2,124 research outputs found
Relations Between Central Black Hole Mass and Total Galaxy Stellar Mass in the Local Universe
Scaling relations between central black hole (BH) mass and host galaxy
properties are of fundamental importance to studies of BH and galaxy evolution
throughout cosmic time. Here we investigate the relationship between BH mass
and host galaxy total stellar mass using a sample of 262 broad-line active
galactic nuclei (AGN) in the nearby Universe (z < 0.055), as well as 79
galaxies with dynamical BH masses. The vast majority of our AGN sample is
constructed using Sloan Digital Sky Survey spectroscopy and searching for
Seyfert-like narrow-line ratios and broad H-alpha emission. BH masses are
estimated using standard virial techniques. We also include a small number of
dwarf galaxies with total stellar masses M_stellar < 10^9.5 Msun and a
sub-sample of the reverberation-mapped AGNs. Total stellar masses of all 341
galaxies are calculated in the most consistent manner feasible using
color-dependent mass-to-light ratios. We find a clear correlation between BH
mass and total stellar mass for the AGN host galaxies, with M_BH proportional
to M_stellar, similar to that of early-type galaxies with dynamically-detected
BHs. However, the relation defined by the AGNs has a normalization that is
lower by more than an order of magnitude, with a BH-to-total stellar mass
fraction of M_BH/M_stellar ~ 0.025% across the stellar mass range 10^8 <
M_stellar/Msun < 10^12. This result has significant implications for studies at
high redshift and cosmological simulations in which stellar bulges cannot be
resolved.Comment: Accepted for publication in the Astrophysical Journal. 15 pages, 12
figure
A ~50,000 solar mass black hole in the nucleus of RGG 118
Scaling relations between black hole (BH) masses and their host galaxy
properties have been studied extensively over the last two decades, and point
towards co-evolution of central massive BHs and their hosts. However, these
relations remain poorly constrained for BH masses below M_sun.
Here we present optical and X-ray observations of the dwarf galaxy RGG 118
taken with the Magellan Echellette Spectrograph on the 6.5m Clay Telescope and
Chandra X-ray Observatory. Based on Sloan Digital Sky Survey spectroscopy, RGG
118 was identified as possessing narrow emission line ratios indicative of
photoionization partly due to an active galactic nucleus. Our higher resolution
spectroscopy clearly reveals broad H emission in the spectrum of RGG
118. Using virial BH mass estimate techniques, we calculate a BH mass of
\msun. We detect a nuclear X-ray point source in RGG 118,
suggesting a total accretion powered luminosity of , and an Eddington fraction of per cent. The BH in RGG 118
is the smallest ever reported in a galaxy nucleus and we find that it lies on
the extrapolation of the relation to the lowest
masses yet.Comment: Accepted to ApJL. 6 pages, 4 figure
Recommended from our members
Litigating the Drug Price Competition and Patent Term Restoration Act of 1984
The Drug Price Competition and Patent Term Restoration Act of 1984, also known as the Hatch-Waxman Act in honor of its sponsors Senator Orrin Hatch and Representative Henry Waxman, was enacted in an attempt to reconcile two seemingly contradictory policy goals. The Act represented a compromise between the interests of generic drug manufacturers and the competing interests of the "pioneer" drug manufacturers who research and develop novel drug products. Thus, the Act was designed to improve the availability of inexpensive generic drugs, while maintaining sufficient incentives for investment in new drug development. The Hatch-Waxman Act creates a complex statutory framework, such that many problems and debates have arisen surrounding its implementation. This paper gives an overview of the issues that have been litigated under the Hatch-Waxman Act in the nearly sixteen years since its enactment
Hubble Space Telescope Imaging of the Active Dwarf Galaxy RGG 118
RGG 118 (SDSS 1523+1145) is a nearby (), dwarf disk galaxy
() found to host an active
solar mass black hole at its core (Baldassare et al. 2015). RGG 118 is one of a
growing collective sample of dwarf galaxies known to contain active galactic
nuclei -- a group which, until recently, contained only a handful of objects.
