SkyMapper Southern Survey: Second data release (DR2)

Abstract

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 $\sim\!18$ mag (10 $\sigma$ ) 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 $\deg^2$ have data in some filters (at either Shallow or Main Survey depth) and over 7 000 $\deg^2$ have deep Main Survey coverage in all six filters. Finally, about 18 000 $\deg^2$ 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.

Photometric flaring fraction of M dwarf stars from the SkyMapper Southern Survey

“…We did, however, find an interesting case of an asteroid being blended with a star, when extending the SkyBoT search to red giants: a giant of 15 mag was blended with the V ≈ 10.6 mag Inner Main Belt asteroid (230) Athamantis for the duration of one visit in June 2014, seeOnken et al 2019 for details.MNRAS 000, 000-000(0000)…”

“…10 shows this flare alongside three weaker ones. Now, that DR2 of SkyMapper is available (Onken et al 2019) and includes deeper images one third of the Southern sky, we can obtain more precise colour indices of this object in quiescence, (r − i, i − z) = (2.295, 0.917), which indicate a spectral type of M4-M5 that lies on the locus of typical M dwarf stars (see Fig. 1).…”

The Fornax Deep Survey with VST

“…To further verify the validity of the calibration obtained with the strategy delineated above, especially for the more elaborate u-band, we matched and compared our photometry to the SkyMapper (SM) data (Wolf et al 2018;Onken et al 2019). The SDSS photometric systems of APASS and SM are not equivalent, the u and g bands, in particular, show differences of up to 0.5 mag in the two systems (Wolf et al 2018).…”

THOR 42: A touchstone ∼24 Myr-old eclipsing binary spanning the fully-convective boundary

“…The images were processed with a modified version of the Science Data Pipeline (SDP) used for Data Release 2 (DR2) of the SkyMapper Southern Survey (Onken et al 2019), where the cosmic-ray subtraction was deactivated in order to avoid spurious flagging of electronic noise peaks. The rest of the data reduction proceeded as for DR2: suppression of high-frequency interference noise, overscan subtraction, 2D bias subtraction, per-row bias structure removed by principal components analysis (PCA), flatfield correction, background equalisation between the two amplifiers on each CCD, and a PCA-based subtraction of detector fringing.…”

“…The rest of the data reduction proceeded as for DR2: suppression of high-frequency interference noise, overscan subtraction, 2D bias subtraction, per-row bias structure removed by principal components analysis (PCA), flatfield correction, background equalisation between the two amplifiers on each CCD, and a PCA-based subtraction of detector fringing. Photometric zero-points were based on the ATLAS All-Sky Stellar Reference Catalog (Tonry et al 2018b) after applying Pan-STARRS1-to-SkyMapper bandpass transformations (for details see Onken et al 2019). In a further modification from DR2 processing, an individual photometric data point consisted of a PSF magnitude determined by a 2D model created from well-measured stars across each CCD using the PSFEX software package (Bertin 2011), where the model was allowed to vary linearly with (x, y) position on the CCD.…”