Extragalactic H i Survey with FAST: First Look at the Pilot Survey Results

Abstract

We present the first data release of H i sources extracted from a pilot extragalactic survey using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We extracted sources from three-dimensional (3D) spectral data cubes datacubes to perform interactive searching and computing, yielding global parameters for each source, extending redshift ranges of H i emission up to z = 0.04. A total of 544 extragalactic H i sources has been detected by the pilot FAST H i drift scan survey covering part of the sky region in R.A. (R.A. or α) and decl. (decl. or δ) range 00h47m < R. A. (J2000) < 23h22m and +24° < decl. (J2000) < +43°. Of which, 528 sources are matched with optical counterparts via examination of digital optical survey databases collected from NED and Vizier data center, and 449 of them have optical velocities. Furthermore, we detect 36 galaxies with H i mass <108 M ⊙, which is significant for the study of low-mass systems in the local universe. We present catalogs for all H i detections with signal-to-noise ratio (S/N) greater than 5.1. The data are classified into four categories based on their S/N and baseline qualities, which are flagged with code 1 to 4: (1) 422 sources with S/N > 6.5; (2) 61 sources with 5.1 ≲ S/N ≲ 6.5; (3) 28 sources with relatively poor baselines; (4) 33 sources that are partly masked by strong radio frequency interferences (RFIs). In addition, we find 16 H i sources that have not been matched with any counterparts in the existing galaxy catalogs. This data release can provide guidance for the future extragalactic H i survey with FAST.