The VMC Survey. XVIII. Radial dependence of the low-mass, 0.55--0.82 $M_\odot$ stellar mass function in the Galactic globular cluster 47 Tucanae

TL;DR

This study analyzes the radial variation of the low-mass stellar mass function in 47 Tucanae, revealing effects of mass segregation and tidal stripping on different stellar populations using combined HST and VISTA data.

Contribution

It provides the first detailed analysis of the radial dependence of the low-mass stellar mass function in 47 Tuc using combined near-infrared and optical data.

Findings

Faint star deficit in the core consistent with mass segregation.

Power-law mass functions with nearly constant slope across radii.

Evidence of mass segregation and tidal stripping affecting different star generations.

Abstract

We use near-infrared observations obtained as part of the {\sl Visible and Infrared Survey Telescope for Astronomy} (VISTA) Survey of the Magellanic Clouds (VMC), as well as two complementary {\sl Hubble Space Telescope} ({\sl HST}) data sets, to study the luminosity and mass functions as a function of clustercentric radius of the main-sequence stars in the Galactic globular cluster 47 Tucanae. The {\sl HST} observations indicate a relative deficit in the numbers of faint stars in the central region of the cluster compared with its periphery, for $18.75\leq m_{\rm F606W}\leq 20.9$ mag (corresponding to a stellar mass range of $0.55<m_\ast/{M_\odot}<0.73$). The stellar number counts at $6.7'$ from the cluster core show a deficit for $17.62\leq m_{\rm F606W}\leq 19.7$ mag (i.e., $0.65<m_\ast/{M_\odot}<0.82$), which is consistent with expectations from mass segregation. The VMC-based stellar mass functions exhibit power-law shapes for masses in the range $0.55<m_\ast/{M_\odot}< 0.82$. These power laws are characterized by an almost constant slope, $\alpha$. The radial distribution of the power-law slopes $\alpha$ thus shows evidence of the importance of both mass segregation and tidal stripping, for both the first- and second-generation stars in 47 Tuc.