Here, we report on new \textit{Hubble Space Telescope} Wide Field Camera 3 UVIS
and IR imaging of RGG 118, with the main goal of analyzing its structure. Using
2-D parametric modeling, we find that the morphology of RGG 118 is best
described by an outer spiral disk, inner component consistent with a
pseudobulge, and central PSF. The luminosity of the PSF is consistent with the
central point source being dominated by the AGN. We measure the luminosity and
mass of the "pseudobulge" and confirm that the central black hole in RGG 118 is
under-massive with respect to the and relations. This result is consistent with a picture in which black
holes in disk-dominated galaxies grow primarily through secular processes.Comment: Accepted to Astrophysical Journal. 11 pages, 8 figure
Optical SETI: A Spectroscopic Search for Laser Emission from Nearby Stars
We have searched for nonastrophysical emission lines in the optical spectra
of 577 nearby F, G, K, and M main-sequence stars. Emission lines of
astrophysical origin would also have been detected, such as from a
time--variable chromosphere or infalling comets. We examined ~20 spectra per
star obtained during four years with the Keck/HIRES spectrometer at a
resolution of 5 km/s, with a detection threshold 3% of the continuum flux
level. We searched each spectrum from 4000-5000 angstroms for emission lines
having widths too narrow to be natural from the host star, as well as for lines
broadened by astrophysical mechanisms. We would have detected lasers that emit
a power, P>60 kW, for a typical beam width of ~0.01 arcsec (diffraction-limit
from a 10-m aperture) if directed toward Earth from the star. No lines
consisstent with laser emission were found.Comment: 27 pages, 11 figures, uses aastex.st
Reactor Neutrinos
We review the status and the results of reactor neutrino experiments, that
toe the cutting edge of neutrino research. Short baseline experiments have
provided the measurement of the reactor neutrino spectrum, and are still
searching for important phenomena such as the neutrino magnetic moment. They
could open the door to the measurement of coherent neutrino scattering in a
near future. Middle and long baseline oscillation experiments at Chooz and
KamLAND have played a relevant role in neutrino oscillation physics in the last
years. It is now widely accepted that a new middle baseline disappearance
reactor neutrino experiment with multiple detectors could provide a clean
measurement of the last undetermined neutrino mixing angle theta13. We conclude
by opening on possible use of neutrinos for Society: NonProliferation of
Nuclear materials and Geophysics
Dwarf Galaxies with Optical Signatures of Active Massive Black Holes
We present a sample of 151 dwarf galaxies (10^8.5 < M_stellar < 10^9.5 Msun)
that exhibit optical spectroscopic signatures of accreting massive black holes
(BHs), increasing the number of known active galaxies in this stellar mass
range by more than an order of magnitude. Utilizing data from the Sloan Digital
Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have
systematically searched for active BHs in ~25,000 emission-line galaxies with
stellar masses comparable to the Magellanic Clouds and redshifts z<0.055. Using
the narrow-line [OIII]/H-beta versus [NII]/H-alpha diagnostic diagram, we find
photoionization signatures of BH accretion in 136 galaxies, a small fraction of
which also exhibit broad H-alpha emission. For these broad-line AGN candidates,
we estimate BH masses using standard virial techniques and find a range of 10^5
< M_BH < 10^6 Msun and a median of M_BH ~ 2 x 10^5 Msun. We also detect broad
H-alpha in 15 galaxies that have narrow-line ratios consistent with
star-forming galaxies. Follow-up observations are required to determine if
these are true type 1 AGN or if the broad H-alpha is from stellar processes.
The median absolute magnitude of the host galaxies in our active sample is Mg =
-18.1 mag, which is ~1-2 magnitudes fainter than previous samples of AGN hosts
with low-mass BHs. This work constrains the smallest galaxies that can form a
massive BH, with implications for BH feedback in low-mass galaxies and the
origin of the first supermassive BH seeds.Comment: 26 pages, 15 figures, 6 tables. Accepted for publication in The
Astrophysical Journa
Proton Spectrum at the Jupiter Laser Facility of LLNL
This paper looks at tungsten samples irradiated by beams of protons, gammas,
electrons and positrons at the Jupiter Laser Facility of Lawrence Livermore
National Laboratory (LLNL). The resulting unstable nuclei created are
identified using their gamma spectra. These spectra were taken, usually within
an hour of irradiation, for periods up to 48 hrs. In several cases there are
two isotopes, one of Rhenium and the other of Tantalum, that emit the same
gamma lines. These pairs often involve a long-lived and a short-lived
candidate. Spectra were taken 80 days after initial exposure and the long-lived
candidates are ruled out
- …
