Thursday, September 24, 2015
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2015 Teaching Conference - Save-the-Date

Katz Receives Prestigious Award for Mathematics

Caltech professor of mathematics Nets Katz has received the 2015 Clay Research Award from the Clay Mathematics Institute. The award was given jointly to Katz and his collaborator, MIT professor of mathematics Larry Guth, for their solution of the Erdős distance problem and for "other joint and separate contributions to combinatorial incidence geometry."

Combinatorial incidence geometry is the study of possible configurations, or arrangements, between geometric objects such as points or lines. One basic open problem in this field is the Erdős distance problem, for which Katz received the Clay award. The Erdős distance problem examines a set "large" number of points distributed in various arrangements in a two-dimensional plane. In some configurations, like a lattice or grid, the points are evenly spaced. In others, as in a random distribution of points, the spacing between points is varied. The problem asks how many times the same distance can occur between these points, and what is the minimum number of distinct distances possible between these points.

In 2010, Guth and Katz proved that the minimum number of unique distances between n points, regardless of their spatial configuration, is the number of points n divided by the logarithm of n: n/log(n).

Katz's work on the Erdős problem is an example of his larger research interest in coincidences. By demonstrating that there is a minimum number of unique distances between points, even when in a uniform arrangement like a lattice, Katz showed that coincidences—such as many sets of points having the same distance between them—can occur only a limited number of times.

Katz received his PhD from the University of Pennsylvania and was a professor of mathematics at Indiana University Bloomington before joining Caltech's faculty in 2013. He was named a Guggenheim Fellow in 2012. Previously, his research was in harmonic analysis, a field concerned with representing functions as superpositions of basic oscillating mathematical "waves."

The Clay Mathematics Institute is a private foundation "dedicated to increasing and disseminating mathematical knowledge." Given annually, the Clay Research Award recognizes contemporary mathematical breakthroughs.

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New Dean of Graduate Studies Named

On July 1, 2015, Doug Rees, the Roscoe Gilkey Dickinson Professor of Chemistry, will begin serving as the new dean of graduate studies at Caltech.

"Doug's experience and concern with graduate education make him an ideal choice for dean of graduate studies. I am very pleased that he is willing to make this commitment to the Institute and its students," says Anneila Sargent, vice president for student affairs and the Ira S. Bowen Professor of Astronomy.

As the new dean, Rees will be the principal administrator and representative of Caltech's graduate education program, responsible for attending to concerns regarding the welfare of graduate students as well as for upholding the Institute's rules and policies.

"There are many groups essential to the effective operation of our graduate program that I want to get to know better, starting with the graduate students, the Graduate Office staff, and the option administrators and option reps," says Rees. "In my 26 years at Caltech, I've gained an appreciation for how the graduate programs in biochemistry and molecular biophysics and in chemistry operate, but the cultures in different options across campus can vary significantly, and I look forward to better understanding these distinctions."

Rees says that he is also very much looking forward to working directly with graduate students, staff, and faculty on behalf of the graduate program. Of particular interest during his tenure will be issues relating to the well-being and professional development of graduate students.

"I find research to be an adventure that, while exhilarating, is also challenging, frustrating, and even stressful; those aspects, however, are not incompatible with having a positive student experience and a supportive environment," Rees says. He adds that his priorities will be to raise fellowship support, increase the diversity of the graduate student body, and ensure that students have access to appropriate support services such as health care, counseling, and day care. "In addition, I also hope to be able to explore mechanisms to better prepare students for life after Caltech, including both academic and nonacademic career options," he says.

In his new post, Rees will take the place of C. L. "Kelly" Johnson Professor of Aeronautics and Mechanical Engineering Joseph Shepherd, who has served as the dean of graduate studies since 2009. "Joe leaves big shoes to fill and the campus owes him a huge debt of gratitude for all he has accomplished as dean of graduate studies. What I have learned from watching him in action over the past six years, and more recently as he has been helping me during this transition period, is that the most important quality for the dean is to care about the students—and I will definitely be working to follow his example," Rees says.

