Active galaxies contain a supermassive black hole at their center that grows by accreting matter from the surrounding galaxy. The accretion process in about the central 10 parsecs has not been directly resolved in previous observations because of the small apparent angular sizes involved. We observed the active nucleus of the Circinus Galaxy using submillimeter interferometry. A dense inflow of molecular gas was evident on subparsec scales. We calculated that less than 3% of this inflow is accreted by the black hole, with the rest being ejected by multiphase outflows, providing feedback to the host galaxy. Our observations also reveal a dense gas disk surrounding the inflow that is gravitationally unstable, which drives the accretion into about the central 1 parsec. Description Editor’s summary Most galaxies contain a supermassive black hole at their center. When gas falls toward the black hole, it heats up and emits radiation and can be observed as an active galactic nucleus. However, it is not known how gas is delivered from the wider galaxy to the inner region around the black hole. Izumi et al. combined submillimeter observations of several gas tracers in the center of the Circinus Galaxy, a nearby active galactic nucleus. By comparing the kinematics of molecular, atomic, and ionized gas, they were able to identify an inflow of dense molecular gas in the central parsec, feeding the black hole. —Keith T. Smith Observations of an active galaxy show an inflow of dense molecular gas into the inner parsec around the supermassive black hole.

Supermassive black hole feeding and feedback observed on subparsec scales

The ionisation cones of NGC\,5728 have a deficit of molecular gas based on millimetre observations of CO\,(2-1) emission. Although photoionisation from the active nucleus may lead to suppression of this transition, warm molecular gas can still be present. We report the detection of eight mid-infrared rotational H$_2$ lines throughout the central kiloparsec, including the ionisation cones, using integral field spectroscopic observations with JWST/MIRI MRS. The H$_2$ line ratios, characteristic of a power-law temperature distribution, indicate that the gas is warmest where it enters the ionisation cone through disk rotation, suggestive of shock excitation. In the nucleus, where the data can be combined with an additional seven ro-vibrational H$_2$ transitions, we find that moderate velocity (30 km $) shocks in dense ($10^5$ cm$^ $) gas, irradiated by an external UV field ($G_0 = 10^3$), do provide a good match to the full set. The warm molecular gas in the ionisation cone that is traced by the H$_2$ rotational lines has been heated to temperatures $&gt;200$ K. Outside of the ionisation cone the molecular gas kinematics are undisturbed. However, within the ionisation cone, the kinematics are substantially perturbed, indicative of a radial flow, but one that is quantitatively different from the ionised lines. We argue that this outflow is in the plane of the disk, implying a short 50 pc acceleration zone up to speeds of about 400 km s$^ $ followed by an extended deceleration over sim 700 pc where it terminates. The deceleration is due to both the radially increasing galaxy mass, and mass-loading as ambient gas in the disk is swept up. 

pdf/gatos-missing-molecular-gas-in-the-outflow-of-ngc-5728-4jvudtfak4.pdf

GATOS: missing molecular gas in the outflow of NGC 5728 revealed by JWST

We introduce Monte Carlo-based non-LTE line radiative transfer calculations in the 3D dust radiative transfer code SKIRT, which was originally set up as a dust radiative transfer code. By doing so, we develop a generic and powerful 3D radiative transfer code that can self-consistently generate spectra with molecular and atomic lines against the underlying continuum. We test the accuracy of the non-LTE line radiative transfer module in the extended SKIRT code using standard benchmarks. We find excellent agreement between the SKIRT results, the published benchmark results, and results obtained using the ray-tracing non-LTE line radiative transfer code MAGRITTE, which validates our implementation. We apply the extended SKIRT code on a 3D hydrodynamic simulation of a dusty AGN torus model and generate multi-wavelength images with CO rotational-line spectra against the underlying dust continuum. We find that the low-J CO emission traces the geometrically thick molecular torus, whereas the higher-J CO lines originate from the gas with high kinetic temperature located in the innermost regions of the torus. Comparing the calculations with and without dust radiative transfer, we find that higher-J CO lines are slightly attenuated by the surrounding cold dust when seen edge-on. This shows that atomic and molecular lines can experience attenuation, an effect that is particularly important for transitions at mid- and near-infrared wavelengths. Therefore, our self-consistent dust and non-LTE line radiative transfer calculations can help interpret the observational data from Herschel, ALMA, and JWST.

pdf/self-consistent-dust-and-non-lte-line-radiative-transfer-10chnyrnpd.pdf

Self-consistent dust and non-LTE line radiative transfer with SKIRT

Mass accretion is a fundamental process for the growth of supermassive black holes and activating the central engine. However, detailed accretion properties have not been observationally identified at the central ~10 parsec of active galaxies due to its compactness. Here we for the first time ever report the direct detection of parsec-scale (i.e., 0.01% scale of the host galaxy) dense molecular inflow in the active nucleus of the Circinus galaxy. Only a tiny portion (< 3%) of this inflow is consumed in the actual black hole growth but a bulk portion is blown-out by multiphase outflows. The dense gas disk is gravitationally unstable and drives accretion down to the central ~1 parsec, but another process will be required for the final subparsec-scale accretion. 

/pdf/resolving-supermassive-black-hole-feeding-and-feedback-2ld4wfc9.pdf

Resolving supermassive black hole feeding and feedback: multiphase flows
  down to sub-parsec

It has been suggested that the bulge-to-total stellar mass ratio or feedback from black holes (BHs), traced by the BH-to-(total stellar) mass ratio, might establish a galaxy's specific star formation rate (sSFR). We reveal that a galaxy's morphology -- reflecting its formation history, particularly accretions and mergers -- is a far better determinant of the sSFR. Consequently, we suggest that galaxy formation models which regulate the sSFR primarily through BH feedback prescriptions or bulge-regulated disc fragmentation consider acquisitions and mergers which establish the galaxy morphology. We additionally make several new observations regarding current ($z\sim0$) star-formation rates. (i) Galaxies with little to no star formation have bulges with an extensive range of stellar masses; bulge mass does not dictate presence/absence on the `star-forming main sequence'. (ii) The (wet merger)-built, dust-rich S0 galaxies are the `green valley' bridging population between elliptical galaxies on the `red sequence' and spiral galaxies on the blue star-forming main sequence. (iii) The dust-poor S0 galaxies are not on the star-forming main sequence nor in the `green valley'. Instead, they wait in the field for gas accretion and/or minor mergers to transform them into spiral galaxies. Mid-infrared sample selection can miss these (primordial) low dust-content and low stellar-luminosity S0 galaxies. Finally, the appearance of the quasi-triangular-shaped galaxy-assembly sequence, previously dubbed the Triangal, which tracks the morphological evolution of galaxies, is revealed in the sSFR-(stellar mass) diagram.

pdf/specific-star-formation-rates-in-the-mbh-m-sph-diagram-and-1vsv1ekbx3.pdf

Specific star formation rates in the Mbh-M*, sph diagram and the evolutionary pathways of galaxies across the sSFR-M* diagram

Context. The central engines of many active galactic nuclei (AGNs) molecular and dusty disk, traced by submillimetre continuum and line emission. The latter is responsible for the bulk of the obscuration of the nucleus. These ﬁndings support the most recent radiative transfer calculations of the obscuring structures in AGNs, which ﬁnd a similar two-component structure.

/pdf/alma-imaging-of-the-cold-molecular-and-dusty-disk-in-the-2dqz15nh.pdf

ALMA imaging of the cold molecular and dusty disk in the type 2 active nucleus of the Circinus galaxy

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ALMA imaging of the cold molecular and dusty disk in the type 2 active nucleus of the Circinus galaxy