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A Neutral Hydrogen Survey of the NGC 7332 Region with the Arecibo L-band Feed Array
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R. F. Minchin1, E. Momjian1, L. Cortese2, K. L. O'Neil3, P. A Henning4, J. I. Davies2, AGES Team recibo Observatory 2Cardiff University 3National Radio Astronomy Observatory 4University of New Mexico
If I'm not here, then try at the Arecibo Observatory stand. rminchin@naic.edu

The Arecibo L-band Feed Array has been used to map a 5 square degree region out to a velocity of 18,000 km/s, covering a volume of ~9,000 Mpc3 (for H0=70 km s-1 Mpc-1). In this region we find 43 HI sources. 16 are previously catalogued, of which 6 have previous redshift measurements. The other 27 sources (63%) are new detections, we have identified optical counterparts for most of these sourcesfrom the DSS, but there remain four sources with only dubious counterparts and one with no obvious candidate. The HI sources have a median redshift of ~12,000 km/s (~170 Mpc) and range in neutral hydrogen content from 5x107 to 3x1010 M .
-1 The noise distribution in 20,000 km s the NGC 7332 field cube. Some of the `noise' can be identified with galaxies entering the analysis, but the lines at ~7,000 km s-1 and ~15,600 km s-1 are due to interference.

10,000 km s-1

The distribution of galaxies in the NGC 7332 field cube. The median redshift is 11,744 km s-1 and the mean is 11,145 km s-1. 60% of the sources lie beyond 10,000 km s-1, and over half of the sources below this velocity lie either in the NGC 7332 group or in an arc of galaxies at ~8,900 km s-1 (see figure to the right).

0 km s-1

The figure above shows the spatial and velocity distribution of the 43 sources found by AGES in the NGC 7332 field. The three sources in the NGC 7332 group can be seen in dark blue. Other sources show possible signs of clustering, in particular the three highest redshift sources f orm a close triangle at R.A. ~22.53h , Dec. ~23.3є (16,619 - 17,019 km s-1) and there is an arc of galaxies between 8,770 and 9,046 km s-1 stretching from R.A. ~22.64h , Dec. ~23.2є to R.A. ~22.69h, Dec. ~24.6є.

HI mass against distance for the AGES sources (assuming H0 = 70 km s-1 Mpc-1 and a distance of 23 Mpc for the NGC 7332 group; Tonry et al. 2001) with completeness limits for AGES (blue), ALFALFA (green; Giovanelli et al. 2005), HIDEEP (magenta; Minchin et al. 2003) and HIPASS/HIJASS (red; Meyer et al. 2004; Lang et al. 2003). Of the 43 sources detected by AGES, one would expect 1520 sources to be seen in a survey with the depth of ALFALFA, 3-4 with HIDEEP and only 1 (NGC 7332) with HIPASS/HIJASS.

NGC 7332 field continuum sources overlaid with contours from the NVSS. The astrometry for AGES appears to be good across the whole field.

Analysis of the offset between radio and optical positions for sources with good optical counterparts. (Left) Cumulative distribution of offsets. T he 1 offset is 18 arcseconds and half of the sources fall within 11.5 arcseconds. (Right) Distribution of offsets in R. A. and Dec. There does not appear to be any significant pattern in the offsets; the average offsets are -3 ± 19 arcseconds i n R. A. and 3 ± 18 arcseconds in Dec.

Comparison of the AGES beam (blue; 3.5ґ 3.5ґ) with the ALFALFA beam (green; 3.8ґ 4.3ґ), HIJASS/VIRGOHI beam (magenta; 12ґ 12ґ) and the HIPASS/HIDEEP beam (red; 15ґ 15ґ)

The AGES beam measured off a high-resolution (0.1 arcmin/pixel) version of the continuum map. The beam was constructed from a number of strong continuum sources using the DAOPHOT routine PSF within IRAF. It can be seen that the half-power radius is ~1.7ґ and that the first sidelobe falls at a radius of ~5.2ґ.