9,203 research outputs found
Accretion disks, precessing jets and the asymmetric emission lines of QSOs
The broad line profiles of active galaxies are consistent with emission from the surface of an accretion disk ionized by an ultraviolet continuum emitted from a linear or point source of continuum above the disk. If the point source is offset from the axis of the disk, then the line peak is shifted from zero velocity in a way that resembles observed cases. This misalignment could result from the Lense-Thirring precession of a rotating black hole
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
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 Monterey event in the Mediterranean: A record from shelf sediments of Malta
Oligo-Miocene carbonate platform and shelf sediments outcropping on the Maltese Islands provide an excellent archive of the paleoceanography of the central Mediterranean. A sequence of shallow water limestones, than shelf limestones, and marls, followed again by shallow water limestones, reflects drowning of a carbonate platform, the establishment of a shelf environment and, in the late Miocene, renewed progradation and aggradation of shallow water carbonates. The sequence recording the deepening of the Maltese platform contains several phosphorite hardgrounds and phosphorite pebble beds. These phosphorites were dated with strontium isotopes. Major episodes of phosphogenesis occurred between 25 and 16 Ma, and they are coeval with those phosphorite events reported from Florida and North Carolina. A Miocene carbon isotope and oxygen isotope stratigraphy was established on planktic and benthic foraminifera and on bulk samples. A major carbon isotope excursion with an amplitude of up to +l‰ between 18 and 12.5 Ma can be correlated with the globally recognized Monterey carbon isotope excursion. This is the first record of this event both in shallow water sediments and in the Mediterranean. The carbon isotope excursion precedes an oxygen isotope excursion which also was recognized in deep-sea records. Major episodes of phosphogenesis and platform drowning preceded the carbon isotope excursion by up to millions of years
The spectral energy distribution of NGC 1275
An analysis of absolute spectral energy distributions of interstellar gas for a galaxy (NGC 1275) is presented. Infrared spectra data shows heavy reddening. It is proposed that the interstellar gas may be ionized by shock waves or by nonthermal or stellar radiation. It is suggested, that high velocity, emission-line knots are H2 regions in a Perseus cluster galaxy or intergalactic gas cloud seen in projection against NGC 1275
User interface enhancement report
The existing user interfaces to TEMPUS, Plaid, and other systems in the OSDS are fundamentally based on only two modes of communication: alphanumeric commands or data input and grapical interaction. The latter are especially suited to the types of interaction necessary for creating workstation objects with BUILD and with performing body positioning in TEMPUS. Looking toward the future application of TEMPUS, however, the long-term goals of OSDS will include the analysis of extensive tasks in space involving one or more individuals working in concert over a period of time. In this context, the TEMPUS body positioning capability, though extremely useful in creating and validating a small number of particular body positions, will become somewhat tedious to use. The macro facility helps somewhat, since frequently used positions may be easily applied by executing a stored macro. The difference between body positioning and task execution, though subtle, is important. In the case of task execution, the important information at the user's level is what actions are to be performed rather than how the actions are performed. Viewed slightly differently, the what is constant over a set of individuals though the how may vary
Coupled cluster benchmarks of water monomers and dimers extracted from DFT liquid water: the importance of monomer deformations
To understand the performance of popular density-functional theory (DFT)
exchange-correlation (xc) functionals in simulations of liquid water, water
monomers and dimers were extracted from a PBE simulation of liquid water and
examined with coupled cluster with single and double excitations plus a
perturbative correction for connected triples [CCSD(T)]. CCSD(T) reveals that
most of the dimers are unbound compared to two gas phase equilibrium water
monomers, largely because monomers within the liquid have distorted geometries.
Of the three xc functionals tested, PBE and BLYP systematically underestimate
the cost of the monomer deformations and consequently predict too large
dissociation energies between monomers within the dimers. This is in marked
contrast to how these functionals perform for an equilibrium water dimer and
other small water clusters in the gas phase, which only have moderately
deformed monomers. PBE0 reproduces the CCSD(T) monomer deformation energies
very well and consequently the dimer dissociation energies much more accurately
than PBE and BLYP. Although this study is limited to water monomers and dimers,
the results reported here may provide an explanation for the overstructured
radial distribution functions routinely observed in BLYP and PBE simulations of
liquid water and are of relevance to water in other phases and to other
associated molecular liquids.Comment: 10 pages, 8 figures, Submitted to Journal of Chemical Physics,
Related information can be found in http://www.fhi-berlin.mpg.de/th
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