Missing Massive Stars: Statistically-significant Density Dependence of the IMF Wen-hsin Hsu Univ. of Michigan, Ann Arbor, MI, USA
To test the proposition that the stellar initial mass function (IMF) depends on the environmental density, we conducted a survey of the young stellar population in L1641, a low-density star-forming region of the Orion A cloud south of the dense Orion Nebula Cluster (ONC). Our result indicates a statistically-significant deficit of massive stars in low-density regions. In our survey of L1641, we identified and spectral-typed members with low-resolution optical spectra and optical photometry, as well as the Spitzer IRAC photometry (Megeath et al. 2012). We have confirmed and spectral-typed a total of 860 optical members of L1641 down to 0.1 solar mass. L1641 has a large number of low-mass stars, within a factor of two of the much denser ONC, but lacks a comparable population of high-mass stars. We therefore show that L1641 is deficient in O and early B stars at a statistically-significant level. We also present the complete IMF and compare it to the IMF of the ONC.
Collaborators: Lee Hartmann, Univ. of Michigan, USA Lori Allen, NOAO, USA Jesus Hernandez, CIDA, Venezuela Tom Megeath, Univ. of Toledo, USA