arXiv subjects

M. Krips

Publications and source records attributed to M. Krips.

At least 19 recordsLinked to original sources

arXiv2025

HerS-3: An Exceptional Einstein Cross Reveals a Massive Dark Matter Halo

We present a study of HerS-3, a dusty star-forming galaxy at zspec = 3.0607, which is gravitationally amplified into an Einstein cross with a fifth image of the background galaxy seen at the center of the cross. Detailed 1-mm spectroscopy and imaging with NOEMA and ALMA resolve the individual images and show that each of the five images display a series of molecular lines that have similar central velocities, unambiguously confirming that they have identical redshifts. The HST F110W image reveals a foreground lensing group of four galaxies with a photometric redshift zphot~1.0. Lens models that only include the four visible galaxies are unable to reproduce the properties of HerS-3. By adding a fifth massive component, lying south-east of the brightest galaxy of the group, the source reconstruction is able to match the peak emission, shape and orientation for each of the five images. The fact that no galaxy is detected near that position indicates the presence of a massive dark matter halo in the lensing galaxy group. In the source plane, HerS-3 appears as an infrared luminous starburst galaxy seen nearly edge-on. The serendipitous discovery of this exceptional Einstein cross offers a potential laboratory for exploring at small spatial scales a nuclear starburst at the peak of cosmic evolution and studying the properties of a massive dark matter halo associated with the lensing galaxy group.

astro-ph.GA↗

arXiv2025

High resolution mapping of molecular tori with ALMA

Recent high resolution mapping of the circum-nuclear regions of Active Galactic Nuclei (AGN) has revealed the existence of geometrically thin nuclear disks, in general randomly oriented with respect to their galaxy hosts. These molecular tori have typical radii of 10~pc, and contain a few 10$^7$ M$_\odot$ of H$_2$, with H$_2$ column densities between 10$^{23}$ and 10$^{25}$ cm$^{-2}$. We mapped two of the most massive of these molecular tori with higher resolution, in order to unveil their morphology and kinematics, their possible warp and clumpiness, and derive their stability and life-time. We used the highest resolution possible with ALMA (16~km baseline) in Band 7, taking into account for mapping CO(3-2) and HCO$^+$(4-3) the compromise between sensitivity and resolution. New features are discovered at the high resolution, obtained with a beam of 0.015\arcsec, equivalent to $\sim$ 1~pc scale, at their $\sim$ 15~Mpc distance. The molecular torus in NGC~613 appears like a ring, depleted in molecular gas near the center. The depletion region is displaced by 3~pc toward the NW from the AGN position, meaning some $m=1$ asymmetry in the torus. The molecular torus in NGC~1672 has a different position angle from previous lower-resolution observations, and is edge-on, revealing a geometrically very thin torus (axis ratio 6.5 to 10), with a clear warp. This confirms that the classical model of a simple geometrically thick dusty torus is challenged by high resolution observations. The nuclear disks appear clumpy, and slightly lopsided. The molecular outflow in NGC~613 is now resolved out. Well inside the sphere of influence of the black holes (BH), we are now able to determine more accurately their mass, for those Seyfert spiral galaxies, in a region of the M-sigma relation where the scatter is maximum.

astro-ph.GA↗

arXiv2024

A dusty proto-cluster surrounding the binary galaxy HerBS-70 at $z = 2.3$

We report on deep SCUBA-2 observations at 850$\mu$m and NOEMA spectroscopic measurements at 2 mm of the environment surrounding the luminous, massive ($M_{*} \approx 2 \times 10^{11}$ M$_{\odot}$) Herschel-selected source HerBS-70. This source was revealed by previous NOEMA observations to be a binary system of dusty star-forming galaxies at $z= 2.3$, with the East component (HerBS-70E) hosting an Active Galactic Nucleus (AGN). The SCUBA-2 observations detected, in addition to the binary system, twenty-one sources at $> 3.5 \sigma$ over an area of $\sim 25$ square comoving Mpc with a sensitivity of $\sigma_{850} = 0.75$ mJy. The surface density of continuum sources around HerBS-70 is three times higher than for field galaxies. The NOEMA spectroscopic measurements confirm the protocluster membership of three of the nine brightest sources through their CO(4 - 3) line emission, yielding a volume density 36 times higher than for field galaxies. All five confirmed sub-mm galaxies in the HerBS-70 system have relatively short gas depletion times ($80 - 500$ Myr), indicating the onset of quenching for this protocluster core due to the depletion of gas. The dark matter halo mass of the HerBS-70 system is estimated around $5 \times{} 10^{13}$ M$_{\odot}$, with a projected current-day mass of $10^{15}$ M$_{\odot}$, similar to the local Virgo and Coma clusters. These observations support the claim that DSFGs, in particular the ones with observed multiplicity, can trace cosmic overdensities.

