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.

Current Status

Two regions behind the Milky Way have been observed with ALFA to date: a 38-square degree area around l = 40, and a 100-square degree region near l = 190. These "precursor" observations, done commensally with Galactic ALFA projects in the meridian-nodding, or "basketweave" mode, reached an RMS sensitivity of 5-6 mJy per beam, as sensitive as the Parkes ZOA survey (e.g. Donley et al. 2005, AJ, 129, 220) but in a small fraction of the time. The first region observed, toward 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 NIR 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 detected by ALFA have counterparts (mostly 2MASS) but only 24 have previously published redshifts.



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

Upcoming Observations

A full survey of the accessible inner Galaxy, l = 30 - 75 deg, and within 10 degrees of either side of the Galactic plane, will begin after the telescope becomes available again, post-painting. These observations will be conducted in the same basketweave mode of the precursor work described here. We will also conduct a deeper ZOA survey simultaneously with both a long-integration survey for pulsars and a survey for Galactic radio recombination lines. This deep survey will cover 5 degrees on either side of the plane, and will start in the inner Galaxy, with plans to cover the ZOA in the anticenter longitude range as well.

*ZOA Observing web page

Publications and Proceedings

We're working on the precursor observations paper and will post it here soon. In the meantime, check out:

* 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

Catinella, Barbara MPIfA
Day, Fonda UNM
Henning, Trish (PI) UNM
Koribalski, Baerbel ATNF
Masters, Karen CfA
Momjian, Emmanuel NRAO
Minchin, Robert NAIC
Muller, Erik ATNF
Pantoja, Carmen UPR
Putman, Mary UMich
Rosenberg, Jessica GMU
Schneider, Stephen UMass
Springob, Christopher NRL
Staveley-Smith, Lister U. West. Aust.

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: Thursday, 15-Nov-2007 11:58:51 AST
E. Momjian