Status Report

Astrophysics astro-ph new abstracts 5 September 2000

By SpaceRef Editor
September 5, 2000
Filed under

Astrophysics


astro-ph new abstracts, Tue, 5 Sep 00 04:00:14 GMT
0009028 — 0009050 received




astro-ph/0009028 [abs, src, ps, other] :




Title: Clusters of Galaxies at High Redshift: The LMT/GTM Perspective

Authors:
Omar Lopez-Cruz (1),
Enrique Gaztanaga (1) ((1) INAOE-Tonantzintla)

Comments: 8 pages, 4 figures, needs newpasp.sty. To be published in the
proceedings of the conference “Mapping the Hidden Universe” held in
Guanjuato, Mexico (February 23-29, 2000), R.C. Kraan-Korteweg, P.A. Henning,
and H. Andernach, eds. ASP Conf. Ser


The lack of reliable cluster samples at intermediate and high redshift has
motivated many optical/infrared and X-ray cluster searches. The motivation of
such searches is well justified: the abundance of massive collapsed regions
gives a direct constraint on Omega(matter). Alternatively, the
Sunyaev-Zeldovich effect (SZE) offers a robust method for the detection of
clusters which is, almost, independent of redshift. In this paper we comment on
the possibility of mapping the SZE at high resolution in the millimeter regime
using the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT/GTM) and
the bolometer array BOLOCAM. The construction of the LMT/GTM facility is
underway atop Cerro La Negra (latitude=18deg 59min; height=4600 m) in Mexico.
(60kb)




astro-ph/0009029 [abs, src, ps, other] :




Title: Photometric Properties of Low-Redshift Galaxy Clusters (LOCOS)

Authors:
Omar Lopez-Cruz (1,2) ((1) INAOE-Tonantzintla, (2) Department of Astronomy, U of Toronto)

Comments: 6 pages, 5 figures, uses rmaa.cls and rmaacite.sty. Invited Ph.D.
Thesis presentation to appear in the proceedings of IX RRLA of the IAU/UAI
held in Tonantzintla, Mexico (November 9-13, 1998), L. Aguilar & A.
Carraminana, eds., Rev. Mex. A & A Serie Conferencias


A comprehensive multicolor survey was undertaken to investigate global
optical properties of Abell clusters of galaxies. This survey was christened
the “Low-Redshift Cluster Optical Survey” (LOCOS). LOCOS was devised to search
for patterns of galaxy evolution induced by the environment. The generated data
base contains accurate deep CCD photometric measurements (Kron-Cousins R,,B and
I) for a sample of 46 low-redshift (0.04 <= z <= 0.18) Abell clusters. This is
one of the few large surveys that included the contribution due to dwarf
galaxies (about 5.5 mag deeper than the R characteristic magnitude (M*); Ho=50
km/s/Mpc, qo=0). Due to space restrictions only the main results concerning the
variations at the bright-end of the luminosity function (LF) are presented
here. Other results are presented elsewhere (Lopez-Cruz & Yee 2000a,b). We have
detected clear variations at both the bright end and the faint end of the LF.
The nature of the variations at the bright end revealed that poor cD clusters
have dimmer M*. We can explain these variations as a result of dynamical
friction. On the other hand, non-cD clusters seem to have unaffected LFs. A
third class termed as binary clusters seems to be a transition class that might
have resulted from cluster-cluster mergers.
(43kb)




astro-ph/0009030 [abs, src, ps, other] :




Title: Dwarf Galaxies in Clusters: the Effects of a Violent Environment

Authors:
Omar Lopez-Cruz (1),
H.K.C. Yee (2) ((1) INAOE-Tonantzintla, (2) Department of Astronomy, U. of Toronto)

Comments: 4 pages, 2 figures. Published in the proceedings of the International
Symposium on Astrophysics Research and Science Education, Castel Gandolfo,
Italy, June 14-21, 1998. edited by C. Impey

Journal-ref: O. Lopez-Cruz and H.K.C. Yee. 1999, in Symposium on Astrophys.
Research and Sci. Edu., edited by C. Impey, (Vatican City: Libreria Editrice
Vaticana) pp. 262-266


Recent observations suggest that dwarf galaxies pervade the universe, for
they have been encountered in large numbers in all the environments. However,
we present evidence that suggests dwarf galaxies may be subject to strong
dynamical processes in high density environments, the combined effects of
multiple encounters and the tidal effects due to the potential well of rich
clusters could result in the effective disruption of dwarf galaxies in the
clusters’ central regions. Alternatively, the lack of dwarf galaxies in rich
environments has been interpreted in terms of a “density-morphology relation”:
dwarf galaxies prefer low density environments (Phillipps et al. 1998). We
argue that such an explanation cannot account for the relationship between the
cD halo luminosity and the gas mass in the ICM, whereas the dwarf disruption
scenario proposed by Lopez-Cruz et al. (1997) addresses this naturally.
(16kb)




astro-ph/0009031 [abs, src, ps, other] :