astro-ph.GA↗

arXiv2023

z-GAL -- A NOEMA spectroscopic redshift survey of bright Herschel galaxies: [I] Overview

(Abridged) Using the IRAM NOEMA interferometer, we measures the redshifts of 126 bright galaxies detected in the Herschel H-ATLAS, HeLMS, and HerS surveys. We report reliable spectroscopic redshifts for a total of 124 of the Herschel-selected galaxies. The redshifts are estimated from scans of the 3 and 2-mm bands (and, in one case, the 1-mm band) and are based on the detection of at least two emission lines. Together with the Pilot Programme (Neri et al. 2020), including spectroscopic redshifts of 11 sources, our survey has derived precise redshifts for 135 bright Herschel-selected galaxies, making it the largest sample of high-z galaxies with robust redshifts to date. Most emission lines detected are from 12CO (mainly from J=2-1 to 5-4), with some sources seen in [CI] and H2O emission lines. The spectroscopic redshifts are in the range 0.8<z<6.55 with a median value of z=2.56 +/- 0.10. The line widths of the sources are large, with a mean value for the full width at half maximum Delta(V) of 590 +/- 25 km/s and with 35% of the sources having widths of 700 km/s < Delta(V) < 1800 km/s. Most of the sources are unresolved or barely resolved on scales of 2 to 3 arcsec (or linear sizes of 15-25 kpc, unlensed). Some fields reveal double or multiple sources and, in some cases, sources at different redshifts. Taking these sources into account, there are, in total, 165 individual sources with robust spectroscopic redshifts, including lensed galaxies, binary systems, and over-densities. We present an overview of the z-GAL survey and provide the observed properties of the emission lines, the derived spectroscopic redshifts, and an atlas of the entire sample. The data presented here will serve as a foundation for the other z-GAL papers in this series reporting on the dust emission, the molecular and atomic gas properties, and a detailed analysis of the nature of the sources.

astro-ph.GA↗

arXiv2023

z-GAL -- A NOEMA spectroscopic redshift survey of bright Herschel galaxies: [III] Physical properties

The z-GAL survey observed 137 bright Herschel-selected targets with the IRAM NOrthern Extended Millimeter Array, with the aim to measure their redshift and study their properties. Several of them have been resolved into multiple sources. Consequently, robust spectroscopic redshifts have been measured for 165 individual galaxies in the range 0.8<z<6.5. In this paper we analyse the millimetre spectra of the z-GAL sources, using both their continuum and line emission to derive their physical properties. At least two spectral lines are detected for each source, including transitions of 12CO, [CI], and H2O. The observed 12CO line ratios and spectral line energy distributions of individual sources resemble those of local starbursts. In seven sources the para-H2O(2_11-2_02) transition is detected and follows the IR versus H2O luminosity relation of sub-millimetre galaxies. The molecular gas mass of the z-GAL sources is derived from their 12CO, [CI], and sub-millimetre dust continuum emission. The three tracers lead to consistent results, with the dust continuum showing the largest scatter when compared to 12CO. The gas-to-dust mass ratio of these sources was computed by combining the information derived from 12CO and the dust continuum and has a median value of 107, similar to star-forming galaxies of near-solar metallicity. The same combined analysis leads to depletion timescales in the range between 0.1 and 1.0 Gyr, which place the z-GAL sources between the `main sequence' of star formation and the locus of starbursts. Finally, we derived a first estimate of stellar masses - modulo possible gravitational magnification - by inverting known gas scaling relations: the z-GAL sample is confirmed to be mostly composed by starbursts, whereas ~25% of its members lie on the main sequence of star-forming galaxies (within +/- 0.5 dex).

astro-ph.GA↗

arXiv2023

Bright Extragalactic ALMA Redshift Survey (BEARS) III: Detailed study of emission lines from 71 Herschel targets

