Galactic H2CO Densitometry I: Pilot survey of Ultracompact HII regions and methodology

[ ADS ] [ Full Version ]

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We examined 24 UCHII regions using the GBT to observe the 2-2 line of ortho-Formaldehyde. We measured the local gas density and compared to GMCs and other galaxies. We found densities in GMCs that are 1-2 orders of magnitude higher than the mean density in GMCs, implying that extreme overdensities are common even in "quiescent" (non-star-forming) GMCs. This work was almost entirely my own, but was seeded by Jeremy Darling Some highlight figures from the paper:

A sample spectrum. On the top, black is Formaldehyde 1-1, red is Formaldehyde 2-2. On the bottom, blue is 13CO, red is H77α, black is H110α.

Histograms of GMC mean densities and the densities measured directly from our survey. Note that even for "serendipitious" line of sight GMCs, the densities are MUCH higher than typical GMC densities.

Comparison of the measured column densities of formaldehyde and inferred number densities of H₂.

Characterizing Precursors to Stellar Clusters with Herschel

[ ADS ] [ arXiv ]
C. Battersby, J. Bally, A. Ginsburg, J.-P. Bernard, C. Brunt, G.A. Fuller, P. Martin, S. Molinari, J. Mottram, N. Peretto, L. Testi, M.A. Thompson 2011

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The paper includes a careful characterization of the properties of both dense and diffuse regions within the two Hi-Gal Science Demonstration Phase fields (l=30 and l=59). It demonstrated that star formation tracers are more common at higher temperatures, and that IRDCs exist on both the near and far side of the galaxy, where the difference between near and far is around 5-7 kpc.

I helped develop the iterative background subtraction method and contributed to the discussion and conclusions; most of the work was Cara's but my experience with iterative flux estimation from the BGPS pipeline proved useful.

An Infrared Through Radio Study of the Properties and Evolution of IRDC Clumps

ADS
arXiv

I assisted in many of the technical aspects of the paper including Bolocam and VLA data reduction.

We identify a potential evolutionary sequence among millimeter "clumps". HCO+ and N2H+ maps are used to measure the physical properties of some of these clumps.

Star-forming Region Sh 2-233IR. I. Deep Near-infrared Observations toward the Embedded Stellar Clusters

ADS
arXiv

My contributions to this paper were minor. Analysis of luminosity functions in the IRAS 05358+3543 region have identified different aged groups. The paper contributes to the picture of sequential (triggered?) star formation in the S233-235 region in Auriga.

Outflows and Massive Stars in the protocluster IRAS 05358+3543

ADS
arXiv

A mm and near-IR study of the IRAS 05358+3543 system. Recently (2011), it has become clear that "protocluster" is unlikely to be the right label for IRAS 05358+3543. "proto-association" might be more accurate.

Perhaps the most interesting result of this paper is the discovery that the central source is likely to be a 400-AU binary with two massive (>8 msun) stars at different evolutionary stages. It is just barely in ALMA's range...