ar X iv : a st ro - p h / 04 10 24 0 v 1 8 O ct 2 00 4 Clusters in the Luminous Giant H II Regions in M 101
نویسنده
چکیده
We have obtained HST WFPC2 observations of three very luminous but morphologically different giant H II regions (GHRs) in M101, NGC5461, NGC5462 and NGC5471, in order to study cluster formation in GHRs. Images obtained in the F547M and F675W bands are used to identify cluster candidates and for photometric measurements, and images in the F656N band are used to show ionized interstellar gas. The measured colors and magnitudes are compared with the evolutionary tracks generated by the Starburst99 and Bruzual & Charlot population synthesis models to determine the ages and masses of the cluster candidates that are more luminous than MF547M = −9.0. The brightest clusters detected in the PC images are measured and found to have effective radii of 0.7–2.9 pc. NGC5461 is dominated by a very luminous core, and has been suggested to host a super-star cluster (SSC). Our observations show that it contains three R136-class clusters superposed on a bright stellar background in a small region. This tight group of clusters may dynamically evolve into an SSC in the future, and may appear unresolved and be identified as an SSC at large distances, but Hubble Fellow and NSF Astronomy and Astrophysics Postdoctoral Fellow. present address: Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903; [email protected].
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تاریخ انتشار 2004