Carbon stars as standard candles: I. The luminosity function of carbon stars in the Magellanic Clouds

Understand

Our goal in this paper is to derive a carbon-star luminosity function that will eventually be used to determine distances to galaxies at $50$-$60$ Mpc and hence yield a value of the Hubble constant.

• Cool N-type carbon stars exhibit redder near-infrared colours than oxygen-rich stars.
• Using Two Micron All Sky Survey near-infrared photometry and the Gaia Data Release 2, we identify carbon stars in the Magellanic Clouds (MC) and the Milky Way (MW).
• Carbon stars in the MC appear as a distinct horizontal feature in the near-infrared ($(J-K_s)_0$, $M_J$) colour-magnitude diagram.