465 research outputs found
SkyMapper Southern Survey: Data Release 4
We present the fourth data release (DR4) of the SkyMapper Southern Survey
(SMSS), the last major step in our hemispheric survey with six optical filters:
u, v, g, r, i, z. SMSS DR4 covers 26,000 sq.deg from over 400,000 images
acquired by the 1.3m SkyMapper telescope between 2014-03 and 2021-09. The
6-band sky coverage extends from the South Celestial Pole to Dec = +16deg, with
some images reaching Dec ~ +28deg. In contrast to previous DRs, we include all
good-quality images from the facility taken during that time span, not only
those explicitly taken for the public Survey. From the image dataset, we
produce a catalogue of nearly 13 billion detections made from ~700 million
unique astrophysical objects. The typical 10sigma depths for each field range
between 18.5 and 20.5 mag, depending on the filter, but certain sky regions
include longer exposures that reach as deep as 22 mag in some filters. As with
previous SMSS catalogues, we have cross-matched with a host of other imaging
and spectroscopic datasets to facilitate additional science outcomes. SMSS DR4
is now available to the worldwide astronomical community.Comment: 32 pages. Submitted to the Publications of the Astronomical Society
of Australi
X-Ray Properties of Narrow-Line Seyfert 1 Galaxies with Very Small Broad-Line Widths
Narrow-line Seyfert\,1 galaxies (NLS1s) with very small broad-line widths
(say, FWHM(\hb) \la 1200\,\kms) represent the extreme type of Seyfert\,1
galaxies that have small black hole masses (\mbh) and/or high Eddington ratios
(\redd). Here we study the X-ray properties of a homogeneously and optically
selected sample of 13 such objects, termed as very narrow line Seyfert\,1
galaxies (VNLS1s), using archival \xmm\ data. It is found that the Fe K
emission line is at most weak in these objects. A soft X-ray excess is
ubiquitous, with the thermal temperatures falling within a strict range of
0.1--0.2\,keV. Our result highlights the puzzling independence of the thermal
temperature by extending the relations to even smaller FWHM(\hb), i.e., smaller
\mbh\ ( \msun) and/or higher \redd. The excess emission can be
modeled by a range of viable models, though the disk reflection and
Comptonization models generally give somewhat better fits over the smeared
absorption and the -free models. At the Eddington ratios around unity and
above, the X-ray spectral slopes in the 2--10\,keV band are systematically
flatter than the Risaliti et al.'s predictions of the relationship with \redd\
suggested previously. Short timescale (1--2 hours) X-ray variability is common,
which, together with the variability amplitude computed for some of the
objects, are supportive of the scenario that NLS1s are indeed AGN with
relatively small \mbh.Comment: 11 figures and 4 table. Accepted for publication in the Astrophysical
Journa
Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
We present improved black hole masses for 35 active galactic nuclei (AGNs)
based on a complete and consistent reanalysis of broad emission-line
reverberation-mapping data. From objects with multiple line measurements, we
find that the highest precision measure of the virial product is obtained by
using the cross-correlation function centroid (as opposed to the
cross-correlation function peak) for the time delay and the line dispersion (as
opposed to full width half maximum) for the line width and by measuring the
line width in the variable part of the spectrum. Accurate line-width
measurement depends critically on avoiding contaminating features, in
particular the narrow components of the emission lines. We find that the
precision (or random component of the error) of reverberation-based black hole
