An Optical-Near-IR Study of a Triplet of Super Star Clusters in the Starburst Core of M82

Type Journal Article
Names M. S. Westmoquette, N. Bastian, L. J. Smith, A. C. Seth, J. S., III Gallagher, R. W. O'Connell, J. E. Ryon, S. Silich, Y. D. Mayya, C. Muñoz-Tuñón, D. Rosa González
Publication The Astrophysical Journal
Volume 789
Issue 2
Pages 94
Journal Abbreviation The Astrophysical Journal
Date July 1, 2014
DOI 10.1088/0004-637X/789/2/94
ISSN 0004-637X
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Abstract We present HST/STIS optical and Gemini/NIFS near-IR IFU spectroscopy and archival Hubble Space Telescope (HST) imaging of the triplet of super star clusters (A1, A2, and A3) in the core of the M82 starburst. Using model fits to the Space Telescope Imaging Spectrograph (STIS) spectra and the weakness of red supergiant CO absorption features (appearing at ~6 Myr) in the NIFS H-band spectra, the ages of A2 and A3 are 4.5 ± 1.0 Myr. A1 has strong CO bands, consistent with our previously determined age of 6.4 ± 0.5 Myr. The photometric masses of the three clusters are 4-7 × 105 M ⊙, and their sizes are R eff = 159, 104, 59 mas (~2.8, 1.8, 1.0 pc) for A1, A2, and A3. The STIS spectra yielded radial velocities of 320 ± 2, 330 ± 6, and 336 ± 5 km s-1 for A1, A2, and A3, placing them at the eastern end of the x 2 orbits of M82's bar. Clusters A2 and A3 are in high-density (800-1000 cm-3) environments, and like A1, are surrounded by compact H II regions. We suggest the winds from A2 and A3 have stalled, as in A1, due to the high ISM ambient pressure. We propose that the three clusters were formed in situ on the outer x 2 orbits in regions of dense molecular gas subsequently ionized by the rapidly evolving starburst. The similar radial velocities of the three clusters and their small projected separation of ~25 pc suggest that they may merge in the near future unless this is prevented by velocity shearing. Based on observations with the NASA/ESA Hubble Space Telescope under program 11641 and the Gemini-North telescope under program GN-2010B-Q-4.
Tags GALAXIES: EVOLUTION, GALAXIES: INDIVIDUAL: M82, Galaxies: ISM, galaxies: star clusters: general, galaxies: starburst
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