0.7)\times10^{9}$ K km s$^{-1}$ pc$^2$, respectively. The northern companion is associated with a pair of merging cluster galaxies, while the southern one shows a southern tail in CO(4$\rightarrow$3), which was also detected in continuum, and we suggest it to be the most distant jellyfish galaxy for which ram pressure stripping is effectively able to strip off its dense molecular gas. This study probes the presence of rare gas-rich systems in the very central region of a distant cluster core, which will potentially merge into the BCG itself. Currently, we may thus be seeing the reversal of the star formation versus density relation at play in the distant universe. This is the first time the assembly of high-$z$ progenitors of our local BCGs can be studied in such great detail.

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arXiv2020

Molecular gas in distant brightest cluster galaxies

The stellar mass assembly of brightest cluster galaxies (BCGs) is still debated. We have observed in CO with the IRAM-30m two star forming BCGs belonging to SpARCS clusters, 3C 244.1 ($z=0.4$) and SDSS J161112.65+550823.5 ($z=0.9$), and compared their molecular gas and star formation properties with those of a compilation of $\sim100$ distant cluster galaxies, including nine additional distant BCGs at ${z\sim0.4-3.5}$. We have set robust upper limits of $M_{{\rm H}_2}<1.0\times10^{10}~M_\odot$ and $<2.8\times10^{10}~M_\odot$ to their molecular gas content, respectively, as well as to the molecular gas to stellar mass ratio $M({\rm H}_2)/M_\star\lesssim0.2$ and depletion time $τ_{\rm dep}\lesssim40$ Myr of the two targeted BCGs. They are thus among the distant cluster galaxies with the lowest gas fractions and shortest depletion times. The majority, $64\%\pm15\%$ and $73\%\pm18\%$, of the 11 BCGs with observations in CO have lower $M({\rm H}_2)/M_\star$ and $τ_{\rm dep}$, respectively, than those estimated for main sequence galaxies. Statistical analysis tentatively suggests that the values of $M({\rm H}_2)/M_\star$ and $τ_{\rm dep}$ for the 11 BCGs deviates, with a significance of $\sim2σ$, from those of the comparison sample of cluster galaxies. A morphological analysis for a subsample of seven BCGs with archival HST observations reveals that $71\%\pm17\%$ of the BCGs are compact or show star-forming substructures/components. Our results suggest a scenario where distant star forming BCGs assemble a significant fraction $\sim16\%$ of their stellar mass in the relatively short timescale $τ_{\rm dep}$, while environmental mechanisms might prevent the replenishment of gas feeding the star formation. We speculate that compact components favor the rapid exhaustion of molecular gas and help to quench the BCGs. Distant star forming BCGs are excellent targets for ALMA and JWST.

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arXiv2019

A CO molecular gas wind 340 pc away from the Seyfert 2 nucleus in ESO 420-G13 probes an elusive radio jet

A prominent jet-driven outflow of CO(2-1) molecular gas is found along the kinematic minor axis of the Seyfert 2 galaxy ESO 420-G13, at a distance of $340-600\, \rm{pc}$ from the nucleus. The wind morphology resembles a characteristic funnel shape, formed by a highly collimated filamentary emission at the base, likely tracing the jet propagation through a tenuous medium, until a bifurcation point at $440\, \rm{pc}$ where the jet hits a dense molecular core and shatters, dispersing the molecular gas into several clumps and filaments within the expansion cone. We also trace the jet in ionised gas within the inner $\lesssim 340\, \rm{pc}$ using the [NeII]$_{\rm 12.8 μm}$ line emission, where the molecular gas follows a circular rotation pattern. The wind outflow carries a mass of $\sim 8 \times 10^6\, \rm{M_\odot}$ at an average wind projected speed of $\sim 160\, \rm{km\,s^{-1}}$, which implies a mass outflow rate of $\sim 14\, \rm{M_\odot\,yr^{-1}}$. Based on the structure of the outflow and the budget of energy and momentum, we discard radiation pressure from the active nucleus, star formation, and supernovae as possible launching mechanisms. ESO 420-G13 is the second case after NGC 1377 where the presence of a previously unknown jet is revealed due to its interaction with the interstellar medium, suggesting that unknown jets in feeble radio nuclei might be more common than expected. Two possible jet-cloud configurations are discussed to explain the presence of an outflow at such distance from the AGN. The outflowing gas will likely not escape, thus a delay in the star formation rather than quenching is expected from this interaction, while the feedback effect would be confined within the central few hundred parsecs of the galaxy.

