635 research outputs found
The effect of gravitational-wave recoil on the demography of massive black holes
The coalescence of massive black hole (MBH) binaries following galaxy mergers
is one of the main sources of low-frequency gravitational radiation. A
higher-order relativistic phenomenon, the recoil as a result of the non-zero
net linear momentum carried away by gravitational waves, may have interesting
consequences for the demography of MBHs at the centers of galaxies. We study
the dynamics of recoiling MBHs and its observational consequences. The
``gravitational rocket'' may: i) deplete MBHs from late-type spirals, dwarf
galaxies, and stellar clusters; ii) produce off-nuclear quasars, including
unusual radio morphologies during the recoil of a radio-loud source; and iii)
give rise to a population of interstellar and intergalactic MBHs.Comment: emulateapj, 5 pages, 2 figures, to appear in the ApJ Letter
Reverberation Mapping and the Physics of Active Galactic Nuclei
Reverberation-mapping campaigns have revolutionized our understanding of AGN.
They have allowed the direct determination of the broad-line region size,
enabled mapping of the gas distribution around the central black hole, and are
starting to resolve the continuum source structure. This review describes the
recent and successful campaigns of the International AGN Watch consortium,
outlines the theoretical background of reverberation mapping and the
calculation of transfer functions, and addresses the fundamental difficulties
of such experiments. It shows that such large-scale experiments have resulted
in a ``new BLR'' which is considerably different from the one we knew just ten
years ago. We discuss in some detail the more important new results, including
the luminosity-size-mass relationship for AGN, and suggest ways to proceed in
the near future.Comment: Review article to appear in Astronomical Time Series, Proceedings of
the Wise Observatory 25th Ann. Symposium. 24 pages including 7 figure
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
Limits on Dust in Rich Clusters of Galaxies from the Color of Background Quasars
I measure the V-I color distribution of two samples of radio-selected
quasars. Quasars from one sample are projected on the sky within 1 degree of a
rich foreground Abell cluster of galaxies, while quasars from the other sample
are more than 3 degrees from any such cluster . There is no significant
difference between the color distributions of the two samples. The 90\% upper
limit on the relative reddening between the two samples is E(B-V)=0.05 mag.
This result limits the allowed quantity of smoothly distributed dust in rich
clusters, and contradicts previous indications for the existence of such a
component.Comment: Submitted to ApJ Letters. 14 pages incl. 2 figures, uuencoded,
compressed postscript. Also available by anonymous ftp to
ftp://wise3.tau.ac.il/pub/dani/dust.ps.
The Murmur of the Sleeping Black Hole: Detection of Nuclear Ultraviolet Variability in LINER Galaxies
LINER nuclei, which are present in many nearby galactic bulges, may be the
manifestation of low-rate or low-radiative-efficiency accretion onto
supermassive central black holes. However, it has been unclear whether the
compact UV nuclear sources present in many LINERs are clusters of massive
stars, rather than being directly related to the accretion process. We have
used HST to monitor the UV variability of a sample of 17 galaxies with LINER
nuclei and compact nuclear UV sources. Fifteen of the 17 galaxies were observed
more than once, with two to five epochs per galaxy, spanning up to a year. We
detect significant variability in most of the sample, with peak-to-peak
amplitudes from a few percent to 50%. In most cases, correlated variations are
seen in two independent bands (F250W and F330W). Comparison to previous UV
measurements indicates, for many objects, long-term variations by factors of a
few over decade timescales. Variability is detected in LINERs with and without
detected compact radio cores, in LINERs that have broad H-alpha wings detected
in their optical spectra (``LINER 1's''), and in those that do not (``LINER
2s''). This variability demonstrates the existence of a non-stellar component
in the UV continuum of all types, and sets a lower limit to the luminosity of
this component. We note a trend in the UV color (F250W/F330W) with spectral
type - LINER 1s tend to be bluer than LINER 2s. This trend may indicate a link
between the shape of the nonstellar continuum and the presence or the
visibility of a broad-line region. In one target, the post-starburst galaxy NGC
4736, we detect variability in a previously noted UV source that is offset by
2.5" (60 pc in projection) from the nucleus. This may be the nearest example of
a binary active nucleus, and of the process leading to black hole merging.Comment: accepted to Ap
Measurement of the Broad Line Region Size in Two Bright Quasars
We present 4 years of spectrophotometric monitoring data for two radio-quiet
quasars, PG 0804+762 and PG 0953+414, with typical sampling intervals of
several months. Both sources show continuum and emission line variations. The
variations of the H line follow those of the continuum with a time lag,
as derived from a cross-correlation analysis, of 9330 days for PG 0804+762
and 11155 days for PG 0953+414. This is the first reliable measurement of
such a lag in active galactic nuclei with luminosity erg s.
