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Register a new userHigh-Velocity Bipolar Molecular Emission from an AGN Torus
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We have detected in ALMA observations CO J = 6 - 5 emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to +/- 70 km/s relative to systemic) CO emission resolves into a 12x7 pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to +/- 400 km/s) is consistent with a bipolar outflow in a direction nearly perpendicular (roughly 80 degrees) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the velocity field may also contain rotation about the disk axis. These observations provide compelling evidence in support of the disk-wind scenario for the AGN obscuring torus.
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We present 1.4 pc resolution observations of 256 GHz nuclear radio continuum and HCN ($J=3 to 2$) in the molecular torus of NGC 1068. The integrated radio continuum emission has a flat spectrum consistent with free-free emission and resolves into an X-shaped structure resembling an edge-brightened bicone. HCN is detected in absorption against the continuum, and the absorption spectrum shows a pronounced blue wing that suggests a high-velocity molecular outflow with speeds reaching 450 km/s. Analysis of the off-nucleus emission line kinematics and morphology reveals two nested, rotating disk components. The inner disk, inside $rsim 1.2$ pc, has kinematics consistent with the nearly edge-on, geometrically thin water megamaser disk in Keplerian rotation around a central mass of $1.66times 10^7,mbox{M}_odot$. The outer disk, which extends to $sim 7$~pc radius, counter-rotates relative to the inner disk. The rotation curve of the outer disk is consistent with rotation around the same central mass as the megamaser disk but in the opposite sense. The morphology of the molecular gas is asymmetric around the nuclear continuum source. We speculate that the outer disk formed from more recently introduced molecular gas falling out of the host galaxy or from a captured dwarf satellite galaxy. In NGC 1068, we find direct evidence that the molecular torus consists of counter-rotating and misaligned disks on parsec scales.
We have mapped 12CO J=3-2 and other molecular lines from the water-fountain bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with ~0.35 resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few x 10^6 cm^{-3}), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to >3.5 x 10^{-4} Msun/yr in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017 Msun) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed.
The Wide-field Infrared Survey Explorer (WISE) has scanned the entire sky with unprecedented sensitivity in four infrared bands, at 3.4, 4.6, 12, and 22 micron. The WISE Point Source Catalog contains more than 560 million objects, among them hundreds of thousands of galaxies with Active Nuclei (AGN). While type 1 AGN, owing to their bright and unobscured nature, are easy to detect and constitute a rather complete and unbiased sample, their type 2 counterparts, postulated by AGN unification, are not as straightforward to identify. Matching the WISE catalog with known QSOs in the Sloan Digital Sky Survey we confirm previous identification of the type 1 locus in the WISE color space. Using a very large database of the popular CLUMPY torus models, we find the colors of the putative type 2 counterparts, and also, for the first time, predict their number vs. flux relation that can be expected to be observed in any given WISE color range. This will allow us to put statistically very significant constraints on the torus parameters. Our results are a successful test of the AGN unification scheme.
We report ALMA observations of a one-sided, high-velocity ($sim$80 km s$^{-1}$) CO($J = 2 rightarrow 1$) jet powered by the intermediate-mass protostellar source Serpens SMM1-a. The highly collimated molecular jet is flanked at the base by a wide-angle cavity; the walls of the cavity can be seen in both 4 cm free-free emission detected by the VLA and 1.3 mm thermal dust emission detected by ALMA. This is the first time that ionization of an outflow cavity has been directly detected via free-free emission in a very young, embedded Class 0 protostellar source that is still powering a molecular jet. The cavity walls are ionized either by UV photons escaping from the accreting protostellar source, or by the precessing molecular jet impacting the walls. These observations suggest that ionized outflow cavities may be common in Class 0 protostellar sources, shedding further light on the radiation, outflow, and jet environments in the youngest, most embedded forming stars.
We use a high-temperature chemical network to derive the molecular abundances in axisymmetric accretion disk models around active galactic nuclei (AGNs) within 100 pc using simple radial and vertical density and temperature distributions motivated by more detailed physical models. We explore the effects of X-ray irradiation and cosmic ray ionization on the spatial distribution of the molecular abundances of CO, CN, CS, HCN, HCO+, HC3N, C2H, and c-C3H2 using a variety of plausible disk structures. These simple models have molecular regions with a layer of X-ray dominated regions, a midplane without the strong influence of X-rays, and a high-temperature region in the inner portion with moderate X-ray flux where families of polyynes (C$_{rm n}$H$_{2}$) and cyanopolyynes can be enhanced. For the high midplane density disks we explore, we find that cosmic rays produced by supernovae do not significantly affect the regions unless the star formation efficiency significantly exceeds that of the Milky Way. We highlight molecular abundance observations and ratios that may distinguish among theoretical models of the density distribution in AGN disks. Finally, we assess the importance of the shock crossing time and the accretion time relative to the formation time for various chemical species. Vertical column densities are tabulated for a number of molecular species at both the characteristic shock crossing time and steady state. Although we do not attempt to fit any particular system or set of observations, we discuss our models and results in the context of the nearby AGN NGC 1068.
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