1,501 research outputs found
Distance Measurement of Galaxies to Redshift of 0.1 using the CO-Line Tully-Fisher Relation
We report on the first results of a long-term project to derive distances of
galaxies at cosmological distances by applying the CO-line width-luminosity
relation. We have obtained deep CO-line observations of galaxies at redshifts
up to 29,000 km/s using the Nobeyama 45-m mm-wave Telescope, and some
supplementary data were obtained by using the IRAM 30-m telescope. We have
detected the CO line emission for several galaxies, and used their CO line
widths to estimate the absolute luminosities using the line-width-luminosity
relation. In order to obtain photometric data and inclination correction, we
also performed optical imaging observations of the CO-detected galaxies using
the CFHT 3.6-m telescope at high resolution. The radio and optical data have
been combined to derive the distance moduli and distances of the galaxies, and
Hubble ratios were estimated for these galaxies. We propose that the CO line
width-luminosity relation can be a powerful method to derive distances of
galaxies to redfhift of z = 0.1 and to derive the Hubble ratio in a significant
volume of the universe.
Key words: Cosmology - Galaxies: general - Distance scale - CO lineComment: To appear in PASJ, Plain Tex, 3 figures (in 10 ps files
New Analytical Formula for Supercritical Accretion Flows
We examine a new family of global analytic solutions for optically thick
accretion disks, which includes the supercritical accretion regime. We found
that the ratio of the advection cooling rate, , to the viscous
heating rate, , i.e., , can be
represented by an analytical form dependent on the radius and the mass
accretion rate. The new analytic solutions can be characterized by the
photon-trapping radius, \rtrap, inside which the accretion time is less than
the photon diffusion time in the vertical direction; the nature of the
solutions changes significantly as this radius is crossed. Inside the trapping
radius,
approaches , which corresponds to the advection-dominated
limit (), whereas outside the trapping radius, the radial dependence
of changes to , which corresponds to the
radiative-cooling-dominated limit. The analytical formula for derived here
smoothly connects these two regimes. The set of new analytic solutions
reproduces well the global disk structure obtained by numerical integration
over a wide range of mass accretion rates, including the supercritical
accretion regime. In particular, the effective temperature profiles for our new
solutions are in good agreement with those obtained from numerical solutions.
Therefore, the new solutions will provide a useful tool not only for evaluating
the observational properties of accretion flows, but also for investigating the
mass evolution of black holes in the presence of supercritical accretion flows.Comment: 14 pages, 7 figures, accepted for publication in the Astrophysical
Journa
Large scale shell model calculations for odd-odd Mn isotopes
Large scale shell model calculations have been carried out for odd-odd
Mn isotopes in two different model spaces. First set of calculations
have been carried out in full shell valence space with two recently
derived shell interactions namely GXPF1A and KB3G treating Ca
as core. The second set of calculations have been performed in
valence space with the interaction treating Ca as core and
imposing a truncation by allowing up to a total of six particle excitations
from the 0f orbital to the upper orbitals for protons and
from the upper orbitals to the 0g orbital for neutron. For
low-lying states in Mn, the KB3G and GXPF1A both predicts good results
and for Mn, KB3G is much better than GXPF1A. For negative parity and
high-spin positive parity states in both isotopes interaction is
required. Experimental data on Mn is sparse and therefore it is not
possible to make any definite conclusions. More experimental data on negative
parity states is needed to ascertain the importance of 0g and higher
orbitals in neutron rich Mn isotopes.Comment: 5 pages, 4 figures, Submitted to Eur. Phys. J.
Star Formation Efficiency in the Central 1 kpc Region of Early-Type Spiral Galaxies
It has been reported recently that there are some early-type spiral (Sa--Sab)
galaxies having evident star-forming regions which concentrate in their own
central 1-kpc. In such central region, is the mechanism of the star formation
distinct from that in disks of spiral galaxies? To reveal this, we estimate the
star formation efficiency (SFE) in this central 1-kpc star-forming region of
some early-type spiral galaxies, taking account of the condition for this 1-kpc
region to be self-gravitating. Using two indicators of present star formation
rate (H and infrared luminosity), we estimate the SFE to be a few
percents. This is equivalent to the observational SFE in the disks of late-type
spiral (Sb--) galaxies. This coincidence may support the universality of the
mean SFE of spiral galaxies reported in the recent studies. That is, we find no
evidence of distinct mechanism of the star formation in the central 1-kpc
region of early-type galaxies. Also, we examine the structure of the central
star-forming region, and discuss a method for estimating the mass of
star-forming regions.Comment: accepted by A
The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118: A Violently Interacting Galaxy with Peculiar Kinematics
We present observations of the distribution and kinematics of neutral and
ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system.
Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk
of NGC 1144, but HI emission is detected over only 1/3 of this velocity range,
in an area that corresponds to the NW half of the disk. In the nuclear region
of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is
observed. Faint, narrow HI absorption lines are also detected against radio
sources in the SE part of the disk of NGC 1144, which includes regions of
massive star formation and a Seyfert nucleus. The peculiar HI distribution,
which is concentrated in the NW disk, seems to be the inverse of the molecular
distribution which is concentrated in the SE disk. Although this may partly be
the result of the destruction of HI clouds in the SE disk, there is
circumstantial evidence that the entire HI emission spectrum of NGC 1144 is
affected by a deep nuclear absorption line covering a range of 600 km/s, and is
likely blueshifted with respect to the nucleus. In this picture, a high
column-density HI stream is associated with the nuclear ionized gas velocity
discontinuity, and the absorption effectively masks any HI emission that would
be present in the SE disk of NGC 1144.Comment: manuscript, arp118.ps: 28 pages; 1 Table: arp118.tab1.ps; 16 Figures:
arp118.fig1-16.ps; Accepted to Ap
Does the Slim-Disk Model Correctly Consider Photon-Trapping Effects?
