30 research outputs found
A Catalog of Galaxies behind the Southern Milky Way. - I. The Hydra/Antlia Extension (l: 266 - 296 deg)
A deep optical galaxy search in the southern Milky Way - aimed at reducing
the width of the Zone of Avoidance - revealed 3279 galaxy candidates above the
diameter limit of D > 0.2 arcmin, of which only 112 (3.4%) were previously
catalogued. The surveyed region (266 < l < 296 and -10 < b < +8) lies in the
extension of the Hydra and Antlia clusters - where a supercluster is suspected
- and in the approximate direction of the dipole anisotropy in the Cosmic
Microwave Background radiation. Here we present the optical properties of the
unveiled galaxies such as positions, diameters, magnitudes, morphological
types, including a detailed discussion on the quality of these data and the
completeness limits as a function of the foreground dust extinction. For 127 of
the 227 positional matches in the IRAS PSC, a reliable cross-identification
could be found. Several distinct overdensities and filaments of galaxies can be
identified that are apparently uncorrelated with the Galactic foreground
extinction hence the probable signature of extragalactic large-scale
structures. This catalog constitutes the first part in a series of five equally
conducted optical searches for galaxies in the southern Milky Way (245 < l <
350). With these surveys, the entire Zone of Avoidance will have been covered
by means of visual inspection. The catalogs build the basis for various
spectroscopic and photometric follow-up programs which eventually will allow a
thorough analyse of the galaxy distribution in redshift space and the peculiar
velocity fields within the Zone of Avoidance, as well an an improved
understanding of the Galactic foreground extinction.Comment: Accepted for publication by A&ASS, 50 pages, LaTex, 7 encapsulated
figures, requires aa.cls end epsf.sty. Full-resolution, color figures 1, 2, 6
and 7 are available upon request (E-mail: [email protected]
Cosmological Structures behind the Milky Way
This paper provides an update to the review on extragalactic large-scale
structures uncovered in the Zone of Avoidance (ZOA) by Kraan-Korteweg & Lahav
2000, in particular in the Great Attractor region. Emphasis is given to the
penetration of the ZOA with the in 2003 released NIR 2MASX Catalog. The
distribution is little affected by the foreground dust. Galaxies can be
identified to extinction levels of over A(B) < 10m except in the wider Galactic
Bulge region (see Fig. 9) where star density is a strong delimiting factor. The
shape of the NIR-ZOA is quite asymmetric due to Galactic features such as
spiral arms and the Bulge, something that should not be ignored when using NIR
samples for studies such as dipole determinations.
Results are presented from the deep blind HI ZOA survey performed with the
Multibeam Receiver at the Parkes telescope (v < 12700km/s). The distribution of
the roughly one thousand discovered spiral galaxies in the optically and NIR
impenetratable part of the ZOA clearly depict the prominence of the Norma
Supercluster. With the optically identified galaxies in the ZOA, a picture
emerges that bears a striking resemblance to the Coma cluster in the Great
Wall: the rich Norma cluster (ACO 3627) lies within a great-wall like structure
that can be traced at the redshift range of the cluster over 90dg on the sky,
with two foreground filaments - reminiscent of the legs in the famous stick man
- that merge in an overdensity at slightly lower redshifts around the radio
galaxy PKS 1343-601 (see Figs. 14 & 16). (abridged)Comment: Invited Review at the joint conference of the Czech Astron. Society
and the Astron. Gesellschaft. To appear in Reviews in Modern Astronomy 18, on
``From Cosmological Structures to the Milky Way'', ed. S. Roeser, 30pages, 16
ps-figures. Full resolution gzipped ps-version (16Mb) available at
http://mensa.ast.uct.ac.za/~kraan/AGreview/AGreview.ps.g
Abell 3627: A Nearby, X-ray Bright, and Massive Galaxy Cluster
The cluster A3627 was recently recognized to be a very massive, nearby
cluster in a galaxy survey close to the galactic plane. We are reporting on
ROSAT PSPC observations of this object which confirm that the cluster is indeed
very massive. The X-ray emission detected from the cluster extends over almost
1 degree in radius. The X-ray image is not spherically symmetric and shows
indications of an ongoing cluster merger. Due to the strong interstellar
absorption the spectral analysis and the gas temperature determination are
difficult. The data are consistent with an overall gas temperature in the range
5 to 10 keV. There are signs of temperature variations in the merger region. A
mass estimate based on the X-ray data yields values of \msu \ if extrapolated to the virial radius of Mpc. In
the ROSAT energy band (0.1 - 2.4 keV) the cluster emission yields a flux of
about erg s cm which makes A3627 the 6
brightest cluster in the ROSAT All Sky Survey. The cluster was missed in
earlier X-ray surveys because it was confused with a neighbouring X-ray bright,
galactic X-ray binary (1H1556-605). The large X-ray flux makes A3627 an
important target for future studies.Comment: 14 pages, Latex file, including aaspp.sty, 9 postscript figures and 1
table, accepted for publication by the Astrophysical Journa