We analyse the molecular and atomic emission lines of 71 bright Herschel-selected galaxies between redshifts 1.4 to 4.6 detected by the Atacama Large Millimetre/submillimetre Array. These lines include a total of 156 CO, [C I], and H2O emission lines. For 46 galaxies, we detect two transitions of CO lines, and for these galaxies we find gas properties similar to those of other dusty star-forming galaxy (DSFG) samples. A comparison to photo-dissociation models suggests that most of Herschel-selected galaxies have similar interstellar medium conditions as local infrared-luminous galaxies and high-redshift DSFGs, although with denser gas and more intense far-ultraviolet radiation fields than normal star-forming galaxies. The line luminosities agree with the luminosity scaling relations across five orders of magnitude, although the star-formation and gas surface density distributions (i.e., Schmidt-Kennicutt relation) suggest a different star-formation phase in our galaxies (and other DSFGs) compared to local and low-redshift gas-rich, normal star-forming systems. The gas-to-dust ratios of these galaxies are similar to Milky Way values, with no apparent redshift evolution. Four of 46 sources appear to have CO line ratios in excess of the expected maximum (thermalized) profile, suggesting a rare phase in the evolution of DSFGs. Finally, we create a deep stacked spectrum over a wide rest-frame frequency (220-890 GHz) that reveals faint transitions from HCN and CH, in line with previous stacking experiments.

astro-ph.GA↗

arXiv2023

The Bright Extragalactic ALMA Redshift Survey (BEARS) II: Millimetre photometry of gravitational lens candidates

We present 101 and 151 GHz ALMA continuum images for 85 fields selected from Herschel observations that have 500 micron flux densities >80 mJy and 250-500 micron colours consistent with z > 2, most of which are expected to be gravitationally lensed or hyperluminous infrared galaxies. Approximately half of the Herschel 500 micron sources were resolved into multiple ALMA sources, but 11 of the 15 brightest 500 micron Herschel sources correspond to individual ALMA sources. For the 37 fields containing either a single source with a spectroscopic redshift or two sources with the same spectroscopic redshift, we examined the colour temperatures and dust emissivity indices. The colour temperatures only vary weakly with redshift and are statistically consistent with no redshift-dependent temperature variations, which generally corresponds to results from other samples selected in far-infrared, submillimetre, or millimetre bands but not to results from samples selected in optical or near-infrared bands. The dust emissivity indices, with very few exceptions, are largely consistent with a value of 2. We also compared spectroscopic redshifts to photometric redshifts based on spectral energy distribution templates designed for infrared-bright high-redshift galaxies. While the templates systematically underestimate the redshifts by ~15%, the inclusion of ALMA data decreases the scatter in the predicted redshifts by a factor of ~2, illustrating the potential usefulness of these millimetre data for estimating photometric redshifts.

astro-ph.GA↗

arXiv2022

A dusty compact object bridging galaxies and quasars at cosmic dawn

Understanding how super-massive black holes form and grow in the early Universe has become a major challenge since the discovery of luminous quasars only 700 million years after the Big Bang. Simulations indicate an evolutionary sequence of dust-reddened quasars emerging from heavily dust-obscured starbursts that then transition to unobscured luminous quasars by expelling gas and dust. Although the last phase has been identified out to a redshift of 7.6, a transitioning quasar has not been found at similar redshifts owing to their faintness at optical and near-infrared wavelengths. Here we report observations of an ultraviolet compact object, GNz7q, associated with a dust-enshrouded starburst at a redshift of z=7.1899+/-0.0005. The host galaxy is more luminous in dust emission than any other known object at this epoch, forming 1,600 solar masses of stars per year within a central radius of 480 parsec. A red point source in the far-ultraviolet is identified in deep, high-resolution imaging and slitless spectroscopy. GNz7q is extremely faint in X-rays, which indicates the emergence of a uniquely ultraviolet compact star-forming region or a Compton-thick super-Eddington black-hole accretion disk at the dusty starburst core. In the latter case, the observed properties are consistent with predictions from cosmological simulations and suggest that GNz7q is an antecedent to unobscured luminous quasars at later epochs.

astro-ph.GA↗

arXiv2022

The Bright Extragalactic ALMA Redshift Survey (BEARS) I: redshifts of bright gravitationally-lensed galaxies from the Herschel ATLAS

