12,657 research outputs found
The Black Hole Mass - Stellar Velocity Dispersion Relationship for Quasars in the Sloan Digital Sky Survey Data Release 7
We assess evolution in the black hole mass - stellar velocity dispersion
relationship (M-sigma relationship) for quasars in the Sloan Digital Sky Survey
Data Release 7 for the redshift range 0.1 < z < 1.2. We estimate the black hole
mass using the "photoionization method," with the broad Hbeta or Mg II emission
line and the quasar continuum luminosity. For the stellar velocity dispersion,
we use the narrow [O III] or [O II] emission line as a surrogate. This study is
a follow-up to an earlier study in which we investigated evolution in the
M-sigma relationship in quasars from Data Release 3. The greatly increased
number of quasars in our new sample has allowed us to break our lower-redshift
subsample into black hole mass bins and probe the M-sigma relationship for
constant black hole mass. The M-sigma relationship for the highest-mass (log M
> 9 solar masses) and lowest-mass (log M < 7.5 solar masses) black holes
appears to evolve significantly, however most or all of this apparent evolution
can be accounted for by various observational biases due to intrinsic scatter
in the relationship and to uncertainties in observed quantities. The M-sigma
relationship for black holes in the middle mass range (7.5 < log M < 9 solar
masses) shows minimal change with redshift. The overall results suggest a limit
of +/- 0.2 dex on any evolution in the M-sigma relationship for quasars out to
z ~ 1 compared with the relationship observed in the local universe. Intrinsic
scatter may also provide a plausible way to reconcile the wide range of results
of several different studies of the black hole - galaxy relationships.Comment: 8 pages, 6 figures, submitted to Ap
Fe II Emission in AGN: The Role of Total and Gas-Phase Iron Abundance
Active galactic nuclei (AGN) have Fe II emission from the broad line region
(BLR) that differs greatly in strength from object to object. We examine the
role of the total and gas-phase iron abundance in determining Fe II strength.
Using AGN spectra from the Sloan Digital Sky Survey (SDSS) in the redshift
range of 0.2 < z < 0.35, we measure the Fe/Ne abundance of the narrow line
region (NLR) using the [Fe VII]/[Ne V] line intensity ratio. We find no
significant difference in the abundance of Fe relative to Ne in the NLR as a
function of Fe II/Hbeta. However, the N II/S II ratio increases a by a factor
of 2 with increasing Fe II strength. This indicates a trend in N/S abundance
ratio, and by implication in the overall metallicity of the NLR gas, with
increasing Fe II strength. We propose that the wide range of Fe II strength in
AGN largely results from the selective depletion of Fe into grains in the low
ionization portion of the BLR. Photoionization models show that the strength of
the optical Fe II lines varies almost linearly with gas-phase Fe abundance,
while the ultraviolet Fe II strength varies more weakly. Interstellar depletion
of Fe can be as large as two orders of magnitude, sufficient to explain the
wide range of optical Fe II strength in AGN. This picture is consistent with
the similarity of the BLR radius to the dust sublimation radius and with
indications of Fe II emitting gas flowing inwards from the dusty torus.Comment: 11 pages, 3 figures, version accepted to The Astrophysical Journal;
revised composite spectra and discussion of grain temperature
Responses of king penguin Aptenodytes patagonicus adults and chicks to two food-related odours
Increasing evidence suggests that penguins are sensitive to dimethyl sulphide (DMS), a scented airborne compound that a variety of marine animals use to find productive areas of the ocean where prey is likely to be found. Here we present data showing that king penguins Aptenodytes patagonicus are also sensitive to DMS. We deployed DMS on a lake near a king penguin colony at Ratmanoff beach in the Kerguelen archipelago. We also presented DMS to ‘sleeping’ adults on the beach. On the lake, penguins responded to the DMS deployments by swimming more, while on the beach, penguins twitched their heads and woke up more for the DMS than for the control presentations. Interestingly, penguins did not respond to cod liver oil deployments on the lake; mirroring at-sea studies of other penguins. Although at-sea studies are needed to confirm that king penguins use DMS as a surface cue that informs them of productivity under the water, this study is an important first step in understanding how these birds locate prey over significant distances
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The Jet-Driven Outflow In The Radio Galaxy SDSS J1517+3353: Implications For Double-Peaked Narrow-Line Active Galactic Nucleus
We report on the study of an intriguing active galaxy that was selected as a potential multiple supermassive black hole merger in the early-type host SDSS J151709.20+335324.7 (z = 0.135) from a complete search for double-peaked [O III] lines from the SDSS spectroscopic quasi-stellar object (QSO) database. Ground-based SDSS imaging reveals two blue structures on either side of the photometric center of the host galaxy, separated from each other by about 5.7 kpc. From a combination of SDSS fiber and Keck/HIRES long-slit spectroscopy, it is demonstrated that, in addition to these two features, a third distinct structure surrounds the nucleus of the host galaxy. All three structures exhibit highly ionized line emission with line ratios characteristic of Seyfert II active galactic nuclei. The analysis of spatially resolved emission-line profiles from the HIRES spectrum reveal three distinct kinematic subcomponents, one at rest and the other two moving at -350 km s(-1) and 500 km s(-1) with respect to the systemic velocity of the host galaxy. A comparison of imaging and spectral data confirm a strong association between the kinematic components and the spatial knots, which implies a highly disturbed and complex active region in this object. A comparative analysis of the broadband positions, colors, kinematics, and spectral properties of the knots in this system lead to two plausible explanations: (1) a multiple active galactic nucleus (AGN) produced due to a massive dry merger, or (2) a very powerful radio jet-driven outflow. Subsequent VLA radio imaging reveals a clear jet aligned with the emission-line gas, confirming the latter explanation. We use the broadband radio measurements to examine the impact of the jet on the interstellar medium of the host galaxy, and find that the energy in the radio lobes can heat a significant fraction of the gas to the virial temperature. Finally, we discuss tests that may help future surveys distinguish between jet-driven kinematics and true black-hole binaries. J1517+3353 is a remarkable laboratory for AGN feedback and warrants deeper follow-up study. In the Appendix, we present high-resolution radio imaging of a second AGN with double-peaked [O III] lines, SDSS J112939.78+605742.6, which shows a sub-arcsecond radio jet. If the double-peaked nature of the narrow lines in radio-loud AGNs are generally due to radio jet interactions, we suggest that extended radio structure should be expected in most of such systems.NSF AST-0507483, AST-0808133University of Texas at AustinAlfred P. Sloan FoundationParticipating InstitutionsNational Aeronautics and Space AdministrationU.S. Department of EnergyJapanese MonbukagakushoMax Planck SocietyAstronom
“Putting on a Happy Face,” “Getting Back to Work,” and “Letting It Go”: Traditional and Restorative Justice Understandings of Emotions at Work
Coping with the emotional consequences of hurtful situations in the workplace can be problematic for organizational members. Traditional approaches depending on rationality and professionalism come with expectations that employees suppress or minimize emotion by focusing on their work and maintaining composure. However, an alternative approach to justice – restorative justice – is gaining notice in organizational scholarship and appears to offer a different approach to managing painful situations and their associated emotions. This study examines how the experience and management of emotion following hurtful events are connected with traditional and restorative principles in a workplace setting. The results of the study offer insight into the consequences of restorative justice in organizational life.Citation: Paul, G. D. & Riforgiate, S. E. (2015). “Putting on a happy face,” “getting back to work,” and “letting it go”: Traditional and restorative justice understandings of emotions at work. Electronic Journal of Communication, 25 (3 & 4)
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