Astrophysics

astro-ph new abstracts, Wed, 6 Sep 00 04:00:11 GMT
0009051 — 0009077 received

astro-ph/0009051 [abs, src, ps, other] :

Title: The Distribution of [OII] Equivalent Widths of LCRS Galaxies

Authors:
Michael Blanton,
Huan Lin

Comments: 8 pages, 1 figure, ApJ Letters, accepted

We present a simple functional form for the joint distribution of R-band
luminosity and [OII] 3727 emission-line equivalent widths of galaxies, and show
that this form is a good fit to the galaxies in the Las Campanas Redshift
Survey. We find a relationship between [OII] equivalent width W and R-band
luminosity L_R of the approximate form: <W> approx (10 AA)
(L_R/L_{R,*})^{-1/2}, where L_{R,*} is the characteristic luminosity in the
Schechter function. Because this joint distribution yields information about
the relationship between stellar mass in a galaxy and its recent star-formation
rate, it can be useful for testing theories of galaxy formation. Furthermore,
understanding this joint distribution locally will make it easier to interpret
the evolution of [OII] emission-line widths to higher redshifts.
(16kb)

astro-ph/0009052 [abs, src, ps, other] :

Title: Spin induced galaxy alignments and their implications for weak lensing
measurements

Authors:
Robert G. Crittenden (DAMTP),
Priyamvada Natarajan (Yale,IoA),
Ue-Li Pen (CITA),
Tom Theuns (IoA)

Comments: 19 pages, submitted to ApJ

Large scale correlations in the orientations of galaxies can result from
alignments in their angular momentum vectors. These alignments arise from the
tidal torques exerted on neighboring proto-galaxies by the smoothly varying
shear field. We compute the predicted amplitude of such ellipticity
correlations using the Zel’dovich approximation for a realistic distribution of
galaxy shapes. Weak gravitational lensing can also induce ellipticity
correlations since the images of neighboring galaxies will be distorted
coherently. On comparing these two effects that induce shape correlations, we
find that for current weak lensing surveys with a median redshift of z_m = 1,
the intrinsic signal is of order 1 – 10 percent of the measured signal.
However, for shallower surveys with z_m < 0.3, the intrinsic correlations
dominate over the lensing signal. The distortions induced by lensing are
curl-free, whereas those resulting from intrinsic alignments are not. This
difference can be used to disentangle these two sources of ellipticity
correlations.
(88kb)

astro-ph/0009053 [abs, src, ps, other] :

Title: N-body simulations of warped galaxies

Authors:
Yves Revaz,
Daniel Pfenniger

Comments: 2 pages, to appear in “Gas & Galaxy Evolution”, VLA 20th Anniversary
Conference, J.E. Hibbard, M.P. Rupen & J.H. van Gorkom (eds.)

Two methods generating warped galaxies with N-body simulations are presented.
One uses an external potential as a disturber while the other is based on
material accretion. The results of both methods are compared. A particular
attention is given on the shape of the line of node (LON).
(8kb)

astro-ph/0009054 [abs, src, ps, other] :

Title: A radio-continuum and photoionization-model study of the two planetary
nebulae in the Sagittarius dwarf galaxy

Authors:
G. Dudziak (Univ. Strathclyde),
D. Pequignot (Observatoire de Paris Meudon),
A. A. Zijlstra (UMIST),
J. R. Walsh (ESO)

Comments: To appear in Astron. Astrophys. (Latex, 17 pages, 1 postscript
figure)

Radio continuum observations at 1.4, 4.8 and 8.6 GHz of the two Planetary
Nebulae (PNe) in the Sagittarius dwarf galaxy reveal the elongated shape of
Wray 16-423 and the extreme compactness of He 2-436. He 2-436 is confirmed as
subject to local dust extinction.

Photoionization models for both PNe are obtained from two different codes,
allowing theoretical uncertainties to be assessed. Wray 16-423, excited by a
star of Teff 1.07×10^5K, is an ellipsoidal, matter-bounded nebula, except for a
denser sector. He 2-436, excited by a 7×10^4K star, includes two
radiation-bounded shells, with the inner one possibly corresponding to a
transitory event. Both stars are on the same (H-burning) evolutionary track of
initial mass (1.2+/-0.1) Msun and may be twins, with the PN ejection of Wray
16-423 having occured ~1500 years before He 2-436.

