Jonathan Foster's Homepage

Astronomy compels the soul to look upwards and leads us from this world to another.

      ~ Plato, The Republic

My Research: Dark Clouds and Bright Young Stars

Me at Keck HQ

I am currently the YCAA Prize Postdoctoral Fellow at Yale, working on understanding how stars form. My research studies the connections between the formation of the most massive stars and the formation of smaller stars (like our own sun).

Previously I was a Post-Doctoral research associate with Jim Jackson working on Infrared-Dark Clouds (IRDCs), the MALT90 Survey and various other topics in high-mass star formation. IRDCs are dense clouds seen in extinction against the diffuse light of galaxy and are great places to look for the early stages of high-mass star formation.

As a Ph.D. student I worked as part of the COMPLETE Survey of Star forming clouds with my advisor, Alyssa Goodman. The COMPLETE survey focused on the Perseus, Ophiuchus, and Serpens molecular clouds, where low- to intermediate-mass star formation is happening.

My research page contains little snapshots focusing on my recent research topics and publications. On this website you can also find my full publications list, my Curriculum Vitae, my contact information, and some notes about setting up astronomy software on a Mac

Characterization of the MALT90 Survey

As part of the MALT90 Survey we have obtained a pointed spectrum towards the center of an ultra-compact HII region on each of our almost 250 observing days over the last three Australian winters. The strengths of the molecular lines in these spectra vary with time. However, this is not true (intrinsic) source variability, but merely fluctuations in how efficient the Mopra telescope is at collecting incoming radiation. We use all these repeated observations to model the two largest sources of efficiency variation and chacterize other properties of our survey and of the Mopra telescope more generally. The full paper is available here and we also have a dedicated webpage hosting this data at the MALT90 Webpage

Grain Growth in Molecular Clouds

This beautiful image is a small slice of a 1 degree optical image we took of the Perseus molecular cloud. We combined the optical colors of background stars with the near-infrared colors from the UKIDSS survey to measure how the extinction law slope changes as a function of column density. We used a hierarchical Bayesian model to infer the properties of each individual star simultaneously with inferring the properties of the full population. We found that the extinction law changes from its value in the diffuse ISM to its value in dense clouds over a range of 2 to 10 magnitudes of visual extinction. You can read the full paper