Date: April 17, 2011
Title: Supermassive Black Hole Research at NOAO
Podcaster: Dr. Tod R. Lauer and Rob Sparks from the National Optical Astronomy Observatory
Organization: National Optical Astronomy Observatory
Links: NOAO, NOAO on Twitter
Description: Black holes are one of the most mysterious types of objects in the universe. Astronomers have found evidence that almost every large galaxy contains a black hole at its center. These black holes have a variety of effects on the surrounding galaxy and may be a major factor that influences galaxy evolution. In this podcast, Tod Lauer of the National Optical Astronomy Observatory discusses some of his research into these supermassive black holes.
Bio: Dr. Tod R. Lauer is an astronomer at the National Optical Astronomy Observatory, headquartered in Tucson, AZ. Lauer received a BS in astronomy from Caltech in 1979, and a PhD from the University of California, Santa Cruz in 1983. He served on the research staff at Princeton University Observatory from 1983 to 1990, before joining the NOAO scientific staff. Lauer was a member of the Hubble Space Telescope WFPC-1 team, and has conducted extensive research with the Hubble; in 1992 he received the NASA Exceptional Scientific Achievement Medal in recognition of his early work with the instrument.
Lauer’s work with the Hubble is largely concerned with the search for massive black holes, the structure of galaxies, and stellar populations. He also conducts research on the large-scale structure of the universe using the ground-based telescopes of NOAO. Lauer has a long standing technical interest in astronomical image processing, and explores algorithms to optimize the use of astronomical cameras.
Rob Sparks is a science education specialist in the EPO group at NOAO and works on the Galileoscope project (www.galileoscope.org), providing design, dissemination and professional development. He also blogs at halfastro.wordpress.com.
Sponsor: This episode of the 365 Days of Astronomy podcast is sponsored by the National Optical Astronomy Observatory. NOAO is a US national research and development center for ground-based nighttime astronomy. We provide astronomers access to world-class observing facilities on a peer-reviewed basis. Our mission is to engage in programs to develop the next generation of telescopes, instruments, and software tools necessary to enable exploration and investigation through the observable Universe. For information on observing proposals or our public programs, please visit www.noao.edu for more information.
Transcript:
Rob: Hi, This is Rob Sparks from the National Optical Astronomy Observatory. I would like to welcome you to this episode of the 365 Days of Astronomy podcast. I am sitting here today with Tod Lauer of the National Optical Astronomy Observatory. Hi, Tod.
Tod: Hi.
Rob: How are you doing today?
Tod: Fine, thank you.
Rob: First, I would like you to tell me a little bit about yourself and what you do here at NOAO.
Tod: Well, I am on the senior research staff at NOAO, I am a research astronomer. I work mostly on things outside the galaxy and as part of my job I also make telescopes available to U.S. astronomers to use for research themselves.
Rob: Which is of course our mission here at NOAO. First of all, I hear your research is mostly on galactic black holes. We should probably start off briefly describing what a black hole is for our listeners.
Tod: Well, I always have to laugh a little bit because I notice black holes are known in every place but astronomy because if you read the newspapers it said “his career has fallen into a political black hole” or “we’re headed toward an economic black hole” but when we talk astronomy we always have to explain what these things mean. A black hole is a place in space where there is so much matter and has gotten so dense, so concentrated, that no light can escape from it. And so to the outside observer it looks black and it’s kind of a hole. You can fall into it but you can’t get back out.
Rob: So what instruments and techniques do you use to study these black holes if they are black?
Tod: Well, you can’t see them from the light they give off, but you can see them from their immense gravity and what affect it has on things around it. So what I am doing with a team of people is we have looked toward the centers of galaxies where we think the most massive black holes live and we look to see if there is a signature. The signature is typically how it pulls on the stars of its galaxy. If gravity is not very strong the stars move kind of slow. If it is very strong the stars move more rapidly than you can explain by accounting for all the other matter at the center of the galaxy. So we’re taking the temperature as it were of the centers of galaxies. Hot they move around very fast, cool they don’t very much so we’re looking for hot centers. We use telescopes that can have very very sharp resolution. We have used the Hubble telescope given that it has exquisite vision given that its above the atmosphere which blurs things. But more recently we have been using large telescopes on the ground with special systems that can correct for atmospheric turbulence. Those telescopes are the Gemini Observatory which our organization supports for U.S. astronomers and the Keck Observatory in Hawaii.
Rob: And if you look in the archives of the 365 Days of Astronomy podcast you will find that last year I did a podcast on adaptive optics so listeners can look that one up in the 2010 archives. One important topic of research is what role black holes play in galaxy evolution. What do we know so far about their role in galaxy evolution and what are the outstanding questions?