The PN abundances re-inforce the common origin of the parent stars,
indicating almost identical depletions with respect to solar for O, Ne, Mg, S,
Cl, Ar, and K (-0.55+/-0.07 dex), large identical overabundances for He and
strong overabundances for carbon, particularly in He2-436. Excess nitrogen
makes Wray 16-423 nearly a Type I PN. These PNe provide a means to calibrate
both metallicity and age of the Sagittarius stellar population, and they
confirm that the youngest, most metal-rich population has an age of 5Gyr and a
metallicity of [Fe/H]=-0.55, in agreement with the slope of the red giant
branch. (Abridged abstract)
(42kb)

astro-ph/0009055 [abs, src, ps, other] :

Title: Dynamical models for dusty disk galaxies

Authors:
Maarten Baes,
Herwig Dejonghe

Comments: to be published in the proceedings of “Galaxy Disks and Disk
Galaxies”, Funes J.G. and Corsini E.M. eds., ASP Conference Series

Disk galaxies contain a large amount of interstellar dust, which affects the
projection of kinematic quantities. We investigate in detail the effects of
dust extinction on the mean projected velocity and the projected velocity
dispersion. We use our results to construct a general strategy to determine the
dynamical structure of disk galaxies, with the aim to constrain their mass
distribution and dynamical history.
(6kb)

astro-ph/0009056 [abs, src, ps, other] :

Title: The HST snapshot survey of the B2 sample of low luminosity
radio-galaxies: a picture gallery

Authors:
A. Capetti (1),
H.R. de Ruiter (2,3),
R. Fanti (3,4),
R. Morganti (5),
P. Parma (3),
M.-H. Ulrich (6) ((1) Osservatorio Astronomico di Torino, Italy (2) Osservatorio Astronomico di Bologna, Italy (3) Istituto di Radioastronomia di Bologna, Italy (4) Dipartimento di Fisica dell’Universita’ di Bologna, Italy (5) Netherlands Foundation for Research in Astronomy, Dwingeloo, The Netherlands (6) European Southern Observatory, Garching, Germany)

Comments: 9 pages, 3 ps figures, 7 jpg figures, accepted for publication in
A&A

A Hubble Space Telescope snapshot survey of the B2 sample of low luminosity
radio galaxies has, at present, produced V and I images of 41 objects. Together
with 16 images of B2 sources taken from the HST archive, there are now high
resolution optical data for 57 % of the sample. All host galaxies are luminous
ellipticals, except one which is a spiral galaxy, while another one turns out
to be a misidentification.

We present an album of the images of the B2 radio galaxies observed so far,
and give a brief description of the optical morphology of the galaxies. Dust
features (in the form of disks, lanes or irregular patches) are seen in most of
the galaxies of the sample, 58 %. Compact optical cores are also very common
(18/57). A preliminary analysis has revealed the presence of an optical jet in
three objects, indicating they can be detected in a sizeable percentage in
these low luminosity radio sources. Brightness profiles of dust-free galaxies
are well represented by a Nuker law and all shows the existence of a resolved
shallow cusp.
(401kb)

astro-ph/0009057 [abs, src, ps, other] :

Title: Cosmological parameters from complementary observations of the Universe

Authors:
R. Durrer (Geneva University),
B. Novosyadlyj (L’viv University)

Comments: 12 pages, 3 figures. Submitted to MNRAS

We use observational data on the large scale structure (LSS) of the Universe
measured over a wide range of scales from sub-galactic up to horizon scale and
on the cosmic microwave background anisotropies to determine cosmological
parameters within the class of adiabatic inflationary models. We show that a
mixed dark matter model with cosmological constant ($Lambda$MDM model) with
parameters $Omega_m=0.37^{+0.25}_{-0.15}$,
$Omega_{Lambda}=0.69^{+0.15}_{-0.20}$, $Omega_{
u}=0.03^{+0.07}_{-0.03}$,
$N_{
u}=1$, $Omega_b=0.037^{+0.033}_{-0.018}$, $n_s=1.02^{+0.09}_{-0.10}$,
$h=0.71^{+0.22}_{-0.19}$, $b_{cl}=2.4^{+0.7}_{-0.7}$ (1$sigma$ confidence
limits) matches observational data on LSS, the nucleosynthesis constraint,
direct measurements of Hubble constant, the high redshift supernova type Ia
results and the recent measurements of the location and amplitude of the first
acoustic peak in the CMB anisotropy power spectrum. The best model is $Lambda$
dominated (65% of the total energy density) and has slightly positive
curvature, $Omega=1.06$. The clustered matter consists in 8% massive
neutrinos, 10% baryons and 82% cold dark matter (CDM). The upper 2$sigma$
limit on the neutrino content can be expressed in the form
$Omega_{
u}h^2/N_{
u}^{0.64}le0.042$ or, via the neutrino mass,
$m_{
u}le4.0$eV. The upper 1(2)$sigma$ limit for the contribution of a
tensor mode to the COBE DMR data is T/S$<1(1.5)$. Furthermore, it is shown that
the LSS observations together with the Boomerang (+MAXIMA-1) data on the first
acoustic peak rule out zero-$Lambda$ models at more than $2sigma$ confidence
limit.
(46kb)