Rees received his undergraduate degree from Yale University in 1974 and his PhD from Harvard in 1980, becoming a professor at Caltech in 1989. An investigator with the Howard Hughes Medical Institute, Rees also served as the executive officer for chemistry from 2002 to 2006 and the executive officer for biochemistry and molecular biophysics from 2007 to 2015.

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Discovering a New Stage in the Galactic Lifecycle

On its own, dust seems fairly unremarkable. However, by observing the clouds of gas and dust within a galaxy, astronomers can determine important information about the history of star formation and the evolution of galaxies. Now thanks to the unprecedented sensitivity of the telescope at the Atacama Large Millimeter Array (ALMA) in Chile, a Caltech-led team has been able to observe the dust contents of galaxies as seen just 1 billion years after the Big Bang—a time period known as redshift 5-6. These are the earliest average-sized galaxies to ever be directly observed and characterized in this way.

The work is published in the June 25 edition of the journal Nature.

Dust in galaxies is created by the elements released during the formation and collapse of stars. Although the most abundant elements in the universe—hydrogen and helium—were created by the Big Bang, stars are responsible for making all of the heavier elements in the universe, such as carbon, oxygen, nitrogen, and iron. And because young, distant galaxies have had less time to make stars, these galaxies should contain less dust. Previous observations had suggested this, but until now nobody could directly measure the dust in these faraway galaxies.

"Before we started this study, we knew that stars formed out of these clouds of gas and dust, and we knew that star formation was probably somehow different in the early universe, where dust is likely less common. But the previous information only really hinted that the properties of the gas and the dust in earlier galaxies were different than in galaxies we see around us today. We wanted to find data that showed that," says Peter Capak, a staff scientist at the Infrared Processing and Analysis Center (IPAC) at Caltech and the first author of the study.

Armed with the high sensitivity of ALMA, Capak and his colleagues set out to perform a direct analysis of the dust in these very early galaxies.

Young, faraway galaxies are often difficult to observe because they appear very dim from Earth. Previous observations of these young galaxies, which formed just 1 billion years after the Big Bang, were made with the Hubble Space Telescope and the W. M. Keck Observatory—both of which detect light in the near-infrared and visible bands of the electromagnetic spectrum. The color of these galaxies at these wavelengths can be used to make inferences about the dust—for example, galaxies that appear bluer in color tend to have less dust, while those that are red have more dust. However, other effects like the age of the stars and our distance from the galaxy can mimic the effects of dust, making it difficult to understand exactly what the color means.

The researchers began their observations by first analyzing these early galaxies with the Keck Observatory. Keck confirmed the distance from the galaxies as redshift greater than 5—verifying that the galaxies were at least as young as they previously had been thought to be. The researchers then observed the same galaxies using ALMA to detect light at the longer millimeter and submillimeter wavelengths of light. The ALMA readings provided a wealth of information that could not be seen with visible-light telescopes, including details about the dust and gas content of these very early galaxies.

Capak and his colleagues were able to use ALMA to—for the first time—directly view the dust and gas clouds of nine average-sized galaxies during this epoch. Specifically, they focused on a feature called the carbon II spectral line, which comes from carbon atoms in the gas around newly formed stars. The carbon line itself traces this gas, while the data collected around the carbon line traces a so-called continuum emission, which provides a measurement of the dust. The researchers knew that the carbon line was bright enough to be seen in mature, dust-filled nearby galaxies, so they reasoned that the line would be even brighter if there was indeed less dust in the young faraway galaxies.

Using the carbon line, their results confirmed what had previously been suggested by the data from Hubble and Keck: these older galaxies contained, on average, 12 times less dust than galaxies from 2 billion years later (at a redshift of approximately 4).

"In galaxies like our Milky Way or nearby Andromeda, all of the stars form in very dusty environments, so more than half of the light that is observed from young stars is absorbed by the dust," Capak says. "But in these faraway galaxies we observed with ALMA, less than 20 percent of the light is being absorbed. In the local universe, only very young galaxies and very odd ones look like that. So what we're showing is that the normal galaxy at these very high redshifts doesn't look like the normal galaxy today. Clearly there is something different going on."