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arXiv2019

Probing the merger history of red early-type galaxies with their faint stellar substructures

Several deep observations such as those carried out at the Canada-France-Hawaii Telescope (CFHT) have revealed prominent Low Surface Brightness (LSB) fine structures that change the apparent morphology of galaxies. Previous photometry surveys have developed observational techniques which exploit the diffuse light detected in the external regions of galaxies. In these studies the outer perturbations have been identified and classified like tidal tails, stellar streams, and shells. These structures are tracers of interacting and merging events and they keep a memory of the mass assembly of galaxies. Cosmological numerical simulations are needed to estimate their visibility time-scale (among other properties) in order to reconstruct the past merger history of galaxies. In the present work, we analyze a hydrodynamical cosmological simulation to build a comprehensive interpretation of the properties of fine structures. We make a census of several types of LSB fine structures by visual inspection of individual snapshots at various time. We reconstruct the evolution of the number of fine structures detected around an early-type galaxy and we compare with the merger history of the galaxy. We find that most of fine structures are associated with major and intermediate mass merger events. Their survival time scale ranges between 0.7 and 4 Gyr. Shells and streams remain visible for a longer time than tidal tails. These estimates of survival times provide clues to interpret the shape and frequency of fine structures observed in deep images in terms of mass assembly. We find that the detectability of stellar streams is the most sensitive to the surface brightness limit. We see 2-3 times more streams with a surface brightness cut of 33 mag arcsec$^{-2}$ than with 29 mag arcsec$^{-2}$. The detection of shells display a strong dependence on the projection angle.

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arXiv2019

ALMA images the many faces of the NGC1068 torus and its surroundings

We investigate the fueling and the feedback of nuclear activity in the Seyfert 2 galaxy NGC1068, by studying the distribution and kinematics of molecular gas in the torus and its connections. We use ALMA to image the emission of a set of molecular gas tracers in the circumnuclear disk (CND) and the torus of the galaxy using the CO(2-1), CO(3-2) and HCO+(4-3) lines with spatial resolutions ~0.03"-0.09"(2-6pc). ALMA resolves the CND as an asymmetric ringed disk of D~400pc-size and mass of ~1.4x10^8 Msun. The inner edge of the ring is associated with edge-brightened arcs of NIR polarized emission identified with the working surface of the AGN ionized wind. ALMA proves the existence of a molecular torus of M_torus ~ 3x10^5Msun, which extends over a large range of spatial scales D=10-30pc around the central engine. The new observations evidence the density radial stratification of the torus: the HCO+(4-3) torus, with a full size D=11pc, is a factor of 2-3 smaller than its CO(2-1) and CO(3-2) counterparts, which have full-sizes D=26pc and D=28pc, respectively. The torus is connected to the CND through a network of gas streamers. The kinematics of molecular gas show strong departures from circular motions in the torus, the gas streamers, and the CND. These velocity distortions are interconnected and are part of a 3D outflow that reflects the effects of AGN feedback on the kinematics of molecular gas across a wide range of spatial scales. We conclude that a wide-angle AGN wind launched from the accretion disk is impacting a sizeable fraction of the gas inside the torus (~0.4-0.6 x M_torus). However, a large gas reservoir (~1.2-1.8 x 10^5Msun) close to the equatorial plane of the torus remains unaffected by the AGN wind and can continue fueling the AGN for ~1-4Myr. AGN fueling seems nevertheless thwarted on intermediate scales (15pc < r < 50pc).