astro-ph/0009058 [abs, src, ps, other] :

Title: Search for High Proper Motion White Dwarfs

Authors:
Jelte de Jong,
Konrad Kuijken,
Mark Neeser (Kapteyn Astronomical Institute)

Comments: 4 pages, 3 figures, uses moriond2000.sty, to appear in the
proceedings of the XXth Moriond Astrophysics Meeting, March 2000, eds. J.-P.
Kneib, Y. Mellier, M. Moniez and J. Tran Thanh Van

Recent results of microlensing surveys, show that 10-20% of the dark halo
mass of the Milky Way consists of compact objects. The masses of these compact
objects range from 0.1 to 1 solar mass. New theoretical cooling models for
white dwarfs, and the detection of faint blue high proper motion objects, imply
that ancient white dwarfs might make up part of this population. In this pilot
project, using data from the C and D patches of the ESO Imaging Survey and data
obtained at CTIO, we attempted to find such halo white dwarfs in the solar
neighbourhood. With a time baseline of approximately one year between data sets
and a limiting I-band magnitude of 23, we can find these high proper motion
objects up to distances of 85 parsecs. In the 2.5 square degrees studied so far
we have found three high proper motion candidates.
(52kb)

astro-ph/0009059 [abs, src, ps, other] :

Title: The evolution of the Milky Way monitored in the solar neighbourhood

Authors:
B. Fuchs,
C. Dettbarn,
H. Jahreiss,
R. Wielen

Comments: 13 pages, 7 figures, uses newpasp.sty, to appear in “Dynamics of
Star Clusters and the Milky Way”, eds. S. Deiters et al

In this review we concentrate on the dynamical evolution of the Milky Way as
monitored in the solar neighbourhood. The relevant data sets are presented and
discussed in detail. In the second part we review various mechanisms, which
drive the dynamical evolution.
(323kb)

astro-ph/0009060 [abs, src, ps, other] :

Title: A relativistic calculation of super-Hubble suppression of inflation with
thermal dissipation

Authors:
W. L. Lee,
L. Z. Fang

Comments: 22 pages, 3 figures, use RevTex, accepted by Class. Quant. Grav

We investigated the evolution of the primordial density perturbations
produced by inflation with thermal dissipation. A full relativistic analysis on
the evolution of initial perturbations from the warm inflation era to a
radiation-dominated universe has been developed. The emphasis is on tracking
the ratio between the adiabatic and the isocurvature mode of the initial
perturbations. This result is employed to calculate a testable factor: the
super-Hubble suppression of the power spectrum of the primordial perturbations.
We show that based on the warm inflation scenario, the super-Hubble suppression
factor, $s$, for an inflation with thermal dissipation is at least 0.5. This
prediction does not depend on the details of the model parameters. If $s$ is
larger than 0.5, it implies that the friction parameter $Gamma$ is larger than
the Hubble expansion parameter $H$ during the inflation era.
(33kb)

astro-ph/0009061 [abs, src, ps, other] :

Title: Magnetic Fields in the Early Universe

Authors:
Dario Grasso (Padua U.),
H.R. Rubinstein (Uppsala and Stockholm U.)

