Yusef-Zadeh, F. and Hewitt, J. W. and Arendt, R. G. and Whitney, B. and Rieke, G. and Wardle, M. and Hinz, J. L. and Stolovy, S. and Lang, C. C. and Burton, M. G. and Ramirez, S. (2009) Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive Young Stellar Objects. Astrophysical Journal, 702 (1). pp. 178-225. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090915-114127322
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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 4.5 μm 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 4.5 μm 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| < 1°.3 and |b| < 10') the star formation rate (SFR) based on the identification of Stage I evolutionary phase of YSO candidates is about 0.14 M_☉ 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 10^5 yr. This suggestion is also consistent with estimates of SFRs within the last ~10^7 yr showing a peak around 10^5 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.
|Additional Information:||© 2009 American Astronomical Society. Print publication: Issue 1 (2009 September 1); received 2009 April 17; accepted for publication 2009 June 16; published 2009 August 10. We acknowledge the use of SCUBA data taken by D. Pierce- Price. This work is partially supported by NSF under award number AST-0807400 and from JPL/Caltech contract 1255094.|
|Subject Keywords:||galaxies: starburst; Galaxy: center; ISM: clouds; masers; stars: formation|
|Official Citation:||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, and S. Ramirez 2009 ApJ 702 178-225 doi: 10.1088/0004-637X/702/1/178|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||16 Sep 2009 20:14|
|Last Modified:||26 Dec 2012 11:22|
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