Astrometric and photometric calibrators for the 4-m International Liquid Mirror Telescope

Abstract

The International Liquid Mirror Telescope (ILMT) is a 4-meter class survey telescope. It achieved its first light on 29${}^{\mathrm{th}}$ April 2022 and is now undergoing the commissioning phase. It scans the sky in a fixed \ang{;22;} wide strip centred at the declination of $+$\ang{29;21;41.4} and works in \emph{Time Delay Integration (TDI)} mode. We present a full catalog of sources in the ILMT strip derived by crossmatching \textit{Gaia} DR3 with SDSS DR17 and PanSTARRS-1 (PS1) to supplement the catalog with apparent magnitudes of these sources in $g,r$, and $i$ filters. These sources can serve as astrometric calibrators. The release of Gaia DR3 provides synthetic photometry in popular broadband photometric systems, including the SDSS $g,r$, and $i$ bands for $\sim$220 million sources across the sky. We have used this synthetic photometry to verify our crossmatching performance and, in turn, create a subset of the catalog with accurate photometric measurements from two reliable sources.

10 pages, 3 figures, 1 table, accepted for publication in the Bulletin of Liège Royal Society of Sciences as a part of 3rd Belgo-Indian Network for Astronomy and Astrophysics (BINA) workshop, 22-24 March 2023