Sloan Digital Sky Survey V Launches Data Release 20, Extending Southern Hemisphere Observations

The Sloan Digital Sky Survey V (SDSS-V) has achieved a significant milestone with the launch of Data Release 20 (DR20), featuring the first optical spectra collected from the Southern Hemisphere. This expansion enhances the survey’s geographic reach and builds upon the foundational work established in prior releases.

By integrating these southern observations with existing northern data, SDSS-V provides a comprehensive view of stars, interstellar gas, and distant galaxies across both hemispheres, contributing to a larger panoptic spectroscopic map.

New Features in Data Release 20

DR20 includes more than three million spectra of stars and galaxies and introduces 18 value-added catalogs. “DR20 represents an enormous leap in the scale of SDSS data products… We’re excited to share DR20 with the world and see what the community discovers with it,” stated Dr. Emily Griffith from the University of Colorado Boulder, spokesperson for the SDSS-V collaboration.

Inaugural Southern Hemisphere Spectra

This release marks the first inclusion of SDSS-V stellar and extra-galactic optical spectra obtained from the du Pont 2.5m Telescope at Las Campanas Observatory (LCO) in Chile. These new data points, combined with updated observations from the Sloan Foundation’s 2.5m Telescope at Apache Point Observatory (APO), enrich the survey’s previously northern-centric observations.

Linking Optical and X-Ray Observations

DR20 also presents the initial substantial data stream from the eROSITA-SDSS-V coordinated observations, part of the SPectroscopic IDentification of ERosita Sources (SPIDERS) program. This initiative aligns with the second release of the eROSITA X-ray All-Sky Survey (eRASS DR2), facilitating optical redshift measurements for numerous X-ray emitting active galactic nuclei (AGN) and galaxy clusters.

Expansion of Black Hole Mapping

The Black Hole Mapper (BHM) has seen a dramatic increase, with DR20 offering 3 to 4 times more data than the previous release. The dataset includes approximately 1.1 million optical BOSS spectra representing around 500,000 unique objects and is bolstered by contributions from the All-Quasar Multi-Epoch Spectroscopy (AQMES) and Reverberation Mapping (RM) programs.

Mapping Stellar Structures

DR20 significantly expands the Milky Way Mapper (MWM), culminating in more than 1.5 million stars represented across BHM and MWM surveys. This collection includes the first carbon-enhanced metal-poor stars found in the Magellanic Clouds, as well as the first intermediate-mass stripped star, both key to understanding stellar evolution.

Updated Spectral Maps and New Visualization Tools

The Local Volume Mapper (LVM) has also grown, now featuring integral field spectroscopy maps covering 169 tiles and approximately 300,000 spectra. This advancement provides high-resolution insights into Galactic HII regions, planetary nebulae, and nearby galaxies.

For enhanced user interaction, the collaborative team has introduced LVMvis, an interactive visualization tool complementing updated interfaces for exploring cosmic gas and the LVM dataset. DR20 additionally introduces numerous updated value-added catalogs to streamline scientific inquiry.

Accessing the Data

As with previous releases, DR20 is cumulative, incorporating all newly reduced BOSS spectroscopic observations collected until February 2, 2025, along with earlier SDSS data. The entire dataset is accessible via the Science Archive Server (SAS), along with updated Python Notebook Tutorials for public use.

“We want everyone to make use of the SDSS data products, whether they are a professional astronomer, a student, or simply an astronomy enthusiast,” noted Dr. Anne-Marie Weijmans, SDSS Data Products Coordinator.

Looking toward future developments, Dr. Juna Kollmeier, SDSS-V Director, remarked, “This data release provides some spectacular SDSS-V data that we are sure people will make excellent use of, but we aren’t stopping here.”

Funding and Institutional Support

Funding for the Sloan Digital Sky Survey V comes from the Alfred P. Sloan Foundation, Heising-Simons Foundation, National Science Foundation, and participating institutions. SDSS operations are supported by the Center for High-Performance Computing at the University of Utah, with telescopes located at Apache Point Observatory and Las Campanas Observatory.

SDSS is managed by the Astrophysical Research Consortium, involving a wide array of esteemed academic institutions and organizations dedicated to advancing astronomical research.