Title: The Proper Motion, Parallax, and Origin of the Isolated Neutron Star RX
J185635-3754

Authors:
Frederick M. Walter

Comments: Accepted by ApJ


The isolated neutron star RX J185635-3754 is the closest known neutron star
to the Sun. Based on HST WFPC2 obervations over a 3 year baseline, I report its
proper motion (332 +/- 1 mas/yr at a position angle of 100.3 +/- 0.1 degrees)
and parallax (16.5 +/- 2.3 mas; 61 pc). This proper motion brings the neutron
star from the general vicinity of the Sco-Cen OB association. For an assumed
neutron star radial velocity of -45 km/s, the runaway O star zeta Oph, the
Upper Sco OB association, and the neutron star come into spatial coincidence
1.15 +/- .15 million years ago. RX J185635-3754 may be the remnant of the
original primary of the zeta Oph system. If so, the space velocity suggests
that the neutron star received a kick of about 200 km/s at birth.
(119kb)




astro-ph/0009032 [abs, src, ps, other] :




Title: Scaling properties of the redshift power spectrum: theoretical models

Authors:
Y.P. Jing (Partner Group of MPA, Shanghai Observatory),
G. Boerner (MPA, Garching)

Comments: submitted for publication in ApJ;24 pages with 7 figures included


We report the results of an analysis of the redshift power spectrum
$P^S(k,mu)$ in three typical Cold Dark Matter (CDM) cosmological models, where
$mu$ is the cosine of the angle between the wave vector and the
line-of-sight. Two distinct biased tracers derived from the primordial
density peaks of Bardeen et al. and the cluster-underweight model of Jing, Mo,
& B”orner are considered in addition to the pure dark matter models. Based on
a large set of high resolution simulations, we have measured the redshift power
spectrum for the three tracers from the linear to the nonlinear regime. We
investigate the validity of the relation -guessed from linear theory-in the
nonlinear regime $$ P^S(k,mu)=P^R(k)[1+etamu^2]^2D(k,mu,sigma_{12}(k)),
$$ where $P^R(k)$ is the real space power spectrum, and $eta$ equals
$Omega_0^{0.6}/b_l$. The damping function $D$ which should generally depend on
$k$, $mu$, and $sigma_{12}(k)$, is found to be a function of only one
variable $kmusigma_{12}(k)$. This scaling behavior extends into the nonlinear
regime, while $D$ can be accurately expressed as a Lorentz function- well
known from linear theory- for values $D > 0.1$. The difference between
$sigma_{12}(k)$ and the pairwise velocity dispersion defined by the 3-D
peculiar velocity of the simulations (taking $r=1/k$) is about 15%. Therefore
$sigma_{12}(k)$ is a good indicator of the pairwise velocity dispersion. The
exact functional form of $D$ depends on the cosmological model and on the bias
scheme. We have given an accurate fitting formula for the functional form of
$D$ for the models studied.
(334kb)




astro-ph/0009033 [abs, src, ps, other] :




Title: HST as a powerful astrometric tool for pulsar astronomy

Authors:
R.P. Mignani (1),
P.A. Caraveo (2),
A. De Luca (2) ((1) STECF-ESO, Garching, Germany, (2) IFC-CNR, Milan, Italy)

Comments: 5 pages, 2 PostScript figures, uses psfig.sty. To appear in the
proceedings of A Decade of HST Science (Baltimore, USA, April 2000)


Given their intrinsic faintness, isolated neutron stars represent an elusive
target for optical astronomy. Up to date, an optical counterpart has been
identified only for a very tiny fraction of the overall population of more than
1000 radio pulsars. The HST contributions to the optical studies of isolated
neutron stars have been recently reviewed by Mignani et al. (2000) and by
Caraveo et al. (these proceedings). Here, we review its specific contribution
in the field of pulsar astrometry and kinematics.
(58kb)




astro-ph/0009034 [abs, src, ps, other] :




Title: HST as a reliable astrometric tool for pulsar astronomy: the cases of
the Vela and Geminga pulsars

Authors:
A. De Luca (1),
R.P. Mignani (2),
P.A. Caraveo (1) ((1) IFC-CNR, Milan, Italy, (2) STECF-ESO, Garching, Germany)

