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New results on the ages of star clusters in region B of M82 |
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| Authors: | Iraklis S. Konstantopoulos Nate Bastian Linda J. Smith Gelys Trancho Mark S. Westmoquette Jay S. Gallagher III |
| Affiliation: | 1. Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK 2. Space Telescope Science Institute and European Space Agency, 3700 San Martin Drive, Baltimore, MD, 21218, USA 3. Universidad de La Laguna, Avenida Astrófisico Francisco Sánchez s/n, 38206, La Laguna, Tenerife, Canary Islands, Spain 4. Gemini Observatory, 670 N. A’ahoku Place, Hilo, HI, 96720, USA 5. Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling, 475 North Charter Street, Madison, WI, 53706, USA |
| Abstract: | The post-starburst region B in M82 and its massive star cluster component have been the focus of multiple studies, with reports that there is a large population of coeval clusters of age ～1 Gyr, which were created with a Gaussian initial mass distribution. This is in disagreement with other studies of young star clusters, which invariably find a featureless power-law mass distribution. Here, we present Gemini-North optical spectra of seven star clusters in M82-B and show that their ages are all between 10 and 300 Myr (a factor of 3–100 younger than previous photometric results) and that their extinctions range between near zero and 4 mag (A V ). Using new HST ACS-HRC U-band observations we age date an additional ～30 clusters whose ages/extinctions agree well with those determined from spectroscopy. Completeness tests show that the reported ‘turn-over’ in the luminosity/mass distributions is most likely an artefact, due to the resolved nature of the clusters. We also show that the radial velocities of the clusters are inconsistent with them belonging to a bound region. |
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