4.6 Article

A new view of the super star clusters in the low-metallicity galaxy SBS 0335-052

期刊

ASTRONOMICAL JOURNAL
卷 136, 期 4, 页码 1415-1426

出版社

IOP PUBLISHING LTD
DOI: 10.1088/0004-6256/136/4/1415

关键词

galaxies : dwarf; galaxies : individual (SBS 0335-052); galaxies : starburst; galaxies : star clusters

资金

  1. NASA [GO-10894.01-A, NAS5-26555]
  2. Association of Universities for Research in Astronomy, Inc.
  3. NSF [0548103]
  4. David and Lucile Packard Foundation

向作者/读者索取更多资源

We present a study of the individual super star clusters (SSCs) in the low-metallicity galaxy SBS 0335-052 using new near-infrared (near-IR) and archival optical Hubble Space Telescope observations. The physical properties of the SSCs are derived from fitting model spectral energy distributions (SEDs) to the optical photometry, as well as from the H alpha and Pa alpha nebular emission lines. Among the clusters, we find a significant age spread that is correlated with position in the galaxy, suggesting that successive cluster formation occurred in SBS 0335-052 triggered by a large-scale disturbance traveling through the galaxy at a speed of similar to 35 km s(-1). The SSCs exhibit I-band (similar to 0.8 mu m) and near-IR (similar to 1.6-2.1 mu m) excesses with respect to model SEDs that are fit to the optical data. We hypothesize that the I-band excess is dominated by a photoluminescent process known as Extended Red Emission; however, this mechanism cannot account for the excesses observed at longer near-IR wavelengths. From the cluster SEDs and colors, we find that the primary origin of the near-IR excess observed in the youngest SSCs (less than or similar to 3 Myr) is hot dust emission, while evolved red supergiants dominate the near-IR light in the older (greater than or similar to 7 Myr) clusters. We also find evidence for a porous and clumpy interstellar medium surrounding the youngest, embedded SSCs: the ionized gas emission underpredicts the expected ionizing luminosities from the optical stellar continuum, suggesting that ionizing photons leak out of the immediate vicinity of the clusters before ionizing hydrogen. The corrected, intrinsic ionizing luminosities of the two SSCs younger than similar to 3 Myr are each similar to 5 x 10(52)s(-1), which is equivalent to each cluster hosting similar to 5000 O7.5 V stars. The inferred masses of these SSCs are similar to 10(6)M(circle dot).

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