| Annu. Rev. Astron. Astrophys. 1991. 29:
499-541
Copyright © 1991 by Annual Reviews. All rights reserved
|
3.5 Targeted Surveys
Numerous surveys include objects selected according to criteria that do
not conform to flux, size, or spatial completeness; their goals can vary
greatly and a brief summary and categorization are difficult tasks.
Below we discuss some examples of major surveys of such special objects.
BlNARIES AND GROUPS
These systems are studied in detail for a variety of reasons: (a)
because relative velocities of members are small, they provide the loci
for the study of environmental effects of a milder nature than those
observed in clusters of galaxies; (b) the distribution of mass can be
probed beyond scales accessible by sampling rotation curves; and (c) the
understanding of their dynamics can lead to insights in the frequency
of mergers, the circumstances associated with starburst phenomena, and
in other evolutionary concerns. The production of binary and group
catalogs is a sort of cottage industry, initially carried out on the
basis of angular separation and size criteria and, as more redshift
data have become available, via the application of more sophisticated
group-finding algorithms. Central contributions are the catalogs of
binaries of Karachentsev
(1983 and
refs. therein) and
Turner (1976).
Humason et al (1956)
and Sandage (1978)
first identified groups in
redshift catalogs, while variations on the ``friends- of-friends''
algorithm have been used by
Press & Davis (1982),
Huchra & Geller
(1982), and
Morgan & Hartwick
(1988),
and the dendogram method introduced by
Materne (1978)
has been most notably applied to generate a catalog of nearby groups
[Tully (1987)].
Notable among the numerous analyses of binary and group properties are those of
Peterson (1979),
White et al (1983),
Schneider et al
(1986),
Schweizer (1987
and refs. therein),
Maia et al (1989),
Ramella et al (1989),
Soares (1989,
based on a catalog developed by van Albada, cf. in
Soares 1989), and
Zepf & Koo (1989).
ISOLATED GALAXIES
Isolated galaxies are thought to provide the most reliable statistical
reference to study global properties of galaxy populations, unaffected
as they might be by environmentally driven evolutionary processes.
Several catalogs of isolated galaxies have been produced using varying
criteria: the one most used is that of
Karachentseva (1973).
Haynes & Giovanelli
(1984)
and Davis & Seaquist
(1983)
have reported 21-cm
results on subsamples of Karachentseva's catalog of, respectively, 324
and 113 galaxies.
DWARFS, LSB, AND EMISSION-LINE GALAXIES
The determination of the faint end of the luminosity function, the
understanding of galaxy formation, evolution processes and the effects
of environment on the latter, and establishing whether segregation
phenomena related to properties such as luminosity, surface brightness,
or gas content are at work, have motivated many surveys of special
objects. Surveys of low-surface-brightness dwarf systems have been
carried out mainly via 21-cm line spectroscopy principally at Arccibo:
Hoffman et al (1987)
in the Virgo cluster region, Thuan and
collaborators for an all-northern sky survey of UGC dwarfs
(Thuan & Seitzer
1979a,
b;
Schneider et al 1990);
Bothun et al (1985),
Eder et al (1989),
Salzer et al
(1990), and
Thuan et al (1987)
for the investigation of surface brightness and morphological segregation with
local galaxian density. A search for faint Local Supercluster members
prompted a 6-m telescope survey of 92 blue galaxies by
Karachentsev (1984)
who, in addition to identifying 28 new supercluster members, also
first suggested the existence of a 70 h-1 Mpc feature
in the galaxian
clustering spectrum. An exhaustive compilation of low surface
brightness dwarf galaxies has been produced by
Karachentseva &
Sharina (1988).
Markarian and collaborators
(1981
and refs. therein) at the Byurakan
Observatory surveyed 15,000 deg2 of sky with objective-prism
plates to
obtain the best known sample of active galaxies. Efforts towards
obtaining redshifts for this sample have been ongoing at the 6-m
telescope of the Soviet Academy of Sciences
(Markarian et al
1988a,
b
and refs. therein).
Stepanian (1985)
has reported on the Second
Byurakan survey and on the space distribution of galaxies associated
with this effort.
Salzer et al (1989)
have similarly reported reshifts
for the University of Michigan objective-prism survey. Searches for
emission-line galaxies that might populate low density regions in the
galaxian distribution have been carried out by
Tifft et al (1986),
Moody et al (1987),
and Weistrop & Downes
(1988).
Salzer (1989)
has analyzed
more generally the relationship between large-scale structure and
emission-line objects.
ZONE OF AVOIDANCE
Galactic extinction exceeds half a magnitude for about one fifth of
the extragalactic sky at optical wavelengths, where catalogs of galaxies
become severely incomplete. The task of mapping the nearby universe in
those regions thus relies on painstaking efforts of identification of
highly absorbed images in red survey plates
(Kraan-Korteweg 1990
and refs. therein) or on the application of a combination of radio and
infrared techniques. The IRAS point source catalog has served as a
source of extragalactic candidates in the zone of avoidance, with 21-cm
line observations used to establish a redshift. In this mode, several
surveys have helped reduce the margins of darkness of the zone of
avoidance, e.g.
Dow et al (1988),
Pfleiderer et al
(1981),
Chamaraux et al (1990),
and Lu et al (1990).
Kerr & Henning (1987)
have carried out
blind 21-cm searches in the galactic plane. Complete coverage of the
zone of avoidance at 21 cm has often been invoked as a desirable goal.
However, the necessary investment of telescope time is exceptionally
large, and blind radio searches out to redshifts of 0.03 can
realistically be limited to only restricted patches of sky.
SUPERCLUSTERS AND VOIDS
Several studies targeted selected areas for redshift survey work,
aiming at the definition of three-dimensional features in the
large-scale structure of the galaxian distribution. They have often been
stimulated by features in the projected galaxy counts, suggestive of
coherent density enhancements.
Oort (1983)
reviews the early work.
Kraan-Korteweg (1986)
gives a useful catalog of 2810 galaxies in the
Local Supercluster. The Coma region continues to receive special attention
(Gavazzi 1987,
1989;
Gregory et al 1988;
Tifft & Gregory 1988),
as have regions around Hercules
(Freudling et al 1988),
Corona
Borealis
(Postman et al 1988),
Hydra-Centaurus
(da Costa et al 1986,
1987),
Centaurus-Pavo
(Fairall 1988),
Horologium-Reticulum
(Lucey et al 1983,
Chincarini et al 1984),
and Lynx-Ursa Major
(Giovanelli & Haynes
1982,
Focardi et al 1986).
Particularly notable in terms of the sample
size are the surveys of the Cancer region by Bicay & Giovanelli
(1986a,
b,
1987),
which included a contribution of 644 redshifts, that of the
Great Attractor
(Dressler 1988,
1990),
which included 1314 redshifts,
and those ongoing at Nancay [Chamaraux (personal communication) is
completing a survey of MCG late spiral galaxies between 0° > 
> - 18°,
while Fouque (personal communication) is targeting a similar sample of
ESO galaxies south of = -
18°].
Haynes & Giovanelli
(1990a) have
presented 300-foot observations of 304 galaxies, mainly north of +38°,
that complement their Arecibo supercluster survey work.
Rood (1988)
recently reviewed the efforts directed at the description of voids in
the galaxian distribution. More recently,
Pellegrini et al
(1989)
surveyed void regions in the southern galactic cap, and
Burns et al (1988) and
Willick et al (1990)
studied voids in the Pisces region.