EPoS Contribution
EPoS Contribution
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.
Lee Hartmann, Univ. of Michigan, USA
Lori Allen, NOAO, USA
Jesus Hernandez, CIDA, Venezuela
Tom Megeath, Univ. of Toledo, USA