Advancing Humanity’s Knowledge About Merging Galaxies and Their Blackholes

Derek Hand and Andreea Petric in their office at the Institute for Astronomy, UH Hilo University Park of Science and Technology.

Derek Hand and Andreea Petric at the Institute for Astronomy, University Park of Science and Technology, UH Hilo campus. Click to enlarge.

A budding scientist double majoring in physics and astronomy at the University of Hawai‘i at Hilo has helped make an astonishing discovery about merging galaxies.

After receiving a bachelor of science in astronomy last fall, UH Hilo senior Derek Hand is now finishing up his second baccalaureate degree, this one in physics. He is a NASA Space Grant Fellow who joined forces with astronomer Andreea Petric when she was a science fellow at Gemini Observatories. She now serves as resident astronomer with the Canada-France-Hawai‘i-Telescope.

Together, student and mentor have been working to analyze data that will advance humanity’s knowledge about merging galaxies and the growth of the central black holes they encompass.

While conducting analysis of their observations, Petric and Hand made a surprising discovery that, once verified, will be a new contribution to science.

They found that Active Galactic Nuclei (AGN), or as Petric describes, “super massive black holes that are eating,” can have a dramatic impact on the matter from which galaxies make their stars. This is surprising because the transfer of energy ranges from the very small physical scale to the very vast galaxy-wide scale.

Derek Hand working on his research project.

Derek Hand working on his research project. Courtesy photo.

The project is an independent research process. Hand came up with the research proposal and does the research while Petric provides guidance. Hand gives this scientific description of the work:

Our CO data comes from the Herschel satellite in the far Infrared (~200 -700) microns. We will be observing transitions of the 12 CO carbon monoxide (CO molecule). The CO molecule has rotational kinetic energy, proportional to its angular momentum. Quantum mechanics tell us tells us that the angular momentum and hence the rotational energy are quantized such that the rotational energy is proportional to angular quantum number J as J (J+1), with higher J at higher energy levels.

So the upper-level energies Eu for CO transitions are proportional to J(J+1). The corresponding minimum temperatures for J upper = 13 are on the order of a few hundred K and so high – J lines are weak in cold molecular gas but strong in regions of star-formation or when there is AGN heating the gas.

So for this project with Herschel we observed warm CO, transitions J=4-3 to 13-12, to compare see if and how the CO excitation conditions change in LIRGs as a function of merger stage and AGN contribution to the IR.

In addition I performed a long and tedious literature search to obtain all the CO 1-0 measurements, as this probes the coldest CO an the one that is most closely associated with star-formation. I found measurements for (168??) but there is a small hitch. These observations were performed with single dish observatories and results in these objects being observed differently while the SPIRE/FTS beam size varies between 20 and 40′′, and to correct for this, we must scale this data. To do so, we will employ Herschel Far Infrared observations to estimate the CO(1-0) that may be present in the Herschel aperture (that is, go from a 1-2 arcminute scale to about a 30 arcsecond scale).

Collaboration

The mentorship of Petric has been invaluable to Hand’s start as a serious scientist. Petric, a member of the physics and astronomy faculty at UH Hilo, received her doctor of philosophy from Columbia University and was a postdoctoral fellow at California Institute of Technology, where she worked on infrared and millimeter observations of interacting galaxies and galaxies hosting Active Galactic Nuclei (AGN).

In order to make their recent discovery about AGN, Petric and Hand collaborated with scientists from the University of Virginia, the Caltech Submillimeter Observatory, the Institute for Astronomy at UH Mānoa, and groups in France and Japan. Working together, they used multiple data sets to study the properties of the molecular gas in Luminous Infrared Galaxies.

Petric and Hand are currently using different methods and data from other sources and telescopes to verify the discovery. Once that is done, they have a plan in-the-works to write and publish a paper on their findings.

Applied learning

All of this may not have been possible without the opportunities provided at UH Hilo where students can apply their knowledge gained in the classroom to real life experience.

Petric and Hand met through the Akamai Internship Program. The six-week program offers college and university students an opportunity to gain a summer work experience at an observatory, company or scientific or technical facility in Hawai‘i. Akamai offers training, skill acquisition and first-hand experience working alongside mentors, managers, and fellow interns. Promising college and university students who excel in their chosen industries are given a jump start into their careers.

After Petric and Hand were matched through the Akamai program, they found shared interests and formulated the research idea that would eventually lead them to new discoveries about the role of interacting galaxies on star formations and black hole growth.

This led Hand to pursue a highly competitive Space Grant from NASA. Funding was awarded and the rest may, quite possibly, go down in history.

Becoming an astronomer at UH Hilo

Derek standing in front of observatory dome

Derek Hand on the summit of Maunakea. Courtesy photo.

Hand, who hails from Bemidji, Minnesota, and graduated from Mount Ayr Community High School, Iowa, in 2012, says, “I came to Hawai‘i because the (UH Hilo) astronomy and physics department does have its own observatory.”

The observatory is currently closed for maintenance, but is scheduled to be up-and-running in about eight months. In the meantime, Hand felt he had enough class work and experience to apply for an internship.

“I wanted to work with real data, with real people, working on real research, that’s where I learn the best,” he says.

Hand feels that it helps to apply the tools acquired in the classroom and believes that the application emphasizes their importance.

He says that one of the most valuable lessons he has learned, thanks to his internship and subsequent NASA fellowship working with Petric, has been the independent research process. In the past people had told him what to do, but Hand is grateful for Petric’s approach.

“Andreea more-or-less says ‘this is what needs to happen, you should figure out how to do it,’” explains Hand.

Petric says the long time period of the grant played a large role in the work.

“We had a long time, that’s why I think the Space Grant is a wonderful opportunity,” she says. “A lot of UH students have classes and they also have jobs. On top of that they want to be involved in research, but it’s quite difficult, there isn’t enough time. That’s why the Space Grant is great, it provides extra funding and time.”

Petric also points out other benefits, such as skill development through specific literature searches, computing faculties and technical language acquirement.

The team will continue their research this semester, looking at other founts that will help them understand whether their discovery is in fact confirmable. They plan to write and publish a paper discussing their findings, should they be successful.

Hand will be graduating this May, completing his double major in astronomy and physics. He has applied to graduate school.

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