50 research outputs found
Reduction of the COSMOS Southern Sky galaxy survey data to the RC3 standard system
After having cross-identified a subsample of LEDA galaxies in the COSMOS
database, we defined the best relations to convert COSMOS parameters
(coordinates, position angle, diameter, axis ratio and apparent magnitude) into
RC3 system used in the LEDA database. Tiny secondary effects can be tested:
distance to plate cenetrs effect and air-mass effect. The converted COSMOS
parameters are used to add missing parameters on LEDA galaxies.
Key words: galaxies - catalogue - photometryComment: 5 pages, postcript including figures, to appear in MNRAS, reprint
requests: [email protected]
The LEDA galaxy distribution: I. Maps of the Local Universe
In order to investigate the properties of large-scale structures of galaxies
in the universe, we present an analysis of their spatial distribution at
z0.033. We used the LEDA extragalactic database containing over 1 million of
galaxies covering the all-sky and the SDSS data included in the public release
DR1, yielding to a sample of around 134,000 galaxies having a measured redshift
in two survey areas representing 690 sq. degrees. The results of the study are
2D, 3D maps and magnitude number counts of galaxies, drawn from B-band samples.
Movies and high resolution figures are available on
http://www-obs.univ-lyon1.fr/cosmologie/helene.htmlComment: Received November 30, 2003; accepted February 2004, in pres
Inclinations and black hole masses of Seyfert 1 galaxies
A tight correlation of black hole mass and central velocity dispersion has
been found recently for both active and quiescent galaxies. By applying this
correlation, we develop a simple method to derive the inclination angles for a
sample of 11 Seyfert 1 galaxies that have both measured central velocity
dispersions and black hole masses estimated by reverberation mapping. These
angles, with a mean value of 36 degree that agrees well with the result
obtained by fitting the iron K lines of Seyfert 1s observed with ASCA,
provide further support to the orientation-dependent unification scheme of AGN.
A positive correlation of the inclinations with observed FWHMs of H line
and a possible anti-correlation with the nuclear radio-loudness have been
found. We conclude that more accurate knowledge on inclinations and broad line
region dynamics is needed to improve the black hole mass determination of AGN
with the reverberation mapping technique.Comment: 12 pages including 4 figures, accepted for publication in The
Astrophysical Journal Letter
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 power spectrum in a strongly inhomogeneous Universe
A crucial issue in cosmology is the determination of the fluctuation power
spectrum.The standard picture of the matter clustering, the Cold Dark Matter
model (and its variant), assumes that,on scales smaller than a certain
``flattening scale'' , the power spectrum increases with the scale,
while on much larger scales it decreases so to match the tiny fluctuations
observed in the microwave background. The standard picture also assumes that,
once a statistically homogeneous sample is reached, the power spectrum
amplitude is fixed, and any major variation should be attributed to luminosity
segregation. However, the determination of and of the absolute
amplitude, if any, is still matter of debate. In particular, there is no
consensus on whether the turnaround has been detected or not, and on the actual
importance of the luminosity segregation effect. We show that, due to the
finiteness of the sample the standard analysis of self-similar (fractal)
distributions yields a turnaround for scales close to the survey scale, and a
systematic amplitude shift with the survey scale. We point out that both
features, bending and scaling, are in agreement with recent determination of
the power spectrum, in particular with the CfA2 spectrum. We remark that the
standard power spectrum is not a well defined statistical tool to characterize
the galaxy distribution when a homogeneity scale has not been reached. In order
to perform an analysis that does not imply any a priori assumption one should
study the PS of the density, rather than the PS of the density contrast.Comment: 11 pages Latex file. 3 .ps figures are available by anonymous ftp in
ftp://oarhp2.rm.astro.it/pub/amendola/ as psfig1.ps psfig2.ps and psfig3.p
AGN Black Hole Masses and Bolometric Luminosities
Black hole mass, along with mass accretion rate, is a fundamental property of
active galactic nuclei. Black hole mass sets an approximate upper limit to AGN
energetics via the Eddington limit. We collect and compare all AGN black hole
mass estimates from the literature; these 177 masses are mostly based on the
virial assumption for the broad emission lines, with the broad-line region size
determined from either reverberation mapping or optical luminosity. We
introduce 200 additional black hole mass estimates based on properties of the
host galaxy bulges, using either the observed stellar velocity dispersion or
using the fundamental plane relation to infer ; these methods assume
that AGN hosts are normal galaxies. We compare 36 cases for which black hole
mass has been generated by different methods and find, for individual objects,
a scatter as high as a couple of orders of magnitude. The less direct the
method, the larger the discrepancy with other estimates, probably due to the
large scatter in the underlying correlations assumed. Using published fluxes,
we calculate bolometric luminosities for 234 AGNs and investigate the relation
between black hole mass and luminosity. In contrast to other studies, we find
no significant correlation of black hole mass with luminosity, other than those
induced by circular reasoning in the estimation of black hole mass. The
Eddington limit defines an approximate upper envelope to the distribution of
luminosities, but the lower envelope depends entirely on the sample of AGN
included. For any given black hole mass, there is a range in Eddington ratio of
up to three orders of magnitude.Comment: 43 pages with 10 figures. Accepted for publication in Ap