Deep Hubble Space Telescope/Advanced Camera for Surveys photometry of the young cluster NGC 602, located in the remote low-density "wing" of the Small Magellanic Cloud (SMC), reveals numerous pre-main-sequence (PMS) stars as well as young stars on the main sequence. The resolved stellar content thus provides a basis for studying the star formation history (SFH) into recent times and constraining several stellar population properties, such as the present-day mass function (PDMF), the initial mass function, and the binary fraction. To better characterize the PMS population, we present a new set of model stellar evolutionary tracks for this evolutionary phase with metallicity appropriate for the SMC (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 SFH in the region by comparing observed and synthetic color-magnitude diagrams. The derived PDMF 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) x 10(-3) M(circle dot) 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.
STAR FORMATION HISTORY IN THE SMALL MAGELLANIC CLOUD: THE CASE OF NGC 602
CIGNONI, MICHELE;DEGL'INNOCENTI, SCILLA;PRADA MORONI, PIER GIORGIO;
2009-01-01
Abstract
Deep Hubble Space Telescope/Advanced Camera for Surveys photometry of the young cluster NGC 602, located in the remote low-density "wing" of the Small Magellanic Cloud (SMC), reveals numerous pre-main-sequence (PMS) stars as well as young stars on the main sequence. The resolved stellar content thus provides a basis for studying the star formation history (SFH) into recent times and constraining several stellar population properties, such as the present-day mass function (PDMF), the initial mass function, and the binary fraction. To better characterize the PMS population, we present a new set of model stellar evolutionary tracks for this evolutionary phase with metallicity appropriate for the SMC (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 SFH in the region by comparing observed and synthetic color-magnitude diagrams. The derived PDMF 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) x 10(-3) M(circle dot) 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
