Astrophysics

astro-ph new abstracts, Fri, 4 Aug 00 04:00:11 GMT
0008053 — 0008071 received

astro-ph/0008053 [abs, src, ps, other] :

Title: The Flared Disc Project: RXTE and ASCA Observations of X 1822-371

Authors:
S. Heinz,
M.A. Nowak

Comments: 14 pages, 6 figures, accepted for publication in MNRAS

We present archival RXTE and simultaneous ASCA data of the eclipsing low mass
X-ray binary (LMXB) X 1822-371. Our spectral analysis shows that a variety of
simple models can fit the spectra relatively well. Of these models, we explore
two in detail through phase resolved fits. These two models represent the case
of a very optically thick and a very optically thin corona. While systematic
residuals remain at high energies, the overall spectral shape is
well-approximated. The same two basic models are fit to the X-ray light curve,
which shows sinusoidal modulations interpreted as absorption by an opaque disc
rim of varying height. The geometry we infer from these fits is consistent with
previous studies: the disc rim reaches out to the tidal truncation radius,
while the radius of the corona (approximated as spherical) is very close to the
circularization radius. Timing analysis of the RXTE data shows a time lag from
hard to soft consistent with the coronal size inferred from the fits. Neither
the spectra nor the light curve fits allow us to rule out either model, leaving
a key ingredient of the X 1822-371 puzzle unsolved. Furthermore, while previous
studies were consistent with the central object being a 1.4 Msol neutron star,
which has been adopted as the best guess scenario for this system, our light
curve fits show that a white dwarf or black hole primary can work just as well.
Based on previously published estimates of the orbital evolution of X 1822-371,
however, we suggest that this system contains either a neutron star or a low
mass (~ 2.5 Msol) black hole and is in a transitional state of duration
shortward of 10^7 years.
(77kb)

astro-ph/0008054 [abs, src, ps, other] :

Title: New Pulsars from an Arecibo Drift Scan Search

Authors:
Andrea N. Lommen,
Alex Zepka,
Donald C. Backer,
Maura McLaughlin,
James C. Cordes,
Zaven Arzoumanian,
Kiriaki Xilouris

Comments: 21 pages, 4 figures, Accepted for Publication in ApJ

We report the discovery of pulsars J0030+0451, J0711+0931, and J1313+0931
that were found in a search of 470 square degrees at 430 MHz using the 305m
Arecibo telescope. The search has an estimated sensitivity for long period, low
dispersion measure, low zenith angle, and high Galactic latitude pulsars of ~1
mJy, comparable to previous Arecibo searches. Spin and astrometric parameters
for the three pulsars are presented along with polarimetry at 430 MHz. PSR
J0030+0451, a nearby pulsar with a period of 4.8 ms, belongs to the less common
category of isolated millisecond pulsars. We have measured significant
polarization in PSR J0030+0451 over more than 50% of the period, and use these
data for a detailed discussion of its magnetospheric geometry. Scintillation
observations of PSR J0030+0451 provide an estimate of the plasma turbulence
level along the line of sight through the local interstellar medium.
(49kb)

astro-ph/0008055 [abs, src, ps, other] :

Title: First Detection of Submillimeter [C I] Emission in the Small Magellanic
Cloud

Authors:
Alberto D. Bolatto (1),
James M. Jackson (1),
Kathleen E. Kraemer (1),
Xiaolei Zhang (2) ((1) Institute for Astrophysical Research, Boston University, (2) Smithsonian Astrophysical Observatory)

Comments: 12 pages including 1 table and 2 figures, using AASTEX macros v4.0,
to appear in The Astrophysical Journal Letters

