From the Inner to Outer Milky Way: A Photometric Sample of 2.6 Million Red Clump Stars

Abstract

Large pristine samples of red clump stars are highly sought after given that they are standard candles and give precise distances even at large distances. However, it is difficult to cleanly select red clumps stars because they can have the same T${}_{\mathrm{eff}}$ and log $g$ as red giant branch stars. Recently, it was shown that the asteroseismic parameters, $\mathrm{\Delta }$P and $\mathrm{\Delta }\nu$, which are used to accurately select red clump stars, can be derived from spectra using the change in the surface carbon to nitrogen ratio ([C/N]) caused by mixing during the red giant branch. This change in [C/N] can also impact the spectral energy distribution. In this study, we predict the $\mathrm{\Delta }$P, $\mathrm{\Delta }\nu$, T${}_{\mathrm{eff}}$ and log $g$ using 2MASS, AllWISE, \gaia, and Pan-STARRS data in order to select a clean sample of red clump stars. We achieve a contamination rate of $\sim$20\%, equivalent to what is achieved when selecting from T${}_{\mathrm{eff}}$ and log $g$ derived from low resolution spectra. Finally, we present two red clump samples. One sample has a contamination rate of $\sim$ 20\% and $\sim$ 405,000 red clump stars. The other has a contamination of $\sim$ 33\% and $\sim$ 2.6 million red clump stars which includes $\sim$ 75,000 stars at distances $>$ 10 kpc. For |b|>30 degrees we find $\sim$ 15,000 stars with contamination rate of $\sim$ 9\%. The scientific potential of this catalog for studying the structure and formation history of the Galaxy is vast given that it includes millions of precise distances to stars in the inner bulge and distant halo where astrometric distances are imprecise.

18 pages, 13 figures, 2 tables, submitted to MNRAS

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• Probing infrared excess connection with Li enhancement among red clump giants
• 3D Parameter Maps of Red Clump Stars in the Milky Way -- Absolute Magnitudes and Intrinsic Colors
• The Outer spiral arm of the Milky Way using Red Clump stars
• GaiaUnlimited: The old stellar disc of the Milky Way as traced by the Red Clump
• Type II and anomalous Cepheids in the Kepler K2 mission
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