643 research outputs found
A Thirty-Four Billion Solar Mass Black Hole in SMSS J2157-3602, the Most Luminous Known Quasar
From near-infrared spectroscopic measurements of the MgII emission line
doublet, we estimate the black hole (BH) mass of the quasar, SMSS
J215728.21-360215.1, as being (3.4 +/- 0.6) x 10^10 M_sun and refine the
redshift of the quasar to be z=4.692. SMSS J2157 is the most luminous known
quasar, with a 3000A luminosity of (4.7 +/- 0.5) x 10^47 erg/s and an estimated
bolometric luminosity of 1.6 x 10^48 erg/s, yet its Eddington ratio is only
~0.4. Thus, the high luminosity of this quasar is a consequence of its
extremely large BH -- one of the most massive BHs at z > 4.Comment: 7 pages, 3 figures. Accepted for publication in MNRA
Spectroscopy of broad absorption line quasars at -- I: evidence for quasar winds shaping broad/narrow emission line regions
We present an observational study of 22 broad absorption line quasars (BAL
QSOs) at based on optical/near-IR spectroscopy, aiming
to investigate quasar winds and their effects. The near-IR spectroscopy covers
the \hb\ and/or \mgii\ broad emission lines (BELs) for these quasars, allowing
us to estimate their central black hole (BH) masses in a robust way. We found
that our BAL QSOs on average do not have a higher Eddington ratio than that
from non-BAL QSOs matched in redshift and/or luminosity. In a subset consisting
of seven strong BAL QSOs possessing sub-relativistic BAL outflows, we see the
prevalence of large \civ-BEL blueshift (3100 km s) and weak \oiii\
emission (particularly the narrow \oiii5007 component), indicative of
nuclear outflows affecting the narrow emission-line (NEL) regions. In another
subset consisting of thirteen BAL QSOs having simultaneous observations of
\mgii\ and \hb, we found a strong correlation between 3000~\AA\ and 5000~\AA\
monochromatic luminosity, consistent with that from non-BAL QSOs matched in
redshift and luminosity; however, there is no correlation between \mgii\ and
\hb\ in FWHM, likely due to nuclear outflows influencing the BEL regions. Our
spectroscopic investigations offer strong evidence that the presence of nuclear
outflows plays an important role in shaping the BEL/NEL regions of these
quasars and possibly, regulating the growth of central supermassive black holes
(SMBHs). We propose that BEL blueshift and BAL could be different
manifestations of the same outflow system viewed at different sightlines and/or
phases.Comment: 13 pages, 10 figures. Accepted for publication in Ap
Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-Infrared Photometric Data
We present a new algorithm to estimate quasar photometric redshifts
(photo-s), by considering the asymmetries in the relative flux distributions
of quasars. The relative flux models are built with multivariate Skew-t
distributions in the multi-dimensional space of relative fluxes as a function
of redshift and magnitude. For 151,392 quasars in the SDSS, we achieve a
photo- accuracy, defined as the fraction of quasars with the difference
between the photo- and the spectroscopic redshift , within 0.1, of 74%. Combining the WISE W1 and W2 infrared
data with the SDSS data, the photo- accuracy is enhanced to 87%. Using the
Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-
accuracies are 79% and 72%, respectively. The prior probabilities as a function
of magnitude for quasars, stars and galaxies are calculated respectively based
on (1) the quasar luminosity function; (2) the Milky Way synthetic simulation
with the Besan\c{c}on model; (3) the Bayesian Galaxy Photometric Redshift
estimation. The relative fluxes of stars are obtained with the Padova
isochrones, and the relative fluxes of galaxies are modeled through galaxy
templates. We test our classification method to select quasars using the DECaLS
, , , and WISE W1 and W2 photometry. The quasar selection completeness
is higher than 70% for a wide redshift range , and a wide magnitude
range mag. Our photo- regression and classification method has
the potential to extend to future surveys. The photo- code will be publicly
available.Comment: 22 pages, 17 figure, accepted by AJ. The code is available at
https://doi.org/10.5281/zenodo.101440
Constraining the Gravitational Lensing of Quasars from their Proximity Zones
Since their discovery twenty years ago, the observed luminosity function of
quasars has been suspected to be biased by gravitational lensing.
