Issue |
A&A
Volume 445, Number 3, January III 2006
|
|
---|---|---|
Page(s) | 857 - 867 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20053616 | |
Published online | 03 January 2006 |
The DPOSS II compact group survey: first spectroscopically confirmed candidates
1
European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile e-mail: epompei@eso.org
2
INPE/MCT, Av. dos Astronautas 1758, S. J. Campos, SP 12227-010, Brazil e-mail: reinaldo@das.inpe.br
3
Osservatorio Astronomico di Brera via Brera 28, 20121 Milano, Italy e-mail: iovino@brera.mi.astro.it
Received:
11
June
2005
Accepted:
30
August
2005
This paper presents the results of a pilot redshift survey
of 18 candidate compact groups from the distant DPOSS survey that extends to redshift ~0.2
the available surveys of compact groups of galaxies, mainly
Hickson Compact Groups and Southern Compact Groups. The goal of our survey was to confirm group
membership via redshift information and to measure the characteristic
parameters of a representative, albeit small, sample of DPOSS survey
groups.
Of the 18 candidates observed, seven are found to be indeed isolated
compact groups, i.e. groups with 3 or more concordant members and with
no neighbouring known cluster, while 7 are chance
projection configurations on the sky. Three remaining candidates,
despite having 3 or more concordant member galaxies, are located in
the neighbourhood of known clusters, while another candidate turned out to be a
dense sub-condensation within Abell 0952.
The median redshift of our 7 confirmed groups is , to be
compared with a median redshift of 0.03 for
the local sample of compact groups by Hickson. The typical group size is
~50 kpc, and the median radial velocity
dispersion is 167 km s-1, while typical crossing times range from
0.005
to 0.03
with a median value of 0.018
, all similar to the values usually found in the
literature for such structures in the local universe. The average
mass-to-light ratio for our groups,
, is 92h,
higher than the value found for nearby Hickson compact groups
but lower than that found for loose groups. Our results suggest that,
once full redshift information for its members
becomes available, the DPOSS sample will provide a reference sample to study the
properties of compact groups beyond the local universe.
Key words: galaxies: clusters: general / techniques: spectroscopic
© ESO, 2006
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