The infrared luminosity function for low-mass stars

We present the first infrared observational luminosity functions (LFs) for M dwarfs towards the South Galactic Pole (SGP) and the Hyades cluster. We also give a definitive compilation of new and published VRIJHK data for 200 parallax stars, for deriving photometric parallaxes in such studies. Two-colour near-infrared/infrared diagrams of these data are used to demonstrate metallicity and gravity effects, and show that I–J is the purest temperature colour index. An MJ:I–J relation is given using high-quality trigonometric parallaxes from the new Yale catalogue. We describe the corrections to the LFs that are necessary to allow for magnitude errors (Malmquist effects), which have been incorrectly applied in recent determinations.

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