mass measurements is typically around 30%, comparable to the precision attained
in measurement of black hole masses in quiescent galaxies by gas or stellar
dynamical methods. Based on results presented in a companion paper by Onken et
al., we provide a zero-point calibration for the reverberation-based black hole
mass scale by using the relationship between black hole mass and host-galaxy
bulge velocity dispersion. The scatter around this relationship implies that
the typical systematic uncertainties in reverberation-based black hole masses
are smaller than a factor of three. We present a preliminary version of a
mass-luminosity relationship that is much better defined than any previous
attempt. Scatter about the mass-luminosity relationship for these AGNs appears
to be real and could be correlated with either Eddington ratio or object
inclination.Comment: 61 pages, including 8 Tables and 16 Figures. Accepted for publication
in The Astrophysical Journa
Reverberation Mapping Measurements of Black Hole Masses in Six Local Seyfert Galaxies
We present the final results from a high sampling rate, multi-month,
spectrophotometric reverberation mapping campaign undertaken to obtain either
new or improved Hbeta reverberation lag measurements for several relatively
low-luminosity AGNs. We have reliably measured thetime delay between variations
in the continuum and Hbeta emission line in six local Seyfert 1 galaxies. These
measurements are used to calculate the mass of the supermassive black hole at
the center of each of these AGNs. We place our results in context to the most
current calibration of the broad-line region (BLR) R-L relationship, where our
results remove outliers and reduce the scatter at the low-luminosity end of
this relationship. We also present velocity-resolved Hbeta time delay
measurements for our complete sample, though the clearest velocity-resolved
kinematic signatures have already been published.Comment: 52 pages (AASTeX: 29 pages of text, 8 tables, 7 figures), accepted
for publication in the Astrophysical Journa
The magellanic quasars survey. III. Spectroscopic confirmation of 758 active galactic nuclei behind the magellanic clouds
The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) hav
A Deep HST H-Band Imaging Survey of Massive Gas-Rich Mergers. II. The QUEST PG QSOs
We report the results from a deep HST NICMOS H-band imaging survey of 28 z <
0.3 QSOs from the Palomar-Green (PG) sample. This program is part of QUEST
(Quasar / ULIRG Evolution STudy) and complements a similar set of data on 26
highly-nucleated ULIRGs presented in Paper I. Our analysis indicates that the
fraction of QSOs with elliptical hosts is higher among QSOs with undetected
far-infrared (FIR) emission, small infrared excess, and luminous hosts. The
hosts of FIR-faint QSOs show a tendency to have less pronounced merger-induced
morphological anomalies and larger QSO-to-host luminosity ratios on average
than the hosts of FIR-bright QSOs, consistent with late-merger evolution from
FIR-bright to FIR-faint QSOs. The spheroid sizes and total host luminosities of
the radio-quiet PG QSOs in our sample are statistically indistinguishable from
the ULIRG hosts presented in Paper I, while those of radio-loud PG QSOs are
systematically larger and more luminous. ULIRGs and PG QSOs with elliptical
hosts fall near, but not exactly on, the fundamental plane of inactive
spheroids. We confirm the systematic trend noted in Paper I for objects with
small (< 2 kpc) spheroids to be up to ~1 mag. brighter than inactive spheroids.
The host colors and wavelength dependence of their sizes support the idea that
these deviations are due at least in part to non-nuclear star formation.
However, the amplitudes of these deviations does not depend on host R-H colors.
