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Quasar catalogue for the astrometric calibration of the forthcoming ILMT survey


Quasars are ideal targets to use for astrometric calibration of large scale astronomical surveys as they have negligible proper motion and parallax. The forthcoming 4-m International Liquid Mirror Telescope (ILMT) will survey the sky that covers a width of about 27\(^\prime \). To carry out astrometric calibration of the ILMT observations, we aimed to compile a list of quasars with accurate equatorial coordinates and falling in the ILMT stripe. Towards this, we cross-correlated all the quasars that are known till the present date with the sources in the Gaia-DR2 catalogue, as the Gaia-DR2 sources have position uncertainties as small as a few milli arcsec (mas). We present here the results of this cross-correlation which is a catalogue of 6738 quasars that is suitable for astrometric calibration of the ILMT fields. In this work, we present this quasar catalogue. This catalogue of quasars can also be used to study quasar variability over diverse time scales when the ILMT starts its observations. While preparing this catalogue, we also confirmed that quasars in the ILMT stripe have proper motion and parallax lesser than 20 mas yr\(^{-1}\) and 10 mas, respectively.

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The authors would like to thank the referee for her/his critical review of our manuscript. AKM and RS thank the National Academy of Sciences, India for a research grant. AKM specially acknowledges the Université de Liège for providing the scholarship “Erasmus + International Credit Mobility”. AKM, CSS and RS acknowledge the Alexander von Humboldt Foundation, Germany for the award of Group linkage long-term research program between IIA, Bengaluru and European Southern Observatory, Garching, Germany. AKM and RS are thankful to the Director, IIA for providing institutional infrastructural support during this work. This research has used data from the SDSS and Gaia, operated by the European Space Agency.

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Correspondence to Amit Kumar Mandal.

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Mandal, A.K., Pradhan, B., Surdej, J. et al. Quasar catalogue for the astrometric calibration of the forthcoming ILMT survey. J Astrophys Astron 41, 22 (2020).

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  • Quasars
  • parallaxes
  • proper motions
  • ILMT
  • astrometry