Comments: 4 pages, 2 PostScript figures, uses psfig.sty. To appear in the
proceedings of A Decade of HST Science (Baltimore, USA, April 2000)


The quest for the distance of the Vela and Geminga pulsars yielded, so far, a
set of four WFPC2 images for each object. The availability of couples of images
taken at the same period of the year, thus affected by the same parallactic
displacement, prompted us to use Vela and Geminga as test cases to assess the
reliability of HST astrometry.
(167kb)




astro-ph/0009035 [abs, src, ps, other] :




Title: SNR0540-69 -the Crab twin- revisited: Chandra vs. HST

Authors:
P.A. Caraveo (1),
R.P. Mignani (2),
A. De Luca (1),
S.Wagner (3),
G.F. Bignami (4) ((1) IFC-CNR, Milan, Italy, (2) STECF-ESO, Garching, Germany, (3) LaundesSternwarte, Konigstuhl-Heidelberg, Germany, (4) ASI, Rome, Italy)

Comments: 4 pages, 2 PostScript figures, uses psfig.sty. To appear in the
proceedings of A Decade of HST Science (Baltimore, USA, April 2000)


High resolution images of the Crab-like SNR SNR0540-69 have been recently
obtained by the HRC, on board the Chandra X-ray Observatory, and by the FORS1
instrument, attached to ESO/VLT1. A detailed comparison of these images with an
archival Planetary Camera one will be presented.
(152kb)




astro-ph/0009036 [abs, src, ps, other] :




Title: Canonical Timing and Spectral Behavior of LMC X-3 in the Low/Hard State

Authors:
Patricia T. Boyd,
Alan P. Smale (NASA/GSFC),
Jeroen Homan,
Peter G. Jonker,
Michiel van der Klis (Univ. Amsterdam, CHEAF),
Erik Kuulkers (SRON, Univ. Utrecht)

Comments: 5 pages, 3 figures, accepted for ApJ Letters


We present results from three observations with the Rossi X-ray Timing
Explorer (RXTE) of LMC X-3, obtained while the source was in an extended
‘low/hard’ state. The data reveal a hard X-ray spectrum which is well fit by a
pure power law with photon index Gamma=1.69+/-0.02, with a source luminosity at
50 kpc of 5-16×10^{36}erg/s (2–10 keV). Strong broad-band (0.01-100 Hz) time
variability is also observed, with fractional rms amplitude 40+/-4%, plus a
quasi-periodic oscillation (QPO) peak at 0.46+/-0.02 Hz with rms amplitude
~14%. This is the first reported observation in which the full canonical
low/hard state behavior (pure hard power law spectrum combined with strong
broad-band noise and QPO) for LMC X-3 is seen. We reanalyze several archival
RXTE observations of LMC X-3 and derive consistent spectral and timing
parameters, and determine the overall luminosity variation between high/soft
and low/hard states. The timing and spectral properties of LMC X-3 during the
recurrent low/hard states are quantitatively similar to that typically seen in
the Galactic black hole candidates.
(34kb)




astro-ph/0009037 [abs, src, ps, other] :




Title: Morphological classification of high redshift galaxies

Authors:
E. Pignatelli (1),
G. Fasano (2) ((1) SISSA/ISAS, (2) Osservatorio Astronomico di Padova)

Comments: 4 pages, 3 encapsulated figures. Proceedings of the Euroconference
“The Evolution of Galaxies.I- Observational clues.” held in Granada (Spain),
23-27 May, 2000. To be published in a special issue of Astrophysics and Space
Science journal


We present GASPHOT, a tool for automated surface photometry and morphological
classification of galaxies in deep and wide fields. The requirements for any
such tool are reviewed, and its use for the classification of high-z galaxies
is presented. In the case if HDF-like images, for galaxies having a magnitude
ranging from 24 to 27.5, the uncertainties on the photometric parameters
derived from GASPHOT are respectively 0.02-0.1 on magnitude, 0.03 on the
logarithm of the scale length, 0.02-0.5 on the Sersic index n used to classify
the surface brightness profile of the galaxies. A comparison with the results
achieved using Sextractor is presented.
(37kb)




astro-ph/0009038 [abs, src, ps, other] :




Title: The Ultra-Luminous IR Galaxy Population

Authors:
K. D. Borne (1 and 2),
H. Bushouse (3),
L. Colina (4),
R. A. Lucas (3),
S. Arribas (5) ((1) Raytheon Information Technology and Scientific Services, (2) NASA Goddard Space Flight Center, (3) Space Telescope Science Institute, (4) Instituto de Fisica de Cantabria, Santander, Spain, (5) Instituto de Astrofisica de Canarias, Tenerife, Spain)

