My Research: Dark Clouds and Bright Young Stars

I am a Ph.D. student working as part of the COMPLETE Survey of Star forming clouds. Our goal is to observe nearby star-forming regions in a variety of ways to learn about (1) how well different methods of studying clouds agree and (2) how stars form.

By "clouds" I mean the great collections of dust and gas which form stars. They look somewhat similar to earthly clouds, but are much more tenuous than anything here on earth. By "nearby", I mean clouds between 500 and 1000 light-years away, so far away that we're seeing light that left these stars during the Middle Ages -- but this is still closer than many of the objects astronomers study.

My advisor is Alyssa Goodman and I've been studying the density structure of molecular clouds. When it's not as cloudy as in the above picture, I take deep near-infrared images and use them to make high-resolution extinction maps of parts of these star forming regions. Extinction mapping is simply measuring how much dust there is in the cloud by observing how light from background stars is made red as the dust scatters blue (shorter wavelength) light. We then can estimate the total mass of the cloud-- most of the mass is in essentially invisible hydrogen molecules, but there is normally a constant ratio between the amount of dust and the amount of hydrogen.

Hunting Galaxies to (and for) Extinction

In these deep near-infrared images we see many objects which are not background stars. Instead, they are galaxies composed of billions of stars. Nearby galaxies look very different from stars, but more distant ones can sometimes be difficult to identify. If we want to study young stars galaxies can be a problem, as their colors mimic the colors of young stars at many infrared wavelengths. If we want to figure out where the dust is from the colors of background stars, galaxies are a potential contaminant, since their intrinsic colors are redder than most stars. However, if we can identify them robustly we can use them as extra background sources to make our maps better. Read the paper on Hunting Galaxies.

Cloudshine

In the course of obtaining these very long exposure images of clouds in the near-infrared, we were very surprised to see the clouds themselves glowing. We named the effect cloudshine and modeled it as ambient starlight from many nearby stars reflecting off dust in the clouds. The pictures provide a beautiful qualitative picture of where the mass is in the clouds and how the wispy and condensed structures in molecular clouds exist together. It will also provide an important way to check simulations of what molecular clouds look like, and hopefully a direct measure of the column density of the cloud. Read more about cloudshine.