Star formation history in the SMC: the case of NGC602

TL;DR

This study uses deep HST/ACS photometry and new stellar evolutionary models to analyze the star formation history of NGC 602 in the Small Magellanic Cloud, revealing recent increased star formation activity and detailed stellar population properties.

Contribution

It introduces new model stellar evolutionary tracks for pre-main sequence stars at SMC metallicity and applies a population synthesis approach to derive the star formation history of NGC 602.

Findings

Star formation rate increased over tens of Myr, reaching 0.3-0.7 x 10^-3 M_sun/yr in the last 2.5 Myr.

The present day mass function aligns with synthetic diagram estimates.

Star formation is ongoing, especially in the gas-rich periphery of NGC 602.

Abstract

Deep HST/ACS photometry of the young cluster NGC 602, located in the remote low density "wing" of the Small Magellanic Cloud, reveals numerous pre-main sequence stars as well as young stars on the main sequence. The resolved stellar content thus provides a basis for studying the star formation history into recent times and constraining several stellar population properties, such as the present day mass function, the initial mass function and the binary fraction. To better characterize the pre-main sequence population, we present a new set of model stellar evolutionary tracks for this evolutionary phase with metallicity appropriate for the Small Magellanic Cloud (Z = 0.004). We use a stellar population synthesis code, which takes into account a full range of stellar evolution phases to derive our best estimate for the star formation history in the region by comparing observed and synthetic color-magnitude diagrams. The derived present day mass function for NGC 602 is consistent with that resulting from the synthetic diagrams. The star formation rate in the region has increased with time on a scale of tens of Myr, reaching $0.3-0.7 \times 10^{-3} M_\odot yr^{-1}$ in the last 2.5 Myr, comparable to what is found in Galactic OB associations. Star formation is most complete in the main cluster but continues at moderate levels in the gas-rich periphery of the nebula.