The Star Clusters in the Irregular Galaxy NGC 444911Based in part on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5‐26555.

Abstract

ABSTRACTWe examine the star clusters in the luminous irregular galaxy NGC 4449. We use a near‐infrared spectrum and broadband images taken with the Hubble Space Telescope to place a limit of 8–15 Myr on the age of the bright central object in NGC 4449. Its luminosity and size suggest that it is comparable to young super star clusters. However, there is a peculiar nucleated‐bar structure at the center of this star cluster, and we suggest that this structure is debris from the interaction that has produced the counterrotating gas systems and extended gas streamers in the galaxy. From the images we identify 60 other candidate compact star clusters in NGC 4449. Fourteen of these could be background elliptical galaxies or old globular star clusters. Of the star clusters, three, in addition to the central object, are potentially super star clusters, and many others are comparable to the populous clusters found in the Large Magellanic Cloud. The star clusters span a large range in ages with no obvious peak in cluster formation that might be attributed to the interaction that the galaxy has experienced.