Apart from the recent discovery of UHS J0439+1634 at , no other
strongly lensed quasar has been conclusively identified. The
hyperluminous quasar SDSS J0100+2802, believed to host a
supermassive black hole of , has recently been claimed to
be lensed by a factor of , which would negate both its extreme
luminosity and black hole mass. However, its Ly-transparent proximity
zone is the largest known at , suggesting an intrinsically extreme
ionizing luminosity. Here we show that the lensing hypothesis of
quasars can be quantitatively constrained by their proximity zones. We first
show that our proximity zone analysis can recover the strongly lensed nature of
UHS J0439+1634, with an estimated magnification
at 68% (95%) credibility that is
consistent with previously published lensing models. We then show that the
large proximity zone of SDSS J0100+2802 rules out lensing magnifications of
at 95% probability, and conclusively rule out the proposed
scenario. Future proximity zone analyses of existing quasar samples
have the potential to identify promising strongly lensed candidates, constrain
the distribution of quasar lensing, and improve our knowledge of
the shape of the intrinsic quasar luminosity function.Comment: 8 pages, 4 figure
Spatially Resolved Interstellar Medium and Highly Excited Dense Molecular Gas in the Most Luminous Quasar at z = 6.327
Among more than 200 quasars known at z greater than or similar to 6, only one object, J0100+2802 (z = 6.327), was found hosting a >10(10) M-circle dot supermassive black hole. In order to investigate the host galaxy properties of J0100+2802, we performed multi-band ALMA observations, aiming at mapping the dust continuum, [C II] and CO(6-5) emission lines with subkiloparsec scale resolution, as well as detecting high-J CO lines in CO(11-10), CO(10-9), and CO(7-6). The galaxy size is measured to be R-major = 3.6 +/- 0.2 kpc from the high-resolution continuum observations. No ordered motion on kiloparsec scales was found in either the [C II] or the CO(6-5) emission. The velocity dispersion is measured to be 161 +/- 7 km s(-1), which is about three times smaller than that estimated from the local M-sigma relation. In addition, we found that the CO emission is more concentrated (a factor of 1.8 +/- 0.4) than the [C II] emission. Together with CO(2-1) detected by the Very Large Array (VLA), we measured the CO spectral line energy distribution, which is best fit by a two-component model that includes a cool component at similar to 24 K with a density of n((H2)) = 10(4.5) cm(-3), and a warm component at similar to 224 K with a density of n((H2)) = 10(3.6) cm(-3). We also fit the dust continuum with a graybody model. This indicated that the continuum has either a high dust emissivity beta greater than or similar to 2 or a hot dust temperature T-dust greater than or similar to 60 K, or a combination of these two factors. The highly excited CO emission and hot dust temperature suggest that the powerful active galactic nucleus in J0100+2802 could contribute to the gas and dust heating, but future observations are needed to confirm this.National Key R&D Program of China [2016YFA0400703]; National Science Foundation of China [11473004, 11533001, 11721303]; US NSF [AST-1515115]; NASA ADAP [NNX17AF28G]; VLA [VLA/14B-151, VLA/15A-494]; JCMT/SCUBA-2 [M15BI055]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
We present the discovery of nine quasars at identified in the Sloan
Digital Sky Survey (SDSS) imaging data. This completes our survey of
quasars in the SDSS footprint. Our final sample consists of 52 quasars at
, including 29 quasars with mag selected from
11,240 deg of the SDSS single-epoch imaging survey (the main survey), 10
quasars with selected from 4223 deg of the SDSS
overlap regions (regions with two or more imaging scans), and 13 quasars down
to mag from the 277 deg in Stripe 82. They span a
wide luminosity range of . This well-defined sample
is used to derive the quasar luminosity function (QLF) at . After
combining our SDSS sample with two faint ( mag) quasars from
the literature, we obtain the parameters for a double power-law fit to the QLF.
The bright-end slope of the QLF is well constrained to be
. Due to the small number of low-luminosity quasars, the
faint-end slope and the characteristic magnitude are
less well constrained, with and
mag. The spatial density of luminous quasars,
parametrized as , drops rapidly
from to 6, with . Based on our fitted QLF and assuming
an IGM clumping factor of , we find that the observed quasar population
cannot provide enough photons to ionize the IGM at \%
confidence. Quasars may still provide a significant fraction of the required
photons, although much larger samples of faint quasars are needed for more
stringent constraints on the quasar contribution to reionization.Comment: 20 pages, 12 figures, Accepted for publication in The Astrophysical
Journa
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