The Second Data Release of the Beijing-Arizona Sky Survey

TL;DR

The paper details the second data release of the Beijing-Arizona Sky Survey, including new $z$-band data, improved reduction methods, and comprehensive data products to support future spectroscopic targeting.

Contribution

This release is the first to include MzLS data covering the same area as BASS, with updated reduction and photometric methods for enhanced data quality.

Findings

Median 5σ depths of 24.05, 23.61, 23.10 mag in g, r, z bands

Inclusion of MzLS data covering the same area as BASS

Updated data reduction pipeline with source detection on stacked images

Abstract

This paper presents the second data release (DR2) of the Beijing-Arizona Sky Survey (BASS). BASS is an imaging survey of about 5400 deg$^2$ in $g$ and $r$ bands using the 2.3 m Bok telescope. DR2 includes the observations as of July 2017 obtained by BASS and Mayall $z$-band Legacy Survey (MzLS). This is our first time to include the MzLS data covering the same area as BASS. BASS and MzLS have respectively completed about 72% and 76% of their observations. The two surveys will be served for the spectroscopic targeting of the upcoming Dark Energy Spectroscopic Instrument. Both BASS and MzLS data are reduced by the same pipeline. We have updated the basic data reduction and photometric methods in DR2. In particular, source detections are performed on stacked images, and photometric measurements are co-added from single-epoch images based on these sources. The median 5$\sigma$ depths with corrections of the Galactic extinction are 24.05, 23.61, and 23.10 mag for $g$, $r$, and $z$ bands, respectively. The DR2 data products include stacked images, co-added catalogs, and single-epoch images and catalogs. The BASS website (http://batc.bao.ac.cn/BASS/) provides detailed information and links to download the data.