Comments: 151 LaTeX pages, 6 figures., to appear on Phys. Rep

This review concerns the origin and the possible effects of magnetic fields
in the early Universe. We start by providing to the reader with a short
overview of the current state of art of observations of cosmic magnetic fields.
We then illustrate the arguments in favour of a primordial origin of magnetic
fields in the galaxies and in the clusters of galaxies. We argue that the most
promising way to test this hypothesis is to look for possible imprints of
magnetic fields on the temperature and polarization anisotropies of the cosmic
microwave background radiation (CMBR). With this purpose in mind, we provide a
review of the most relevant effects of magnetic fields on the CMBR. A long
chapter of this review is dedicated to particle physics inspired models which
predict the generation of magnetic fields during the early Universe evolution.
Although it is still unclear if any of these models can really explain the
origin of galactic and intergalactic magnetic fields, we show that interesting
effects may arise anyhow. Among these effects, we discuss the consequences of
strong magnetic fields on the big-bang nucleosynthesis, on the masses and
couplings of the matter constituents, on the electroweak phase transition, and
on the baryon and lepton number violating sphaleron processes. Several
intriguing common aspects, and possible interplay, of magnetogenesis and
baryogenesis are also dicussed.
(166kb)

astro-ph/0009062 [abs, src, ps, other] :

Title: The minimum orbital period in thermal-timescale mass transfer

Authors:
A.R. King (1),
K. Schenker (1),
U. Kolb (2),
M.B. Davies (1) ((1) University of Leicester, (2) Open University)

Comments: 6 pages, 5 figures; to appear in MNRAS

We show that the usual picture of supersoft X-ray binary evolution as driven
by conservative thermal-timescale mass transfer cannot explain the short
orbital periods of RX J0537.7-7034 (3.5 hr) and 1E 0035.4-7230 (4.1 hr).
Non-conservative evolution may produce such periods, but requires very
significant mass loss, and is highly constrained.
(51kb)

astro-ph/0009063 [abs, src, ps, other] :

Title: Dynamical and content evolution of a sample of clusters from z~0 to
z~0.5

Authors:
C. Adami (LAM),
B.P. Holden (University of Chicago),
F.J. Castander (Observatoire Midi-Pyrenees),
A. Mazure (LAM),
R.C. Nichol (CMU),
M.P. Ulmer (NU)

Comments: 11 pages, 4 figures, accepted in A&A

In this paper, we present an analysis of the dynamics and segregation of
galaxies in rich clusters from z~0.32 to z~0.48 taken from the CFHT Optical
PDCS (COP) survey and from the CNOC survey (Carlberg et al. 1997). Our results
from the COP survey are based upon the recent observational work of Adami et
al. (2000) and Holden et al. (2000) and use new spectroscopic and photometric
data on six clusters selected from the Palomar Distant Cluster Survey (PDCS;
Postman et al. 1996). We have compared the COP and CNOC samples to the ESO
Nearby Abell Cluster Survey (ENACS: z~0.07). Our sample shows that the z<0.4
clusters have the same velocity dispersion versus magnitude, morphological type
and radius relationships as nearby Abell clusters. The z~0.48 clusters exhibit,
however, departures from these relations. Furthermore, there appears to be a
higher fraction of late-type (or bluer, e.g. Butcher and Oemler, 1984) galaxies
in the distant clusters compared to the nearby ones. The classical scenario in
which massive galaxies virialize before they evolve from late into early type
explain our observations. In such a scenario, the clusters of our sample began
to form before a redshift of ~0.8 and the late-type galaxy population had a
continuous infall into the clusters.
(23kb)

astro-ph/0009064 [abs, src, ps, other] :

Title: Optical photometry of the PSR B0656+14 and its neighborhood

Authors:
A. B. Koptsevich (1,2,3),
G. G. Pavlov (2),
S. V. Zharikov (3,4),
V. V. Sokolov (3),
Yu. A. Shibanov (1),
V. G. Kurt (5) ((1) Ioffe Inst., Russia; (2) PSU; (3) SAO RAS, Russia; (4) OANIA UNAM, Mexico; (5) ASC RAS, Russia)

Comments: 12 pages, 20 figures, submitted to A&A. Images are available in FITS
format at this http URL

We present the results of the broad-band photometry of the nearby middle-aged
radio pulsar PSR B0656+14 and its neighborhood obtained with the 6-meter
telescope of the SAO RAS and with the Hubble Space Telescope. The broad-band
spectral flux $F_
u$ of the pulsar decreases with increasing frequency in the
near-IR range and increases with frequency in the near-UV range. The increase
towards UV can be naturally interpreted as the Rayleigh-Jeans tail of the soft
thermal component of the X-ray spectrum emitted from the surface of the cooling
neutron star. Continuation of the power-law component, which dominates in the
high-energy tail of the X-ray spectrum, to the IR-optical-UV frequencies is
consistent with the observed fluxes. This suggests that the non-thermal pulsar
radiation may be of the same origin in a broad frequency range from IR to hard
X-rays. We also studied 4 objects detected in the pulsar’s 5″ neighborhood.
(444kb)

astro-ph/0009065 [abs, src, ps, other] :