Comments: 2 pages; requires newpasp.sty. Paper to appear in the ASP Conference
Series for the May 2000 conference “Gas and Galaxy Evolution” (Socorro, NM),
edited by J. E. Hibbard, M. P. Rupen and J. H. van Gorkom


We summarize results from an on-going Hubble Space Telescope (HST) survey of
a large sample of ULIRGs (Ultra-Luminous IR Galaxies). New ground-based
multi-fiber spectroscopic observations are now being obtained to complement the
HST data and to assist in the interpretation of these complex objects.
(8kb)




astro-ph/0009039 [abs, src, ps, other] :




Title: Southern Hemisphere Observation of a $10^{18}$eV Cosmic Ray Near the
Direction of the Galactic Centre

Authors:
J. A. Bellido,
R. W. Clay,
B. R. Dawson,
M. Johnston-Hollitt (The University of Adelaide)

Comments: 14 pages, 5 postscript figures, to be published in Astroparticle
Physics


We report on an analysis of data from the southern hemisphere SUGAR cosmic
ray detector. We confirm the existence of an excess of $10^{18}$eV cosmic rays
from a direction close to the Galactic Centre, first reported by the AGASA
group. We find that the signal is consistent with that from a point source, and
we find evidence for an excess of cosmic rays coming from the direction of the
Galactic Centre itself.
(126kb)




astro-ph/0009040 [abs, src, ps, other] :




Title: Secondary CMB anisotropies from the kinetic SZ effect

Authors:
P. Valageas,
A. Balbi,
J. Silk

Comments: 16 pages, submitted to A&A


We present an analytic model, based on previous works which tackled the
reionization history of the universe, which allows us to describe the
generation of the secondary CMB anisotropies due to the kinetic SZ effect. We
take into account the “patchy pattern” of reionization (HII bubbles), the
cross-correlations of these ionized regions, the small-scale fluctuations of
the matter density field and the contribution from collapsed objects. For an
open universe, we find that the power-spectrum $l(l+1)C_l/(2pi)$ exhibits a
plateau of height $10^{-13}$ in the range $10^3 < l < 10^6$. We find that for
large wavenumbers $l > 10^4$ the signal is dominated by the contribution from
collapsed halos while for $l < 10^4$ it is governed by the large-scale
correlations of HII bubbles. This implies that one cannot discriminate
reionization by stars from a quasar-driven scenario since the size of ionized
regions never dominates the behaviour of the anisotropies. Moreover, the
secondary CMB anisotropies arise from a broad range of redshifts (7.5<z<10 for
the IGM and 0<z<7 for galactic halos). The signal expected in our model might
bias the cosmological parameter estimation from CMB experiments such as Planck
and could be detected by future mm-wavelength interferometers (e.g., ALMA).
(60kb)




astro-ph/0009041 [abs, src, ps, other] :




Title: Maximum Galactic Disks vs. Hot Dark Halos

Authors:
Daniel Pfenniger

Comments: 5 pages, 1 figure, to appear in “Gas & Galaxy Evolution”, VLA 20th
Anniversary Conference, J.E. Hibbard, M.P. Rupen & J.H. van Gorkom (eds.)


A series of arguments is presented for heavy galaxy disks not only in the
optical regions, but also in the dark matter dominated regions of spirals. We
are testing this possibility with extreme maximum disk N-body models without
any conventional spheroidal dark halo.
(65kb)




astro-ph/0009042 [abs, src, ps, other] :




Title: Constraining our Universe with X-ray & Optical Cluster Data

Authors:
J.M. Diego,
E. Martinez-Gonzalez,
J.L. Sanz,
L. Cayon,
J. Silk

Comments: 11 pages, 7 figures. Submitted to MNRAS


We have used recent X-ray and optical data in order to impose some
constraints on the cosmology and cluster scaling relations. Generically two
kind of hypotheses define our model. First we consider that the cluster
population is well described by the standard Press-Schechter (PS) formalism,
and second, these clusters are supposed to follow scaling relations with mass:
Temperature-Mass (T-M) and X-ray Luminosity-Mass (L_x – M). As a difference
with many other authors we do not assume specific scaling relations to model
cluster properties such as the usual $T-M$ virial relation or one observational
determination of the $L_x-T$ relation. Instead we consider general free
parameter scaling relations. With the previous model (PS plus scalings) we fit
our free parameters to several X-ray and optical data with the advantage over
many other works that we consider all the data sets at the same time. This
prevents us from being inconsistent with some of the available observations.
Among other interesting conclusions, we find that only low-density universes
are compatible with all the data considered and that the degeneracy between
$Omega_m$ and $sigma_8$ is broken. Also we obtain interesting limits on the
parameters characterizing the scaling relations.
(135kb)




astro-ph/0009043 [abs, src, ps, other] :




