A panchromatic view of NGC 602: Time-resolved star formation with the hubble and Spitzer space telescopes

Abstract

We present the photometric catalogs for the star-forming cluster NGC 602 in the wing of the Small Magellanic Cloud covering a range of wavelengths from optical (HST/ACS F555W, F814W, and SMARTS/ANDICAM V, I) to infrared (Spitzer/IRAC 3.6, 4.5, 5.8, and 8 μm and MIPS 24 μm). Combining this with Infrared Survey Facility near-infrared photometry (J, H, Ks ), we compare the young main sequence (MS) and pre-main sequence (PMS) populations prominent in the optical with the current young stellar object (YSO) populations revealed by the infrared. We analyze the MS and PMS population with isochrones in color-magnitude diagrams to derive ages and masses. The optical data reveal 565 PMS candidates, low-mass StageIII YSOs. We characterize 40 YSOs by fitting their spectral energy distributions to a grid of models (Robitaille etal.) to derive luminosities, masses, and evolutionary phase (Stages I-III). The higher resolution HST images reveal that 70% of the YSO candidates are either multiples or protoclusters. For YSOs and PMS sources found in common, we find a consistency in the masses derived. We use the YSO mass function to derive a present-day star formation rate of 0.2-1.0 M 1yr-1kpc -2, similar to the rate derived from the optical star formation history suggesting a constant star formation rate for this region. We demonstrate a progression of star formation from the optical star cluster center to the edge of the star-forming dust cloud. We derive lifetimes of a few 105 years for the YSO Stages I and II. © 2011. The American Astronomical Society. All rights reserved.