Title: The template type Ia supernova 1996X

Authors:
M. E. Salvo (1),
E. Cappellaro (1),
P. A. Mazzali (2,3),
S. Benetti (4),
I. J. Danziger (2),
F. Patat (5),
M. Turatto (1) ((1) Osservatorio Astronomico di Padova, (2) Osservatorio Astronomico di Trieste,(3) Research Centre for the Early Universe, School of Science, University of Tokyo, (4) Telescopio Nazionale “Galileo”, (5) European Southern Observatory)

Comments: 17 pages, 17 figures. Accepted for publication in MNRAS

UBVRIJ photometry and optical spectra of the Type Ia SN 1996X obtained at ESO
during a one-year-long observational campaign are presented, and supplemented
by late time HST photometry. Spectroscopically, SN 1996X appears to be a
`normal’ SN Ia. The apparent magnitude at maximum was B=13.24 +/- 0.02, and the
colour B-V=0.00 +/- 0.03. The luminosity decline rate, Delta m_B(15) = 1.31 +/-
0.08, is close to average for a SN Ia. The best estimate of the galactic
extinction is A_B=0.30 +/- 0.05, and there is evidence that reddening within
the parent galaxy is negligible. Detailed comparison of the light and colour
curves of various `normal’ SNe Ia shows that the assumption that multicolour
light curves can be described simply as a one-parameter family is not perfect.
Together with problems in the calibration of the templates, this may explain
the discrepancies in the distance modulus derived adopting different
calibrations of the absolute magnitude vs. light curve shape relations. Indeed
we found that M_B ranges from -19.08 to -19.48 and M-m range from 32.02 to
32.48 depending on the method used (Hamuy et al. 1996a,Phillips et al. 1999,
Riess et al. 1998a). Computations of model light curve and synthetic spectra
for both early- and late-times, confirm that 1996X is a normal Type Ia SN and
that a satisfactory fit can be obtained using a W7 progenitor structure only if
we adopt the short distance. A larger distance would imply a too large Ni mass
for this fainter than average SNIa.
(476kb)

astro-ph/0009066 [abs, src, ps, other] :

Title: Searching for Tidal Tails in Galactic Dwarf Spheroidal Satellites

Authors:
D. Martinez-Delgado,
A. Aparicio,
M.A. Gomez-Flechoso

Comments: To be published in the Proceeding of the Euroconference “The
Evolution of Galaxies. I. Observational Clues”, Granada, May 2000

We present preliminary results of a long-term project to investigate the
process of accretion and tidal disruption of dSph satellites in the Galactic
halo and, in particular, to search for new tidal tails in a sample of nearby
dSph satellites of the Milky Way. Here we present our finding of extra-tidal
debris in the Ursa Minor dS ph and discuss the detection by the Sloan Digitized
Sky Survey team of what could be a tidal stream associated to the Sagittarius
dSph.
(116kb)

astro-ph/0009067 [abs, src, ps, other] :

Title: Submillimetre sources in rich cluster fields – source counts, redshift
estimates, and cooling flow limits

Authors:
Scott C. Chapman,
Douglas Scott,
Colin Borys,
Gregory G. Fahlman

Comments: 13 pages, submitted to MNRAS

Recent submillimetre surveys have revealed a population of dusty, high
redshift sources of great cosmological significance for understanding
dust-enshrouded star formation in distant galaxies, and for determining the
origin of the far-IR background. In this paper, we analyze nine rich cluster
fields mapped at 850 and 450 microns with the SCUBA array on the James Clerk
Maxwell telescope. Lensing models of the clusters are developed in order to
derive accurate source counts for our sample. VLA maps of the same clusters are
used to help constrain the redshift distribution of our SCUBA detections.
Implications for high redshift galaxies and for the far-IR background are
discussed. We also provide limits on distributed dust produced by cooling flows
in these clusters.
(496kb)

astro-ph/0009068 [abs, src, ps, other] :

