1,605 research outputs found
A method for the microlensed flux variance of QSOs
A fast and practical method is described for calculating the microlensed flux
variance of an arbitrary source by uncorrelated stars. The required inputs are
the mean convergence and shear due to the smoothed potential of the lensing
galaxy, the stellar mass function, and the absolute square of the Fourier
transform of the surface brightness in the source plane. The mathematical
approach follows previous authors but has been generalized, streamlined, and
implemented in publicly available code. Examples of its application are given
for Dexter and Agol's inhomogeneous-disk models as well as the usual gaussian
sources. Since the quantity calculated is a second moment of the magnification,
it is only logarithmically sensitive to the sizes of very compact sources.
However, for the inferred sizes of actual QSOs, it has some discriminatory
power and may lend itself to simple statistical tests. At the very least, it
should be useful for testing the convergence of microlensing simulations.Comment: 10 pages, 6 figure
Sizes and Kinematics of Extended Narrow-Line Regions in Luminous Obscured AGN Selected by Broadband Images
To study the impact of active galactic nuclei (AGN) feedback on the galactic
ISM, we present Magellan long-slit spectroscopy of 12 luminous nearby type 2
AGN (L_bol~10^{45.0-46.5} erg/s, z~0.1). These objects are selected from a
parent sample of spectroscopically identified AGN to have high
[OIII]{\lambda}5007 and WISE mid-IR luminosities and extended emission in the
SDSS r-band images, suggesting the presence of extended [OIII]{\lambda}5007
emission. We find spatially resolved [OIII] emission (2-35 kpc from the
nucleus) in 8 out of 12 of these objects. Combined with samples of higher
luminosity type 2 AGN, we confirm that the size of the narrow-line region
(R_NLR) scales with the mid-IR luminosity until the relation flattens at ~10
kpc. Nine out of 12 objects in our sample have regions with broad [OIII]
linewidths (w_80>600 km/s), indicating outflows. We define these regions as the
kinematically-disturbed region (KDR). The size of the KDR (R_KDR) is typically
smaller than R_NLR by few kpc but also correlates strongly with the AGN mid-IR
luminosity. Given the unknown density in the gas, we derive a wide range in the
energy efficiency {\eta}=dot{E}/L_bol=0.01%-30%. We find no evidence for an AGN
luminosity threshold below which outflows are not launched. To explain the
sizes, velocity profiles, and high occurrence rates of the outflows in the most
luminous AGN, we propose a scenario in which energy-conserving outflows are
driven by AGN episodes with ~10^8-year durations. Within each episode the AGN
flickers on shorter timescales, with a cadence of ~10^6 year active phases
separated by ~10^7 years.Comment: 32 pages, 21 figures, ApJ in revie
ALMA Observations of a Candidate Molecular Outflow in an Obscured Quasar
We present Atacama Large Millimeter/Submillimeter Array (ALMA) CO (1-0) and
CO (3-2) observations of SDSS J135646.10+102609.0, an obscured quasar and
ultra-luminous infrared galaxy (ULIRG) with two merging nuclei and a known
20-kpc-scale ionized outflow. The total molecular gas mass is M_{mol} ~
9^{+19}_{-6} x 10^8 Msun, mostly distributed in a compact rotating disk at the
primary nucleus (M_{mol} ~ 3 x 10^8 Msun) and an extended tidal arm (M_{mol} ~
5 x 10^8 Msun). The tidal arm is one of the most massive molecular tidal
features known; we suggest that it is due to the lower chance of shock
dissociation in this elliptical/disk galaxy merger. In the spatially resolved
CO (3-2) data, we find a compact (r ~ 0.3 kpc) high velocity (v ~ 500 km/s)
red-shifted feature in addition to the rotation at the N nucleus. We propose a
molecular outflow as the most likely explanation for the high velocity gas. The
outflowing mass of M_{mol} ~ 7 x 10^7 Msun and the short dynamical time of
t_{dyn} ~ 0.6 Myr yield a very high outflow rate of \dot{M}_{mol} ~ 350 Msun/yr
and can deplete the gas in a million years. We find a low star formation rate
(< 16 Msun/yr from the molecular content and < 21 Msun/yr from the far-infrared
spectral energy distribution decomposition) that is inadequate to supply the
kinetic luminosity of the outflow (\dot{E} ~ 3 x 10^43 erg/s). Therefore, the