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arXiv2019

Driving massive molecular gas flows in central cluster galaxies with AGN feedback

We present an analysis of new and archival ALMA observations of molecular gas in twelve central cluster galaxies. We examine emerging trends in molecular filament morphology and gas velocities to understand their origins. Molecular gas masses in these systems span $10^9-10^{11}\mathrm{M}_{\odot}$, far more than most gas-rich galaxies. ALMA images reveal a distribution of morphologies from filamentary to disk-dominated structures. Circumnuclear disks on kiloparsec scales appear rare. In most systems, half to nearly all of the molecular gas lies in filamentary structures with masses of a few $\times10^{8-10}\mathrm{M}_{\odot}$ that extend radially several to several tens of kpc. In nearly all cases the molecular gas velocities lie far below stellar velocity dispersions, indicating youth, transience or both. Filament bulk velocities lie far below the galaxy's escape and free-fall speeds indicating they are bound and being decelerated. Most extended molecular filaments surround or lie beneath radio bubbles inflated by the central AGN. Smooth velocity gradients found along the filaments are consistent with gas flowing along streamlines surrounding these bubbles. Evidence suggests most of the molecular clouds formed from low entropy X-ray gas that became thermally unstable and cooled when lifted by the buoyant bubbles. Uplifted gas will stall and fall back to the galaxy in a circulating flow. The distribution in morphologies from filament to disk-dominated sources therefore implies slowly evolving molecular structures driven by the episodic activity of the AGN.

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arXiv2019

Dense gas formation and destruction in a simulated Perseus-like galaxy cluster with spin-driven black hole feedback

Extended filamentary H$α$ emission nebulae are a striking feature of nearby galaxy clusters but the formation mechanism of the filaments, and the processes which shape their morphology remain unclear. We conduct an investigation into the formation, evolution and destruction of dense gas in the center of a simulated, Perseus-like, cluster under the influence of a spin-driven jet. We particularly study the role played by condensation of dense gas from the diffuse intracluster medium, and the impact of direct uplifting of existing dense gas by the jets, in determining the spatial distribution and kinematics of the dense gas. We present a hydrodynamical simulation of an idealised Perseus-like cluster using the adaptive mesh refinement code {\sc ramses}. Our simulation includes a supermassive black hole (SMBH) that self-consistently tracks its spin evolution via its local accretion, and in turn drives a large-scale jet whose direction is based on the black hole's spin evolution. We show that the formation and destruction of dense gas is closely linked to the SMBH's feedback cycle, and that its morphology is highly variable throughout the simulation. While extended filamentary structures readily condense from the hot intra-cluster medium, they are easily shattered into an overly clumpy distribution of gas during their interaction with the jet driven outflows. Condensation occurs predominantly onto infalling gas located 5 - 15 kpc from the center during quiescent phases of the central AGN, when the local ratio of the cooling time to free fall time falls below 20, i.e. when $t_{\rm cool}/t_{\rm ff} < 20$. We find evidence for both condensation and uplifting of dense gas, but caution that purely hydrodynamical simulations struggle to effectively regulate the cluster cooling cycle and produce overly clumpy distributions of dense gas morphologies, compared to observation.

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arXiv2019

Towards sub-kpc scale kinematics of molecular and ionized gas of star-forming galaxies at $z\sim1$

We compare the molecular and ionized gas kinematics of two strongly lensed galaxies at $z\sim1$ based on observations from ALMA and MUSE. We derive the CO and [OII] rotation curves and dispersion profiles of these two galaxies. We find a difference between the observed molecular and ionized gas rotation curves for one of the galaxies, the Cosmic Snake, for which we obtain a spatial resolution of few hundred parsecs along the major axis. The rotation curve of the molecular gas is steeper than the rotation curve of the ionized gas. In the second galaxy, A521, the molecular and ionized gas rotation curves are consistent, but the spatial resolution is only of few kpc on the major axis. Using simulations, we investigate the effect of the thickness of the gas disk and effective radius on the observed rotation curves and find that a more extended and thicker disk smooths the curve. We also find that the presence of a strongly inclined thick disk (>1 kpc) can smooth the rotation curve because it degrades the spatial resolution along the line of sight. By building a model using a stellar disk and two gas disks, we reproduce the rotation curves of the Cosmic Snake with a molecular gas disk that is more massive and more radially and vertically concentrated than the ionized gas disk. Finally, we also obtain an intrinsic velocity dispersion in the Cosmic Snake of 18.5+-7 km/s and 19.5+-6 km/s for the molecular and ionized gas, respectively, which is consistent with a molecular disk with a smaller and thinner disk. For A521, the intrinsic velocity dispersion values are 11+-8 km/s and 54+-11 km/s, with a higher value for the ionized gas. This could indicate that the ionized gas disk is thicker and more turbulent in this galaxy. These results highlight the different spatial distribution of the molecular and ionized gas disks at $z\sim1$ and suggest the presence of thick ionized gas disks at this epoch.

