215 research outputs found
Outflows and the Physical Properties of Quasars
We have investigated a sample of 5088 quasars from the Sloan Digital Sky
Survey Second Data Release in order to determine how the frequency and
properties of broad absorptions lines (BALs) depend on black hole mass,
bolometric luminosity, Eddington fraction (L/L_Edd), and spectral slope. We
focus only on high-ionization BALs and find a number of significant results.
While quasars accreting near the Eddington limit are more likely to show BALs
than lower systems, BALs are present in quasars accreting at only a
few percent Eddington. We find a stronger effect with bolometric luminosity,
such that the most luminous quasars are more likely to show BALs. There is an
additional effect, previously known, that BAL quasars are redder on average
than unabsorbed quasars. The strongest effects involving the quasar physical
properties and BAL properties are related to terminal outflow velocity. Maximum
observed outflow velocities increase with both the bolometric luminosity and
the blueness of the spectral slope, suggesting that the ultraviolet luminosity
to a great extent determines the acceleration. These results support the idea
of outflow acceleration via ultraviolet line scattering.Comment: Uses emulateapj.cls, 14 pages including 7 tables and 7 figures.
Accepted for publication in the Astrophysical Journal, Unabridged version of
Table 4 can be downloaded from http://physics.uwyo.edu/agn
Black Hole - Bulge Relationship of Post-Starburst Quasars at z \sim 0.3
The MBH - {\sigma}\ast relation has been studied extensively for local
galaxies, but to date there have been scarce few direct measurements of stellar
velocity dispersions for systems beyond the local universe. We investigate
black hole and host galaxy properties of six "post-starburst quasars" at z \sim
0.3. Spectra of these objects simultaneously display features from the active
nucleus including broad emission lines and a host galaxy Balmer absorption
series indicative of the post-starburst stellar population. These are the first
measurements of {\sigma}\ast in such objects, and we significantly increase the
number of directly-measured non-local objects on the MBH - {\sigma}\ast
diagram. The "post-starburst quasars" of our sample fall on or above the
locally defined MBH - {\sigma}\ast relation, a result that is consistent with
previous MBH - {\sigma}\ast studies of samples at z > 0.1. However, they are
generally consistent with the MBH-Lbulge relation. Futhermore, their location
on the Faber-Jackson relation suggests that some of the bulges may be
dynamically peculiar.Comment: 15 pages, 9 figures, accepted for publication in Ap
Welcome to the Twilight Zone: The Mid-Infrared Properties of Poststarburst Galaxies
We investigate the optical and Wide-field Survey Explorer (WISE) colors of
"E+A" identified post-starburst galaxies, including a deep analysis on 190
post-starbursts detected in the 2{\mu}m All Sky Survey Extended Source Catalog.
The post-starburst galaxies appear in both the optical green valley and the
WISE Infrared Transition Zone (IRTZ). Furthermore, we find that post-starbursts
occupy a distinct region [3.4]-[4.6] vs. [4.6]-[12] WISE colors, enabling the
identification of this class of transitioning galaxies through the use of
broad-band photometric criteria alone. We have investigated possible causes for
the WISE colors of post-starbursts by constructing a composite spectral energy
distribution (SED), finding that mid-infrared (4-12{\mu}m) properties of
post-starbursts are consistent with either 11.3{\mu}m polycyclic aromatic
hydrocarbon emission, or Thermally Pulsating Asymptotic Giant Branch (TP-AGB)
and post-AGB stars. The composite SED of extended post- starburst galaxies with
22{\mu}m emission detected with signal to noise >3 requires a hot dust
component to produce their observed rising mid-infrared SED between 12 and
22{\mu}m. The composite SED of WISE 22{\mu}m non-detections (S/N<3), created by
stacking 22{\mu}m images, is also flat, requiring a hot dust component. The
most likely source of this mid-infrared emission of these E+A galaxies is a
buried active galactic nucleus. The inferred upper limit to the Eddington
ratios of post-starbursts are 1e-2 to 1e-4, with an average of 1e-3. This
suggests that AGNs are not radiatively dominant in these systems. This could
mean that including selections able to identify active galactic nuclei as part
of a search for transitioning and post-starburst galaxies would create a more
complete census of the transition pathways taken as a galaxy quenches its star
formation.Comment: 13 pages, 11 figures, accepted for publication in the Astrophysical
Journa
Comparison of accuracy of fibrosis degree classifications by liver biopsy and non-invasive tests in chronic hepatitis C