active galactic nucleus, with a bolometric luminosity of 10^46 erg/s, likely
powers the outflow. The momentum boost rate of the outflow (\dot{p}/(Lbol/c) ~
3) is lower than typical molecular outflows associated with AGN, which may be
related to its compactness. The molecular and ionized outflows are likely two
distinct bursts induced by episodic AGN activity that varies on a time scale of
10^7 yr.Comment: 16 pages, 7 figures, ApJ accepte
Extended X-ray Emission From a Quasar-Driven Superbubble
We present observations of extended, 20-kpc scale soft X-ray gas around a
luminous obscured quasar hosted by an ultra-luminous infrared galaxy caught in
the midst of a major merger. The extended X-ray emission is well fit as a
thermal gas with a temperature of kT ~ 280 eV and a luminosity of L_X ~ 10^42
erg/s and is spatially coincident with a known ionized gas outflow. Based on
the X-ray luminosity, a factor of ~10 fainter than the [OIII] emission, we
conclude that the X-ray emission is either dominated by photoionization, or by
shocked emission from cloud surfaces in a hot quasar-driven wind.Comment: Accepted for publication in ApJ, 6 pages, 2 figure
Joint Device-Edge Digital Semantic Communication with Adaptive Network Split and Learned Non-Linear Quantization
Semantic communication, an intelligent communication paradigm that aims to
transmit useful information in the semantic domain, is facilitated by deep
learning techniques. Although robust semantic features can be learned and
transmitted in an analog fashion, it poses new challenges to hardware,
protocol, and encryption. In this paper, we propose a digital semantic
communication system, which consists of an encoding network deployed on a
resource-limited device and a decoding network deployed at the edge. To acquire
better semantic representation for digital transmission, a novel non-linear
quantization module is proposed with the trainable quantization levels that
efficiently quantifies semantic features. Additionally, structured pruning by a
sparse scaling vector is incorporated to reduce the dimension of the
transmitted features. We also introduce a semantic learning loss (SLL) function
to reduce semantic error. To adapt to various channel conditions and inputs
under constraints of communication and computing resources, a policy network is
designed to adaptively choose the split point and the dimension of the
transmitted semantic features. Experiments using the CIFAR-10 dataset for image
classification are employed to evaluate the proposed digital semantic
communication network, and ablation studies are conducted to assess the
proposed modules including the quantization module, structured pruning and SLL
Refining the M_BH-V_c scaling relation with HI rotation curves of water megamaser galaxies
Black hole - galaxy scaling relations provide information about the
coevolution of supermassive black holes and their host galaxies. We compare the
black hole mass - circular velocity (MBH - Vc) relation with the black hole
mass - bulge stellar velocity dispersion (MBH - sigma) relation, to see whether
the scaling relations can passively emerge from a large number of mergers, or
require a physical mechanism, such as feedback from an active nucleus. We
present VLA H I observations of five galaxies, including three water megamaser
galaxies, to measure the circular velocity. Using twenty-two galaxies with
dynamical MBH measurements and Vc measurements extending to large radius, our
best-fit MBH - Vc relation, log MBH = alpha + beta log(Vc /200 km s^-1), yields
alpha = 7.43+/-0.13, beta = 3.68+1.23/-1.20, and intrinsic scatter epsilon_int
= 0.51+0.11/-0.09. The intrinsic scatter may well be higher than 0.51, as we
take great care to ascribe conservatively large observational errors. We find
comparable scatter in the MBH - sigma relations, epsilon_int = 0.48+0.10/-0.08,
while pure merging scenarios would likely result in a tighter scaling with the
dark halo (as traced by Vc) than baryonic (sigma) properties. Instead, feedback
from the active nucleus may act on bulge scales to tighten the MBH - sigma
relation with respect to the MBH - Vc relation, as observed.Comment: 27 pages, 15 figures, ApJ accepte
'Ruiduxiangyu': A new table grape with muscat flavor
Research Note
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