SkyMapper Southern Survey: Second data release (DR2)

We present the second data release (DR2) of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia, using six optical filters: u, v, g, r, i, z. DR2 is the first release to go beyond the ∼18 mag (10 σ) limit of the Shallow Survey released in the first data release (DR1), and includes portions of the sky at full survey depth that reach >21 mag in g and r filters. The DR2 photometry has a precision as measured by internal reproducibility of 1% in u and v, and 0.7% in griz. More than 21 000 °-2 have data in some filters (at either Shallow or Main Survey depth) and over 7 000 °-2 have deep Main Survey coverage in all six filters. Finally, about 18 000 °-2 have Main Survey data in i and z filters, albeit not yet at full depth. The release contains over 120 000 images, as well as catalogues with over 500 million unique astrophysical objects and nearly 5 billion individual detections. It also contains cross-matches with a range of external catalogues such as Gaia DR2, Pan-STARRS1 DR1, GALEX GUVcat, 2MASS, and AllWISE, as well as spectroscopic surveys such as 2MRS, GALAH, 6dFGS, and 2dFLenS.