7,252 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 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
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
Accretion Disk Temperatures of QSOs: Constraints from the Emission Lines
QSO emission-line spectra are compared to predictions based on theoretical
ionizing continua of accretion disks. Observed line intensities do not show the
expected trend of higher ionization with higher accretion disk temperature as
derived from the black hole mass and accretion rate. This suggests that, at
least for accretion rates close to the Eddington limit, the inner disk does not
reach temperatures as high as expected from standard disk theory. Modified
radial temperature profiles, taking account of winds or advection in the inner
disk, achieve better agreement with observation. This conclusion agrees with an
earlier study of QSO continuum colors as a function of disk temperature. The
emission lines of radio-detected and radio-undetected sources show different
trends as a function of disk temperature.Comment: 9 pages, 8 figures, submitted to Ap
A review of melt and vapor growth techniques for polydiacetylene thin films for nonlinear optical applications
Methods for the growth of polydiacetylene thin films by melt and vapor growth and their subsequent polymerization are summarized. Films with random orientations were obtained when glass or quartz were used as substrates in the vapor growth process. Oriented polydiacetylene films were fabricated by the vapor deposition of diacetylene monomer onto oriented polydiacetylene on a glass substrate and its subsequent polymerization by UV light. A method for the growth of oriented thin films by a melt-shear growth process as well as a method of film growth by seeded recrstallization from the melt between glass plates, that may be applied to the growth of polydiacetylene films, are described. Moreover, a method is presented for the fabrication of single crystal thin films of polyacetylenes by irradiation of the surface of diacetylene single crystals to a depth between 100 and 2000 angstroms
The Black Hole Mass - Galaxy Bulge Relationship for QSOs in the SDSS DR3
We investigate the relationship between black hole mass and host galaxy
velocity dispersion for QSOs in Data Release 3 of the Sloan Digital Sky Survey.
We derive black hole mass from the broad Hbeta line width and continuum
luminosity, and the bulge stellar velocity dispersion from the [OIII] narrow
line width. At higher redshifts, we use MgII and [OII] in place of Hbeta and
[OIII]. For redshifts z < 0.5, our results agree with the black hole mass -
bulge velocity dispersion relationship for nearby galaxies. For 0.5 < z < 1.2,
this relationship appears to show evolution with redshift in the sense that the
bulges are too small for their black holes. However, we find that part of this
apparent trend can be attributed to observational biases, including a Malmquist
bias involving the QSO luminosity. Accounting for these biases, we find ~0.2
dex evolution in the black hole mass-bulge velocity dispersion relationship
between now and redshift z ~ 1.Comment: Accepted by ApJ, 15 pages, 9 figure
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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