<p>Abstract</p> <p>Background</p> <p>Non-invasive tests have been constructed and evaluated mainly for binary diagnoses such as significant fibrosis. Recently, detailed fibrosis classifications for several non-invasive tests have been developed, but their accuracy has not been thoroughly evaluated in comparison to liver biopsy, especially in clinical practice and for Fibroscan. Therefore, the main aim of the present study was to evaluate the accuracy of detailed fibrosis classifications available for non-invasive tests and liver biopsy. The secondary aim was to validate these accuracies in independent populations.</p> <p>Methods</p> <p>Four HCV populations provided 2,068 patients with liver biopsy, four different pathologist skill-levels and non-invasive tests. Results were expressed as percentages of correctly classified patients.</p> <p>Results</p> <p>In population #1 including 205 patients and comparing liver biopsy (reference: consensus reading by two experts) and blood tests, Metavir fibrosis (F<sub>M</sub>) stage accuracy was 64.4% in local pathologists vs. 82.2% (p < 10<sup>-3</sup>) in single expert pathologist. Significant discrepancy (≥ 2F<sub>M </sub>vs reference histological result) rates were: Fibrotest: 17.2%, FibroMeter<sup>2G</sup>: 5.6%, local pathologists: 4.9%, FibroMeter<sup>3G</sup>: 0.5%, expert pathologist: 0% (p < 10<sup>-3</sup>). In population #2 including 1,056 patients and comparing blood tests, the discrepancy scores, taking into account the error magnitude, of detailed fibrosis classification were significantly different between FibroMeter<sup>2G </sup>(0.30 ± 0.55) and FibroMeter<sup>3G </sup>(0.14 ± 0.37, p < 10<sup>-3</sup>) or Fibrotest (0.84 ± 0.80, p < 10<sup>-3</sup>). In population #3 (and #4) including 458 (359) patients and comparing blood tests and Fibroscan, accuracies of detailed fibrosis classification were, respectively: Fibrotest: 42.5% (33.5%), Fibroscan: 64.9% (50.7%), FibroMeter<sup>2G</sup>: 68.7% (68.2%), FibroMeter<sup>3G</sup>: 77.1% (83.4%), p < 10<sup>-3 </sup>(p < 10<sup>-3</sup>). Significant discrepancy (≥ 2 F<sub>M</sub>) rates were, respectively: Fibrotest: 21.3% (22.2%), Fibroscan: 12.9% (12.3%), FibroMeter<sup>2G</sup>: 5.7% (6.0%), FibroMeter<sup>3G</sup>: 0.9% (0.9%), p < 10<sup>-3 </sup>(p < 10<sup>-3</sup>).</p> <p>Conclusions</p> <p>The accuracy in detailed fibrosis classification of the best-performing blood test outperforms liver biopsy read by a local pathologist, i.e., in clinical practice; however, the classification precision is apparently lesser. This detailed classification accuracy is much lower than that of significant fibrosis with Fibroscan and even Fibrotest but higher with FibroMeter<sup>3G</sup>. FibroMeter classification accuracy was significantly higher than those of other non-invasive tests. Finally, for hepatitis C evaluation in clinical practice, fibrosis degree can be evaluated using an accurate blood test.</p
The rest-frame ultraviolet properties of radio-loud broad absorption line quasars
We recently presented radio observations of a large sample of radio-loud
broad absorption line (BAL) quasars from the SDSS and FIRST surveys, as well as
a well matched sample of unabsorbed quasars, primarily to measure their radio
spectral indices and estimate ensemble orientations. Here, we analyze the SDSS
spectra of these samples and compare the rest-frame ultraviolet properties of
radio-loud BAL and non-BAL quasars. Ultraviolet properties include the
continuum shape, emission-line measurements of C IV, Al III, C III], Fe II, and
Mg II, and BAL properties including the balnicity index (BI), absorption index
(AI), and minimum and maximum outflow velocities. We find that radio-loud BAL
quasars have similar ultraviolet properties compared to radio-loud non-BAL
sources, though they do appear to have redder continua and stronger Fe II
emission, which is consistent with what is found for radio-quiet BAL sources.
No correlations exist between outflow properties and orientation (radio
spectral index), suggesting that BAL winds along any line of sight are driven
by the same mechanisms. There are also few correlations between spectral index
and other properties. We conclude that BAL outflows occur along all lines of
sight with similar strengths and velocities.Comment: Accepted for publication in MNRAS. Tables 1 and 2 will be published
in full with the final online publicatio
Suppression of Star Formation in NGC 1266
NGC1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (AGN). It has been speculated that such outflows hinder star formation (SF) in their host galaxies, providing a form of feedback to the process of galaxy formation. Previous studies, however, indicated that only jets from extremely rare, high power quasars or radio galaxies could impart significant feedback on their hosts. Here we present detailed observations of the gas and dust continuum of NGC1266 at millimeter wavelengths. Our observations show that molecular gas is being driven out of the
nuclear region at Ṁ_(out) ≈ 110M_⊙ yr^(−1), of which the vast majority cannot escape the nucleus. Only 2M_⊙ yr^(−1)
is actually capable of escaping the galaxy. Most of the molecular gas that remains is very inefficient at forming
stars. The far-infrared emission is dominated by an ultra-compact (≾50 pc) source that could either be powered
by an AGN or by an ultra-compact starburst. The ratio of the SF surface density (Σ_(SFR)) to the gas surface
density (Σ_(H2)) indicates that SF is suppressed by a factor of ≈ 50 compared to normal star-forming galaxies if
all gas is forming stars, and ≈150 for the outskirt (98%) dense molecular gas if the central region is is powered
by an ultra-compact starburst. The AGN-driven bulk outflow could account for this extreme suppression by
hindering the fragmentation and gravitational collapse necessary to form stars through a process of turbulent
injection. This result suggests that even relatively common, low-power AGNs are able to alter the evolution of
their host galaxies as their black holes grow onto the M-σ relation
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