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Boroson T.A.,National Optical Astronomy Observatory
Astrophysical Journal Letters | Year: 2011

The velocities of the [O III] λ5007 and optical Fe II emission lines, measured relative to the systemic redshifts of 2265 QSOs by Hu et al., show the signature of a disklike BLR structure with polar outflows. Objects with large [O III] outflows show no Fe II offset velocity and are seen pole-on. Objects with large Fe II inflow show no [O III] offset velocity and are seen edge-on. This interpretation is supported by the morphology of the radio-loud objects within the sample and by previous determinations of the geometry of the broad- and narrow-line regions. Analysis of the objects with neither Fe II or [O III] velocity offsets, however, shows that the two groups also differ in Eddington ratio (ER), and, within this subset, corresponding groups with high and low ER but with the opposite orientation can be identified. Using these four subsets of the sample, the effects of orientation and ER can be separated, and, in some cases, quantified. The changes in apparent continuum luminosity and broad Hβ width and strength suggest a model in which both continuum and Hβ are emitted from the surface of the disk, which is less flattened in high ER objects. The effects of orientation on the derived properties, black hole mass and ER, are significant, though not large. The [O III] outflow appears to influence the width of that line, as well as its centroid. © 2011. The American Astronomical Society. All rights reserved. Source

Carr J.S.,U.S. Navy | Najita J.R.,National Optical Astronomy Observatory
Astrophysical Journal | Year: 2011

We report high signal-to-noise Spitzer Infrared Spectrograph spectra of a sample of 11 classical T Tauri stars. Molecular emission from rotational transitions of H2O and OH and rovibrational bands of simple organic molecules (CO2, HCN, C2H2) is common among the sources in the sample. The emission shows a range in both flux and line-to-continuum ratio for each molecule and in the flux ratios of different molecular species. The gas temperatures (200-800 K) and emitting areas we derive are consistent with the emission originating in a warm disk atmosphere in the inner planet formation region at radii <2AU. The H2O emission appears to form under a limited range of excitation conditions, as demonstrated by the similarity in relative strengths of H2O features from star to star and the narrow range in derived temperature and column density. Emission from highly excited rotational levels of OH is present in all stars; the OH emission flux increases with the stellar accretion rate, and the OH/H 2O flux ratio shows a relatively small scatter. We interpret these results as evidence for OH production via FUV photodissociation of H 2O in the disk surface layers. No obvious explanation is found for the observed range in the relative emission strengths of different organic molecules or in their strength with respect to water. We put forward the possibility that these variations reflect a diversity in organic abundances due to star-to-star differences in the C/O ratio of the inner disk gas. Stars with the largest HCN/H2O flux ratios in our sample have the largest disk masses. While larger samples are required to confirm this, we speculate that such a trend could result if higher mass disks are more efficient at planetesimal formation and sequestration of water in the outer disk, leading to enhanced C/O ratios and abundances of organic molecules in the inner disk. A comparison of our derived HCN-to-H2O column density ratio to comets, hot cores, and outer TTauri star disks suggests that the inner disks are chemically active. © 2011. The American Astronomical Society. All rights reserved. Source

Van Dyk S.D.,Spitzer Science Center | Matheson T.,National Optical Astronomy Observatory
Astrophysical Journal | Year: 2012

Reports of the death of the precursor of supernova (SN) 1961V in NGC1058 are exaggerated. Consideration of the best astrometric data shows that the star, known as "Object 7," lies at the greatest proximity to SN1961V and is the likely survivor of the "SN impostor" super-outburst. SN1961V does not coincide with a neighboring radio source and is therefore not a radio SN. Additionally, the current properties of Object 7, based on data obtained with the Hubble Space Telescope, are consistent with it being a quiescent luminous blue variable (LBV). Furthermore, post-explosion non-detections by the Spitzer Space Telescope do not necessarily and sufficiently rule out a surviving LBV. We therefore consider, based on the available evidence, that it is still a bit premature to reclassify SN1961V as a bona fide SN. The inevitable demise of this star, though, may not be too far off. © 2012. The American Astronomical Society. All rights reserved. Source

Lauer T.R.,National Optical Astronomy Observatory
Astrophysical Journal | Year: 2012

I have combined the Emsellem etal. ATLAS3D rotation measures of a large sample of early-type galaxies with Hubble Space Telescope based classifications of their central structure to characterize the rotation velocities of galaxies with cores. "Core galaxies" rotate slowly, while "power-law galaxies" (galaxies that lack cores) rotate rapidly, confirming the analysis of Faber etal. Significantly, the amplitude of rotation sharply discriminates between the two types in the -19 > MV > -22 domain over which the two types coexist. The slow rotation in the small set of core galaxies with MV > -20, in particular, brings them into concordance with the more massive core galaxies. The ATLAS3D "fast-rotating" and "slow-rotating" early-type galaxies are essentially the same as power-law and core galaxies, respectively, or the Kormendy & Bender two families of elliptical galaxies based on rotation, isophote shape, and central structure. The ATLAS3D fast rotators do include roughly half of the core galaxies, but their rotation amplitudes are always at the lower boundary of that subset. Essentially, all core galaxies have ATLAS3D rotation amplitudes λRe/2 ≪ 0.25, while all galaxies with λRe/2 > 0.25 and figure eccentricity >0.2 lack cores. Both figure rotation and the central structure of early-type galaxies should be used together to separate systems that appear to have formed from "wet" versus "dry" mergers. © 2012. The American Astronomical Society. All rights reserved. Source

De Young D.S.,National Optical Astronomy Observatory
Astrophysical Journal | Year: 2010

The possible role of radio active galactic nucleus (AGN) "feedback" in conventional hierarchical cosmological models has become widely discussed. This paper examines some of the details of how such feedback might work. A basic requirement is the conversion of radio AGN outflow energy into heating of the circumgalactic medium in a time comparable to the relevant cooling times. First, the class of radio AGN relevant to this process is identified as FR-I radio sources. Second, it is argued via comparisons with experimental data that these AGN outflows are strongly decelerated and become fully turbulent sonic or subsonic flows due to their interaction with the surrounding medium. Using this, a three-dimensional time-dependent calculation of the evolution of such turbulent magnetohydrodynamic flows is made to determine the time scale required for conversion of the turbulent energy into heat. This calculation, when coupled with observational data, suggests that the onset of heating can occur ∼ 108 yr after the fully turbulent flow is established, and this time is less than or comparable to the local cooling times in the interstellar or circumgalactic medium for many of these objects. The location of where heat deposition occurs remains uncertain, but estimates of outflow speeds suggest that heating may occur many tens of kpc from the center of the parent galaxy. Recent observations suggest that such radio AGN outflows may become dispersed on much larger scales than previously thought, thus possibly satisfying the requirement that heating occurs over a large fraction of the volume occupied by the circumgalactic gas. © 2010. The American Astronomical Society. All rights reserved. Source

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