That "something different" gives astronomers like Capak a peek into the lifecycle of galaxies. Galaxies form because gas and dust are present and eventually turn into stars—which then die, creating even more gas and dust, and releasing energy. Because it is impossible to watch this evolution from young galaxy to old galaxy happen in real time on the scale of a human lifespan, the researchers use telescopes like ALMA to take a survey of galaxies at different evolutionary stages. Capak and his colleagues believe that this lack of dust in early galaxies signifies a never-before-seen evolutionary stage for galaxies.

"This result is really exciting. It's the first time that we're seeing the gas that the stars are forming out of in the early universe. We are starting to see the transition from just gas to the first generation of galaxies to more mature systems like those around us today. Furthermore, because the carbon line is so bright, we can now easily find even more distant galaxies that formed even longer ago, sooner after the Big Bang," Capak says.

Lin Yan, a staff scientist at IPAC and coauthor on the paper, says that their results are also especially important because they represent typical early galaxies. "Galaxies come in different sizes. Earlier observations could only spot the largest or the brightest galaxies, and those tend to be very special—they actually appear very rarely in the population," she says. "Our findings tell you something about a typical galaxy in that early epoch, so they're results can be observed as a whole, not just as special cases."

Yan says that their ability to analyze the properties of these and earlier galaxies will only expand with ALMA's newly completed capabilities. During the study, ALMA was operating with only a portion of its antennas, 20 at the time; the capabilities to see and analyze distant galaxies will be further improved now that the array is complete with 66 antennas, Yan adds.

"This is just an initial observation, and we've only just started to peek into this really distant universe at redshift of a little over 5. An astronomer's dream is basically to go as far distant as we can. And when it's complete, we should be able to see all the distant galaxies that we've only ever dreamed of seeing," she says.

The findings are published in a paper titled, "Galaxies at redshifts 5 to 6 with systematically low dust content and high [C II] emission." The work was supported by funds from NASA and the European Union's Seventh Framework Program. Nick Scoville, the Francis L. Moseley Professor of Astronomy, was an additional coauthor on this paper. In addition to Keck, Hubble, and ALMA data, observations from the Spitzer Space Telescope were used to measure the stellar mass and age of the galaxies in this study. Coauthors and collaborators from other institutions include C. Carilli, G. Jones, C.M. Casey, D. Riechers, K. Sheth, C.M. Corollo, O. Ilbert, A. Karim, O. LeFevre, S. Lilly, and V. Smolcic.

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PMA Announces a New Division Chair

Fiona Harrison, the Benjamin M. Rosen Professor of Physics, has been named the new chair of the Division of Physics, Mathematics and Astronomy (PMA). When she begins her five-year term on September 1, she will assume the Kent and Joyce Kresa Leadership Chair, replacing current division chair Tom Soifer, professor of physics and director of the Spitzer Science Center.

Harrison first came to Caltech as a research fellow in 1993 after earning her PhD in physics at UC Berkeley. She joined Caltech's professorial faculty in 1995 and was named the Benjamin M. Rosen Professor in 2013. Harrison's research focuses on understanding some of the hottest, densest, and most energetic phenomena in the universe, as well as developing advanced detectors and instrumentation for future space missions. Currently, she is the principal investigator for NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), the most powerful high-energy X-ray telescope ever developed, which has provided unprecedented views of black holes, neutron stars, and stellar remnants since it was launched into low-Earth orbit in June 2012.

"I'm delighted that Fiona Harrison is taking charge of PMA," says Jim Eisenstein, the Frank J. Roshek Professor of Physics and Applied Physics, who was the chair of the faculty search committee. "She is in many ways the ideal person for this job. Fiona brings top-drawer scientific chops, steady hands, and a genuine appreciation for the enormous breadth of research in PMA to the challenges the division faces going forward. I am very optimistic for her term as division chair."

The Board of Trustees formally approved Harrison's selection earlier this month.

In her new position, Harrison says she looks forward to working with the division's faculty, staff, and students "to advance the division's path-breaking research agenda and to focus on developing the most effective ways to educate our students."

