Issue |
A&A
Volume 410, Number 2, November I 2003
|
|
---|---|---|
Page(s) | 461 - 470 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20031233 | |
Published online | 17 November 2003 |
Galaxies in group and field environments: A comparison of optical–NIR luminosities and colors
1
Dipartimento di Astronomia, Università degli Studi di Trieste, Via Tiepolo 11, 34131 Trieste, Italy e-mail: mardiros,mezzetti,rigoni@ts.astro.it
2
Laboratoire d'Astrophysique de Marseille, Marseille, France e-mail: marinoni@astrsp-mrs.fr
Corresponding author: M. Girardi, girardi@ts.astro.it
Received:
19
May
2003
Accepted:
29
July
2003
We compare properties of galaxies in loose groups with
those in field environment by analyzing the Nearby Optical Galaxy
(NOG) catalog of galaxy systems. We consider as group galaxies
objects belonging to systems with at least five members identified by
means of the “friends of friends method”, and, as field galaxies,
all galaxies with no companions. We analyze both a magnitude-limited
sample of 959 and 2035 galaxies (groups vs. field galaxies,
respectively, mag, and
km s-1) and a
volume-limited sample (
mag,
km s-1 369 group and 548 field galaxies). For
all these galaxies, blue corrected magnitudes and morphological types
are available. The cross-correlation of NOG with the 2MASS second
release allow us to assign K magnitudes and obtain
colors for
about half of the galaxies in our samples. We analyze luminosity and
color segregation-effects in relation with the morphological
segregation. For both B and K bands, we find that group galaxies
are, on average, more luminous than field galaxies and this effect is
not entirely a consequence of the morphological
segregation. After taking into account the morphological segregation,
the luminosity difference between group and field galaxies is about
. When considering only very early-type galaxies (
) the
difference is larger than
. We also find that group galaxies
are redder than field galaxies,
mag.
However, after taking into account the morphological segregation, we
find a smaller
difference, poorly significant (only at the c.l. of
~80%). We discuss our results considering that the analyzed
groups define a very low density environment (projected mean density
~
h2 Mpc-2 galaxies).
Key words: galaxies: clusters: general / galaxies: fundamental parameters / galaxies: evolution / cosmology: observations
© ESO, 2003
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