Title: Gravitational Lensing by Galaxy Groups in the Hubble Deep Field

Authors:
David C. Fox,
Ue-Li Pen

Comments: 33 pages, 12 EPS figures, accepted by ApJ

We investigate strong lensing of galaxies in the Hubble Deep Field by
foreground groups and clusters of galaxies with masses from $10^{13}$ to
$10^{15} MSun$. Over this mass range, groups with the profile of Navarro,
Frenk, & White (1995) are less efficient than singular isothermal spheres at
producing multiple images of galaxies, by factors of $5 imes 10^{- 2}$ to
$10^{- 3}$. This difference highlights the sensitivity of the lensing cross
section to the central density profile. Nonetheless, with either profile we
find that the expected number of galaxies lensed by groups in the Hubble Deep
Field is at most $lesssim 1$, consistent with the lack of clearly identified
group lens systems.
(61kb)

astro-ph/0009069 [abs, src, ps, other] :

Title: Star Formation and the ISM in Dwarf Galaxies

Authors:
L. M. Young (New Mexico Tech),
L. van Zee (HIA),
R. C. Dohm-Palmer (U. Michigan),
K. Y. Lo (Academica Sinica, Taiwan R.O.C.)

Comments: 5 pages, 2 figures; to appear in the proceedings of the conference
“Gas and Galaxy Evolution” (ASP Conference Series), eds. J. Hibbard, M.
Rupen, and J. van Gorkom

High spatial and spectral resolution observations of the atomic interstellar
medium in nearby dwarf galaxies reveal evidence for warm and cold neutral gas,
just like the phases in our own Galaxy. The cold or quiescent phase (about 20%
of the HI in the galaxies studied, except for LGS 3) seems to be associated
with star formation activity— it may mark the regions where the conditions
are right for star formation. These results help to explain the patterns of
star formation activity which are seen in color-magnitude data for the dwarf
irregulars.
(170kb)

astro-ph/0009070 [abs, src, ps, other] :

Title: Molecular Gas in Elliptical Galaxies

Authors:
L. M. Young (New Mexico Tech)

Comments: 2 pages, 1 figure; to appear in the proceedings of the conference
“Gas and Galaxy Evolution” (ASP Conference Series), eds. J. Hibbard, M.
Rupen, and J. van Gorkom

The distribution and kinematics of the molecular gas in elliptical galaxies
give information on the origin and history of the gas and the rate of star
formation activity in ellipticals. I describe some preliminary results of a
survey which will more than double the number of elliptical galaxies with
resolved molecular distributions.
(36kb)

astro-ph/0009071 [abs, src, ps, other] :

Title: A simple model of the hierarchical formation of galaxies

Authors:
B. Hoeneisen

Comments: 17 pages, 9 Postscript figures

We develop a simple, fast and predictive model of the hierarchical formation
of galaxies which is in quantitative agreement with observations. Comparing
simulations with observations we place constraints on the density of the
universe and on the power spectrum of density fluctuations.
(46kb)

astro-ph/0009072 [abs, src, ps, other] :

Title: A vorton gun

Authors:
Ken D. Olum,
J. J. Blanco-Pillado,
Xavier Siemens

Comments: 11 pages; revtex

In about half of all near-cusp events in superconducting cosmic strings with
chiral currents (and probably with general currents as well), the string
intersects itself near the cusp. Intercommutation causes the conversion of the
string near the cusp into a vorton (in the chiral case) with very high Lorentz
boost. We demonstrate how to analyze the cusp shape in a Lorentz frame that
makes the motion simple, by the use of a 5-dimensional procedure, and analyze
the resulting production of vortons.
(11kb)

astro-ph/0009073 [abs, src, ps, other] :

Title: Star Formation in Galaxies between 0.7 < z < 1.8

Authors:
A. M. Hopkins,
A. J. Connolly,
A. S. Szalay

Comments: 11 pages, 6 figures, accepted by AJ (to appear Dec. 2000)

We present an analysis of the star formation rate in galaxies between
0.7<z<1.8 using Near Infrared Camera and Multi-Object Spectrograph (NICMOS)
grism spectral observations. We detect 163 galaxies in an area of ~4.4 square
arcminutes, 37 of which show possible H-alpha emission. We extend the observed
H-alpha luminosity function (LF) in this redshift range to luminosities a
factor of two fainter than earlier work, and are consistent in the region of
overlap. Using the H-alpha LF, we estimate a star formation rate (SFR) density
in this redshift range of 0.166 M_sun/yr/Mpc^3 (H0=75 km/s/Mpc), consistent
with other estimates based on emission lines, and supporting the order of
magnitude increase in SFR density between z=0 and z=1. Our measurement of SFR
density is a factor of ~2-3 greater than that estimated from UV data,
comparable to the factor observed locally, implying little evolution in the
relative extinctions between UV and H-alpha out to z~1.3.
(815kb)

astro-ph/0009074 [abs, src, ps, other] :

Title: Does Dark Matter Exist?

