Empirical completeness assessment of the Gaia DR2, Pan-STARRS 1 and ASAS-SN-II RR Lyrae catalogues

TL;DR

This study empirically evaluates the completeness of the three largest RR Lyrae star catalogues—Gaia DR2, Pan-STARRS-1, and ASAS-SN-II—using probabilistic analysis to produce detailed 2D and 3D completeness maps across different magnitudes and galactic latitudes.

Contribution

It provides the first comprehensive empirical assessment and detailed completeness maps of these major RR Lyrae catalogues, highlighting their strengths and limitations.

Findings

Gaia DR2 is over 95% complete for bright RR Lyrae stars outside the ecliptic.

ASAS-SN-II has the best completeness at low latitudes for RRab stars.

PanSTARRS-1 maintains high completeness (~91%) down to G~18, with lower completeness at low galactic latitudes.

Abstract

RR Lyrae stars are an important and widely used tracer of the most ancient populations of our Galaxy, mainly due to their standard candle nature. The availability of large scale surveys of variable stars is allowing us to trace the structure of our entire Galaxy, even in previously inaccessible areas like the Galactic disc. In this work we aim to provide an empirical assessment of the completeness of the three largest RR Lyrae catalogues available: Gaia DR2, PanSTARRS-1 and ASAS-SN-II. Using a joint probabilistic analysis of the three surveys we compute 2D and 3D completeness maps in each survey's full magnitude range. At the bright end (G<13) we find ASAS-SN-II and Gaia are near 100% complete in RRab at high latitude (|b|>20deg); ASAS-SN-II has the best completeness at low latitude for RRab and at all latitudes for RRc. At the faint end (G>13), Gaia DR2 is the most complete catalogue for both RR Lyrae types, at any latitude, with median completeness rates of 95% (RRab) and >85% (RRc) outside the ecliptic plane (|\beta|>25deg). We confirm a high and uniform completeness of PanSTARRS-1 RR Lyrae at 91% (RRab) and 82% (RRc) down to G~18, and provide the first estimate of its completeness at low galactic latitude (|b|<20deg) at an estimated median 65% (RRab) and 50-60% (RRc). Our results are publicly available as 2D and 3D completeness maps, and as functions to evaluate each survey's completeness versus distance or per line-of sight.