The 100 Myr star formation history of NGC5471 from cluster and resolved stellar photometry

Abstract

We show that star formation in the giant H II region NGC5471 has been ongoing during the past 100 Myr. Using Hubble Space Telescope/Wide-Field Planetary Camera 2 F547M and F675W, ground-based JHKs , and GALEX FUV and NUV images, we have conducted a photometric study of the star formation history (SFH) in the massive giant extragalactic H II region NGC5471 in M101. We perform a photometric study of the color-magnitude diagram (CMD) of the resolved stars and an integrated analysis of the main individual star-forming clusters and of NGC5471 as a whole. The integrated UV-optical-NIR photometry for the whole region provides two different reference ages, 8 Myr and 60 Myr, revealing a complex SFH, clearly confirmed by the CMD-resolved stellar photometry analysis. The spatial distribution of the stars shows that the star formation in NGC5471 has proceeded along the whole region during, at least, the last 100 Myr. The current ionizing clusters are enclosed within a large bubble, which is likely to have been produced by the stars that formed in a major event 20 Myr ago. © 2011. The American Astronomical Society. All rights reserved.