Taken at face value (i.e., no correction for extinction or the presence of a
young stellar population), the H-band spheroid-host luminosities imply BH
masses ~5 -- 200 x 10^7 M_sun and sub-Eddington mass accretion rates for both
QSOs and ULIRGs. These results are compared with published BH mass estimates
derived from other methods. (abridged)Comment: Accepted for publication in the Astrophysical Journal, Vol. 701,
August 20 issue. Paper with high-resolution figures can be downloaded at
http://www.astro.umd.edu/~veilleux/pubs/nicmos2.pd
Balmer Emission Line Profiles and the Complex Properties of Broad Line Regions in Active Galactic Nuclei
In this work we analyze a sample of AGN spectra, selected from the 6th Data
Release of the Sloan Digital Sky Survey, exploiting a generalized technique of
line profile analysis, designed to take into account the whole profiles of
their broad emission lines. We find that the line profile broadening functions
result from a complex structure, but we may be able to infer some constraints
about the role of the geometrical factor, thus improving our ability to
estimate AGN properties and their relation with the host galaxy. Our results
suggest that flattening and inclination within the structure of the Broad Line
Region (BLR) must be taken into account. We detect low inclinations of the BLR
motion plane with respect to our line of sight, typically i < 20 degrees, with
a geometrical effect which generally decreases as the line profile becomes
broader.Comment: 13 pages, 11 figures, updated reference list. ApJ accepte
The radio luminosity, black hole mass and Eddington ratio for quasars from the Sloan Digital Sky Survey
We investigate the \mbh- \sigma_* relation for radio-loud quasars with
redshift in Data Release 3 of the Sloan Digital Sky Survey (SDSS). The
sample consists of 3772 quasars with better model of H and \oiii lines
and available radio luminosity, including 306 radio-loud quasars, 3466
radio-quiet quasars with measured radio luminosity or upper-limit of radio
luminosity (181 radio-quiet quasars with measured radio luminosity). The virial
supermassive black hole mass (\mbh) is calculated from the broad \hb line, the
host stellar velocity dispersion () is traced by the core \oiii
gaseous velocity dispersion, and the radio luminosity and the radio loudness
are derived from the FIRST catalog. Our results are follows: (1) For
radio-quiet quasars, we confirm that there is no obvious deviation from the
\mbh- \sigma_* relation defined in inactive galaxies when \mbh uncertainties
and luminosity bias are concerned. (2) We find that radio-loud quasars deviate
much from the \mbh- \sigma_* relation respect to that for radio-quiet
quasars. This deviation is only partly due to the possible cosmology evolution
of the \mbh- \sigma_* relation and the luminosity bias. (3) The radio
luminosity is proportional to
\mbh^{1.28^{+0.23}_{-0.16}}(\lb/\ledd)^{1.29^{+0.31}_{-0.24}} for radio-quiet
quasars and \mbh^{3.10^{+0.60}_{-0.70}}(\lb/\ledd)^{4.18^{+1.40}_{-1.10}} for
radio-loud quasars. The weaker correlation of the radio luminosity dependence
upon the mass and the Eddington ratio for radio-loud quasars shows that other
physical effects would account for their radio luminosities, such as the black
hole spin.Comment: 15 pages, 8 figures, 2 tables, accepted for publication in ChJA
A unified framework for the orbital structure of bars and triaxial ellipsoids
We examine a large random sample of orbits in two self-consistent simulations of N-body bars. Orbits in these bars are classified both visually and with a new automated orbit classification method based on frequency analysis. The well-known prograde x1 orbit family originates from the same parent orbit as the box orbits in stationary and rotating triaxial ellipsoids. However, only a small fraction of bar orbits (~4%) have predominately prograde motion like their periodic parent orbit. Most bar orbits arising from the x1 orbit have little net angular momentum in the bar frame, making them equivalent to box orbits in rotating triaxial potentials. In these simulations a small fraction of bar orbits (~7%) are long-axis tubes that behave exactly like those in triaxial ellipsoids: they are tipped about the intermediate axis owing to the Coriolis force, with the sense of tipping determined by the sign of their angular momentum about the long axis. No orbits parented by prograde periodic x2 orbits are found in the pure bar model, but a tiny population (~2%) of short-axis tube orbits parented by retrograde x4 orbits are found. When a central point mass representing a supermassive black hole (SMBH) is grown adiabatically at the center of the bar, those orbits that lie in the immediate vicinity of the SMBH are transformed into precessing Keplerian orbits that belong to the same major families (short-axis tubes, long-axis tubes and boxes) occupying the bar at larger radii. During the growth of an SMBH, the inflow of mass and outward transport of angular momentum transform some x1 and long-axis tube orbits into prograde short-axis tubes. This study has important implications for future attempts to constrain the masses of SMBHs in barred galaxies using orbit-based methods like the Schwarzschild orbit superposition scheme and for understanding the observed features in barred galaxies
- …