22,127 research outputs found
Intermediate-mass Black Holes in Galactic Nuclei
We present the first homogeneous sample of intermediate-mass black hole
candidates in active galactic nuclei. Starting with broad-line active nuclei
from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling
relation to select a sample of 19 galaxies in the mass range M_BH ~ 8 x 10^4 -
10^6 solar masses. In contrast to the local active galaxy population, the host
galaxies are ~1 mag fainter than M* and thus are probably late-type systems.
The active nuclei are also faint, with M_g ~ -15 to -18 mag, while the
bolometric luminosities are close to the Eddington limit. The spectral
properties of the sample are compared to the related class of objects known as
narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as
observational analogues of primordial black holes, contributors to the
integrated signal for future gravitational wave experiments, and as a valuable
tool in the calibration of the M-sigma relation.Comment: 4 pages, 4 figures. To appear in "The Interplay among Black Holes,
Stars and ISM in Galactic Nuclei," Proc. IAU 222 (Gramado, Brazil), eds Th.
Storchi Bergmann, L.C. Ho, H.R. Schmit
Steep-Spectrum Radio Emission from the Low-Mass Active Galactic Nucleus GH 10
GH 10 is a broad-lined active galactic nucleus (AGN) energized by a black
hole of mass 800,000 Solar masses. It was the only object detected by Greene et
al. in their Very Large Array (VLA) survey of 19 low-mass AGNs discovered by
Greene & Ho. New VLA imaging at 1.4, 4.9, and 8.5 GHz reveals that GH 10's
emission has an extent of less than 320 pc, has an optically-thin synchrotron
spectrum with a spectral index -0.76+/-0.05, is less than 11 percent linearly
polarized, and is steady - although poorly sampled - on timescales of weeks and
years. Circumnuclear star formation cannot dominate the radio emission, because
the high inferred star formation rate, 18 Solar masses per year, is
inconsistent with the rate of less than 2 Solar masses per year derived from
narrow Halpha and [OII] 3727 emission. Instead, the radio emission must be
mainly energized by the low-mass black hole. GH 10's radio properties match
those of the steep-spectrum cores of Palomar Seyfert galaxies, suggesting that,
like those Seyferts, the emission is outflow-driven. Because GH 10 is radiating
close to its Eddington limit, it may be a local analog of the starting
conditions, or seeds, for supermassive black holes. Future imaging of GH 10 at
higher resolution thus offers an opportunity to study the relative roles of
radiative versus kinetic feedback during black-hole growth.Comment: 7 pages; 2 figures; emulateapj; to appear in Ap
On the Appearance of Families of Efimov States in the Spinor Three-Body Problem
Few-body systems with access to multiple internal levels exhibit richness
beyond that typically found in their single-level counterparts. One example is
that of Efimov states in strongly-correlated spinor three-body systems. In [V.
E. Colussi, C. H. Greene, and J. P. D'Incao, Phys. Rev. Lett. {\bf 113}, 045302
(2014)] this problem was analyzed for spinor condensates finding a complex
level structure as in an early work [Bulgac and Efimov, Sov. J. Nucl. Phys. 22,
153 (1976)] in nuclear physics, and the impact of Efimov physics on the general
form of the scattering observables was worked out. In this paper we discuss the
appearance of novel families of Efimov states in the spinor three-body problem.Comment: Conference proceedings for the 21st International Conference on
Few-Body Problems in Physic
A Study of Polymers Containing Silicon-nitrogen Bonds Annual Summary Report, 4 May 1966 - 3 Jun. 1967
Polymers containing silicon-nitrogen bond
Dual Supermassive Black Hole Candidates in the AGN and Galaxy Evolution Survey
Dual supermassive black holes (SMBHs) with kiloparsec scale separations in
merger-remnant galaxies are informative tracers of galaxy evolution, but the
avenue for identifying them in large numbers for such studies is not yet clear.
One promising approach is to target spectroscopic signatures of systems where
both SMBHs are fueled as dual active galactic nuclei (AGNs), or where one SMBH
is fueled as an offset AGN. Dual AGNs may produce double-peaked narrow AGN
emission lines, while offset AGNs may produce single-peaked narrow AGN emission
lines with line-of-sight velocity offsets relative to the host galaxy. We
search for such dual and offset systems among 173 Type 2 AGNs at z<0.37 in the
AGN and Galaxy Evolution Survey (AGES), and we find two double-peaked AGNs and
five offset AGN candidates. When we compare these results to a similar search
of the DEEP2 Galaxy Redshift Survey and match the two samples in color,
absolute magnitude, and minimum velocity offset, we find that the fraction of
AGNs that are dual SMBH candidates increases from z=0.25 to z=0.7 by a factor
of ~6 (from 2/70 to 16/91, or 2.9% to 18%). This may be associated with the
rise in the galaxy merger fraction over the same cosmic time. As further
evidence for a link with galaxy mergers, the AGES offset and dual AGN
candidates are tentatively ~3 times more likely than the overall AGN population
to reside in a host galaxy that has a companion galaxy (from 16/173 to 2/7, or
9% to 29%). Follow-up observations of the seven offset and dual AGN candidates
in AGES will definitively distinguish velocity offsets produced by dual SMBHs
from those produced by narrow-line region kinematics, and will help sharpen our
observational approach to detecting dual SMBHs.Comment: 10 pages, 8 figures, accepted for publication in Ap
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