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The TMT Infrared Guide Star Catalog

Overview of the TMT Infrared Guide Star Catalog (TMT-IRGSC)

To support TMT operations, a near-infrared guide star catalog which goes as faint as 22 mag in JVega band is essential. However a catalog of stars as faint as this does not presently exist. A method has been developed and successfully validated that computes the expected near-infrared magnitudes in J, H and K between 16th to 22nd magnitude for stellar sources from their optical magnitudes.

Development of the TMT-IRGSC

As no catalog of stars exists that reaches the required faintness levels in the infrared, groups within the TMT partnership are actively developing methods to generate a suitable catalog. At present, the expected NIR magnitudes of stellar sources are computed from their optical magnitudes using stellar atmospheric models. The method has been verified for stars with temperatures above 3500K using test fields (at galactic latitudes of ~ 45 degrees) which have deep optical (CFHTLS g,r,i data) and NIR (UKIDSS DXS data) observations. Further development of the method is taking place to improve the accuracy for stars with temperatures less than 3500K and improve the identification of galaxies from stars.

Once the method has been fully developed, the full catalog will be computed using the Pan-STARRS data. The Pan-STARRS observations cover the entire northern sky of interest for TMT, they reach grizy magnitudes sufficiently faint to support generation of J band catalog reaching 22nd Magnitude and have sufficient astrometric accuracy.

The development of the TMT-IRGSC is being led from the Indian Institute of Astrophysics by the India-TMT team.