Mike Dunham (UT Austin)

Identifying the Low Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores

As part of the Spitzer Space Telescope Legacy Project "From Molecular Cores
to Planet Forming Disks" (c2d), we have identified a group of protostars
with very low internal luminosities (< 0.1 Lsun), below that detectable
with IRAS in the nearest star-forming regions.  We call these VeLLOs (Very
Low Luminosity Objects), and they are difficult to understand in the
context of the standard model of low-mass star formation, as there
luminosities are well below that expected from accretion onto a protostar
with a mass greater than a brown-dwarf.  VeLLOs may have accretion rates
well below that predicted by the standard model, they may be
proto-brown-dwarfs, or perhaps some combination of the two.  In any event,
their identification shows that the known sample of embedded protostars is
not complete at the low luminosity end, and raises several fundamental
questions:  How many such objects are there?  How many cores classified as
starless actually harbor low-luminosity protostars?  What are the
implications of these objects on our understanding of low-mass star
formation?  We address these questions with a sample constructed by
identifying the complete population of embedded protostars in the c2d
dataset with internal luminosities less than or equal to 1 solar
luminosity.