Title: Molecular cloud complexes in detail: Interferometric observations of
GMCs in M31

Authors:
N. Neininger

Comments: 4 pages, 3 figures, includes procl.sty; presented at “The
interstellar medium of M31 and M33”


We have accumulated 12CO(1-0) and (2-1) data of several GMCs in M31 using the
Plateau de Bure Interferometer. The sample covers a range of 5 to 18 kpc
galactocentric distance and various physical conditions. The spatial resolution
attains values down to 3 pc. All GMCs investigated have been resolved into
several components, also seemingly quiescent clouds and not only the cases
where already the survey positions show obvious multiple-peaked spectra. Such
kinematically disjunct emission is however spatially coincident in the small
volume of the interferometer beam in M31, which strongly favours local effects
as the cause of the velocity splitting. This is well consistent with the
observed absence of strong streaming motions in the survey data. The nature of
the sometimes strong separation in velocity space needs further investigation.
The complete data set (i.e. including the large-scale survey) yields a uniquely
complete view of the molecular gas which allows to investigate the conditions
for star formation in detail and helps to establish guide lines for the
derivation of the properties of molecular gas.
(193kb)




astro-ph/0009044 [abs, src, ps, other] :




Title: Hard X-rays from Type II bursts of the Rapid Burster and its transition
toward quiescence

Authors:
N. Masetti,
F. Frontera,
L. Stella,
M. Orlandini,
A.N. Parmar,
S. Del Sordo,
L. Amati,
E. Palazzi,
D. Dal Fiume,
G. Cusumano,
G. Pareschi,
I. Lapidus,
R.A. Remillard

Comments: 11 pages, 8 figures, accepted by A&A, main journal


We report on 4 BeppoSAX Target Of Opportunity observations of MXB 1730-335,
the Rapid Burster (RB), made during the 1998 February-March outburst. In the
first observation, approximately 20 days after the outburst peak, the X-ray
light curve showed Type II bursts at a rate of 43 per hour. Nine days later,
during the second BeppoSAX pointing, only 5 Type II bursts were detected at the
beginning of the observation. During the third pointing no X-ray bursts were
detected and in the fourth and final observation the RB was not detected at
all. Persistent emission from the RB was detected up to 10 keV during the first
three pointings. The spectra of the persistent and bursting emissions below 10
keV were best fit with a model consisting of two blackbodies. An additional
component (a power law) was needed to describe the 1-100 keV bursting spectrum
when the persistent emission was subtracted. To our knowledge, this is the
first detection of the RB beyond 20 keV. We discuss the evolution of the
spectral parameters for the bursting and persistent emission during the
outburst decay. The light curve, after the second BeppoSAX pointing, showed a
steepening of the previous decay trend, and a sharper decay rate leading to
quiescence was observed with BeppoSAX in the two subsequent observations. We
interpret this behaviour as caused by the onset of the propeller effect.
Finally, we infer a neutron star magnetic field B ~ 4 10^8 Gauss.
(191kb)




astro-ph/0009045 [abs, src, ps, other] :




Title: Depletion of background galaxies due to the cluster lens CL0024+1654: U
and R band observations

Authors:
O. E. Rognvaldsson (1),
T. R. Greve (2),
J. Hjorth (2),
E. H. Gudmundsson (3),
V. S. Sigmundsson (3),
P. Jakobsson (2,3),
A. O. Jaunsen (4),
L. L. Christensen (5),
E. van Kampen (6),
A. N. Taylor (6) ((1) NORDITA, (2) Univ. of Copenhagen, (3) Univ. of Iceland, (4) Univ. of Oslo, (5) ST-ECF/ESO Garching, (6) Univ. of Edinburgh)

Comments: 11 pages, 12 figures, submitted to MNRAS


We have obtained U and R band observations of the depletion of background
galaxies due to the gravitational lensing of the galaxy cluster CL0024+1654
(z=0.39). The radial depletion curves show a significant depletion in both
bands within a radius of 40”-70” from the cluster center. This is the first
time depletion is detected in the U band. This gives independent evidence for a
break in the slope of the U band luminosity function at faint magnitudes. The
radially averaged R band depletion curve is broader and deeper than in the U
band. The differences can be attributed to the wavelength dependence of the
slope of the luminosity function and to the different redshift distribution of
the objects probed in the two bands. We estimate the Einstein radius of a
singular isothermal sphere lens model using maximum likelihood analysis.
Adopting a slope of the number counts of 0.2 and using the background density
found beyond 150” from the cluster center we find an Einstein radius of
17”+/-3” and 25”+/-3” in the U and R band, respectively. When combined with
the redshift of the single background galaxy at z=1.675 seen as four giant arcs
around 30” from the cluster center, these values indicate a median redshift in
the range 0.7 to 1.1 for the U_AB > 24 mag and R_AB > 24 mag populations.
(462kb)




astro-ph/0009046 [abs, src, ps, other] :