Another top priority will be making sure PMA continues to attract the best people for its faculty, students, and staff. "I plan to help the division identify, recruit, and retain diverse and talented individuals at all levels," she says. "I am excited about the next five years, and about all the scientific discoveries we will make."

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Kimm Fesenmaier
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Caltech, JPL Team Up to Take On Big-Data Projects

Acknowledging not only the growing need among scientists and engineers for resources that can help them handle, explore, and analyze big data, but also the complementary strengths of Caltech's Center for Data-Driven Discovery (CD3) and JPL's Center for Data Science and Technology (CDST), the two centers have formally joined forces, creating the Joint Initiative on Data Science and Technology.

A kickoff event for the collaboration was held at the end of April at Caltech's Cahill Center for Astronomy and Astrophysics.

"This is a wonderful example of a deep cooperation between Caltech and JPL that we think will serve to strengthen connections between the campus and the lab," says George Djorgovski, professor of astronomy and director of CD3. "We believe the joint venture will enable and stimulate new projects and give both campus and JPL researchers a new competitive advantage."

Individually, each center strives to provide the intellectual infrastructure, including expertise and advanced computational tools, to help researchers and companies from around the world analyze and interpret the massive amounts of information they now collect using computer technologies, in order to make data-driven discoveries more efficient and timely.

"We've found a lot of synergy across disciplines and an opportunity to apply emerging capabilities in data science to more effectively capture, process, manage, integrate, and analyze data," says Daniel Crichton, manager of the CDST. " JPL's work in building observational systems can be applied to several disciplines from planetary science and Earth science to biological research."

The Caltech center is also interested in this kind of methodology transfer—the application of data tools and techniques developed for one field to another. The CD3 recently collaborated on one such project with Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology at Caltech. They used tools based on machine learning that were originally developed to analyze data from astronomical sky surveys to process neurobiological data from a study of autism.

"We're getting some promising results," says Djorgovski. "We think this kind of work will help researchers not only publish important papers but also create tools to be used across disciplines. They will be able to say, 'We've got these powerful new tools for knowledge discovery in large and complex data sets. With a combination of big data and novel methodologies, we can do things that we never could before.'"

Both the CD3 and the CDST began operations last fall. The Joint Initiative already has a few projects under way in the areas of Earth science, cancer research, health care informatics, and data visualization.

"Working together, we believe we are strengthening both of our centers," says Djorgovski. "The hope is that we can accumulate experience and solutions and that we will see more and more ways in which we can reuse them to help people make new discoveries. We really do feel like we're one big family, and we are trying to help each other however we can."

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Kimm Fesenmaier
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Caltech Seniors Win Library Friends Thesis Prize

Two Caltech seniors, Adam Jermyn and Kerry Betz, were named as winners of this year's Library Friends' Senior Thesis Prize. The Thesis Prize is intended to encourage undergraduates to complete a formal work of scholarship as a capstone project for their undergraduate career and to recognize sophisticated in-depth use of library and archival research. For their achievement, recipients of the $1,200 prize are listed in the commencement program.

Caltech faculty nominate seniors whose theses they deem to be deserving of the prize. Nominated students then supply a research narrative that explains their research methodology, detailing not only the sources they used, but the way they obtained access to them.

Adam Jermyn, a physics major from Longmeadow, Massachusetts, won the prize for his thesis titled "The Atmospheric Dynamics of Pulsar Companions." The Library Friends committee described it as a "tour de force in its breadth of scholarship, creativity and significance," and Jermyn's faculty adviser Sterl Phinney, professor of theoretical astrophysics and executive officer for astronomy, said in his nomination that the thesis is "comparable to the best PhDs in impact and innovation."

Jermyn's work is a study of the ways in which the radiation emitted from pulsars changes the atmospheres of other nearby stars. Pulsars are a highly magnetized and rapidly rotating type of neutron star, the dense remnants of a star gone supernova. They often orbit closely together with a low-mass "companion star" that can receive enormous amounts of radiation from the nearby pulsar.

"It's been a really fantastic experience. My mentor, Professor Phinney, has been amazing at encouraging me in productive directions and enthusiastically went along with me when I wanted to go off in a strange direction on a hunch," Jermyn says. "You think you've rounded the corner and found the answer, only to realize that you've just walked into more rich and complicated phenomena."