We investigate the photon-trapping effects in the super-critical black hole
accretion flows by solving radiation transfer as well as the energy equations
of radiation and gas. It is found that the slim-disk model generally
overestimates the luminosity of the disk at around the Eddington luminosity
(L_E) and is not accurate in describing the effective temperature profile,
since it neglects time delay between energy generation at deeper inside the
disk and energy release at the surface. Especially, the photon-trapping effects
are appreciable even below L ~ L_E, while they appear above ~ 3L_E according to
the slim disk. Through the photon-trapping effects, the luminosity is reduced
and the effective temperature profile becomes flatter than r^{-3/4} as in the
standard disk. In the case that the viscous heating is effective only around
the equatorial plane, the luminosity is kept around the Eddington luminosity
even at very large mass accretion rate, Mdot>>L_E/c^2. The effective
temperature profile is almost flat, and the maximum temperature decreases in
accordance with rise in the mass accretion rate. Thus, the most luminous radius
shifts to the outer region when Mdot/(L_E/c^2) >> 10^2. In the case that the
energy is dissipated equally at any heights, the resultant luminosity is
somewhat larger than in the former case, but the energy-conversion efficiency
still decreases with increase of the mass accretion rate, as well. The most
luminous radius stays around the inner edge of the disk in the latter case.
Hence, the effective temperature profile is sensitive to the vertical
distribution of energy production rates, so is the spectral shape. Future
observations of high L/L_E objects will be able to test our model.Comment: 10 pages, 7 figures, accepted for publication in Ap
A Population of Faint Non-Transient Low Mass Black Hole Binaries
We study the thermal and viscous stability of accretion flows in Low Mass
Black Hole Binaries (LMBHBs). We consider a model in which an inner
advection-dominated accretion flow (ADAF) is surrounded by a geometrically thin
accretion disk, the transition between the two zones occurring at a radius
R_tr. In all the known LMBHBs, R_tr appears to be such that the outer disks
could suffer from a global thermal-viscous instability. This instability is
likely to cause the transient behavior of these systems. However, in most
cases, if R_tr were slightly larger than the estimated values, the systems
would be globally stable. This suggests that a population of faint persistent
LMBHBs with globally stable outer disks could be present in the Galaxy. Such
LMBHBs would be hard to detect because they would lack large amplitude
outbursts, and because their ADAF zones would have very low radiative
efficiencies, making the systems very dim. We present model spectra of such
systems covering the optical and X-ray bands.Comment: LateX, 37 pages, 11 figures; Accepted for publication in The
Astrophysical Journa
Model for Relaxation Oscillations of Luminous Accretion Disk in GRS1915+105: Variable Inner Edge
To understand the bursting behavior of the microquasar GRS 1915+105, we
calculate time evolution of a luminous, optically thick accretion disk around a
stellar mass black hole undergoing limit-cycle oscillations between the high-
and low- luminosity states. We, especially, carefully solve the behavior of the
innermost part of the disk, since it produces significant number of photons
during the burst, and fit the theoretical spectra with the multi-color disk
model. The fitting parameters are \Tin (the maximum disk temperature) and
\Rin (the innermost radius of the disk). We find an abrupt, transient
increase in \Tin and a temporary decrease in \Rin during a burst, which are
actually observed in GRS 1915+105. The precise behavior is subject to the
viscosity prescription. We prescribe the radial-azimuthal component of
viscosity stress tensor to be ,
with being the height integrated pressure, and being the
parameter, and and being the total pressure and gas pressure
on the equatorial plane, respectively. Model with can produce the
overall time changes of \Tin and \Rin, but cannot give an excellent fit to
the observed amplitudes. Model with , on the other hand, gives the
right amplitudes, but the changes of \Tin and \Rin are smaller. Although
precise matching is left as future work, we may conclude that the basic
properties of the bursts of GRS 1915+105 can be explained by our ``limit-cycle
oscillation'' model. It is then required that the spectral hardening factor at
high luminosities should be about 3 at around the Eddington luminosity instead
of less than 2 as is usually assumed.Comment: 11 pages, 5 figures, accepted for publication in Ap
Magic numbers in exotic nuclei and spin-isospin properties of {\it NN} interaction
The magic numbers in exotic nuclei are discussed, and their novel origin is
shown to be the spin-isospin dependent part of the nucleon-nucleon interaction
in nuclei. The importance and robustness of this mechanism is shown in terms of
meson exchange, G-matrix and QCD theories. In neutron-rich exotic nuclei, magic
numbers such as N = 8, 20, etc. can disappear, while N = 6, 16, etc. arise,
affecting the structure of lightest exotic nuclei to nucleosynthesis of heavy
elements.Comment: 4 pages, 3 figures, revte
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