7,141 research outputs found
A Captured Runaway Black Hole in NGC 1277?
Recent results indicate that the compact lenticular galaxy NGC 1277 in the
Perseus Cluster contains a black hole of approximately 10 billion solar masses.
This far exceeds the expected mass of the central black hole in a galaxy of the
modest dimensions of NGC 1277. We suggest that this giant black hole was
ejected from the nearby giant galaxy NGC 1275 and subsequently captured by NGC
1277. The ejection was the result of gravitational radiation recoil when two
large black holes merged following the merger of two giant ellipticals that
helped to form NGC 1275. The black hole wandered in the cluster core until it
was captured in a close encounter with NGC 1277. The migration of black holes
in clusters may be a common occurrence.Comment: Four pages, accepted by The Astrophysical Journal Letters. Major
revisions, especially Section
Recommended from our members
Macroeconomic Shocks, Job Security and Health: Evidence from the Mining Industry
How do exogenous changes in the macroeconomic environment affect workersâ perceived job security, and consequently, their mental and physical health? To answer this question, we exploit variation in world commodity prices over the period 2001-17 and analyse panel data that includes detailed classifications of mining workers. We find that commodity price increases cause increases in perceived job security, which in turn, significantly and substantively improve the mental health of workers. In contrast, we find no effects on physical health. Our results imply that the estimated welfare costs of recessions are much larger when the effects of job insecurity, and not only unemployment, are considered
A ruggedized thin-window proportional-counter tube
Design and testing of ruggedized, thin window proportional counter tube for detecting X rays in light element
BIOECONOMIC MODELLING OF ENDANGERED SPECIES CONSERVATION
Resource /Energy Economics and Policy,
USING LAND AS A CONTROL VARIABLE IN DENSITY-DEPENDENT BIOECONOMIC MODELS
The bioeconomic analysis of endangered species without consumptive values can be problematic when analysed with density-dependent models that assume a fixed environment size. Most bioeconomic models use harvest as a control variable, yet when modelling non-harvestable species, frequently the only variable under control of conservationists is the quantity of habitat to be made available. The authors explore the implications of this in a model developed to analyse the potential population recovery of New Zealand's yellow-eyed penguin. The penguin faces severe competition with man for the terrestrial resources required for breeding and has declined in population to perilously low levels. The model was developed to estimate the land use required for recovery and preservation of the species and to compare the results to current tourism-driven conservation efforts. It is demonstrated that land may serve as a useful control variable in bioeconomic models and that such a model may be useful for determining whether sufficient incentives exist to preserve a species. However, the model may generate less useful results for providing a specific estimate of the optimal allocation of land to such a species.Land Economics/Use,
The Black Hole Mass - Galaxy Luminosity Relationship for Sloan Digital Sky Survey Quasars
We investigate the relationship between the mass of the central supermassive
black hole, M_bh, and the host galaxy luminosity, L_gal, in a sample of quasars
from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We use composite
quasar spectra binned by black hole mass and redshift to assess galaxy features
that would otherwise be overwhelmed by noise in individual spectra. The black
hole mass is calculated using the photoionization method, and the host galaxy
luminosity is inferred from the depth of the Ca II H + K features in the
composite spectra. We evaluate the evolution in the M_bh - L_gal relationship
by examining the redshift dependence of Delta log M_bh, the offset in black
hole mass from the local black hole - bulge relationship. There is little
systematic trend in Delta log M_bh out to z = 0.8. Using the width of the [O
III] emission line as a proxy for the stellar velocity dispersion, sigma_*, we
find agreement of our derived host luminosities with the locally-observed
Faber-Jackson relation. This supports the utility of the width of the [O III]
line as a proxy for sigma_* in statistical studies.Comment: 10 pages, 5 figures; final version; major revision
The Lyman Continuum Polarization Rise in the QSO PG 1222+228
Some QSOs show an abrupt, strong rise in polarization near rest wavelength
750 A. If this arises in the atmosphere of an accretion disk around a
supermassive black hole, it may have diagnostic value. In PG 1222+228, the
polarization rise occurs at the wavelength of a sharp drop in flux. We examine
and reject interpretations of this feature involving a high velocity outflow.
The observations agree with a model involving several intervening Lyman limit
systems, two of which happen to coincide with the Lyman continuum polarization
rise. After correction for the Lyman limit absorption, the continuum shortward
of 912 A is consistent with a typical power-law slope, alpha = -1.8. This
violates the apparent pattern for the Lyman limit polarization rises to occur
only in ``candidate Lyman edge QSOs''. The corrected, polarized flux rises
strongly at the wavelength of the polarization rise, resembling the case of PG
1630+377. The rise in polarized flux places especially stringent requirements
on models.Comment: 19 pages, including 5 EPS figures. Uses aaspp4.sty. Accepted for
publication in Publications of the Astronomical Society of the Pacific, 2000
Ma
Unconditionally secure one-way quantum key distribution using decoy pulses
We report here a complete experimental realization of one-way decoy-pulse
quantum key distribution, demonstrating an unconditionally secure key rate of
5.51 kbps for a 25.3 km fibre length. This is two orders of magnitudes higher
than the value that can be obtained with a non-decoy system. We introduce also
a simple test for detecting the photon number splitting attack and highlight
that it is essential for the security of the technique to fully characterize
the source and detectors used.Comment: 10 pages, 5 figure
- âŠ