Download 1 Research Experience for Cara Battersby I include very briefly here

Research Experience for Cara Battersby
I include very briefly here more information about the science I have published and my
contributions to each work.
First Author Publications:
[P1 and P3] “The Temperature and Density Structure of a Massive Star-Forming IRDC” and
“The Dense Gas Kinematics in a Massive Molecular Filament” with Prof. John Bally, Prof.
Jeremy Darling, Adam Ginsburg, Dr. Miranda Dunham and Dr. Steve Longmore – done while at
the University of Colorado, Boulder. I have been working on this project off and on for the last
two years, and will be submitting the first paper within the next month.
This project involved extensive observation preparation and data reduction for the Karl
G. Jansky Very Large Array (VLA). We observed three inversion transitions of ammonia near
1cm. These data were fit with a detailed radiative transfer model to derive gas temperatures,
column densities, velocities, and velocity dispersions. We compare these data with Herschel,
Spitzer, GBT, and Bolocam data.
In the first paper, we present the observations, data reduction techniques, the radiative
transfer model, and finally, the temperature and density structure of two clumps in a massivestar-forming Infrared Dark Cloud (IRDC) on sub-pc scales. We compare the dust temperatures
and column densities derived from Herschel with the gas temperatures and column densities
derived from ammonia on the VLA. We also derive an ammonia abundance, calculate core
properties (masses, temperatures, densities) and their typical fragmentation scale.
The second paper presents the large-scale environment of the IRDC, which we
discovered to be embedded within a massive molecular filament. Additionally, we present the
1 gas dynamics of the clumps observed with ammonia on the VLA, including the typical line
widths, core-core velocity dispersions. We also present the gas flows within the filament on
small and large scales (with the VLA and the 13CO from the Galactic Ring Survey, respectively).
[P2] “The Lifetimes of Evolutionary Phases in Clustered Star-Forming Regions” with Prof. John
Bally at the University of Colorado, Boulder. This project builds upon Publication 6. I have
been working on it off and on since summer 2012, and anticipate the submission of the let by
December 2012.
This paper has a simple goal: to estimate the lifetimes of two evolutionary phases in the
formation of stellar clusters. These phases are the cold dense pre-cluster-clump (PCC) phase and
the warm, diffuse, actively star-forming clump phase, as identified by Battersby et al. (2011).
We use the Herschel-derived temperatures and column densities, along with Spitzer star
formation tracers to identify the fraction of sources (above a critical density threshold for
forming massive stars) in each phase, and estimate a relative lifetime from these fractions. We
tie this to an absolute lifetime using the fraction of sources showing Class II 6.7 GHz methanol
masers and their literature-derived absolute lifetimes.
[6] “Characterizing precursors to stellar clusters with Herschel” with a host of collaborators
from the Herschel Infrared Galactic Plane Survey (Hi-GAL; see publication list for a full list of
authors), while at the University of Colorado, Boulder. I worked on this project from about
January 2010 to Fall 2011.
This project presents a novel and unique approach to identifying the dense, cold clumps
in our Galaxy that are the likely precursors to stellar clusters. We present an iterative routine to
2 subtract off the diffuse Galactic cirrus emission from the Hi-GAL images, and fit a pixel-bypixel modified blackbody to the data. We present the dust temperatures and column densities
across the two Science Demonstration Phase fields.
We compare the Herschel-derived physical properties with Spitzer and methanol-maser
star formation tracers in s systematic way to create a robust evolutionary sequence. We find a
clear evolution from cold, dense, dark clumps (PCCs) to warm, bright, diffuse active clumps.
We also identify the first PCC candidates on the far-side of the Galactic Plane.
The analysis tools created for this analysis can easily be applied throughout the Galaxy
with the full Hi-GAL Survey (from -70° to 70° in Galactic longitude, -1° to +1° in Galactic
latitude). I have applied this automated, iterative algorithm to the Galactic center successfully
with no changes in Longmore et al. 2012a.
[13] “An Infrared Through Radio Study of the Properties and Evolution of IRDC Clumps” with
Prof. John Bally, Prof. Jim Jackson, Adam Ginsburg, Prof. Yancy L. Shirley, Wayne
Schlingman, and Prof. Jason Glenn. The work for this project was done partially while at Boston
University and partially at the University of Colorado Boulder. I worked on and off on this
project roughly from Fall 2007 to summer 2010.
For this project, we took observations of a sample of IRDCs from radio to sub-mm and
compiled literature observations to determine the physical properties and evolutionary sequence
for IRDC clumps. I observed the sample of IRDC clumps (8 IRDCs with 17 clumps within
them) at 3.6 cm free-free continuum emission with the VLA to look for Ultra-Compact HII
Regions.
3 We also mapped the clouds in the HCO+ and N2H+ submm dense gas spectral lines using
the Heinrich Hertz Telescope (HHT) in Arizona. We compared the line properties and star
formation tracers to identify quiescent, intermediate, and active clumps. We also used Bolocam
Galactic Plane Survey (BGPS 1.1 mm dust continuum) observations to derive masses, which we
compared with masses that we derived using 8 micron extinction (from Spitzer), and the virial
masses. Additionally, we performed a Monte Carlo simulation to estimate the systematic and
statistical errors associated with typical mass estimates using various tracers.
Co-authored Publications:
I have worked on many interesting publications throughout the years as a collaborator. I group
these collaborations and describe them briefly below:
Identifying Proto-Massive Clusters with Eli Bressert, Adam Ginsburg, and Prof. John Bally
(publications 1 and 2). All of us worked closely to develop the theoretical model and
observational test during the last year.
Galactic Center Star Formation with Dr. Steve Longmore and collaborators (publications 3
and 5). I worked with Dr. Longmore to produce background-subtracted pixel-by-pixel
temperature and column density maps in the Galactic Center and provided useful comments on
the science direction.
4 The Hi-GAL Collaboration (publications 4, 9, 10, 14, 16, 17, 18). I have worked with the HiGAL team for the last two years on interesting papers. Many projects are done pretty
independently, but we all work together to provide critical feedback on the work.
H2CO Densitometry with Adam Ginsburg, Prof. Jeremy Darling, Ben Zeiger, and Prof. John
Bally (publication 7). I traveled to the GBT and led the observing run and helped with much of
the data reduction and interpretation for this work.
The BGPS Team (publications 8, 11, 12, 15, 19). I have worked with the BGPS team for the
last four years. I have traveled to the CSO on Mauna Kea to lead an observing run for the BGPS,
as well as to the HHT in Arizona for the BGPS spectral line follow-up survey. I have helped
with analysis, data reduction, and science direction with the project.
Haystack Methanol Maser Survey (publication 20). I worked on this project as an
undergraduate at the MIT Haystack Observatory. I took and reduced most of the data for this
project and helped with science comments prior to publication.
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