Title: Using Perturbative Least Action (PLA) to Reconstruct Redshift Space
Distortions

Authors:
David M. Goldberg (Yale University; Princeton University Observatory)

Comments: 18 Pages LaTeX, including 5 postscript figures. Submitted to
Astrophysical Journal


In this paper, we apply the Perturbative Least Action Method to model the
Local Group of galaxies for various Cosmological models. We show that though
the galaxy masses are theoretically good discriminators of $Omega_M$ given
some observed MW and M31 separation and radial velocity, current estimates of
the masses are insufficient to make any cosmological claims. We then discuss
additional complications to expand this analysis.
(29kb)




astro-ph/0009047 [abs, src, ps, other] :




Title: Neon abundances in normal late-B and mercury-manganese stars

Authors:
M. M. Dworetsky (University College London)
J. Budaj (UCL and Astron. Inst. Slovak Acad. Sciences)

Comments: 10 pages, 1 figure, received 23 June 2000, accepted 4 August 2000, by
Monthly Notices of the Royal Astronomical Society


We make new Non-LTE calculations to deduce abundances of neon from
visible-region echelle spectra of selected Ne I lines in 7 normal stars and 20
HgMn stars. We find that the best strong blend-free Ne line which can be used
at the lower end of the Teff range is 6402 A, although several other
potentially useful Ne I lines are found in the red region of the spectra of
these stars. The mean neon abundance in the normal stars (log A =8.10) is in
excellent agreement with the standard abundance of neon (8.08). However, in
HgMn stars, neon is almost universally underabundant, ranging from marginal
deficits of 0.1-0.3 dex to underabundances of an order of magnitude or more. In
many cases, the lines are so weak that only upper limits can be established.
The most extreme example found is upsilon Her with an underabundance of at
least 1.5 dex. These underabundances are qualitatively expected from radiative
acceleration calculations, which show that Ne has a very small radiative
acceleration in the photosphere and is expected to undergo gravitational
settling if mixing processes are sufficiently weak, and there is no strong
stellar wind. According to the theoretical predictions of Landstreet et al.
(1998), the low Ne abundances place an important constraint on the intensity of
such stellar winds, which must be less than $10^-14 M_sun per yr if they are
non-turbulent.
(55kb)




astro-ph/0009048 [abs, src, ps, other] :




Title: H_0 from gravitational lenses: recent results

Authors:
Paul L. Schechter

Comments: 10 pages, no figures, uses newpasp.sty, invited review to be
published in IAU Symposium No. 201: New Cosmological and the Values of the
Fundamental Parameters, eds. A.N. Lasenby and A. Wilkinson


The 0th, 1st and 2nd derivatives of a “Fermat potential” give the three D’s
of gravitational lensing: delay, deflection and distortion. Observations of
these delays, deflections and distortions for doubly and quadruply imaged
quasars give estimates of Hubble’s constant, H_0. The single largest
contribution to the uncertainty in H_0 arises from the difficulty in
constraining the degree of central concentration of the lensing potential.
Fortunately, astronomers have spent a good deal of effort over the past quarter
century addressing just this question. If galaxies at z=0.5 are like nearby
galaxies, the associated systematic uncertainty in H_0 is less than 10%. The
expected lens-to-lens scatter is 20%. Results from three particularly well
constrained systems are reported.
(15kb)




astro-ph/0009049 [abs, src, ps, other] :




Title: The Orbital Period of Intermediate Polar 1WGA J1958.2+3232

Authors:
Sergei. V. Zharikov,
Gaghik. H. Tovmassian,
Juan Echevarria,
Aixa Aube Cardenas; (Observatorio Astronomico Nacional, Instituto de Astronomia, UNAM, Ensenada, B.C., Mexico)

Comments: 6 pages, Latex, aa.cls style, submitted to Astronomy and Astrophysics


The detection of the orbital period of 4.36his reported for the new
Intermediate Polar 1 WGA 1958.2+3232. The orbital period was derived from
time-resolved photometric and spectral observations. We also confirmed the 733
sec spin period of the White Dwarf consistent with the X-ray pulsations and
were able to distinguish the beat period in the light curve. Strong modulations
with orbital period are detected in the emission spectral lines from spectral
observations. They show the presence of a bright hot spot on the edge of the
accretion disk.

