# Survey of Surveys I: The largest catalogue of radial velocities for the Galaxy

**Authors:** M. Tsantaki, E. Pancino, P. Marrese, S. Marinoni, M. Rainer, N. Sanna, A. Turchi, S. Randich, C. Gallart, G. Battaglia, T. Masseron  
**arXiv:** [2110.09316](https://arxiv.org/abs/2110.09316)  
**Date:** 2021-10-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2110.09316v1/

## Key points

- Large spectroscopic surveys have become increasingly popular in recent years due to the vast amount of data they generate.
- A team of researchers has developed the Survey of Surveys (SoS), a comprehensive catalogue that merges radial velocity (RV) determinations from the largest ground-based spectroscopic surveys to date.
- The SoS catalogue was created using a multi-staged procedure that involved cross-matching between Gaia and the spectroscopic surveys using the official Gaia cross-match algorithm.
- The RVs were cross-calibrated as a function of various parameters such as magnitude, effective temperature, surface gravity, metallicity and signal-to-noise ratio to remove trends and zero-point offsets.
- The result is an impressive homogenized RV catalogue containing almost 11 million stars; half from Gaia alone while half are from a combination of ground based surveys.
- The accuracy of its RV zero point is estimated to be about 0.16 - 0.31 km/s while RV precision ranges from 0.05 - 1.50 km/s depending on star type and survey provenance.
- The SoS catalogue is publicly available for use in various research projects such as studying star clusters, Galactic archaeology, stellar streams or characterizing planet hosting stars; making it a significant contribution to astronomy that will undoubtedly aid in future discoveries and research.

## Summary

Large spectroscopic surveys have become increasingly popular in recent years due to the vast amount of data they generate. To address this complexity, a team of researchers has developed the Survey of Surveys (SoS), a comprehensive catalogue that merges radial velocity (RV) determinations from the largest ground-based spectroscopic surveys to date. These include APOGEE, GALAH, Gaia-ESO, RAVE and LAMOST with Gaia serving as the reference point. The SoS catalogue was created using a multi-staged procedure that involved cross-matching between Gaia and the spectroscopic surveys using the official Gaia cross-match algorithm. The uncertainties were then normalized using repeated measurements or the three-cornered hat method. The RVs were also cross-calibrated as a function of various parameters such as magnitude, effective temperature, surface gravity, metallicity and signal-to-noise ratio to remove trends and zero-point offsets. Additionally, external high-resolution samples such as the Gaia RV standards and Geneva-Copenhagen survey were used to validate the homogenization procedure and calibrate the RV zero-point of the SoS catalogue. The result is an impressive homogenized RV catalogue containing almost 11 million stars; half from Gaia alone while half are from a combination of ground based surveys. The accuracy of its RV zero point is estimated to be about 0.16 - 0.31 km/s while RV precision ranges from 0.05 - 1.50 km/s depending on star type and survey provenance. To further validate their findings open clusters from high resolution homogeneous samples were used to confirm SoS's RVs with median RVs provided for 532 clusters recently discovered by Gaia data. The SoS catalogue is publicly available for use in various research projects such as studying star clusters, Galactic archaeology, stellar streams or characterizing planet hosting stars; making it a significant contribution to astronomy that will undoubtedly aid in future discoveries and research.