Authors:
J. A. Sellwood,
A. Kosowsky (Rutgers University)

Comments: To appear in “Gas & Galaxy Evolution” eds Hibbard, Rupen & van
Gorkom, 8 pages, no figures, LaTeX uses newpasp.sty (included)

The success of the Lambda-CDM model on large scales does not extend down to
galaxy scales. We list a dozen problems of the dark matter hypothesis, some of
which arise in specific models for the formation of structure in the universe,
while others are generic and require fine tuning in any dark matter theory.
Modifications to the theory, such as adding properties to the DM particles
beyond gravitational interactions, or simply a better understanding of the
physics of galaxy formation, may resolve some problems, but a number of
conspiracies and correlations are unlikely to yield to this approach. The
alternative is that mass discrepancies result from of a non-Newtonian law of
gravity, a hypothesis which avoids many of the more intractable problems of
dark matter. A modified law of gravity is not without formidable difficulties
of its own, but it is no longer obvious that they are any more daunting than
those facing DM.
(13kb)

astro-ph/0009075 [abs, src, ps, other] :

Title: Galactic Superwinds at Low and High Redshift

Authors:
Timothy M. Heckman

Comments: In “Gas & Galaxy Evolution” conference proceedings 14 pages, 3
figures. Requires newpasp.sty

In this contribution I summarize our current knowledge of the nature and
significance of starburst-driven galactic superwinds. These flows are driven
primarily by the kinetic energy supplied by supernovae. Superwinds are complex,
multiphase phenomena requiring a panchromatic observational approach. They are
ubiquitous in galaxies in which the global star-formation rate per unit area
exceeds roughly 10$^{-1}$ M$_{odot}$ yr$^{-1}$ kpc$^{-2}$ (a condition
satisfied by local starbursts and high-z Lyman Break galaxies). Data on X-ray
emission, optical line-emission, and optical/UV interstellar absorption-lines
together imply that the mass outflow rates are comparable to the
star-formation-rates and that the conversion of kinetic energy from supernovae
to superwind is quite efficient ($sim$ 30 to 100%). Measured/inferred outflow
speeds range from a few $ imes 10^2$ to 10$^3$ km/s and appear to be
independent of the rotation speed of the “host” galaxy. The outflows are
dusty (dust/gas ratios of $sim$ 1% by mass). These properties imply that
superwinds may have established the mass-metallicity relation in elliptical and
bulges, polluted the inter-galactic medium to a metallicity of $sim$ 10 to 30%
solar, heated the inter-galactic medium by up to $sim$1 kev per baryon, and
ejected enough dust into the inter-galactic medium to have potentially
observable consequences.
(125kb)

astro-ph/0009076 [abs, src, ps, other] :

Title: Black Hole Demographics from the M(BH)-sigma Relation

Authors:
David Merritt,
Laura Ferrarese (Rutgers University)

Comments: 12 Latex pages, 4 postscript figures

We analyze a sample of 32 galaxies for which a dynamical estimate of the mass
of the hot stellar component, M_bulge, is available. For each of these
galaxies, we calculate the mass of the central black hole, M_BH, using the
tight empirical correlation between M_BH and the bulge stellar velocity
dispersion. The frequency function N(log M_BH/M_bulge) is reasonably well
described as a Gaussian with <M_BH/M_bulge> ~ -2.90 and standard deviation
~0.45; the implied mean ratio of black hole to bulge mass is a factor ~5
smaller than generally quoted in the literature. We comment on marginal
evidence for a lower, average black-hole mass fraction in more massive
galaxies, which should be investigated using larger samples. The total mass
density in black holes in the local Universe is estimated to be ~5 x 10^5 solar
masses per cubic megaparsec, consistent with that inferred from high redshift
(z ~ 2) AGNs.
(24kb)

astro-ph/0009077 [abs, src, ps, other] :

