New Datasets Bonanza at Astro Data Lab

By Robert Nikutta and the Astro Data Lab team

The Astro Data Lab science platform recently incorporated several exciting new survey datasets which are now available to the community. These include the DESI Legacy Surveys (LS DR9), the Southern Photometric Local Universe Survey (S-PLUS DR2), the SkyMapper’s Southern Sky Survey (SkyMapper DR2), the VISTA Hemisphere Survey (VHS DR5), and the Rubin/LSST TRILEGAL simulated survey (LSST-SIM DR2). The four observed surveys’ object tables yield almost four billion rows (see Table 1), and together cover over 33,000 square degrees, with significant mutual overlaps (see Table 2). The LSST-SIM dataset simulates almost 27,000 square degrees and covers practically the entire footprint of SkyMapper DR2, VHS DR5, S-PLUS DR2, and half of LS DR9’s footprint.

Object number density (per square degree) in Mollweide projection for the five new surveys at Astro Data Lab. LS DR9 and S-PLUS DR2 (upper row) are shown in Equatorial coordinates, and SkyMapper DR2, VHS DR5, and LSST-SIM DR2 (lower row) are shown in Galactic coordinates.

The Data Lab team has already pre-crossmatched the four observational surveys with our reference datasets: Gaia EDR3 or DR2 (for astrometry), AllWISE, NSC DR2, unWISE DR1 (for photometry), and SDSS DR16 (for spectroscopy). We also routinely add other useful columns such as nest4096, ring256, and htm9 for Healpix-based and Hierarchical Triangular Mesh (HTM)-based sky tessellation use cases.

LS DR9  The Legacy Surveys data release 9 (DR9) comprises almost six years of data from the Dark Energy Camera (DECam) on the Víctor M. Blanco 4-meter Telescope (CTIO), the Mosaic-3 camera on the Nicholas U. Mayall 4-meter Telescope (KPNO), and the 90Prime camera on the UArizona Bok 2.3-meter Telescope (Steward Observatory). DR9 covers over 20,000 square degrees and is also the target selection dataset for the Dark Energy Spectroscopic Instrument (DESI) survey. Almost two billion individual objects have been detected to a 5-sigma depth of g = 24.7, r = 23.9, z = 23.0 AB magnitudes. The DR9 imagery is available through Astro Data Lab and Astro Data Archive at CSDC, while Data Lab also hosts most of the LS DR9 catalog tables, including the main object table (“tractor”), a forced photometry table, a table with WISE photometric light-curves that average up to 15 epochs together, and a photometric redshift table. Data Lab also hosts previous data releases LS DR3 through DR8. Keep an eye out for the forthcoming issue of The Mirror where LS DR9 will be featured in more detail.

S-PLUS DR2  The Southern Photometric Local Universe Survey (S-PLUS) is an international survey led by our Brazilian colleagues using the robotic T80-South Telescope at CTIO. The ongoing survey photographs the sky through twelve Javalambre filters — seven narrow-bands centered on [OII], Ca H+K, Hδ, G-band, Mgb triplet, Hα, and the Ca triplet and five Sloan-like filters. Data Release 2 comprises 950 square degrees observed between 2016 and 2020, to a S/N > 3 depth of g = 21.3 mag, and includes and updates the previous DR1 (which covers the Stripe 82 region). All data products are available from the survey team, while Astro Data Lab hosts the photometric object catalog, a photo-z table created using deep learning, and a star-galaxy-quasar classification table. Data Lab also hosts the DR1 catalog of S-PLUS.

SkyMapper DR2  SkyMapper is a 1.35-m wide-field survey telescope built and operated by our partners at the Australian National University. Located at Siding Spring Observatory, it currently conducts the SkyMapper Southern Sky Survey. Its data release 2 delivers half a billion objects over 17,000 square degrees of the Southern sky, detected in six optical filters (u, v, g, r, i, z), with some portions of the sky reaching > 21 mag in the g and r bands. Astro Data Lab hosts the main photometric object table, and more detailed per-image/CCD detection catalogs, including shape information. Data Lab also hosts DR1 of SkyMapper.

VHS DR5  Courtesy of the ESO Science Archive, Astro Data Lab now hosts the latest release of the VISTA Hemisphere Survey, VHS DR5. Generated by the dedicated 4.1-m VISTA telescope, VHS is one of five VISTA surveys, and DR5 delivers almost 1.4 billion individual objects detected in the NIR (bands Y, J, H, Ks) over an area of 16,500 square degrees visible from the Paranal Observatory in Chile. VHS DR5 reaches 5-sigma point source depths of J = 20.8 and Ks = 20.0 mag. For a subset of 4500 square degrees (the Southern Galactic Cap) the limiting magnitudes are deeper, at J = 21.4, H = 20.7 and Ks = 20.3 mag. Astro Data Lab hosts the multi-band photometric catalog, which also contains, e.g., star/galaxy classification columns.

LSST-SIM DR2  With simulations becoming ever more important for wide-field surveys, the community needs to find ways to serve large-area simulations as if they were actually observed, meaning that we employ the same data formats, same access protocols, and same tools as are used for any observed survey. Data Lab leads the way by serving to our community the second release of the simulated Milky Way dataset over the entire LSST footprint (LSST-SIM DR2), generated by Leo Girardi and collaborators using their TRILEGAL stellar population code. The catalog provides positions, proper motions, and LSST photometry (u, g, r, i, z, y) for 10.5 billion simulated stars in the Milky Way and the Magellanic Clouds down to the LSST stacked depth limit of 27.5 mag in the r band. Because this is a simulated sky, everything is known about the objects in this catalog, including their distance, age, metallicity, and extinction along our line of sight toward the objects.

Data access at Astro Data Lab  All catalogs are accessible at Astro Data Lab through Python APIs, the TAP protocol (familiar to users of TOPCAT), and a web query interface. Users can conveniently write SQL queries against databases and continue to process the returned tables using the full power of the Python programming language using only a web browser and a Data Lab account. The Data Lab team curates a large suite of tutorial Jupyter notebooks to get new users started and is happy to assist our users with any questions. We are looking forward to welcoming you at Astro Data Lab!

Data transfers, catalog ingestions, QA, and releases have been performed by Data Lab team members Alice Jacques, David Herrera, Mike Fitzpatrick, Ben Weaver, Knut Olsen, Stéphanie Juneau, and Robert Nikutta. We are grateful to our friends from DESI/Legacy Surveys, ANU/SkyMapper, Brazil/S-PLUS, ESO/VHS, and Padova/TRILEGAL for their generous help in making the new datasets available for Astro Data Lab.

References:

• VHS DR5 description paper: Pons et al. (2020), http://www.eso.org/rm/api/v1/public/releaseDescriptions/144
• SkyMapper DR2 paper: Onken et al. (2019), PASA, 36, 33O, https://ui.adsabs.harvard.edu/abs/2019PASA...36...33O/abstract 
• S-PLUS DR2 paper: Almeida-Fernandes et al. (2021), https://ui.adsabs.harvard.edu/abs/2021arXiv210400020A/abstract 
• DESI Legacy Surveys overview paper: Dey et al. (2019), AJ, 157, 168D, https://ui.adsabs.harvard.edu/abs/2019AJ....157..168D/abstract 
• TRILEGAL paper: Girardi et al. (2012), https://ui.adsabs.harvard.edu/abs/2012ASSP...26..165G/abstract
• LSST-SIM DR2 presentation slides: Pastorelli (2017), https://project.lsst.org/meetings/lsst2017/sites/lsst.org.meetings.lsst2017/files/03_trilegalSims_pastorelli_2017-08-15_MwMicrolensing.pdf