The Arecibo Zone of Avoidance (ZOA) Survey

The Extragalactic ALFA Zone of Avoidance team is mapping the distribution of low-Galactic-latitude galaxies and large scale structures through detection of galaxies' 21-cm emission with ALFA. This Zone of Avoidance (ZOA) survey finds new HI galaxies which lie hidden behind the Milky Way, and also provides redshifts and other HI parameters for partially-obscured galaxies known at other wavelengths. In this way, we are illuminating the large scale structure in the local Universe in the low-Galactic-latitude sky where it is currently poorly mapped. The ZOA survey is one of the Extragalactic ALFA projects, and proceeds in tandem with Galactic ALFA and Pulsar ALFA projects. This "commensal" style of observing, using multiple backends simultaneously, increases enormously the scientific throughput of the telescope, making very efficient use of observing hours, particularly important during the popular Galactic time.

Precursor Results

Two regions behind the Milky Way were observed in the early observations: a 30 square degree area around l = 40 deg, and a 100 square degree area around l = 190. These precursor observations, done commensally with Galactic ALFA projects in the meridian-nodding mode, reached an RMS sensitivity of 5-6 mJy per beam, as sensitive as the Parkes ZOA survey, but in a small fraction of the time. The first region observed, through the heavily-obscured inner Galaxy, was selected to overlap the northern extension of the Parkes ZOA survey, so we could quickly check performance of the observing and analysis systems with known HI sources. We detected 10 HI galaxies in this area, including 7 of the Parkes galaxies as expected, and three more HI sources - one associated with an IRAS galaxy, and two newly-discovered galaxies. Because of the thick obscuration in the optical and confusion in the IR in this region, only the one IRAS galaxy has a cataloged counterpart in any other waveband. In the lower-extinction, less confused outer Galaxy region, 51 of the 62 galaxies detection by ALFA ZOA have cataloged counterparts, but only 24 have previously published redshifts. Further details on the precursor observations may be found in Henning et al. AJ, 139, 2130, 2010.

Figure: Spectrum of an HI galaxy in the Zone of Avoidance discovered by ALFA. This galaxy has no cataloged counterpart in any other waveband.

Current Observations

Observations for the full survey of the accessible inner Galaxy, l = 30 - 75 deg, and within 10 degrees of either side of the Galactic plane, have been completed, and data analysis is ongoing. These observations were conducted in the same nodding mode of the precursor work. We have begun the deep phase of the survey, commensal with PALFA and RRL projects, which is reaching RMS better than 1 mJy. The deep survey will cover 5 degrees on either side of the plane, and has started in the inner Galaxy, with plans to cover the ZOA in the anticenter region longitude range in a later phase.

ZOA Observing web page

Publications and Proceedings

The Arecibo L-band Feed Array Zone of Avoidance Survey I: Precursor Observations through the Inner and Outer Galaxy. Henning P. A., Springob C. M., Minchin R. F., Momjian E., Catinella B., McIntyre T., Day F., Muller E., Koribalski B., Rosenberg J. L., Schneider S., Staveley-Smith L., van Driel W., 2010, AJ, 139, 2130.
ADS Bibcode: 2010AJ....139.2130H.

The ALFA Zone of Avoidance Survey: Results from the Precursor Observations. Springob C. M., Henning P. A., Catinella B., Day F., Minchin R., Momjian E., Koribalski B., Masters K. L., Muller E., Pantoja C., Putman M., Rosenberg J. L, Schneider S., Staveley-Smith L., 2007, IAU Symp. 244.
ArXiv:0708.1724
Download PDF of the poster

The abstract for our poster at the Calgary AAS meeting, June 2006
The abstract for our poster at the Seattle AAS meeting, January 2007

The ALFA ZOA Team

Useful links:

Arecibo Astronomy pages
E-ALFA pages
Arecibo Legacy Fast ALFA (ALFALFA) survey project page
Arecibo Ultra Deep Survey (AUDS) project page
Arecibo Galaxy Environmet Survey (AGES) project page
Arecibo Observatory Telescope Schedule Database

Last updated: Wednesday, 17-Nov-2010 17:06:38 AST
E. Momjian