Title: Orbital solution for the MACHO*05:34:41.3 -69:31:39 O3 If*+O6:V
eclipsing binary system in the LMC

Authors:
P. G. Ostrov

Comments: 3 pages, 2 postscript figures, submitted to MNRAS

An orbital solution to the MACHO*05:34:41.3 -69:31:39 eclipsing binary system
is presented, based on the published light curve and spectral data obtained
with the 2.15-m telescope at CASLEO. The radial velocity data along with the
published light curve were analysed with the Wilson-Devinney code to derive the
following masses and radii for the components of this system: M1 = 41 +- 1.2,
R1 = 9.6 +- 0.02, M2 = 27 +- 1.2 and R2 = 8.0 +- 0.05, in solar units. The
solution shows that the system is in over-contact as one would expect from the
derived masses and the very short orbital period ($sim$ 1.4 days).
(45kb)

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Cross-listings

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gr-qc/0009008 [abs, src, ps, other] :

Title: Accelerating Universes with Scaling Dark Matter

Authors:
M. Chevallier,
D. Polarski

Comments: submitted to IJMPD (uses Latex, 12 pages, 6 Figures)

Friedmann-Robertson-Walker universes with a presently large fraction of the
energy density stored in an $X$-component with $w_X<-1/3$, are considered. We
find all the critical points of the system for constant equations of state in
that range. We consider further several background quantities that can
distinguish the models with different $w_X$ values. Using a simple toy model
with a varying equation of state, we show that even a large variation of $w_X$
at small redshifts is very difficult to observe with $d_L(z)$ measurements up
to $zsim 1$. Therefore, it will require accurate measurements in the range
$1<z<2$ and independent accurate knowledge of $Omega_{m,0}$ (and/or
$Omega_{X,0}$) in order to resolve a variable $w_X$ from a constant $w_X$.
(20kb)

hep-ph/0009017 [abs, src, ps, other] :

Title: High Energy Neutrinos From Superheavy Dark Matter Annihilation

Authors:
Ivone F. M. Albuquerque,
Lam Hui,
Edward W. Kolb

Comments: 24 pages, 7 figures

Superheavy ($M>10^{10}$ GeV) particles produced during inflation may be the
dark matter, independent of their interaction strength. Strongly interacting
superheavy particles will be captured by the sun, and their annihilation in the
center of the sun will produce a flux of energetic neutrinos that should be
detectable by neutrino telescopes. Depending on the particle mass, event rates
in a cubic-kilometer detector range from several per hour to several per year.
The signature of the process is a predominance of tau neutrinos, with a
relatively flat energy spectrum of events ranging from 50 GeV to many TeV, and
with the mean energy of detected tau neutrinos about 3 TeV.
(100kb)

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Replacements

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astro-ph/0003426 [abs, src, ps, other] :

Title: Possible evidence of quark matter in neutron star X-ray binaries

Authors:
Norman K. Glendenning,
F. Weber (Lawrence Berkeley National Laboratory)

Comments: 4 pages (latex) 3 figures. Figure of calculated distribution of x-ray
neutron stars as a function of frequency is included

Note: replaced with revised version Tue, 5 Sep 2000 21:43:25 GMT (65kb)

astro-ph/0007123 [abs, src, ps, other] :

Title: Black Hole Mass Estimates from Reverberation Mapping and from Spatially
Resolved Kinematics

Authors:
Karl Gebhardt,
John Kormendy,
Luis Ho,
Ralf Bender,
Gary Bower,
Alan Dressler,
S.M. Faber,
Alexei Filippenko,
Richard Green,
Carl Grillmair,
Tod Lauer,
John Magorrian,
Jason Pinkney,
Douglas Richstone,
Scott Tremaine

Comments: 4 pages, 1 figure, ApJ Letters accepted, minor revisions

Note: replaced with revised version Tue, 5 Sep 2000 19:48:37 GMT (18kb)

astro-ph/0008520 [abs, src, ps, other] :

Title: Infrared Observations of AR Ursa Majoris: Modeling the Ellipsoidal
Variations

Authors:
Steve B. Howell,
Dawn M. Gelino,
Thomas E. Harrison

Comments: Submitted to AJ

Note: replaced with revised version Tue, 5 Sep 2000 20:27:13 GMT (63kb)

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