Dr. Di Li, JPL

"Early Phases of Star Formation"

Abstract:

We have obtained measurements that affect our
understanding of several fundamental aspects of molecular
cloud evolution and star formation.
I will introduce two main results on the early phases of star formation.

1) We have obtained a lower limit of formation time of
molecular cloud (> ~10 Myr) through studies of HI narrow self-absorption
(HINSA).
Our recent simulation of the time evolution of HI profile
from H2 clouds confirms that HINSA is a sign of late
stages in the formation of molecular clouds.
These results limit the applicability of simulations
and/or  theories which
propose "fast star formation".


2) Our submillimeter survey of quiescent cores in Orion reveals a core
mass function (CMF) significantly flatter than the Salpeter IMF.
Our analysis also raises doubt about some of the previous studies
that find a turning point in the CMF. A CMF different than IMF suggest
environmental effects in the formation of IMF.