Telephonic Interview with American astrophysicist George Privon. About his field of research and his experience at Indian observatory GMRT – Giant Metrewave Radio Telescope. This interview was published in “Satellite Science” magazine Feb-2012 issue in Marathi language.
Question: Mr. Privon As I have through your profile we find that your field of work is very large. Tell us about it.
Ans: I started out studying active Galactic Nuclei (AGN): Supermassive black holes which have gas falling into it. After that I started studying the galaxies which have significantly higher rates of star formation than our own Milkyway. This all work comes under “Galaxy Evolution”. This essentially dominates my research interest. And this all research leads to resolving a main question “why galaxies we see today are the way they are?” This is very ambitious undertaking and researchers select very small area to focus on.
Question: Could you elaborate more about this Active Galactic Nuclei?
Ans: Sure!There’s evidence that all massive galaxies have a supermassive black hole in their centers. These black holes are roughly 0.1% of the mass of the galaxy. In most galaxies, this black hole isn’t doing much. But in about 10% of galaxies, there is gas falling into the black hole. As the gas falls in, it releases energy. Much of the energy is emitted as radiation, from radio waves through X-rays. Releasing energy this way is much more efficient than fusion (which is how stars produce their energy), so in some cases the small region around the supermassive black hole can actually outshine the galaxy in which it sits. The fact that all massive galaxies seem to have a supermassive black hole and that the mass of the black hole is roughly a set fraction of the total galaxy mass, it suggests that the growth of the black hole and the growth of the galaxy are linked, which is a bit surprising because the black hole’s gravity only dominates very close to it, and so the rest of the galaxy essentially doesn’t even know the black hole is there.
Question: which are the groups you are working with, is this with Virginia University where you are currently working?
Ans: Yes, there is a general “Galaxy Evolution” group which includes members from the University of Virginia and the National Radio Astronomy Observatory. There’s a wide range of interests in the group, from local galaxies, to galaxies in the early Universe. I mostly focus on extreme systems in the local Universe. They are called the Luminous Infra-red Galaxies” (LIRGs). Essentially they are systems (often where two galaxies are merging), where stars are forming at 20-100 times the rate of our own Galaxy. But there is much gas and dust in these mergers, which absorbs the light from the newly formed stars. So instead of seeing lots of optical and ultraviolet light, all of that energy comes out in the infra-red To obtain a better understanding of what is happening in these galaxies we are collecting data in multiple bands like radio, infra-red optical, ultraviolet, X-rays. because each band gives you different information. This was the motivation for the trip to the Giant Metrewave Radio Telescope a few months ago.
Question: So how many galaxies or which did you focus on, while at GMRT?
Ans: The whole sample I am looking at has about 200 galaxies, about 50 which are well suited to observe from the GMRT. While the galaxies are relatively close to us (compared to the size of the Universe), they are still far enough away that it takes at least a few hours to detect the gas in them. So I selected three galaxies to observe as tests. I’m happy to say that the observations were successful. Also I found the faculty and staff at the National Centre for Radio Astrophysics very friendly and helpful both in helping with the observations and in talking about science.
Question: which are the other telescopes you have used for your regular observation?
Ans: The other two telescopes I use are the Expanded Very Large Array (EVLA) in New Mexico (USA), and the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands. With the GMRT, someone needs to physically go to the telescope and collect data. With the EVLA and WSRT, you send them a script and someone there does the observations for you. But after that, analyzing the data is very similar. I much prefer going to telescopes and taking the data myself. There’s something about being there that is just so much fun.
Question: Your website also mentions “Hubble” in your work. Tell us something about it.
Ans: My work with data from the Hubble Space Telescope is actually for projects on AGN. But for the AGN projects essentially we were looking to study how AGNs can interact with gas farther out in the galaxy. A previous project, while I was at the Rochester Institute of Technology, studied at about 80 galaxies with AGN to look at how interactions between jets of particles and gas clouds in the galaxies have changed over the age of the Universe. Some of the well known objects we looked at are: 3C 231, 3C 84, 3C 213.1, plus 3C 273 (quasar located in the constellation Virgo) which you can see with amateur telescopes.
Question: When did you develop interest in Astronomy and what were your initial projects?
Ans: Well, my grandfather is an amateur astronomer, so I guess my first bit of astronomy was seeing Halley’s Comet through a telescope when I was 2 years old. But I never really considered a career in astronomy until I was studying physics for my bachelor’s degree. I decided to take a year off from school, to spend 6 months doing research for a professor, and 6 months working for a company, to decide if I wanted to go on to graduate school or get a job. My advisor at the time (David Axon) is an astronomer. He pointed me towards another astronomer at RIT (Chris O’Dea), and I spent 6 months working for him, on the survey of radio galaxies with Hubble. I decided I liked that so much I didn’t do the 6 months of working for a company, and applied to grad school in astronomy.
Question: currently working on AGN, what do you plan to do next? What after AGN, LIRGs?
Ans: My main focus right now is the LIRGs and the work with the GOALS team. But I am hoping to continue doing both AGN and LIRGs. There is some overlap between them (many AGNs are LIRGs). The most exciting thing recently is certainly the observations at the GMRT. It was a great trip and I also got great data. I think my project can make great use of it and I am hoping to be back again for more observations. But, I think there’s enough we don’t know to keep me busy for a lifetime.