We report the first detection of [CI] (3P1-3P0) emission at 609 um in a
region of the Small Magellanic Cloud (N27). Environments poor in heavy elements
and dust such as the SMC are thought to be dominated by photodissociation
regions. This is the lowest metallicity source where submillimeter neutral
carbon emission has been detected. Studying the [CI]/CO intensity ratio in
several sources spanning more than an order of magnitude in metallicity, Z, we
find that the [CI]/CO ratio increases for decreasing Z. The existence of such a
trend points to a photodissociation origin for most of neutral carbon in
molecular clouds, in agreement with standard PDR models. We also report ISO FIR
spectroscopic observations of N27, and use them to derive its physical
properties. Comparison between the density and radiation field revealed by FIR
diagnostics (n~300-1000 cm-3, Xuv~30-100 Xo) and those derived from millimeter
and submillimeter data (n~10^5 cm-3, Xuv<30 Xo) suggests that the FIR lines
originate in more diffuse gas, and are perhaps dominated by the interclump
medium. Regardless of the cause, analysis of the FIR and mm-submm data produces
a discrepancy of two orders of magnitude for the density of this source.
(15kb)

astro-ph/0008056 [abs, src, ps, other] :

Title: Stellar Mass-to-Light Ratios and the Tully-Fisher relation

Authors:
Roelof S.de Jong,
Eric F. Bell (Steward Observatory)

Comments: 2 pages, 3 figures. To appear in ASP Conference Series, “Galaxy Disks
and Disk Galaxies”, J.G. Funes S.J. and E.M. Corsini, eds

We use spiral galaxy evolution models to argue that there are substantial
variations in stellar mass-to-light ratio (M/L) within and among galaxies. Our
models show a strong correlation between stellar M/L and galaxy color. We
compare the colors and maximum-disk M/L values of a sample of galaxies to the
model color-M/L relation, finding that a Salpeter IMF is too massive but that
an IMF with fewer low mass stars fits the observations well. Applying our
color-M/L relation to the Tully-Fisher (TF) relation, we find a stellar mass
TF-relation that is independent of originating passband. Adding the HI gas
mass, we find that the maximum slope of the baryonic TF-relation is 3.5.
(19kb)

astro-ph/0008057 [abs, src, ps, other] :

Title: Evidence from Type Ia Supernovae for an Accelerating Universe

Authors:
A. V. Filippenko,
A. G. Riess

Comments: 20 pages, 11 included figures, aipproc style file included, to appear
in Second Tropical Workshop on Particle Physics and Cosmology: Neutrino and
Flavor Physics, ed. J. F. Nieves (New York: American Institute of Physics)

We review the use of Type Ia supernovae for cosmological distance
determinations. Low-redshift SNe Ia (z < 0.1) demonstrate that the Hubble
expansion is linear, that H_0 = 65 +/- 2 (statistical) km/s/Mpc, and that the
properties of dust in other galaxies are similar to those of dust in the Milky
Way. We find that the light curves of high-redshift (z = 0.3-1) SNe Ia are
stretched in a manner consistent with the expansion of space; similarly, their
spectra exhibit slower temporal evolution (by a factor of 1 + z) than those of
nearby SNe Ia. The luminosity distances of our first set of 16 high-redshift
SNe Ia are, on average, 10-15% farther than expected in a low mass-density
(Omega_M=0.2) universe without a cosmological constant. Preliminary analysis of
our second set of 9 SNe Ia is consistent with this. Our work supports models
with positive cosmological constant and a current acceleration of the
expansion. We address the main potential sources of systematic error; at
present, none of them appears to reconcile the data with Omega_Lambda=0 and q_0
>= 0. The dynamical age of the Universe is estimated to be 14.2 +/- 1.7 Gyr,
consistent with the ages of globular star clusters.
(337kb)

astro-ph/0008058 [abs, src, ps, other] :

Title: Water in Emission in the ISO Spectrum of the Early M Supergiant Star mu
Cephei

