| Discovery of an extraordinarily massive cluster of red supergiants (2006) | |||||||||||||||
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| Also archived in: arXiv:astro-ph/0602146 v1 7 Feb 2006 AND Space Telescope Science Institute [STScI] Eprint #1712. We report the discovery of an extraordinarily massive young cluster of stars in the Galaxy, having an inferred total initial cluster mass comparable to the most massive young clusters in the Galaxy. Using IRMOS, 2MASS, and Spitzer observations, we conclude that there are 14 red supergiants in the cluster, compared with five, in what was previously thought to be the richest Galactic cluster of such stars. We infer spectral types from near-infrared spectra that reveal deep CO bandhead absorption that can only be fit by red supergiants. We identify a gap of Ks 4 magnitudes between the stars and the bulk of the other stars in the region that can only be fit by models if the brightest stars in the cluster are red supergiants. We estimate a distance of 5.8 kpc to the cluster by associating an OH maser with the envelope of one of the stars. We also identify a “yellow” supergiant of G6 I type in the cluster. Assuming a Salpeter IMF, we infer an ini- tial cluster mass of 20,000 to 40,000 M⊙ for cluster ages of 7-12 Myr. Continuing with these assumptions, we find 80% of the intial mass and 99% of the number of stars remain at the present time. We associate the cluster with an x-ray source (detected by ASCA and Einstein), a recently discovered very high energy-ray source (detected by INTEGRAL and HESS), and several non-thermal radio sources, finding that these objects are likely related to recent supernovae in the cluster. In particular, we claim that the cluster has produced at least one recent supernova remnant with properties similar to the Crab nebula. It is not unlikely to find such a source in this cluster, given our estimated supernova rate of one per 40,000 to 80,000 yr. (Refer to PDF file for exact formulas).. The material in this paper is based upon work supported by NASA under award No. NNG05-GC37G, through the Long Term Space Astrophysics program. F.N. acknowledges PNAYA2003-02785-E and AYA2004-08271- C02-02 grants and the Ramon y Cajal program. IRMOS is supported by NASA/JWST, NASA/GSFC, STScI DDRF, and KPNO. This research has made use of data obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC), provided by NASAs Goddard Space Flight Center. This work made use of data from, MAGPIS: The Multi-Array Galactic Plane Imaging Survey (White et al. 2005; Helfand et al. 2005), and the MAGPIS web site: http://third.ucllnl.org/gps/index.html. | |||||||||||||||
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