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arXiv2019

SIGNALS: I. Survey Description

SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing program designed to investigate massive star formation and HII regions in a sample of local extended galaxies. The program will use the imaging Fourier transform spectrograph SITELLE at the Canada-France-Hawaii Telescope. Over 355 hours (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved HII regions : the largest, most complete, and homogeneous database of spectroscopically and spatially resolved extragalactic HII regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363 -386 nm), SN2 (482 - 513 nm), and SN3 (647 - 685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the project sample will facilitate the study of small-scale nebular physics and many other phenomena linked to star formation at a mean spatial resolution of 20 pc. This survey also has considerable legacy value for additional topics including planetary nebulae, diffuse ionized gas, andsupernova remnants. The purpose of this paper is to present a general outlook of the survey, notably the observing strategy, galaxy sample, and science requirements.

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arXiv2019

Complex molecular gas kinematics in the inner 5 kpc of 4C12.50 as seen by ALMA

The nearby system 4C12.50, also known as IRAS 13451+1217 and PKS 1345+12, is a merger of gas-rich galaxies with infrared and radio activity. It has a perturbed interstellar medium (ISM) and a dense configuration of gas and dust around the nucleus. The radio emission at small ($\sim$100 pc) and large ($\sim$100 kpc) scales, as well as the large X-ray cavity in which the system is embedded, are indicative of a jet that could have affected the ISM. We carried out observations of the CO(1-0), (3-2), and (4-3) lines with the Atacama Large Millimeter Array (ALMA) to determine basic properties (i.e., extent, mass, and excitation) of the cold molecular gas in this system, including its already-known wind. The CO emission reveals the presence of gaseous streams related to the merger, which result in a small ($\sim$4kpc-wide) disk around the western nucleus. The disk reaches a rotational velocity of 200 $kms^{-1}$ , and has a mass of 3.8($\pm$0.4)$\times$10${^9}M_{\odot}$. It is truncated at a gaseous ridge north of the nucleus that is bright in [O III]. Regions with high-velocity CO emission are seen at signal-to-noise ratios of between 3 and 5 along filaments that radially extend from the nucleus to the ridge and that are bright in [O III] and stellar emission. A tentative wind detection is also reported in the nucleus and in the disk. The molecular gas speed could be as high as 2200 $kms^{-1}$ and the total wind mass could be as high as 1.5($\pm$0.1)$\times$10$^9M_{\odot}$. Energetically, it is possible that the jet, assisted by the radiation pressure of the active nucleus or the stars, accelerated clouds inside an expanding bubble.

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arXiv2019

Constraining cold accretion onto supermassive black holes: molecular gas in the cores of eight brightest cluster galaxies revealed by joint CO and CN absorption

To advance our understanding of the fuelling and feedback processes which power the Universe's most massive black holes, we require a significant increase in our knowledge of the molecular gas which exists in their immediate surroundings. However, the behaviour of this gas is poorly understood due to the difficulties associated with observing it directly. We report on a survey of 18 brightest cluster galaxies lying in cool cores, from which we detect molecular gas in the core regions of eight via carbon monoxide (CO), cyanide (CN) and silicon monoxide (SiO) absorption lines. These absorption lines are produced by cold molecular gas clouds which lie along the line of sight to the bright continuum sources at the galaxy centres. As such, they can be used to determine many properties of the molecular gas which may go on to fuel supermassive black hole accretion and AGN feedback mechanisms. The absorption regions detected have velocities ranging from -45 to 283 km s$^{-1}$ relative to the systemic velocity of the galaxy, and have a bias for motion towards the host supermassive black hole. We find that the CN N = 0 - 1 absorption lines are typically 10 times stronger than those of CO J = 0 - 1. This is due to the higher electric dipole moment of the CN molecule, which enhances its absorption strength. In terms of molecular number density CO remains the more prevalent molecule with a ratio of CO/CN $\sim 10$, similar to that of nearby galaxies. Comparison of CO, CN and HI observations for these systems shows many different combinations of these absorption lines being detected.