Authors:
T. Tsuji

Comments: 14 pages, 5 postscript figures, to appear in ApJL

We report a detection of water in emission in the spectrum of the M2
supergiant atar mu Cep (M2Ia) observed by the Short Wavelength Spectrometer
(SWS) aboard Infrared Space Observatory (ISO) and now released as the ISO
Archives. The emission first appears in the 6 micron region (nu2 fundamental)
and then in the 40 micron region (pure rotation lines) despite the rather
strong dust emission. The intensity ratios of the emission features are far
from those of the optically thin gaseous emission. Instead, we could reproduce
the major observed emission features by an optically thick water sphere of the
inner radius about two stellar radii (1300Rsun), Tex = 1500K, and Ncol (H2O) =
3.0E+20/cm2. This model also accounts for the H2O absorption bands in the near
infrared (1.4, 1.9, and 2.7 micron) as well. The detection of water in emission
provides strong constraints on the nature of water in the early M supergiant
stars, and especially its origin in the outer atmosphere is confirmed against
other models such as the large convective cell model. We finally confirm that
the early M supergiant star is surrounded by a huge optically thick sphere of
the warm water vapor, which may be referred to as MOLsphere for simplicity.
Thus, the outer atmosphere of M supergiant stars should have a complicated
hierarchical and/or hybrid structure with at least three major constituents
including the warm MOLsphere (T about 1.0E+3K) together with the previously
known hot chromosphere (T about 1.0E+4K) and cool expanding gas-dust envelope
(T about 1.0E+2K).
(526kb)

astro-ph/0008059 [abs, src, ps, other] :

Title: Cygnus X-1 from RXTE: Variability on Timescales from Milliseconds to
Years

Authors:
K. Pottschmidt (1),
J. Wilms (1),
R. Staubert (1),
M. A. Nowak (2),
W. A. Heindl (3),
D. M. Smith (4) ((1) IAA Tuebingen, (2) Jila, Boulder, (3) CASS, UCSD, (4) SSL, UCB)

Comments: 6 pages, 3 figures, Proc. 33rd COSPAR Scientific Assembly (B. Czerny,
ed.), Adv. Space Res., submitted

We present temporal and spectral results from monitoring Cygnus X-1 with the
Rossi X-ray Timing Explorer (RXTE) in 1998 and 1999. We concentrate on the long
term evolution of the hard state timing properties, comparing it to the 1996
soft state evolution. This leads to the following results: 1. the hard and soft
state time lag spectra are very similar, 2. during state transitions, the lags
in the 1-10 Hz range increase by more than an order of magnitude, 3. in the
hard state itself, flaring events can be seen — the temporal and spectral
evolution during the flare of 1998 July identifies it as a “failed state
transition”. During (failed) state transitions, the time lag spectra and the
power spectra change predominantly in the 1-10 Hz range. We suggest that this
additional variability is produced in ejected coronal material disrupting the
synchrotron radiation emitting outflows present in the hard state.
(79kb)

astro-ph/0008060 [abs, src, ps, other] :

Title: First results of UVES at VLT: revisiting RR Tel

Authors:
Pier Luigi Selvelli (1),
Piercarlo Bonifacio (2) ((1)C.N.R.-G.N.A.- Osservatorio Astronomico di Trieste, (2)Osservatorio Astronomico di Trieste)

Comments: To be published in the special Dec.1 issue of A&AL “Early Science
with VLT : the Opening of Kueyen”

We present here the first results of UVES observations of RR Tel. The
exceptional performances of the instrument have allowed the detection of new
spectral features and have led to an improvement in the identifications of
several emission lines. A direct comparison with the IUE observations in the
range 3045-3300 A has revealed the appearance of many weak and shallow lines,
most of them lacking a convincing identification. The Balmer lines are visible
up to H38 and are accompanied by the He II lines of the Pickering series. Also,
all of the He II emissions of the Pfund series, from 5858 A to 6408 A have been
detected. We made definite identifications of additional TiO bands at 4955 A
(alpha R_2 1-0), 5167 A (alpha R_2 0-0), 5445 A (alpha R_2 0-1), 5598 A (beta
R_1 0-0), 5847 A (gamma ‘R_1 1-0), and 6148 A (gamma ‘ {^S} R_21 0-0). The
Halpha line has very wide wings, extending to at least 5000 km/s, which are
similar to those reported for the planetary nebula IC 4997 and attributed to
Raman scattering by Ly beta photons. A selective pumping mechanism via the HeII
237 A emission is proposed to explain the intensity of the high-lying lines of
O IV mult. 1 and 2.
(207kb)

astro-ph/0008061 [abs, src, ps, other] :

