EPoS Contribution
EPoS Contribution
Early Phases of Massive Star Formation in GLIMPSE and MIPSGAL

Randolf Klein
SOFIA - USRA, Moffett Field, USA
In order to find the right questions to ask and to interpret the answers in the framework of a new paradigm for massive star formation, one has to first establish what can and should be observed. Most astrophysicists familiar with the field will agree that the early phases of massive star formation (MSF) happen deeply embedded in molecular clouds. Thus, the infrared is needed to peek into the nurseries of massive stars and clusters. The Spitzer archive, especially the legacy programs GLIMPSE and MIPSGAL, provides a treasure trove of observations of star-forming regions in any stage. But where to look? "Infrared Dark Clouds (IRDCs)" is one answer, but it samples only regions with high infrared background. We have searched for early phases of star formation among cold and massive (M>100Mo) cloud cores by selecting cores from millimeter continuum surveys (Faundez et al. 2004, Sridharan et al. 2005, Klein et al. 2005, Beltran et al. 2006) without associations at short wavelengths. We compared the millimeter continuum peak positions with IR and radio catalogs (2MASS, MSX, IRAS, and NVSS) and excluded cores that had sources associated with the cores' peaks. We compiled a list of 173 cores in over 117 regions that are candidates for very early phases of MSF. Now with the sensitive Spitzer results, these cores can be characterized further. The GLIMPSE and MIPSGAL programs alone covered 86 of these regions. Spitzer measures the rise of the spectral energy distribution (SED) in the mid-infrared with good spatial resolution and broad spectral coverage. This allow us to disentangle the complex regions and model the SED of the deeply embedded protostars/clusters. We will be presenting the MIR properties of all cores and their embedded source, attempt a characterization, and order the cores in an evolutionary sequence. The resulting properties can be compared to e.g. IRDCs, a class of objects suggested to be the earliest stages of MSF. With the relative large number of cores, we can try to answer questions like: How homogeneous or diverse are our regions in terms of their evolutionary stage? Where do the embedded sources fit in the evolutionary sequence of IRDCs, hot molecular cores, ultra-compact HII regions, etc? How is the MSF shaping the environment and vice versa? Can we extrapolate to the initial conditions of MSF using our evolutionary sequence? We should discuss, if these questions can be answered with the data and if these questions can help to establish a new paradigm for massive star formation.
L. Looney, UIUC, USA, Th. Henning, MPIA, D, S. Chakrabarti, CfA, USA,
S. Shenoy, NASA Ames, USA