The parameters of this recently discovered Intermediate Polar are determined.
(213kb)




astro-ph/0009050 [abs, src, ps, other] :




Title: Do High-Velocity Clouds Really Fuel Galactic Star Formation?

Authors:
Brad K. Gibson (Swinburne),
Mark L. Giroux (Colorado),
John T. Stocke (Colorado),
J. Michael Shull (Colorado)

Comments: 6 pages, LaTeX (newpasp, included), also available at
this http URL, to appear in Gas &
Galaxy Evolution (ASP Conf. Series), eds. J.E. Hibbard, M.P. Rupen & J.H. van
Gorkom (2001, in press)


Tantalizing evidence has been presented supporting the suggestion that a
large population of extragalactic gas clouds permeates the Local Group, a
population which has been associated with the Galactic High-Velocity Clouds
(HVCs). We comment on both the strengths and weaknesses of this suggestion,
informally referred to as the Blitz/Spergel picture. Theoretical predictions
for the spatial and kinematic distributions, metallicities, distances, and
emission properties of Blitz/Spergel HVCs will be confronted with extant
observational data.
(11kb)




Cross-listings




gr-qc/0009003 [abs, src, ps, other] :




Title: Minimal Model of Dilatonic Gravity and Cosmological Constant

Authors:
P.Fiziev

Comments: 4 pages, latex, no figures

We consider: minimal scalar-tensor model of gravity with Brans-Dicke factor
$omega(Phi)equiv 0$ and cosmological factor $Pi(Phi)$; restrictions on it
from gravitational experiments; qualitative analysis of new approach to
cosmological constant problem based on the huge amount of action in Universe;
determination of $Pi(Phi)$ using time evolution of scale factor of Universe.
(10kb)




hep-ph/0008288 [abs, src, ps, other] :




Title: Primordial magnetic fields from metric perturbations

Authors:
Antonio L. Maroto

Comments: 8 pages, 2 figures

We study the amplification of electromagnetic vacuum fluctuations induced by
the evolution of scalar metric perturbations at the end of inflation. Such
perturbations break the conformal invariance of Maxwell equations in
Friedmann-Robertson-Walker backgrounds and allow the growth of magnetic fields
on super-Hubble scales. We estimate the strength of the fields generated by
this mechanism on galactic scales and compare the results with the present
bounds on the galactic dynamo seed fields.
(27kb)




hep-th/0009010 [abs, src, ps, other] :




Title: Density perturbations in the brane-world

Authors:
Christopher Gordon (Portsmouth),
Roy Maartens (Portsmouth)

Comments: 6 pages, 1 figure


In Randall-Sundrum-type brane-world cosmologies, density perturbations
generate Weyl curvature in the bulk, which in turn backreacts on the brane via
stress energy gradients. On super-Hubble scales, the perturbation equations
form a closed system on the brane, which may be solved without knowledge of the
bulk dynamics. Bulk effects produce a non-adiabatic mode, even when the matter
perturbations are adiabatic, thus altering the standard evolution of
large-scale fluctuations in general relativity. The metric perturbation is not
constant during high-energy inflation and the early high-energy radiation era.
(14kb)




nucl-th/0008065 [abs, src, ps, other] :




Title: Nuclear Aspects of Nucleosynthesis in Massive Stars

Authors:
T. Rauscher (1,2),
R.D. Hoffman (3),
A. Heger (2),
S.E. Woosley (2) ((1) University of Basel, Switzerland; (2) UCSC, USA; (3) Lawrence Livermore National Laboratory, USA)

Comments: 6 pages, 2 figures; invited talk, to appear in the Proceedings of the
Int. Conf. “Structure of the Nucleus at the Dawn of the Century”, May 2000,
Bologna, Italy


Preliminary results of a new set of stellar evolution and nucleosynthesis
calculations for massive stars are presented. These results were obtained with
an extended reaction network up to Bi. The discussion focuses on the importance
of nuclear rates in pre- and post-explosive nucleosynthesis. The need for
further experiments to study specific reactions and nuclear properties (optical
alpha+nucleus potentials) is emphasized.
(35kb)




Replacements




gr-qc/9907063 [abs, pdf] :