We present spectroscopic measurements for 71 galaxies associated with 62 of the brightest high-redshift submillimeter sources from the Southern fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), while targeting 85 sources which resolved into 142. We have obtained robust redshift measurements for all sources using the 12-m Array and an efficient tuning of ALMA to optimise its use as a redshift hunter, with 73 per cent of the sources having a robust redshift identification. Nine of these redshift identifications also rely on observations from the Atacama Compact Array. The spectroscopic redshifts span a range $1.41<z<4.53$ with a mean value of 2.75, and the CO emission line full-width at half-maxima range between $\rm 110\,km\,s^{-1} < FWHM < 1290\,km\,s^{-1}$ with a mean value of $\sim$ 500kms$^{-1}$, in line with other high-$z$ samples. The derived CO(1-0) luminosity is significantly elevated relative to line-width to CO(1-0) luminosity scaling relation, which is suggestive of lensing magnification across our sources. In fact, the distribution of magnification factors inferred from the CO equivalent widths is consistent with expectations from galaxy-galaxy lensing models, though there is a hint of an excess at large magnifications that may be attributable to the additional lensing optical depth from galaxy groups or clusters.

astro-ph.GA↗

arXiv2021

SEEDisCS II. Molecular gas in galaxy clusters and their large scale structure: low gas fraction galaxies, the case of CL1301.7$-$1139

This paper is the second of a series that tackles the properties of molecular gas in galaxies residing in clusters and their related large-scale structures. Out of 21 targeted fields, 19 galaxies were detected in CO(3-2) with the Atacama Large Millimeter Array (ALMA), including two detections within a single field. These galaxies are either bona fide members of the CL1301.7$-$1139 cluster ($z=0.4828$, $\sigma_{cl}=681$ km s$^{-1}$), or located within $\sim 7 \times R_{200}$, its virial radius. They have been selected to sample the range of photometric local densities around CL1301.7$-$1139, with stellar masses above log($M_{\rm star}$) = 10, and to be located in the blue clump of star-forming galaxies derived from the $u$, $g$, and $i$ photometric bands. Unlike previous works, our sample selection does not impose a minimum star formation rate or detection in the far-infrared. As such and as much as possible, it delivers an unbiased view of the gas content of normal star-forming galaxies at $z \sim 0.5$. Our study highlights the variety of paths to star formation quenching, and most likely the variety of physical properties (i.e. temperature, density) of the corresponding galaxy's cold molecular gas. Just as in the case of CL1411.1$-$1148, although to a smaller extent, we identify a number of galaxies with lower gas fraction than classically found in other surveys. These galaxies can still be on the star-forming main sequence. When these galaxies are not inside the cluster virialised region, we provide hints that they are linked to their infall regions within $\sim 4 \times R_{200}$.

astro-ph.GA↗

arXiv2020

SEEDisCS I. Molecular gas in galaxy clusters and their large scale structure: the case of CL1411.1$-$1148 at $z\sim0.5$

We investigate how the galaxy reservoirs of molecular gas fuelling star formation are transformed while the host galaxies infall onto galaxy cluster cores. As part of the Spatially Extended ESO Distant Cluster Survey (SEEDisCS), we present CO(3-2) observations of 27 star-forming galaxies obtained with the Atacama Large Millimeter Array (ALMA). These sources are located inside and around CL1411.1$-$1148 at $z=0.5195$, within five times the cluster virial radius. These targets were selected to have stellar masses M$_{\rm star}$), colours, and magnitudes similar to those of a field comparison sample at similar redshift drawn from the Plateau de Bure high-$z$ Blue Sequence Survey (PHIBSS2). We compare the cold gas fraction ($\mu_{\rm H_2}=$ M$_{\rm H_2}$/M$_{\rm star}$), specific star formation rates (SFR/M$_{\rm star}$) and depletion timescales ($t_{\rm depl}=$ M$_{\rm H_2}$/SFR) of our main-sequence galaxies to the PHIBSS2 subsample. While the most of our galaxies (63\%) are consistent with PHIBSS2, the remainder fall below the relation between $\mu_\mathrm{H_2}$ and M$_{\rm star}$ of the PHIBSS2 galaxies at $z\sim0.5$. These low-$\mu_\mathrm{H_2}$ galaxies are not compatible with the tail of a Gaussian distribution, hence they correspond to a new population of galaxies with normal SFRs but low gas content and low depletion times ($\lesssim 1$ Gyr), absent from previous surveys. We suggest that the star formation activity of these galaxies has not yet been diminished by their low fraction of cold molecular gas.