Jermyn, also the recipient of a Hertz Fellowship, a Marshall Scholarship, and a National Science Foundation Graduate Research Fellowship, will start his graduate work at the University of Cambridge in the fall.

 

Kerry Betz, a chemistry major from Boulder, Colorado, won the prize for her thesis titled "A Novel, General Method for the Construction of C-Si Bonds by an Earth-Abundant Metal Catalyst." Robert Grubbs, the Victor and Elizabeth Atkins Professor of Chemistry and Betz's faculty adviser, praised the thesis in his nomination for its "significance, creativity, and novelty."

Betz's work concerns the use of a new catalyst to form carbon-silicon bonds through a process called silylation. The newly discovered catalyst is highly efficient and can operate at room temperature and pressure. Traditionally these reactions require expensive and inefficient precious metal catalysts, such as platinum or palladium. Betz's catalyst is made from the abundant metal potassium, which is more effective than state-of-the-art precious metal complexes at running very challenging chemical reactions.

"I've done this research over the last three years, and I really enjoyed how writing it up brought it all together," says Betz. "Writing up my work revealed new questions and directions to pursue. It showed me how unpredictable and exciting research can be." She will continue her research at Caltech for a year and will then begin graduate studies at Stanford University in the fall of 2016.

 

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Diversity Retreat at Caltech

In September 2013, Caltech, UC Berkeley, UCLA, and Stanford University founded a new consortium—the California Alliance for Graduate Education and the Professoriate (AGEP)—to support underrepresented minority graduate students in the STEM fields of mathematics, the physical sciences, computer science, and engineering. The Alliance, launched through a grant from the National Science Foundation, was created to address the fact that minority students enter STEM fields in disproportionately low numbers and that, as a group, their progress slows at each step in their academic careers.

This April, Caltech was host to "The Next Generation of Researchers," the Alliance's second annual retreat. The retreats are designed to bring together graduate students, postdoctoral fellows, research scientists, and faculty from the four institutions and national labs in California for mentoring and network-building opportunities.

We recently spoke with Joseph E. Shepherd (PhD '81), dean of graduate studies and the C. L. "Kelly" Johnson Professor of Aeronautics and professor of mechanical engineering, about AGEP, the recent retreat, and Caltech's diversity initiatives.

 

What was Caltech's motivation for entering into the California Alliance, and what has the program accomplished so far?

Caltech joined the Alliance to encourage underrepresented minorities to pursue academic careers in mathematics, physical science, computer science, and engineering fields. We seek to not only diversify our own campuses (Caltech, Berkeley, Stanford, and UCLA) but also contribute to diversity throughout the nation.

During the first year, the Alliance members identified participants at the four campuses. We have conducted two retreats—the first at Stanford University in 2014 and the second at Caltech. Graduate students, postdoctoral scholars, and faculty gathered at these retreats and learned about opportunities and challenges for underrepresented minority students transitioning from graduate studies to a career as a faculty member.

In 2014, the Alliance established a postdoctoral scholar fellowship program, accepted applications in the fall, and is in the process of finalizing awards for this coming academic year (2015–16). The Alliance has also accepted applications for the mentor-matching program through which graduate students can visit faculty at Alliance institutions to learn about opportunities and faculty careers in specific research areas.

 

AGEP programs are funded by the NSF. What are they hoping to achieve through these programs?

The AGEP programs were originated at NSF as a response to the recognition of the obstacles that underrepresented minority students faced in graduate education and advancing to faculty careers. These issues are highlighted in "Losing Ground," a 1998 report of a study led by Dr. Shirley Malcom, director of Education and Human Resources Programs of the American Association for the Advancement Science. Dr. Malcolm is a Caltech trustee and was a featured speaker at our 2015 retreat.

 

What are we doing at Caltech to support underrepresented minority students in the graduate sciences, and has anything at Caltech changed as a result of our involvement in this consortium?

The Caltech Center for Diversity has a number of programs that support various segments of our student population, and we are increasing the number of underrepresented minority postdoctoral scholars at Caltech.