The broad line region (BLR) size that is implied is almost an order of
magnitude larger than that measured in several Seyfert 1 galaxies and is
consistent with the hypothesis that the BLR size grows as .Comment: 5 pages, LaTeX (including aas2pp4 and epsf), including 4 EPS figures.
Accepted for publication in Astrophysical Journal Letter
Radiation from the non-extremal fuzzball
The fuzzball proposal says that the information of the black hole state is
distributed throughout the interior of the horizon in a `quantum fuzz'. There
are special microstates where in the dual CFT we have `many excitations in the
same state'; these are described by regular classical geometries without
horizons. Jejjala et.al constructed non-extremal regular geometries of this
type. Cardoso et. al then found that these geometries had a classical
instability. In this paper we show that the energy radiated through the
unstable modes is exactly the Hawking radiation for these microstates. We do
this by (i) starting with the semiclassical Hawking radiation rate (ii) using
it to find the emission vertex in the CFT (iii) replacing the Boltzman
distributions of the generic CFT state with the ones describing the microstate
of interest (iv) observing that the emission now reproduces the classical
instability. Because the CFT has `many excitations in the same state' we get
the physics of a Bose-Einstein condensate rather than a thermal gas, and the
usually slow Hawking emission increases, by Bose enhancement, to a classically
radiated field. This system therefore provides a complete gravity description
of information-carrying radiation from a special microstate of the nonextremal
hole.Comment: corrected typo
A Venus-Mass Planet Orbiting a Brown Dwarf: Missing Link between Planets and Moons
The co-planarity of solar-system planets led Kant to suggest that they formed
from an accretion disk, and the discovery of hundreds of such disks around
young stars as well as hundreds of co-planar planetary systems by the Kepler
satellite demonstrate that this formation mechanism is extremely widespread.
Many moons in the solar system, such as the Galilean moons of Jupiter, also
formed out of the accretion disks that coalesced into the giant planets. We
report here the discovery of an intermediate system OGLE-2013-BLG-0723LB/Bb
composed of a Venus-mass planet orbiting a brown dwarf, which may be viewed
either as a scaled down version of a planet plus star or as a scaled up version
of a moon plus planet orbiting a star. The latter analogy can be further
extended since they orbit in the potential of a larger, stellar body. For
ice-rock companions formed in the outer parts of accretion disks, like Uranus
and Callisto, the scaled masses and separations of the three types of systems
are similar, leading us to suggest that formation processes of companions
within accretion disks around stars, brown dwarfs, and planets are similar.Comment: 8 pages, 5 figures, 2 table
Anatomy of bubbling solutions
We present a comprehensive analysis of holography for the bubbling solutions
of Lin-Lunin-Maldacena. These solutions are uniquely determined by a coloring
of a 2-plane, which was argued to correspond to the phase space of free
fermions. We show that in general this phase space distribution does not
determine fully the 1/2 BPS state of N=4 SYM that the gravitational solution is
dual to, but it does determine it enough so that vevs of all single trace 1/2
BPS operators in that state are uniquely determined to leading order in the
large N limit. These are precisely the vevs encoded in the asymptotics of the
LLM solutions. We extract these vevs for operators up to dimension 4 using
holographic renormalization and KK holography and show exact agreement with the
field theory expressions.Comment: 67 pages, 6 figures; v2: typos corrected, refs added; v3: expanded
explanations, more typos correcte
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