Star formation in the central 400 PC of the milky way: Evidence for a population of massive young stellar objects

F. Yusef-Zadeh*, J. W. Hewitt, R. G. Arendt, B. Whitney, G. Rieke, M. Wardle, J. L. Hinz, S. Stolovy, C. C. Lang, M. G. Burton, S. Ramirez

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

137 Scopus citations

Abstract

The central kpc of the Milky Way might be expected to differ significantly from the rest of the Galaxy with regard to gasdynamics and the formation of young stellar objects (YSOs). We probe this possibility with mid-infrared observations obtained with Infrared Array Camera and Multiband Imaging Photometer on Spitzer and with Midcourse Space Experiment. We use color-color diagrams and spectral energy distribution (SED) fits to explore the nature of YSO candidates (including objects with 4.5μm excesses possibly due to molecular emission). There is an asymmetry in the distribution of the candidate YSOs, which tend to be found at negative Galactic longitudes; this behavior contrasts with that of the molecular gas, approximately 2/3 of which is at positive longitudes. The small-scale height of these objects suggests that they are within the Galactic center region and are dynamically young. They lie between two layers of infrared dark clouds and may have originated from these clouds. We identify new sites for this recent star formation by comparing the mid-IR, radio, submillimeter, and methanol maser data. The methanol masers appear to be associated with young, embedded YSOs characterized by 4.5μm excesses. We use the SEDs of these sources to estimate their physical characteristics; their masses appear to range from 10 to 20 M. Within the central 400 × 50 pc (|l| < 13 and |b| < 10′) the star formation rate (SFR) based on the identification of Stage I evolutionary phase of YSO candidates is about 0.14M yr-1. Given that the majority of the sources in the population of YSOs are classified as Stage I objects, we suggest that a recent burst of star formation took place within the last 105 yr. This suggestion is also consistent with estimates of SFRs within the last 107 yr showing a peak around 105 yr ago. Lastly, we find that the Schmidt-Kennicutt Law applies well in the central 400 pc of the Galaxy. This implies that star formation does not appear to be dramatically affected by the extreme physical conditions in the Galactic center region.

Original languageEnglish (US)
Pages (from-to)178-225
Number of pages48
JournalAstrophysical Journal
Volume702
Issue number1
DOIs
StatePublished - 2009

Keywords

  • Galaxies: starburst
  • Galaxy: center
  • ISM: clouds
  • Masers
  • Stars: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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