Title: Carbon Star Survey of Local Group Dwarf Galaxies. II. Pegasus, DDO 210
and Tucana

Authors:
P. Battinelli (Oss. Astron. Roma, Italy),
S. Demers (Univ. de Montreal, Canada)

Comments: 18 pages, 7 figures, 6 tables

We present the latest results of our ongoing four filter photometric survey
of C stars in Local Group dwarf irregular galaxies. Observations of the two low
luminosity dwarf irregular galaxies, Pegasus and DDO 210, revealed respectively
40 and 3 C stars, assuming that the reddening of Pegasus is negligible. No C
stars were identified in Tucana. Our observations permit the estimation of the
CMD contamination by foreground M dwarf thus yielding reliable C/M ratios. Our
R, I photometry of the C stars cannot be used to solve the extinction
controversy toward Pegasus. The three C stars in DDO 210 are quite bright when
compared to C star populations in dwarf galaxies. A larger fainter population
in that galaxy seems however improbable. The statistics of C stars, currently
on hand for dwarf galaxies, show a well-defined trend with the absolute
magnitude of galaxies.
(129kb)

astro-ph/0008062 [abs, src, ps, other] :

Title: Dynamics of Stars and Globular Clusters in M87

Authors:
Aaron J. Romanowsky,
Christopher S. Kochanek

Comments: 23 pages, with 11 inline Postscript figures, LaTeX, aaspp4.sty,
submitted to ApJ

We examine the dynamics of the stars and globular clusters in the nearby
giant galaxy M87 and constrain the mass distribution, using all the available
data over a large range of radii, including higher-order moments of the stellar
line-of-sight velocity distributions and the discrete velocities of over two
hundred globular clusters. We introduce an extension of the spherical orbit
modeling method that makes full use of all the information in the data, and
provides very robust constraints on the mass models. We conclusively rule out a
constant mass-to-light ratio model. Using the stellar constraints, the mass of
the dark halo is determined to 9% accuracy, assuming a singular isothermal
density profile. The globular cluster constraints determine the mass to 14%.
However, the masses that we infer separately with these constraints are
inconsistent. This implies that the halo’s radial density profile falls off
more slowly than 1/r^2, suggesting that the potential of the Virgo Cluster is
already dominant at r ~ 300″ ~ 20 kpc.
(214kb)

astro-ph/0008063 [abs, src, ps, other] :

Title: Origin of the highest energy cosmic rays observed

Authors:
P.L.Biermann (Max Planck Institut fur Radioastronomie, Bonn, Germany),
E.-J. Ahn (Department of Physics, Seoul National University, Seoul, Korea),
G. Medina Tanco (Institute of Astronomy and Geophysics, University of Sao Paulo, Sao Paulo, Brasil),
T. Stanev (Bartol Research Institute, University of Delaware, Newark, DE, USA)

Comments: At TAUP99, the 6th international workshop on topics in Astroparticle
Physics and Underground Physics, College de France, Eds. J. Dumarchez, M.
Froissart, D. Vignaud, (Sep 1999)

Journal-ref: Nucl.Phys.B, 87, 417-419, 2000

Introducing a simple Galactic wind model patterned after the solar wind we
show that back-tracing the orbits of the highest energy cosmic events suggests
that they may all come from the Virgo cluster, and so probably from the active
radio galaxy M87. This confirms a long standing expectation. Those powerful
radio galaxies that have their relativistic jets stuck in the interstellar
medium of the host galaxy, such as 3C147, will then enable us to derive limits
on the production of any new kind of particle, expected in some extensions of
the standard model in particle physics. New data from HIRES will be crucial in
testing the model proposed here.
(10kb)

astro-ph/0008064 [abs, src, ps, other] :

Title: A Structure for Quasars

Authors:
Martin Elvis

Comments: 35 pages, including 8 color figures (figures 4abc are big).
Astrophysical Journal, in press. Expanded version of conference paper
astro-ph/0005161