Title: Holography, Quantum Geometry, and Quantum Information Theory

Authors:
P. A. Zizzi

Comments: 41 pages. Typos corrected, minor changes, references added.
Contribution to the 8th UK Foundations of Physics Meeting, 13-17 September,
1999, Imperial College, London, UK replaced corrupted ps file with PDF file

Subj-class: General Relativity and Quantum Cosmology; Mathematical Physics

Journal-ref: Entropy, 2 (2000) 39-69

Note: replaced with revised version Mon, 4 Sep 2000 07:40:24 GMT (190kb)



astro-ph/0003050 [abs, src, ps, other] :




Title: Systematic uncertainties in gravitational lensing models: a
semi-analytical study of PG1115+080

Authors:
HongSheng Zhao,
Danny Pronk (Leiden Observatory)

Comments: Some small corrections and clarifications added. 20 pages, 11
figures, accepted by MNRAS

Note: replaced with revised version Mon, 4 Sep 2000 13:14:55 GMT (413kb)



astro-ph/0004334 [abs, src, ps, other] :




Title: Linear Redshift Distortions and Power in the PSCz Survey

Authors:
A. J. S. Hamilton (JILA),
Max Tegmark (Penn),
Nikhil Padmanabhan (Stanford)

Comments: Minor changes to agree with accepted version. Slight changes to power
spectrum, including one more point added at large scales, from binning points
formerly discarded as too noisy. 5 pages, including 4 embedded PostScript
figures. Accepted for publication in MNRAS Letters (pink pages). Power
spectrum data available at this http URL

Note: replaced with revised version Sat, 2 Sep 2000 14:41:52 GMT (86kb)



astro-ph/0005042 [abs, src, ps, other] :




Title: Carbon and Oxygen Galactic Abundance Gradients: A Comparative Study of
Stellar Yields

Authors:
Leticia Carigi

Comments: 30 pages, 5 figures, submitted Rev. Mex. Astrono. Astrop

Note: replaced with revised version Mon, 4 Sep 2000 15:46:12 GMT (78kb)



astro-ph/0007044 [abs, src, ps, other] :




Title: Suppression of giant planet formation in stellar clusters

Authors:
Philip J. Armitage

Comments: A&A in press. Minor revisions to match accepted version

Note: replaced with revised version Sat, 2 Sep 2000 21:31:15 GMT (16kb)



astro-ph/0008036 [abs, src, ps, other] :




Title: PMN J1838-3427: A new gravitationally lensed quasar

Authors:
Joshua N. Winn,
Jacqueline N. Hewitt,
Paul L. Schechter,
Alan Dressler,
E.E. Falco,
C.D. Impey,
C.S. Kochanek,
J. Lehar,
J.E.J. Lovell,
B.A. McLeod,
Nicholas D. Morgan,
J.A. Munoz,
H.-W. Rix,
Maria Teresa Ruiz

Comments: 23 pages, incl. 6 figures, to appear in A.J.; replaced with accepted
version; minor changes to text, improved figures

Note: replaced with revised version Sat, 2 Sep 2000 17:48:55 GMT (409kb)



astro-ph/0008496 [abs, src, ps, other] :




Title: A moving cold front in the intergalactic medium of A3667

Authors:
A. Vikhlinin,
M. Markevitch,
S. S. Murray

Comments: Submitted to ApJ. 9 pages with embedded color figures, uses
emulateapj5. Postscript with higher quality figures is available at
this http URL

Note: replaced with revised version Sat, 2 Sep 2000 00:03:45 GMT (503kb)



hep-ph/0007117 [abs, src, ps, other] :




Title: Dynamical Cosmological Constant from A Very Recent Phase Transition

Author:
John McDonald (Glasgow)

Comments: 13 pages LaTeX, 10 figures

Note: replaced with revised version Mon, 4 Sep 2000 19:02:22 GMT (269kb)



hep-th/0007203 [abs, src, ps, other] :




Title: Black holes in the brane world:Time symmetric initial data

Authors:
Tetsuya Shiromizu (AEI-Golm & Tokyo),
Masaru Shibata (UIUC & Osaka)

Comments: 4 pages, 2 figures, minor changes, references added, to appear in
Physical Review D

Note: replaced with revised version Sat, 2 Sep 2000 03:27:03 GMT (13kb)



nucl-th/0005011 [abs, src, ps, other] :




Title: Screened Coulomb potentials for astrophysical nuclear fusion reactions

Authors:
Theodore E. Liolios

Comments: 11 (RevTex) pages + 3 ps figures. Accepted for publication in
Eur.Phys.J. A

Subj-class: Nuclear Theory; Atomic Physics

Note: replaced with revised version Mon, 4 Sep 2000 08:03:19 GMT (26kb)




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