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J. Serena Kim, F. M. Walter (SUNY at Stony Brook), S. J. Wolk (CfA)
We present multi-wavelength photometric studies of low mass star forming regions, in/around cometary globules (CGs) and HII regions in the Gum Nebula. Our goals are to study the roles high mass stellar activities play on low mass star formation (LMSF) under different physical conditions, and to reconstruct the star formation history of the nebula. High mass stars can halt LMSF, however the ionizing radiation, winds, and shocks can also trigger LMSF by collapsing the denser cores of evaporating molecular clouds. The Gum Nebula is a useful site to study how high mass stars may terminate and/or trigger LMSF. The nebula contains supernova remnants, \zeta~Pup (O4If), \gamma2~Vel (WC8+O7.5I), OB~associations, HII regions, and a large number of CGs - bright rimmed evaporating dense cores of molecular clouds with cometary geometry. CGs are often associated with low mass pre-main sequence (PMS) stars around OB stars in HII regions. Here we present a multi-wavelength photometric study of selected regions: CG30/31/38, CG26-29 complexes, RCW~27 (Vela~T1), RCW~33 (Vela~T2), and optical photometry for the CG4/6/SA101 region in the Gum Nebula. We present color-magnitude and color-color diagrams, and identify loci of likely PMS stars. We witness LMSF both coeval with high mass stars and those formed in triggered mode. We compare the differences in circumstellar disk fraction in CGs complexes, which may be influenced by O star radiation and winds, with that of T associations in two HII regions (RCW27 and 33). Among the PMS candidates around CG30/31/38 ~1-2% of candidates show IR excess, while ~10% of PMS candidates in RCW~33 (Vela~T2) show IR excess. From the spatial analysis of PMS stars in these regions, as well as relative age differences in each regions, we try to reconstruct a model of the star formation history of the Gum Nebula.