This paper proposes a simple, empirically derived, unifying structure for the
inner regions of quasars. This structure is constructed to explain the broad
absorption line (BAL) regions, the narrow `associated’ ultraviolet and X-ray
warm absorbers (NALs); and is also found to explain the broad emission line
regions (BELR), and several scattering features, including a substantial
fraction of the broad X-ray Iron-K emission line, and the bi-conical extended
narrow emission line region (ENLR) structures seen on large kiloparsec scales
in Seyfert images. Small extensions of the model to allow luminosity dependent
changes in the structure may explain the UV and X-ray Baldwin effects and the
greater prevalence of obscuration in low luminosity AGN.
(238kb)

astro-ph/0008065 [abs, src, ps, other] :

Title: The European Large Area ISO Survey III: 90micron extragalactic source
counts

Authors:
A.Efstathiou,
S.Oliver,
M.Rowan-Robinson,
C.Surace,
T.Sumner,
P.Heraudeau,
M.J.D.Linden-Vornle,
D.Rigopoulou,
S.Serjeant,
R.G.Mann,
C.J.Cesarsky,
L.Danese,
A.Franceschini,
R.Genzel,
A.Lawrence,
D.Lemke,
R.G.McMahon,
G.Miley,
J-L.Puget,
B.Rocca-Volmerange

Comments: 13 pages, accepted by MNRAS. For more details on the ELAIS project
see this http URL

We present results and source counts at 90micron extracted from the
Preliminary Analysis of the European Large Area ISO Survey (ELAIS). The survey
covered about 11.6 square degrees of the sky in four main areas and was carried
out with the PHOT instrument onboard the Infrared Space Observatory (ISO). The
survey is at least an order of magnitude deeper than the IRAS 100micron survey
and is expected to provide constraints on the formation and evolution of
galaxies. The majority of the detected sources are associated with galaxies on
optical images. In some cases the optical associations are interacting pairs or
small groups of galaxies suggesting the sample may include a significant
fraction of luminous infrared galaxies. The source counts extracted from a
reliable subset of the detected sources are in agreement with strongly evolving
models of the starburst galaxy population.
(85kb)

astro-ph/0008066 [abs, src, ps, other] :

Title: Supernova Remnants in the Sedov Expansion Phase: Thermal X-Ray Emission

Authors:
K. J. Borkowski,
W. J. Lyerly,
S. P. Reynolds

Comments: 19 pages, 11 figures, submitted to Astrophysical Journal

Improved calculations of X-ray spectra for supernova remnants (SNRs) in the
Sedov-Taylor phase are reported, which for the first time include reliable
atomic data for Fe L-shell lines. This new set of Sedov models also allows for
a partial collisionless heating of electrons at the blast wave and for energy
transfer from ions to electrons through Coulomb collisions. X-ray emission
calculations are based on the updated Hamilton-Sarazin spectral model. The
calculated X-ray spectra are succesfully interpreted in terms of three
distribution functions: the electron temperature and ionization timescale
distributions, and the ionization timescale averaged electron temperature
distribution. The comparison of Sedov models with a frequently used single
nonequilibrium ionization (NEI) timescale model reveals that this simple model
is generally not an appropriate approximation to X-ray spectra of SNRs. We find
instead that plane-parallel shocks provide a useful approximation to X-ray
spectra of SNRs, particularly for young SNRs. Sedov X-ray models described
here, together with simpler plane shock and single ionization timescale models,
have been implemented as standard models in the widely used XSPEC v11 spectral
software package.
(159kb)

astro-ph/0008067 [abs, src, ps, other] :

