The GALFA-HI Survey: Data Release 1

TL;DR

The GALFA-HI survey provides high-resolution, large-area, and high-spectral-resolution data of Galactic neutral hydrogen, significantly advancing the capabilities of Galactic HI observations with detailed data processing techniques.

Contribution

This paper introduces the first data release of the GALFA-HI survey, showcasing new data reduction methods for high-resolution Galactic HI mapping.

Findings

Coverage of 7520 square degrees of sky.

Achieved typical noise levels of 80 mK RMS.

Demonstrated effective mitigation of instrumental noise effects.

Abstract

We present the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey, and its first full data release (DR1). GALFA-HI is a high resolution (~ 4'), large area (13000 deg^2), high spectral resolution (0.18 km/s), wide band (-700 < v_LSR < +700 km/s) survey of the Galactic interstellar medium in the 21-cm line hyperfine transition of neutral hydrogen conducted at Arecibo Observatory. Typical noise levels are 80 mK RMS in an integrated 1 km/s channel. GALFA-HI is a dramatic step forward in high-resolution, large-area Galactic HI surveys, and we compare GALFA-HI to past, present, and future Galactic HI surveys. We describe in detail new techniques we have developed to reduce these data in the presence of fixed pattern noise, gain variation, and inconsistent beam shapes, and we show how we have largely mitigated these effects. We present our first full data release, covering 7520 square degrees of sky and representing 3046 hours of integration time, and discuss the details of these data.