The ALFA Zone of Avoidance Survey: Results from the Precursor Observations

TL;DR

The ALFA ZOA survey aims to map large regions near the Galactic plane to discover new galaxies, including potentially dark galaxies, by detecting HI signals in obscured regions, with precursor observations revealing many previously unknown objects.

Contribution

This paper presents the first precursor observations of the ALFA ZOA survey, providing HI measurements for new and previously uncharacterized galaxies in the Zone of Avoidance.

Findings

Many detected objects are new and lack previous detections.

A significant number of sources have no known redshift or HI detection.

Precursor observations demonstrate the survey's potential to uncover hidden galaxies.

Abstract

The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map 1350-1800 square degrees at low Galactic latitude, providing HI spectra for galaxies in regions of the sky where our knowledge of local large scale structure remains incomplete, owing to obscuration from dust and high stellar confusion near the Galactic plane. Because of these effects, a substantial fraction of the galaxies detected in the survey will have no optical or infrared counterparts. However, near infrared follow up observations of ALFA ZOA sources found in regions of lowest obscuration could reveal whether some of these sources could be objects in which little or no star formation has taken place ("dark galaxies"). We present here the results of ALFA ZOA precursor observations on two patches of sky totaling 140 square degrees (near l=40 degrees, and l=192 degrees). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database (NED). A significant fraction of the objects have never been detected at any wavelength. For those galaxies that have been previously detected, a significant fraction have no previously known redshift, and no previous HI detection.