In collaboration with several offices across the campus, we are developing and maintaining a strong network focused on outreach, recruitment, matriculation, and the eventual awarding of degrees to underrepresented minorities in the campus' graduate programs.  

Specifically, the Office of Graduate Studies, the Center for Diversity, and the Center for Teaching, Learning, and Outreach focus on programming that creates access to resources, builds community, and leverages relationships to help to address the challenges highlighted in the AGEP program, including facilitated discussion groups that address issues of inclusion and equality, various graduate student clubs that promote cultural awareness and community education, and an annual "Celebration of Excellence" reception to recognize student successes and the efforts of staff, faculty, and students who promote equity and inclusion on campus.

In addition, the graduate recruitment initiative coordinated by the Office of Graduate Studies works to ensure that the campus is able to recruit at underrepresented minority STEM-focused conferences and research meetings around the United States, and encourages graduate student ambassadorship and provides opportunities for underrepresented minority graduate students to network across national professional communities with similar research and academic interests.

 

What can we do better?

Encourage greater diversity in graduate admissions by identifying and recruiting underrepresented minority graduate students and ensuring that every student thrives at Caltech. Encourage more of the current underrepresented minority students and postdoctoral scholars at Caltech to take advantage of the professional development opportunities in the Alliance and facilitate their transition to the next stage of their academic careers. Provide more professional development opportunities for all Caltech students and postdoctoral scholars to learn about academic careers.

 

What was the goal of this year's annual retreat?

One goal was to promote introductions and discussion among students, postdoctoral scholars, and faculty at the Alliance schools. In addition to informal meetings between participants, we held a number of roundtables and panel discussions on topics such as knowing what to expect of grad school, the postdoctoral experience, and, in general, life as a researcher and faculty member. Our retreat highlighted the research between done by faculty, students, and postdoctoral scholars in the Alliance by holding a poster session that enabled the participants to learn about each other's research activity. The retreat participants learned about some of the exciting research being done in protein design at Caltech from the other featured speaker, Steve Mayo (PhD '88), Caltech's William K. Bowes Jr. Leadership Chair of the Division of Biology and Biological Engineering and Bren Professor of Biology and Chemistry.

 

Who were participants in this year's retreat, and what do you think they gained from the program?

There were a total of 111 attendees: 40 percent were faculty, 42 percent were graduate students, 8 percent postdoctoral scholars, and the remainder were staff members, including some from JPL and Sandia National Laboratory.

The participants were recruited by the Alliance leadership at each university. The student participants gained the opportunity to network with scientists and faculty at other Alliance institutions, learned about academic careers and postdoctoral scholar opportunities, and were able engage in wide-ranging discussions about careers in science. The faculty and staff participants were able to provide information and advice to students as well as learn about prospective postdoctoral scholars and faculty members.

In addition, a total of 18 faculty from Caltech participated out of a total of 43 faculty members who attended from all four Alliance universities. The faculty at Caltech are very positive about this program, and we are encouraged by the high level of participation.

 

Were the sessions specifically focused on the particular needs of underrepresented groups?

The focus of the Alliance is on helping young people from diverse backgrounds to consider and succeed in academic careers in science. Many of the issues that contribute to success or failure in academic science careers do not depend on the particular perspective or background of a prospective postdoctoral scholar or professor. The pathway to the professoriate and the mechanics of succeeding in an academic career are far from obvious, particularly for students with disadvantaged backgrounds as well as those who are the first in their family to obtain a college degree or consider a career in science. One of the important roles of the Alliance retreat is in providing information about the many career aspects to which our student participants are exposed early enough in their careers so that it may make a difference. 

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Kathy Svitil
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Celebrating 45 Years at Caltech

The 60th Annual Staff Service Awards will be presented in Beckman Auditorium on Thursday, June 4, at 10 a.m. During the ceremony, nearly 250 staff members whose service ranges from 10 to 45 years will be honored for their commitment to Caltech. A full list of awardees is online.

Among the honorees is Robert A. Taylor, who has worked at the Institute for the last 45 years, most recently in the Division of Physics, Mathematics and Astronomy (PMA) for the Laser Interferometry Gravitational-Wave Observatory (LIGO) project. We spoke with Taylor about his four-and-a-half decades at Caltech.

