Exchange Report by Kevin Corneilus Harrington

SFB 956 sub-project: A1 
Supervisors: Prof. Dr. Frank Bertoldi, Argelander-Institut für Astronomie, Universität Bonn (Germany) 
Hosting institution: University of Massachusetts, Amherst (UMass) 
Supervisor at the hosting institution: Prof. Dr. Min Yun
Duration of stay abroad: Feb. Mar. 2019

Background Context

In the first SFB exchange program (Aug.-Nov. 2017) I spent roughly one month in three different locations: the University of Massachusetts, Amherst (UMass), Cornell University and the Green Bank Telescope (GBT). Working with Prof. Yun at UMass and Prof. Riechers at Cornell, and also other PhD students and faculty, enabled me to write a successful proposal for the IRAM 30m telescope to systematically measure the complete energy distribution of the CO molecule within one of the largest samples of strongly gravitationally lensed, star-forming galaxies at high-redshift. While at the GBT I was able to measure the faint CO(1-0) line for most of these galaxies. Over the past 1.5 yr, these programs, along with another two successful programs using the APEX telescope, mark a legacy dataset for the community. I am one of many PhD students within the A1 sub-group of the observational astrophysics group, A in the SFB-956. This group is devoted to the study of galaxy evolution and mass assembly, and the A1 subgroup in particular provides the observational context in the early universe that motivates and complements the research by the sub-groups focused on the observations of the Milky Way and local extragalactic systems, as well as for the theoretical and instrumentation groups.

Work Experiences

My brief visit earlier this year was full of planning meetings, workshops and discussions. The selection method used to identify these galaxies I am studying will be presented in an upcoming publication, and this visit solidified a publication strategy for the remaining datasets we have obtained thus far. Through our group meetings we were able to develop a strategy for which proposals we will write. In my time at Umass I wrote, as Principal Investigator, a proposal for the SMA, APEX and NOEMA facilities. We also organized our plans for the very competitive ALMA proposal, and I was able to contribute to the science case we would later propose for the recent HST​ proposal. Lots of time was spent calculating the sensitivities required for the proposed experiments, and often convening to discuss the ongoing proposal drafts.

One fellow PhD student and collaborator at UMass is working almost exclusively on the challenging lens modeling software analyses of these lensed galaxies. To better place my work in context, I need to know the details of the lens modeling to get an impression of the intrinsic properties of the magnified galaxies I study through CO and other tracers of the star-forming interstellar medium. We spent hours discussing the nuances of the LENSTOOL modeling software and examining different input parameters, the implications of these inputs, the limitations of the current datasets (e.g. angular resolution, foreground contamination from the lensing galaxy) and how to run the software.

I recently obtained 25h of data with the Very Large Array (VLA) to resolve the CO(1-0) data from the GBT measurements. Now that all of the data is transferred to Bonn, I will soon reduce this dataset. The VLA datasets, however, can be challenging to reduce. My collaborators at UMass have lower frequency VLA data for our sample, therefore I could look at the reduction steps and ask the subtle questions related to radio interferometric reduction/imaging techniques. As we are all working on multiple things, this became an opportunity for me to take a look at our VLA data and for us to design a path to our immediate science objectives.

During my time there I gave an interview to discuss the purpose of my visit and to share my insights and takeaways as an alumnus of UMass. The interview can be found here

Aside from a few astronomy department colloquium talks I attended, I gave a lunch colloquium talk about my ongoing work to the galaxy evolution group. It was helpful to receive unique feedback from the faculty, which will serve as a useful reference to the comments/questions I will receive from others. Most importantly, before the end of my stay, I had submitted a manuscript I had been working on for months. Upon minor revisions, this will soon be accepted in the ​Monthly Notices of the Royal Astronomical Society​ Journal. There are two additional publications as lead author that I will write this year, and the ground-work for these manuscripts were thoroughly discussed in multiple meetings throughout this month.

Life Experiences

One thing I will remember is joining the students and faculty for their daily 10 a.m. coffee hour to scroll through the abstracts of the day in the ‘arxiv’. The ritualistic activity brings together the majority of the astronomy department and has encouraged me to stay more engaged with the latest articles in the field. It was indeed an exciting time to be at UMass because there were multiple visits from prospective students (allowing me to see how the department/graduate students present the department to potential PhD candidates). In addition, I sat in on a couple of meetings for the state-of-the-art instrument being built at UMass, called TolTEC, which is planned to be installed and taking first-light with the ​Large Millimeter Telescope​ owned by Mexico/UMass by next spring/summer.

The snowy UMass campus was still lively right in the middle of the semester. There were two events that stood out to me in particular, both offered by the African-American studies department. One was an event celebrating the life of African-American activist/athlete/singer/actor Paul Robeson. This had inspired me to continue pursuing all of my interests in life as Paul had remarkably exemplified throughout his life in the early-mid 1900s. The other event was a conversation among authors, each experts in the cultural and socio-economic history of the West Indies and Jamaica in particular. Despite being from a completely different field, I was able to still ask the authors, “What is your approach to writing? Where and how do you write best?”. They both found that early morning writing, between 3-7 a.m., seems to be when they get a lot of their work on the page, but that being disciplined is the key. For a PhD student, that means writing every day....even a little bit!

Upon reflecting on the most recent SFB research exchange (Feb. Mar. 2019), I have realized how much effort is involved in maintaining a long-standing collaboration. At the time I began research in the field of extragalactic star-formation and galaxy evolution as a Bachelor student at UMass, to the point I am at now in my PhD career, sustained communication and personal visits have made all of the difference in making sure there is a mutual agreement on steps forward in our collaborative work. Fortunately, I find myself as one of the major leaders of this collaboration. Thanks to this opportunity provided by the SFB, I have been able to nourish this network through these vital face to face visits, and I look forward to the ongoing work and upcoming publications.