Properties of Starless and Protostellar Cores

Plotted here are dust temperature (top) and column density (bottom) maps of the starless core TMC-1C. These maps were made using data from SCUBA on the JCMT (at 450 and 850 microns) and MAMBO on the IRAM 30m (at 1200 microns). Taken from Schnee et al. (2007).

Starless cores are the link between molecular clouds and protostars, and represent objects in the first stage of star formation. In the image above you can see that the starless core TMC-1C has one dense and cold condensation near the (0,0) position, and two possible smaller condensations to the North and Northwest. I have collected a lot of continuum and spectral line data on TMC-1C, and it continues to be an object of special interest to me. I have also begun work on surveys of starless and protostellar cores in the Perseus molecular cloud.

TMC-1C is a starless core in the Taurus molecular cloud, at a distance of 140 pc. I have studied the thermal emission from dust in TMC-1C with SCUBA, MAMBO, and recently Bolocam from 450 - 2100 microns. Because of the especially high quality of the 450 micron data (usually the worst affected by atmospheric opacity), I was able to make detailed maps of the temperature and column density (see the figure above). I also attempted a 3D deprojection to study the temperature, density and mass profiles of TMC-1C. It turns out that the mass of TMC-1C, derived from its dust emission, is much larger than its virial mass and is unstable to gravitational collapse. In fact, when studying its spectra, there is clear evidence for inward motions consistent with a (magnetically?) controlled collapse. To see the papers describing these results, click here and here.

Using spectroscopic data from the IRAM 30m telescope at 1mm and 3mm, I have studied the chemsitry of TMC-1C. As seen in other dense and cold starless cores, CO and its isotopologues are seen to leave the gas phase as they freeze out onto the surfaces of dust grains. This chemical evolution within TMC-1C allows nitrogen-bearing species like ammonia to exist without being destroyed by CO in chemical reactions. The data show that TMC-1C is chemically evolved, with less depletion than in L1544, and with some evidence of recent or current accretion of material from its envelope. To see the paper describing these results, cleck here.

I have completed a project that studies the temperature of starless cores in the Perseus molecular cloud. We have shown that cores in clusters are warmer than isolated cores, and that cores in higher column density regions are warmer than those in less dense regions. To learn more about what affects the temperature of a starless core, and what doesn't, click here.

I am starting a few more projects on starless and protostellar cores. I have GBT and VLA ammonia (1,1) and (2,2) data on TMC-1C, and VLA data coming this summer. With these data I will be able to test the hypothesis that in dense cores like TMC-1C the dust and gas temperatures are equal. I have also obtained IRAM 30m data to study the deuteration of TMC-1C, which will help constrain the chemical age of the core (older cores will have greater deuterium fractionation). I am working a project to combine IRAM 30m, GBT, VLA and CARMA data to make a deuteration survey of Perseus starless and protostellar cores.