Ministerio de Economía y Competitividad Gobierno de Canarias Universidad de La Laguna CSIC Centro de Excelencia Severo Ochoa

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Dec. 13, 2017

CAITLIN CASEY: "We want to know how the most extreme galaxies in the early universe were formed"

When she was a little girl Caitlin Casey often visited the planetarium in her school as she was fascinated by the wonders of the sky she could find there. Years later, now a Professor of Astronomy at the University of Texas, Austin (USA) she admits that her passion for this science started at that time, and that now she enjoys teaching it, and researching in her favourite subjects: the mos massive and luminous galaxies in the universe, objects so extreme and complicated that they are a challenge to those performing cosmological simulations. Using submillimetre wavelength observations the plan is to see how these galaxies formed and evolved from the epoch just after the Big Bang until the present time. With this programme in mind she recently visited the Instituto de Astrofísica de Canarias (IAC) as a Visiting Researcher in the Severo Ochoa Programme, whose aim is to foster scientific collaboration among leading research institutions.

“If we want to learn about star formation in the universe we must observe not only the light from the stars, but also the light which the dust re-emits.”

“When I teach astronomy it is important that my students understand what it is, and what science means for when they need to take important decisions for the future.”

By Viktor Rivera and Elena Mora (IAC)

Question: In which research project have you been collaborating with the IAC?

Answer: I am working with Helmut Dannerbaouer on ultraluminous galaxies. We are trying to understand how clusters of galaxies formed in the early universo. Observations gave us the cosmic microwave background, which gives us information about the earliest moments of the universe, but afterwards we don’t have any information until we detect the first clusters of galaxies at a redshift of 1.5 (some 4,000 years after the Big Bang). So that for more than half the age of the universo we have not information about how these huge structures collapsed. What we are trying to do is to see if these ultralumionous galaxies are good tracers of the clusters of galaxies which are collapsing or forming.

Q. You are interested especially in dusty galaxies which are forming stars at a high rate-. Why? How to they help us understand the universo?

A. Those objects present us with unique questions about the formation and evolution of galaxies in general. They are relatively rare, complex and unique because they form stars at a very high rate, so that cosmological simulations often do not manage to reproduce them. We use this population of galaxies to understand in detail how galaxy formation occurs in this extreme regime, and if we do not reproduce this type of objects maybe our understanding of galaxy formation in general is not really correct.

Q. What is the importance of infrared and submillimetre observations?

A. Both are very important when there is a lot of dust. Even though the mass of dust is not a significant fraction of all the mass in the universo- the stars, the gas, and especially dark matter dominate the mass- dust is special because it is a very good absorber of the light emitted by young, massive, very hot stars. It then re-radiates at long wavelengths. The galaxies which form many hot young stars are very dusty, so that if we want to learn about star formation in the early universo we need to observe not only the light from these stars, but we must also study the radiation emitted by the dust. This is the importance of the infrared and submillimetre ranges of the spectrum, to be able to see through the dust.

Q. What are your other lines of research?

A. During my stay at the IAC I was working mainly in the use of these submillimetre tracers to find clusters of forming galaxies, or the progenitors of the massive galaxy clusters, but I am also involved in research which is trying to find dusty galaxies with high star formation rates at greater distances, in the early universo. To do  this we must be very creative with our sky surveys, because it is very difficult to find them, and this is part of the reason why we do not know them well. It is particularly interesting to find these galaxies in the very early universo when they had not had much time to form and evolve. Even so, the galaxies we have found so far are quite extreme compared with more common galaxies. They have a lot of dust, gas, and star, and we want to know how this can have occurred at less than a thousand million years after the big bang.

Q. As a woman have you found any obstacles during your training or your research career?

A. Yes, many. I would say that most of the obstacles I have found occurred as I advanced in my career. As a student I have to admit that all my tutors and professors were very encouraging.Then, when I began to become more independent I realized that there were more obstacles. In particular when was a postdoctoral researcher I had to fend off a lot of harrassment, often indirect or subtle, which can be a drag on one’s work, one’s productivity and  creativity, when you have to spend 10%-20% of your time thinking of those other things which have nothing to do with science, but with human interaction, and knowing that this would not have happened had I been a man.

Q. What do  you like most about your work in astronomy?

A. I like the fact that every day I can be creative and can do something different. I enjoy advising the students, teaching astronomy in lectures, helping others in their careers, and thinking about scientific ideas every dat. It is amazing that every day is new and different. Sometimes I have to travel, and it is exciting to know new people in new centres.

Q. Do you think that it is necessary to communicate science to society?

A. I think that it is  very important. The majority of the scientific community is financed by public funds, and I consider that the government plays a very important role in this. But also, as we are paid with public money, we owe it ot society to communicate the work we do. When I teach astronomy in the university, I don’t need the students to memorize certain facts about what I am teaching. I only demand that they are not scientifically illiterate, because it is important that when they are older, and in positions of power, or in position to vote about certain policies, to elect our representatives, o simply to understand the role of the different organisms of the government and how to educate the public, they understand what science is, and what it means.

 

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