index

postdoc

Max Planck Institute for Astronomy

Königstuhl 17

69117 Heidelberg

Germany

+49 6221 528 458

ragan -at- mpia -dot- de

I am a post-doc in the planet and star formation group at MPIA since January 2010. Before that, I received my Ph.D. in Astronomy and Astrophysics at the University of Michigan working with Ted Bergin.

The Earliest Phases of Star Formation (EPoS):
Stars form deeply embedded in cold, dense molecular clouds (MCs). The cold dust within MCs serves as a reliable tracer of their structure. In a recent publication (Ragan et al. 2012b), we use the Herschel Space Observatory to image 45 massive MCs called infrared-dark clouds (IRDCs) to study the very earliest stages of star formation, just as protostars begin to form. With Herschel, we probe more deeply into these stellar nurseries than was
ever before possible, such that we are able to
identify small scale structures which will likely
go on to form individual stars or small systems.
In doing so, we set important constraints on the
initial conditions of star formation.
In the Figure, we show an example three-color
image of an IRDC (G316.72-0.07), where red
corresponds to where dust is coldest, and blue
indicates the warmer regions. The crosses mark
where we identify new protostars with Herschel.
We have modeled these protostellar cores and
find they are very cold (~20K) and range in mass
from 1 to hundreds of time the mass of our sun.
There is ten times the amount of mass in the host
cloud as there is already in protostellar cores, and
another population of cores in even earlier
stages that will require additional follow-up observations to model.
Our suite of Herschel observations help guide future investigations of the various stages of star and cluster formation in environments like IRDCs. We now understand that along with the most massive object(s) that IRDCs sometimes form, there is an underlying population of protostars similar to what is seen in nearby MCs. This work enables us to probe the complexity of the early phases of star formation and better understand the role of the environment in which it takes place.