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Parkes HI observations of galaxies behind the southern Milky Way. II. The Crux and Great Attractor regions (l ~ 289 degree to 338 degree) | | Anja C. Schroeder
; Renee C. Kraan-Korteweg
; Patricia A. Henning
; | | Date: |
24 Jul 2009 | | Abstract: | As part of our programme to map the large-scale distribution of galaxies
behind the southern Milky Way, we observed 314 optically-selected,
partially-obscured galaxies in the Zone of Avoidance (ZOA) in the Crux and
Great Attractor (GA) regions. The observations were conducted with the Parkes
64m radio telescope, in a single-pixel pointed mode, reaching an rms noise
level of typically 2-6 mJy over the velocity search range of 400<v<10500km/s. A
total of 162 galaxies were detected. This can be explained by the prominence of
the GA overdensity in the survey regions, which leads to a relatively higher
fraction of nearby galaxies. It is also evident from the quite narrow velocity
distribution (largely confined to 3000-6000km/s) and deviates significantly
from the expectation of a uniform galaxy distribution for the given sensitivity
and velocity range. No systematic differences were found between detections and
non-detections, in terms of latitude, foreground extinction, or environment,
except for the very central part of the rich Norma cluster, where hardly any
galaxies were detected. A detailed investigation of the HI content of the
galaxies reveals strong HI deficiency at the core of the Norma cluster (within
about a 0.4 Abell radius), similar to what has been found in the Coma cluster.
The redshifts obtained by this observing technique result in a substantial
reduction of the so-called redshift ZOA. This is obvious when analysing the
large-scale structure of the new HI data in combination with data from optical
ZOA redshift surveys. The lower latitude detections provide further evidence of
the extension of the Norma Wall, across the ZOA, in particular its bending
towards the Cen-Crux clusters above the Galactic plane at slightly higher
redshift, rather than a straight continuation towards the Centaurus clusters. | | Source: | arXiv, 0907.4312 | | Services: | Forum | Review | PDF | Favorites | |
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