astro-ph.GA↗

arXiv2020

Close-up view of a luminous star-forming galaxy at z=2.95

(Abridged) Exploiting the sensitivity and broad band width of NOEMA, we have studied the molecular gas and dust in the galaxy HerBS-89a, at z=2.95. High angular resolution images reveal a partial 1.0" diameter Einstein ring in the dust continuum emission and the molecular emission lines of 12CO(9-8) and H2O(2_02-1_11). We report the detection of the three fundamental transitions of the molecular ion OH+, seen in absorption; the molecular ion CH+(1-0) seen in absorption (and tentatively in emission); two transitions of amidogen (NH2), seen in emission; and HCN(11-10) and/or NH(1_2-0_1) seen in absorption. The NOEMA data are complemented with VLA data tracing the 12CO(1-0) emission line, which provides a measurement of the total mass of molecular gas and an anchor for a CO excitation analysis. In addition, we present HST imaging that reveals the foreground lensing galaxy in the near-infrared. Together with data from the GTC, we derive a photometric redshift of z(phot)~0.9 for the foreground lensing galaxy. Modelling the lensing of HerBS-89a, we reconstruct the dust continuum and molecular emission lines (magnified by a factor ~4-5) in the source plane. The 12CO(9-8) and H2O emission lines have comparable spatial and kinematic distributions; the source-plane reconstructions do not clearly distinguish between a one-component and a two-component scenario, but the latter accounts for the observed broad line widths. HerBS-89a is a powerful star forming galaxy with a dust-to-gas ratio delta(GDR)~80, a SFR = 614 +/- 59 Msun/yr and a depletion timescale tau(depl) = (3.4 +/- 1.0) 1e8 years. The OH+ and CH+ absorption lines, all have their main velocity component red-shifted by \Delta(V)~100 km/s relative to the global CO reservoir. We argue that these absorption lines trace a rare example of gas inflow towards the center of the galaxy.

astro-ph.CO↗

arXiv2020

Black hole feeding and star formation in NGC 1808

We report on Atacama Large Millimeter Array (ALMA) observations of CO(3-2) emission in the Seyfert2/starburst galaxy NGC1808, at a spatial resolution of 4pc. Our aim is to investigate the morphology and dynamics of the gas inside the central 0.5kpc and to probe the nuclear feeding and feedback phenomena. We discovered a nuclear spiral of radius 1"=45pc. Within it, we found a decoupled circumnuclear disk or molecular torus of a radius of 0.13"=6pc. The HCN(4-3) and HCO$\rm^+$(4-3) and CS(7-6) dense gas line tracers were simultaneously mapped and detected in the nuclear spiral and they present the same misalignment in the molecular torus. At the nucleus, the HCN/HCO$^+$ and HCN/CS ratios indicate the presence of an active galactic nucleus (AGN). The molecular gas shows regular rotation, within a radius of 400pc, except for the misaligned disk inside the nuclear spiral arms. The computations of the torques exerted on the gas by the barred stellar potential reveal that the gas within a radius of 100pc is feeding the nucleus on a timescale of five rotations or on an average timescale of ~60Myr. Some non-circular motions are observed towards the center, corresponding to the nuclear spiral arms. We cannot rule out that small extra kinematic perturbations could be interpreted as a weak outflow attributed to AGN feedback. The molecular outflow detected at $\geqslant$250pc in the NE direction is likely due to supernovae feedback and it is connected to the kpc-scale superwind.

astro-ph.GA↗

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.

astro-ph.GA↗

arXiv2020

Molecular gas and star formation activity in LIRGs in clusters at intermediate redshifts