Title: Cosmological Studies from Radio Source Samples

Authors:
Steve Rawlings

Comments: 16 pages, invited review at IAU 199

I review some recent cosmological studies based on redshift surveys of radio
sources selected at low frequencies. The accretion rate onto the central black
hole is identified as the basis of a crude physical division of the
low-frequency population into two sub-populations: the first comprises
`Eddington-tuned’ (high accretion rate) quasars and their torus-hidden
counterparts; the second comprises `starved quasars’ like M87. There exist
remarkable similarities between the shapes and evolutionary behaviours of the
luminosity functions of radio sources and radio-quiet quasars; all luminous AGN
are $sim300-$times rarer at epochs corresponding to $z sim 0$ than at $z sim
2.5$. I argue that any evidence that quasars were intrinsically rarer at $z
sim 5$ than at $z sim 2.5$ is as yet both tentative and indirect. A simple
calculation suggests that the radio source population has been over-looked as a
potentially important contributor to the entropy budget of the Universe. A
recent sub-mm survey of radio sources is used to demonstrate a connection
between the events which trigger jets and intense bursts of star formation, and
a close link between the histories of star formation and AGN activity is
proposed. I discuss the aims and methods of future large redshift surveys of
radio sources, emphasising the importance of dovetailing these with the
development of robust physical models for radio sources and their
epoch-dependent environments.
(62kb)

astro-ph/0008068 [abs, src, ps, other] :

Title: A spectroscopic survey for strong galaxy-galaxy lenses

Authors:
J. P. Willis (1 and 2),
P. C. Hewett (1),
S. J. Warren (3),
G. F. Lewis (4) ((1) IoA, Cambridge, (2) PUC, Chile, (3) Imperial College, UK, (4) AAO, Australia)

Comments: 4 pages, 2 figures, Proceedings of the XXth Moriond Astrophysics
Meeting “Cosmological Physics with Gravitational Lensing”, J.-P. Kneib, Y.
Mellier, M. Moniez and J. Tran Thanh Van eds., 2000

We present a spectroscopic survey for strong galaxy-galaxy lenses. Exploiting
optimal sight-lines to massive, bulge-dominated galaxies at redshifts $z sim
0.4$ with wide-field, multifibre spectroscopy, we anticipate the detection of
10-20 lensed Lyman-$alpha$ emitting galaxies at redshifts $z simgreat 3$ from
a sample of 2000 deflectors. Initial spectroscopic observations are described
and the prospects for constraining the emission-line luminosity function of the
Lyman-$alpha$ emitting population are outlined.
(119kb)

astro-ph/0008069 [abs, src, ps, other] :

Title: Binary quasars

Authors:
Daniel J. Mortlock (1),
Rachel L. Webster (1),
Paul J. Francis (2) ((1) University of Melbourne, (2) The Australian National University)

Comments: 12 pages, 12 figures

Journal-ref: 1999, MNRAS, 309, 836

Quasar pairs are either physically distinct binary quasars or the result of
gravitational lensing. The majority of known pairs are in fact lenses, with a
few confirmed as binaries, leaving a population of objects that have not yet
been successfully classified. Building on the arguments of Kochanek, Falco &
Munoz (1999), it is shown that there are no objective reasons to reject the
binary interpretation for most of these. In particular, the similarity of the
spectra of the quasar pairs appears to be an artifact of the generic nature of
quasar spectra. The two ambiguous pairs discovered as part of the Large Bright
Quasar Survey (Q 1429-053 and Q 2153-0256) are analysed using principle
components analysis, which shows that their spectral similarities are not
greater than expected for a randomly chosen pair of quasars from the survey.
The assumption of the binary hypothesis allows the dynamics, time-scales and
separation distribution of binary quasars to be investigated and constrained.
The most plausible model is that the quasars’ activity is triggered by tidal
interactions in a galatic merger, but that the (re-)activation of the galactic
nuclei occurs quite late in the interaction, when the nuclei are within 80+/-30
kpc of each other. A simple dynamical friction model for the decaying orbits
reproduces the observed distribution of projected separations, but the decay
time inferred is comparable to a Hubble time. Hence it is predicted that binary
quasars are only observable as such in the early stages of galactic collisions,
after which the quiescent super-massive black holes orbit in the merger remnant
for some time.
(121kb)

astro-ph/0008070 [abs, src, ps, other] :

