41 research outputs found
An Off-Axis Telescope Concept for Antarctic Astronomy
International audienc
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]
The atmospheric parameters and spectral interpolator for the stars of MILES
Context. Empirical libraries of stellar spectra are used for stellar
classification and synthesis of stellar populations. MILES is a medium
spectral-resolution library in the optical domain covering a wide range of
temperatures, surface gravities and metallicities. Aims. We re-determine the
atmospheric parameters of these stars in order to improve the homogeneity and
accuracy. We build an interpolating function that returns a spectrum as a
function of the three atmospheric parameters, and finally, we characterize the
precision of the wavelength calibration and stability of the spectral
resolution. Methods. We use the ULySS program with the ELODIE library as a
reference and compare the results with literature compilations. Results. We
obtain precisions of 60 K, 0.13 and 0.05 dex respectively for Teff, log g and
[Fe/H] for the FGK stars. For the M stars, the mean errors are 38 K, 0.26 and
0.12 dex, and for the OBA 3.5%, 0.17 and 0.13 dex. We construct an interpolator
that we test against the MILES stars themselves. We test it also by measuring
the atmospheric parameters of the CFLIB stars with MILES as reference and find
it to be more reliable than the ELODIE interpolator for the evolved hot stars,
like in particular those of the blue horizontal branch.Comment: A&A accepted, 29 pages, 6 figure
Thermal InfraRed Observations at Dôme C: A Valuable Extension for HYPERLEDA
The outstanding atmospheric conditions of the Dôme C give a unique
opportunity to survey the sky in the thermal infrared reaching interesting
sensitivity limits for extragalactic astronomy. It will allow to
survey the very obscured region of the Galactic Plane, to detect numerous
Ultra-Luminous InfraRed Galaxies, a class of extremely powerful
galaxies in the infrared wavelengths.
The detection of individual Cepheids in nearby galaxies will be possible
and will lead to eliminate a biais in the
determination of the extragalactic distances scale.
Our extragalactic database HyperLeda will benefit from new infrared data.
A wide field IR imager at Concordia and HyperLeda
The ARENA consortium proposes the construction and operation of a 2 meter
class telescope at Dôme C dedicated to wide field imaging, and driven by
major astrophysical key projects. We present here the foreseen contribution
of the Observatoire de Lyon, concerning the data management and the databases
Thermal InfraRed surveys from Antarctica for extragalactic astronomy
The outstanding atmospheric conditions of the Dome C give a unique
opportunity to survey deeply large areas of the sky in the thermal
infrared reaching interesting
sensitivity limits for extragalactic astronomy.
Our extragalactic database HyperLeda will benefit from new infrared data,
especially for
characterizing nuclear and starburst activity of AGNs and ULIRGs