We investigate the role of dense Mpc-scale environments in processing molecular gas of cluster galaxies as they fall into the cluster cores. We consider $\sim20$ luminous infrared galaxies (LIRGs) in intermediate-$z$ clusters, from the Hershel Lensing Survey and the Local Cluster Substructure Survey. They include MACS J0717.5+3745 at $z=0.546$ and Abell 697, 963, 1763, and 2219 at $z=0.2-0.3$. We have performed far infrared to ultraviolet spectral energy distribution modeling of the LIRGs, which span cluster-centric distances within $r/r_{200}\simeq0.2-1.6$. We have observed the LIRGs in CO(1$\rightarrow$0) or CO(2$\rightarrow$1) with the Plateau de Bure interferometer and its successor NOEMA, as part of five observational programs carried out between 2012 and 2017. We have compared the molecular gas to stellar mass ratio $M(H_2)/M_\star$, star formation rate (SFR), and depletion time ($\tau_{\rm dep}$) of the LIRGs with those of a compilation of cluster and field star forming galaxies. The targeted LIRGs have SFR, $M(H_2)/M_\star$, and $\tau_{\rm dep}$ that are consistent with those of both main sequence (MS) field galaxies and star forming galaxies from the comparison sample. However we find that the depletion time, normalized to the MS value, increases with increasing $r/r_{200}$, with a significance of $2.8\sigma$, which is ultimately due to a deficit of cluster core LIRGs with $\tau_{\rm dep}\gtrsim\tau_{\rm dep,MS}$. We suggest that a rapid exhaustion of the molecular gas reservoirs occurs in the cluster LIRGs and is effective in suppressing their star formation. This mechanism may explain the exponential decrease of the fraction of cluster LIRGs with cosmic time. The compression of the gas in LIRGs, possibly induced by intra-cluster medium shocks, may be responsible for the short depletion timescales, observed in a large fraction of cluster core LIRGs.

astro-ph.GA↗

arXiv2019

NOEMA redshift measurements of bright Herschel galaxies

Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we conducted a program to measure redshifts for 13 bright galaxies detected in the Herschel Astrophysical Large Area Survey (H-ATLAS) with $S_{500μ\rm m}\ge$80 mJy. We report reliable spectroscopic redshifts for 12 individual sources, which are derived from scans of the 3 and 2 mm bands, covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. The spectroscopic redshifts are in the range $2.08 10^{13}\,L_\odot$ galaxies. We also present a reanalysis of the spectral energy distributions including the continuum flux densities measured at 3 and 2 mm to derive the overall properties of the sources. Future prospects based on these efficient measurements of redshifts of high-z galaxies using NOEMA are outlined, including a comprehensive survey of all the brightest Herschel galaxies.

astro-ph.GA↗

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).

astro-ph.GA↗

arXiv2019

ALMA captures feeding and feedback from the active galactic nucleus in NGC613

We report ALMA observations of CO(3-2) emission in the Seyfert galaxy NGC613, at a spatial resolution of 17pc, as part of our NUclei of GAlaxies sample. Our aim is to investigate the morphology and dynamics of the gas inside the central kpc, and to probe nuclear fueling and feedback phenomena. The morphology of CO(3-2) line emission reveals a 2-arm trailing nuclear spiral at $r\lesssim$100pc and a circumnuclear ring at ~350pc radius, that is coincident with the star-forming ring seen in the optical images. The molecular gas in the galaxy disk is in a remarkably regular rotation, however, the kinematics in the nuclear region is very skewed. The nuclear spectrum of CO and dense gas tracers HCN(4-3), HCO+(4-3), and CS(7-6) show broad wings up to $\pm$300km/s, associated with a molecular outflow emanating from the nucleus (r~25pc). We derive a molecular outflow mass $M_{out}$=2x10$^6$M$_\odot$ and a mass outflow rate of $\dot{M}_{out}=$27$\rm M_\odot yr^{-1}$. The molecular outflow energetics exceed the values predicted by AGN feedback models: the kinetic power of the outflow corresponds to 20%L_AGN and the momentum rate is $\dot{M}_{out}v\sim400L_{AGN}/c$. The outflow is mainly boosted by the AGN through entrainment by the radio jet, but given the weak nuclear activity of NGC613, we might be witnessing a fossil outflow, resulted from a strong past AGN that now has already faded. The nuclear trailing spiral observed in CO emission is inside the ILR ring of the bar. We compute the gravitational torques exerted in the gas to estimate the efficiency of the angular momentum exchange. The gravity torques are negative from 25 to 100pc and the gas loses its angular momentum in a rotation period, providing evidence of a highly efficient inflow towards the center. This phenomenon shows that the massive central black hole has a significant dynamical influence on the gas, triggering its fueling.

astro-ph.GA↗