Tod: That covers a lot of territory. The first thing I can say is that at one time we thought black holes were very rare exotic objects. They were predicted by theory but we really hadn’t seen evidence for them. What we see now is that they are probably a normal part of every big galaxy. Just like a peach has a pit in it, you are used to things at the center of fruit, well, all galaxies have a pit except that’s the black hole.
Rob: I like that analogy of the pit.
Tod: So they are really a normal part of everything, as exotic as they are something we expect that every galaxy has at its center. And they do play a critical role because as things go into a black hole they can’t get out, as they approach all the energy from falling into it gets splashed around and the gas, the matter and everything that falls into the black hole gives off a tremendous amount of radiation and we can see this activity at the centers of galaxies. We also know it was much stronger in the past when the universe was starting to form galaxies. This radiation in turn has an effect on all the matter in the galaxy that surrounds the black hole. It may heat it up, it may prevent it from forming stars or it may just clear out all the gas out of the galaxy when stars are made. So actually black holes probably play a very very important role in making galaxies the way they are today.
Rob: So I got to ask this one: Which came first? The black holes or the galaxies?
Tod: Well, that’s a very big question, and by me I think it’s hard to even frame it in such questions. You put them together. Galaxies started off small and black holes probably started off small. They grew together. The gas that made the galaxies, some of it made the black hole get bigger and the black hole regulated how big the galaxy got to be so they did in lockstep I think is the best answer.
Rob: There’s a relationship between the mass of the black hole and the size of the galaxy’s central bulge, isn’t there? There’s like a ratio we see repeated in a lot of galaxies.
Tod: Well this is one of the things that we found with observations from the Hubble Space Telescope. The team that I work on discovered this that the mass of the black hole is related to how much light there is at the center of the galaxy and, I have to be careful how I explain this, how fast the stars move in the galaxy far enough away from the black hole so that their speed has nothing to do with the black hole. So we see the stars moving around quickly or slowly but far enough away that we know the black hole doesn’t have an effect and that helps us predict what the black hole is. And this is a very very powerful relationship because it allows us now to figure out whether a black hole is likely to be in the galaxy before we ever observe it and if we survey a large region of the universe for distant galaxies at the same time we can guess how many black holes are out there in that part of the universe. In fact, to take it further, this relationship now enables us to learn, or guess, how many black holes are in the universe overall and how much matter in the universe has gone into black holes given all the light we see from galaxies in every direction we look.
Rob: Anyway, looking through your list of publications there are lots of interesting topics, but one that caught my eye was a sub parsec binary super massive black hole. Sub-parsec means they are really close together. Could you describe this system a little bit?
Tod: Well, this is work I did here with another staff member, Todd Boroson who also works at NOAO and Todd has a nice technique for looking at the activity of galaxies that had black holes at the center. They put off a certain kind of spectrum as gas falls into the black holes. And working together with him we found a galaxy that appeared to have two centers of activity based on the spectrum that we took. And we said, well, the best way to explain this is a case where there are two black holes in the process of merging together. And this is something that we have been looking for for a long time. If we have all galaxies with a black hole at the center, we think galaxies merge to make bigger galaxies, so the black holes in the centers of those galaxies will find each other, will sink to the bottom of the newly formed large galaxy, they will form an orbital pair and eventually they will merge themselves just to make one black hole. It is thought that this happens, we have never actually seen it. The case that we advanced was a set of quasars which are active galaxies that put out light where we thought this was happening. So far we haven’t been able to confirm this. So right now it’s an idea, it’s a suggestion that hasn’t been proven, but such things should be out there and we certainly hope to see them one day or another.
Rob: Yeah, if I remember correctly in the paper title, it said something like “a candidate” didn’t it instead of a proven one.
Tod: That’s correct. And that’s the way it is. You have an idea and you put it out there with the best evidence you have. You don’t wait for it to be completely proven otherwise you would never say it’s there. We sent out this letter and we said this is what we think we found and other people went and looked at it and got other observations some of which support our idea some of which don’t. It has yet to be sorted out, so we’ll have to stay tuned to see what happens.
Rob: I will link to that in the show notes so people can look at that if they like to. One last question, what is the next big question you would like to work on (or maybe you are already working on it)?
Tod: Well, there are a lot of questions and they come in big and small. I think one question I have been working on a little bit is where dark energy came from that makes the universe acceleration expand. I am part of a team of people that want to develop a spacecraft to probe dark energy so that’s something that’s occupying my thoughts.
Rob: Okay, thanks for joining me today, Tod;
Tod: It’s been a pleasure.
Rob: Thanks for listening to this episode of the 365 Days of Astronomy podcast. This is Rob Sparks from the National Optical Astronomy Observatory.
End of podcast:
365 Days of Astronomy
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