Issue |
Astron. Astrophys. Suppl. Ser.
Volume 130, Number 2, June I 1998
|
|
---|---|---|
Page(s) | 341 - 358 | |
DOI | https://doi.org/10.1051/aas:1998229 | |
Published online | 15 June 1998 |
Loose groups of galaxies in the Perseus–Pisces survey*
Dipartimento di Fisica dell'Università, via Celoria 16, I-20133 Milano, Italy Present address: Ludwig–Maximilians–Universität, Sektion Physik, Lehrstuhl Wagner, Theresienstr. 37, D-80333 München, Germany
Send offprint request to: R. Trasarti–Battistoni
Received:
5
August
1997
Accepted:
24
December
1997
We present a large catalog
of loose groups of galaxies in the Southern Galactic Hemisphere,
selected from the Perseus–Pisces redshift Survey (PPS).
Particular care is taken in order to obtain group samples
as homogeneous as possible to previously published catalogs.
All our catalogs contain about 200 groups,
significantly more than in most previous studies
where group samples were obtained from galaxy data sets
of comparable quality to (but smaller extent than) PPS.
Groups are identified with the adaptive Friends–Of–Friends (FOF) algorithm of
Huchra & Geller (1982), with suitable normalizations
and
at
.
The luminosity function (LF) normalization
appropriate for PPS yields
a number density threshold
for the adopted D0,
instead of
used in previous studies of other samples.
However, the customary choice of D0 obtained (through the LF) from
a fixed mass overdensity
, well motivated in theory,
suffers from
important observational uncertainties
and sample–to–sample variations of the LF normalization,
and from
major uncertainties in the relation between
galaxy density n and mass density ρ .
We discuss how to self–consistently match
FOF parameters among different galaxy samples.
We then separately vary several FOF and sample parameters,
and discuss their effect on group properties.
Loose groups in PPS nicely trace the large scale structure (LSS)
in the parent galaxy sample.
The group properties vary little with different redshift corrections,
redshift cut–off, and galaxy LF, but
are rather sensitive to the adopted links D0 and V0.
More precisely, the typical group size (velocity dispersion) is
linearly related to the adopted distance (velocity) link, while
it is rather insensitive to the adopted velocity (distance) link.
Physical properties of groups in PPS
and in directly comparable samples show good agreement.
There is a complex interplay among LSS features, sample depth,
FOF grouping procedure, and group properties.
Key words: catalogs / galaxies: clusters of luminosity function / cosmology: large scale structure of the Universe
© European Southern Observatory (ESO), 1998