The mass function of M4 from near IR and optical HST observations

TL;DR

This study uses HST near IR and optical data to derive detailed local luminosity and mass functions of the globular cluster M4, revealing variations in the mass distribution between inner and outer regions.

Contribution

It provides the first detection of white dwarfs on a constant luminosity color sequence and derives detailed local mass functions using updated theoretical relations.

Findings

White dwarfs detected on a constant luminosity color sequence.

Inner regions have a single power-law mass function with x = -0.8.

Outer regions show a two-segment power-law with x = 1 and x = -0.3.

Abstract

Deep images of the galactic globular cluster M4 taken at various locations with the NIC3 and the WFPC2 cameras on HST were used to derive detailed local optical and near IR luminosity functions. White dwarfs have been detected for the first time on a color sequence at constant luminosity in the F110W band. Transformation of the observed luminosity functions into mass functions via the most up to date theoretical mass luminosity relations currently available results in best fit local mass functions, that consist of a power-law with single exponent x = -0.8 for the inner regions and a two-segment power-law which rises with x = 1 down to M_{814}=8.5 and then drops all the way to the detection limit with x = -0.3 for the outer regions.