197 research outputs found
First DENIS I-band extragalactic catalog
This paper presents the first I-band photometric catalog of the brightest
galaxies extracted from the Deep Near Infrared Survey of the Southern Sky
(DENIS) An automatic galaxy recognition program has been developed to build
this provisional catalog. The method is based on a discriminating analysis. The
most discriminant parameter to separate galaxies from stars is proved to be the
peak intensity of an object divided by its array. Its efficiency is better than
99%. The nominal accuracy for galaxy coordinates calculated with the Guide Star
Catalog is about 6 arcseconds. The cross-identification with galaxies available
in the Lyon-Meudon Extragalactic DAtabase (LEDA) allows a calibraton of the
I-band photometry with the sample of Mathewson et Al. Thus, the catalog
contains total I-band magnitude, isophotal diameter, axis ratio, position angle
and a rough estimate of the morphological type code for 20260 galaxies. The
internal completeness of this catalog reaches magnitude , with a
photometric accuracy of . 25% of the Southern sky has been
processed in this study.
This quick look analysis allows us to start a radio and spectrographic
follow-up long before the end of the survey.Comment: 13 pages, 17 figures, to appear A&A Supl.
Extragalactic database. VII Reduction of astrophysical parameters
The Lyon-Meudon Extragalactic database (LEDA) gives a free access to the main
astrophysical parameters for more than 100,000 galaxies. The most common names
are compiled allowing users to recover quickly any galaxy. All these measured
astrophysical parameters are first reduced to a common system according to well
defined reduction formulae leading to mean homogeneized parameters. Further,
these parameters are also transformed into corrected parameters from widely
accepted models. For instance, raw 21-cm line widths are transformed into mean
standard widths after correction for instrumental effect and then into maximum
velocity rotation properly corrected for inclination and non-circular velocity.
This paper presents the reduction formulae for each parameter: coordinates,
morphological type and luminosity class, diameter and axis ratio, apparent
magnitude (UBV, IR, HI) and colors, maximum velocity rotation and central
velocity dispersion, radial velocity, mean surface brightness, distance modulus
and absolute magnitude, and group membership. For each of these parameters
intermediate quantities are given: galactic extinction, inclination,
K-correction etc..
All these parameters are available from direct connexion to LEDA (telnet
lmc.univ-lyon1.fr, login: leda, no passwd
OR http://www-obs.univ-lyon1.fr/leda ) and distributed on a standard CD-ROM
(PGC-ROM 1996) by the Observatoire de Lyon via the CNRS (mail to
[email protected]).Comment: 13 pages, 12 figures. The CDROM of the extragalactic database LEDA is
available by mailing to: [email protected]
Calibration of the distance scale from galactic Cepheids: I Calibration based on the GFG sample
New estimates of the distances of 36 nearby galaxies are presented based on
accurate distances of galactic Cepheids obtained by Gieren, Fouque and Gomez
(1998) from the geometrical Barnes-Evans method.
The concept of 'sosie' is applied to extend the distance determination to
extragalactic Cepheids without assuming the linearity of the PL relation. Doing
so, the distance moduli are obtained in a straightforward way.
The correction for extinction is made using two photometric bands (V and I)
according to the principles introduced by Freedman and Madore (1990). Finally,
the statistical bias due to the incompleteness of the sample is corrected
according to the precepts introduced by Teerikorpi (1987) without introducing
any free parameters (except the distance modulus itself in an iterative
scheme).
The final distance moduli depend on the adopted extinction ratio {R_V}/{R_I}
and on the limiting apparent magnitude of the sample. A comparison with the
distance moduli recently published by the Hubble Space Telescope Key Project
(HSTKP) team reveals a fair agreement when the same ratio {R_V}/{R_I} is used
but shows a small discrepancy at large distance.
In order to bypass the uncertainty due to the metallicity effect it is
suggested to consider only galaxies having nearly the same metallicity as the
calibrating Cepheids (i.e. Solar metallicity). The internal uncertainty of the
distances is about 0.1 magnitude but the total uncertainty may reach 0.3
magnitude.Comment: 12 pages, 4 figures, access to a database of extragalactic Cepheids.
Astronomy & Astrophysics (in press) 200
A method for isolating and culturing placental cells from failed early equine pregnancies
Early pregnancy loss occurs in 6â10% of equine pregnancies making it the main cause of reproductive wastage. Despite this, reasons for the losses are known in only 16% of cases. Lack of viable conceptus material has inhibited investigations of many potential genetic and pathological causes. We present a method for isolating and culturing placental cells from failed early equine pregnancies. Trophoblast cells from 18/30 (60%) failed equine pregnancies of gestational ages 14â65 days were successfully cultured in three different media, with the greatest growth achieved for cells cultured in AmnioChromeâą Plus. Genomic DNA of a suitable quality for molecular assays was also isolated from 29/30 of these cases. This method will enable future investigations determining pathologies causing EPL
Adapting Component-based Systems at Runtime via Policies with Temporal Patterns
International audienceDynamic reconfiguration allows adding or removing components of component-based systems without incurring any system downtime. To satisfy specific requirements, adaptation policies provide the means to dynamically reconfigure the systems in relation to (events in) their environment. This paper extends event-based adaptation policies by integrating temporal requirements into them. The challenge is to reconfigure component-based systems at runtime while considering both their functional and non-functional requirements. We illustrate our theoretical contributions with an example of an autonomous vehicle location system. An implementation using the Fractal component model constitutes a practical contribution. It enables dynamic reconfigurations guided by either enforcement or reflection adaptation policies
Calibration of the distance scale from galactic Cepheids:II Use of the HIPPARCOS calibration
New estimate of the distances of 36 nearby galaxies is presented. It is based
on the calibration of the V- and I-band Period-Lumi- nosity relations for
galactic Cepheids measured by the HIPPARCOS mission. The distance moduli are
obtained in a classical way. The statistical bias due to the incompleteness of
the sample is corrected according to the precepts introduced by Teerikorpi
(1987).
We adopt a constant slope (the one obtained with LMC Cepheids). The
correction for incompleteness bias introduce an uncertainty which depends on
each galaxy. On the mean, this uncertainty is small (0.04 mag) but it may reach
0.3 mag. We show that the un- certainty due to the correction of the extinction
is small (propably less than 0.05 mag.). The correlation between the
metallicity and the morphological type of the host galaxy sug- gests us to
reduce the application to spiral galaxies in order to bypass the problem of
metallicity. We suspect that the adopted PL slopes are not valid for all
morphological types of galaxies. This may induce a mean systematic shift of 0.1
mag on distance moduli.
A comparison with the distance moduli recently published by Freedman et al.
(2001) shows there is a reasonably good agreement with our distance moduli.Comment: Accepted for Astron & Astrophys. (2002) Cepheid database available at
ftp://www-obs.univ-lyon1.fr via anonymous ftp. Directory:
pub/base/CEPHEIDES.tar.g
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