Title: Bayesian joint estimation of non-Gaussianity and the power spectrum

Authors:
Graca Rocha,
Joao Magueijo,
Mike Hobson,
Anthony Lasenby

Comments: 11pages, 4 figures, submitted to MNRAS

We propose a rigorous, non-perturbative, Bayesian framework which enables one
jointly to test Gaussianity and estimate the power spectrum of CMB
anisotropies. It makes use of the Hilbert space of an harmonic oscillator to
set up an exact likelihood function, dependent on the power spectrum and on a
set of parameters $alpha_i$, which are zero for Gaussian processes. The latter
can be expressed as series of cumulants; indeed they perturbatively reduce to
cumulants. However they have the advantage that their variation is essentially
unconstrained. Any truncation(i.e.: finite set of $alpha_i$) therefore still
produces a proper distribution – something which cannot be said of the only
other such tool on offer, the Edgeworth expansion. We apply our method to Very
Small Array (VSA) simulations based on signal Gaussianity, showing that our
algorithm is indeed not biased.
(205kb)

astro-ph/0008071 [abs, src, ps, other] :

Title: The local space density of Sb-Sdm galaxies as function of their
scalesize, surface brightness and luminosity

Authors:
Roelof S. de Jong (Steward Observatory),
Cedric Lacey (SISSA)

Comments: 15 pages, 10 figures. Accepted for publication in the Astrophysical
Journal

We investigate the dependence of the local space density of spiral galaxies
on luminosity, scalesize and surface brightness. We derive bivariate space
density distributions in these quantities from a sample of about 1000 Sb-Sdm
spiral galaxies, corrected for selection effects in luminosity and surface
brightness. The structural parameters of the galaxies were corrected for
internal extinction using a description depending on galaxy surface brightness.
We find that the bivariate space density distribution of spiral galaxies in the
(luminosity, scalesize)-plane is well described by a Schechter luminosity
function in the luminosity dimension and a log-normal scale size distribution
at a given luminosity. This parameterization of the scalesize distribution was
motivated by a simple model for the formation of disks within dark matter
halos, with halos acquiring their angular momenta through tidal torques from
neighboring objects, and the disk specific angular momentum being proportional
to that of the parent halo. However, the fractional width of the scalesize
distribution at a given luminosity is narrower than what one would expect from
using the distribution of angular momenta of halos measured in N-body
simulations. We present several possible explanations for the narrowness of the
observed distribution. Using our bivariate distribution, we find that
determinations of the local luminosity function of spiral galaxies should not
be strongly affected by the bias against low surface brightness galaxies, even
when the galaxies are selected from photographic plates. This may not be true
for studies at high redshift, where (1+z)^4 surface brightness dimming can
cause a significant selection bias against lower surface brightness galaxies.
(353kb)

---

Replacements

---

astro-ph/0001382 [abs, src, ps, other] :

Title: Chemical enrichment and star formation in the Milky Way disk; I. Sample
description and chromospheric age-metallicity relation

Authors:
H. J. Rocha-Pinto (IAG/USP – Brazil),
W. J. Maciel (IAG/USP – Brazil),
John Scalo (Univ. Texas),
Chris Flynn (Tuorla Observ. – Finland)

Comments: 19 pages, 18 eps figures, 19 pages, 18 eps figures, replacement
includes some modifications after the referee’s report

Journal-ref: Rocha-Pinto et al. (2000), Astron. & Astrophys., 358, 869

Note: replaced with revised version Thu, 3 Aug 2000 21:27:10 GMT (269kb)

astro-ph/0001383 [abs, src, ps, other] :

Title: Chemical enrichment and star formation in the Milky Way disk; II. Star
formation history

Authors:
H. J. Rocha-Pinto (IAG/USP – Brazil),
John Scalo (Univ. Texas),
W. J. Maciel (IAG/USP – Brazil),
Chris Flynn (Tuorla Observ. – Finland)

Comments: 18 pages, 21 eps figures, 19 pages, 18 eps figures, replacement
includes some modifications after the referee’s report

Journal-ref: Rocha-Pinto et al. (2000), Astr. & Astrophys., 358, 869

Note: replaced with revised version Thu, 3 Aug 2000 21:54:29 GMT (262kb)

astro-ph/0003177 [abs, src, ps, other] :

