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T h e A L F A Z o n e o f A v o id a n c e S u rv e y : R e s u lts fro m th e P re c u rs o r O b s e rv a tio n s
C.M. Springob (NRC-Naval Research Lab), P.A. Henning (UNM), B. Catinella (NAIC), F. Day (UNM), R. Minchin, E. Momjian (NAIC), B. Koribalski (ATNF), K.L. Masters (CfA), E. Muller (ATNF), C. Pantoja (U. Puerto Rico), M. Putman (U. Michigan), J.L. Rosenberg (George Mason U.), S. Schneider (U. Mass.), L. Staveley-Smith (U. Western Australia) Introduction
The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map 1350-1800 deg2 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 this extinction and stellar confusion, 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 deg2 (one near l=40o, and the other near l=192o ). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database. A significant fraction of the objects are new, having 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.

Data Reduction
Data reduced using software originally developed for the Parkes Multibeam surveys (LiveData, Gridzilla), adapted for Arecibo. Data are gridded using a median filter, taking advantage of the re-observations of sky p ointings afforded by the basketweave technique. Cubes are searched by eye, parameters fit in M iriad.

Why survey the ZOA in HI?
The ZOA has been narrowed by deep optical / IR searches, but both fail in regions of high extinction and stellar confusion. Galaxies which contain HI can be found in regions of thickest obscuration and worst IR confusion. Scientific Goals: Reveal large scale structure in an unexplored region of the local universe Combine with HI detections of other ALFA surveys to produce HI parameter statistical measures such as the HI mass function Compute Tully-Fisher distances at low Galactic latitudes, to be incorporated into 2MASS Tully-Fisher Survey (Masters et al. 2005), to reveal extragalactic velocity field at low Galactic latitudes Because Galactic extinction is patchy, detection of dark galaxies (esp. at high |b| and in Galactic anti-center d irection) is possible, with IR followup observations: AB ~1.0 in certain parts of the anti-center d irection, so this should be possible.

Figure 3 Spectrum of a p reviously unknown galaxy from the precursor observations.

Figure 4 HI Image of the galaxy from Figure 3.

Results
72 galaxies detected in the 140 deg2 of sky covered by precursor observations.

Figure 5 Left heliocentric
redshift and right HI flux distributions for the 72 detections.

O f th e 7 2 d e t e c t io n s :
15 have no known counterpart -- observed here for the first time But only 32 of the 57 known objects have previously known redshifts (mostly radio) 23 objects with previously known HI fluxes and widths 10 gals are in the inner Galaxy region, where all but one of the counterparts have been detected in the radio only Figure 6 Left HI fluxes and right HI widths for galaxies with HI parameters in the literature-- comparison
between our values and literature values.

Figure 1

(From Henning et al. 2006) redshift slices of known galaxies in and near the inner and outer Galaxy regions accessible to Arecibo. Top panels show galaxies with vh el < 3500 km/s, middle panels with 3 500 < vh el < 6500 km/s, and bottom panels with 6500 < vhel < 9500 km/s. Known and suspected large-scale structures are l abeled (Fairall 1 998).

Precursor Observations
While the full survey begins in Summer 2007, we conducted precursor observations in 2005-2006 on a 40 deg2 patch of sky, in the vicinity of l~40o, and a separate 100 deg2 patch of sky near l~192o. Each point on the sky is covered by two passes, reaching RMS sensitivities of 5-6 mJy per beam.

b

Our fluxes and widths are consistent with the values from the literature, given the typical errors associated with each quantity.

Summary
- We will map the ZOA behind the inner Galaxy in the Arecibo sky, within |b|<10o , to an RMS of ~5-6 mJy. - Will also map both the inner and outer Galaxy Arecibo ZOA, within |b|<5°, with ~20 times longer integration time. - The majority of our detections have known counterparts in the literature, but less than half have previously known redshifts---exploring new part of LSS. - Only one of our detections in the inner Galaxy region has been observed in wavelengths other than radio; most of those in the outer Galaxy were detected by 2MASS. - We find a strong correlation between our HI parameters and those from the literature.

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EDA galaxies within 12,000 km/s in and near the two ZOA regions accessible to Arecibo, the inner (left) and outer Galaxy (right). Dashed curves show the regions of sky Arecibo can see. The rectangles containing the Galactic equator show the overlap with the HI Parkes ZOA survey, with galaxies detected by Parkes plotted with heavy dots. Green boxes indicate ALFA ZOA precursor regions.

Acknowledgements
This research was performed while C.M.S. held a National Research Council Research Associateship Award at the Naval Research Laboratory. Basic research in astronomy at the Naval Research Laboratory is supported by 6.1 base funding. P.A.H. acknowledges support from NSF grant AST-0506676. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.

R e fe re n c e s
D onley e t a l. 2005 A J 1 29, 2 20. Fairall 1998, Large-Scale Structures in the Local Universe (Chichester: Wiley). Henning et al. 2006 BAAS 208.5304. Masters et al. 2005 BAAS 37, 1427. Pantoja e t al. 1997 AJ 113, 905. Wong et al. 2006 MNRAS in press (astro-ph/0607491).