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arXiv2019

A nuclear molecular outflow in the Seyfert galaxy NGC3227

We present ALMA observations of the CO(2-1) and CO(3-2) molecular gas transitions and associated (sub)-mm continua of the nearby Seyfert 1.5 galaxy NGC3227 with angular resolutions 0.085-0.21" (7-15pc). On large scales the cold molecular gas shows circular motions as well as streaming motions on scales of a few hundred parsecs associated with a large scale bar. We fitted the nuclear ALMA 1.3mm emission with an unresolved component and an extended component. The 850$μ$m emission shows at least two extended components, one along the major axis of the nuclear disk and the other along the axis of the ionization cone. The molecular gas in the central region (1" ~73pc) shows several CO clumps with complex kinematics which appears to be dominated by non-circular motions. While we cannot demonstrate conclusively the presence of a warped nuclear disk, we also detected non-circular motions along the kinematic minor axis. They reach line-of-sight velocities of v-vsys =150-200km/s. Assuming that the radial motions are in the plane of the galaxy, then we interpret them as a nuclear molecular outflow due to molecular gas in the host galaxy being entrained by the AGN wind. We derive molecular outflow rates of $5\,M_\odot\,{\rm yr}^{-1}$ and $0.6\,M_\odot\,{\rm yr}^{-1}$ at projected distances of up to 30pc to the northeast and southwest of the AGN, respectively. At the AGN location we estimate a mass in molecular gas of $5\times 10^{5}\,M_\odot$ and an average column density $N({\rm H}_2) = 2-3\times 10^{23}\,{\rm cm}^{-2}$ in the inner 15pc. The nuclear molecular gas and sub-mm continuum emission of NGC3227 do not resemble the classical compact torus. Rather, these emissions extend for several tens of parsecs and appear connected with the circumnuclear ring in the host galaxy disk, as found in other local AGN. (Abridged)

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arXiv2019

The hidden heart of the luminous infrared galaxy IC 860 I. A molecular inflow feeding opaque, extreme nuclear activity

High-resolution (0."03 - 0."09) (9 - 26 pc)) ALMA (100 - 350 GHz (3 - 0.8 mm)) and VLA 45 GHz measurements have been used to image continuum and spectral line emission from the inner region of the nearby infrared luminous galaxy IC 860. We detect compact (r=8-10 pc), luminous, mm continuum emission in the core of IC 860, with brightness temperatures $T_{\rm B}>$ 280 K. The 45 GHz continuum is equally compact, but fainter in flux. We suggest that the 3 to 0.8 mm continuum is opaque at mm-wavelengths, implying a very large H$_2$ column density $N$(H$_2$) of 1e26 cm-2, and that it emerges from hot dust with temperature $T_{\rm d} \sim 280$ K. Vibrationally excited lines of HCN $ν_2$=1f J=4-3 and 3-2 (HCN-VIB) are seen in emission and resolved on scales of 40-50 pc. The HCN-VIB emission reveals a north-south nuclear velocity gradient with projected rotation velocities of v=100 kms$^{-1}$ at r=10 pc. The brightest HCN-VIB emission is oriented perpendicular to the velocity gradient. Ground state lines of HCN 3-2, 4-3, HC$^{15}$N 4-3, HCO$^+$ 3-2, 4-3 and CS 7-6, show complex line absorption and emission features. HCN and HCO$^+$ have red-shifted, reversed P-Cygni profiles consistent with gas inflows of $\sim$50 kms$^{-1}$. The absorption features can be traced from the north-east into the nucleus. In contrast, CS 7-6 shows blue-shifted line wings extending to -180 kms$^{-1}$. We suggest that a dense and slow outflow is hidden behind a foreground layer of inflowing gas. It appears that the centre of IC 860 is in a phase of rapid evolution where an inflow is building up the nuclear column density of gas. A slow, dense outflow may be signalling the onset of feedback. The inner, r=10 pc, IR luminosity can be powered by an accreting black hole and/or a compact starburst with a top-heavy initial mass function.

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