Title: The DENIS Point Source Catalogue towards the Magellanic Clouds

Authors:
M-R. Cioni,
C. Loup,
H. J. Habing,
P. Fouque’,
E. Bertin,
E. Deul,
D. Egret,
C. Alard,
B. de Batz,
J. Borsenberger,
M. Dennefeld,
N. Epchtein,
T. Forveille,
F. Garzon,
J. Hron,
S. Kimeswenger,
F. Lacombe,
T. Le Bertre,
G. A. Mamon,
A. Omont,
G. Paturel,
P. Persi,
A. Robin,
D. Rouan,
G. Simon,
D. Tiphene,
I. Vauglin,
S. Wagner

Comments: 1 figure changed, published

Journal-ref: A&AS 144, 235-245, 2000

Note: replaced with revised version Thu, 3 Aug 2000 09:59:39 GMT (533kb)

astro-ph/0003321 [abs, src, ps, other] :

Title: Detectability of Gravitational Radiation from Prompt and Delayed Star
Collapse to a Black Hole

Authors:
Cristiano Palomba

Comments: strongly revised version, 19 pages, 7 figures. Submitted to the
International Journal of Modern Physics D

Note: replaced with revised version Thu, 3 Aug 2000 15:17:11 GMT (44kb)

astro-ph/0007201 [abs, src, ps, other] :

Title: The very red afterglow of GRB 000418 – further evidence for dust
extinction in a GRB host galaxy

Authors:
S. Klose,
B. Stecklum,
N. Masetti,
E. Pian,
E. Palazzi,
A. A. Henden,
D. H. Hartmann,
O. Fischer,
J. Gorosabel,
C. Sanchez-Fernandez,
D. Butler,
Th. Ott,
S. Hippler,
M. Kasper,
R. Weiss,
A. Castro-Tirado,
J. Greiner,
C. Bartolini,
A. Guarnieri,
A. Piccioni,
S. Benetti,
F. Ghinassi,
A. Magazzu,
K. Hurley,
T. Cline,
J. Trombka,
T. McClanahan,
R. Starr,
J. Goldsten,
R. Gold,
E. Mazets,
S. Golenetskii,
K. Noeske,
P. Papaderos,
P. M. Vreeswijk,
N. Tanvir,
A. Oscoz,
J. M. Munnoz,
J. M. Castro Ceron

Comments: Accepted for publication in The Astrophysical Journal. 12 pages;
citations & references updated; minor textual changes

Note: replaced with revised version Thu, 3 Aug 2000 08:47:06 GMT (57kb)

astro-ph/0007375 [abs, src, ps, other] :

Title: New Constraints on inflation from the Cosmic Microwave Background

Authors:
William H. Kinney,
Alessandro Melchiorri,
Antonio Riotto

Comments: 16 pages, 4 figures, some typos corrected, references added

Note: replaced with revised version Thu, 3 Aug 2000 08:31:46 GMT (107kb)

astro-ph/0008018 [abs, src, ps, other] :

Title: Calculations at Series Limits in One-Electron Systems

Authors:
Charles R. Cowley

Comments: 4 pages

Note: replaced with revised version Thu, 3 Aug 2000 13:36:58 GMT (4kb)

For subscribe options to combined physics archives,

e-mail To: physics@arXiv.org, Subject: subscribe

—————————————————————————–

For help on viewing and making submissions, see this http URL

For a list of archive mirror sites, see this http URL

—————————————————————————–

Third-party submissions cause excessive problems.

Author self-submissions are exceedingly preferred. Format if by e-mail:

\

Title: Recent Seminal Results

Authors: Author One and Author Two

Comments: 3 pages, latex, no figures, mpeg simulations available at

  ftp://myhost.mydomain/path/file.mpg or at http://myhost.mydomain/RSR/file.mpg

Report-no: EFI-2000-18

\

text of abstract (you do not need  Abstract: …)

\

body of paper (as mime attachments, uuencoded .tar.gz .zip, etc.)