 

Can you tell us how you originally came to Caltech and a little about your career?

In 1969, I was attending Pasadena City College, majoring in electronics analysis. I came to class one evening and my instructor, who was the chief engineer for the Seismology Laboratory at Caltech, asked if I would like to work for Caltech. I said yes. The job was in the Division of Geology and Planetary Sciences with Dr. Anderson [Don L. Anderson, the late Eleanor and John R. McMillan Professor of Geophysics, Emeritus, and former director of the Seismology Lab] to help build the seismometer that was to go to the moon.

In GPS, I enjoyed working with the students on their thesis projects and on other projects that have come along over the years. Some of those projects have taken me to places that most people never get to go. I observed an atomic bomb detonation in Nevada, serviced a seismic station at the base of the Andes Mountains in Peru, and dove on coral reefs off Sumatra, Indonesia. In the deserts of California, Arizona, and New Mexico, I did experiments with the first rocks brought back from the moon. That is just the first half of my time here at Caltech.

The second half is still ongoing. In 2001, I transferred to PMA, to continue my journey with LIGO, running the ultrahigh-vacuum bake lab. The purpose is to clean the parts that go into the vacuum envelope of the interferometer. LIGO is by far the most interesting project I have worked on since I have been here at Caltech.

What were your first impressions of Caltech?

Quite frankly, I was a bit intimidated at first. I had never worked in an academic atmosphere before with the kind of prestigious people that I come in contact with on a daily basis. For example, the first office that I had was across the hall from Dr. Charles F. Richter [developer of the Gutenberg-Richter law for measuring the size of an earthquake]. Could that be more awesome? But I soon realized that the people around me were accepting me as part of the team at Caltech.

What has been the most exciting moment for you so far at Caltech?

There are two moments that stick in my mind. The first is the research that we did in Indonesia with Dr. Sieh [Kerry Sieh, formerly Caltech's Robert P. Sharp Professor of Geology], taking coral samples from reefs in the Batu Islands off Sumatra. The other was the first time I visited the LIGO Livingston Observatory and saw firsthand a full-size interferometer.

What has changed the most for you here over the last 45 years?

I think what has changed most is my idea of what is possible. At Caltech, the possibilities are limitless.

How much longer do you think you will stay?

Let's just put it this way: I love what I do. I feel like the luckiest person alive to have been invited to participate and be a part of Caltech.

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Kathy Svitil
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Celebrating 11 Years of CARMA Discoveries

For more than a decade, large, moveable telescopes tucked away on a remote, high-altitude site in the Inyo Mountains, about 250 miles northeast of Los Angeles, have worked together to paint a picture of the universe through radio-wave observations.

Known as the Combined Array for Research in Millimeter-wave Astronomy, or CARMA, the telescopes formed one of the most powerful millimeter interferometers in the world. CARMA was created in 2004 through the merger of the Owens Valley Radio Observatory (OVRO) Millimeter Array and the Berkeley Illinois Maryland Association (BIMA) Array and initially consisted of 15 telescopes. In 2008, the University of Chicago joined CARMA, increasing the telescope count to 23.

Dalmation Drawing

An artist's depiction of a gamma ray burst, the most powerful explosive event in the universe. CARMA detected the millimeter-wavelength emission from the afterglow of the gamma ray burst 130427A only 18 hours after it first exploded on April 27, 2013. The CARMA observations revealed a surprise: in addition to the forward moving shock, CARMA showed the presence of a backward moving shock, or "reverse" shock, that had long been predicted, but never conclusively observed until now.
Credit: Gemini Observatory/AURA, artwork by Lynette Cook

CARMA's higher elevation, improved electronics, and greater number of connected antennae enabled more precise observations of radio emission from molecules and cold dust across the universe, leading to ground-breaking studies that encompass a range of cosmic objects and phenomena—including stellar birth, early planet formation, supermassive black holes, galaxies, galaxy mergers, and sudden, unexpected events such as gamma-ray bursts and supernova explosions.

"Over its lifetime, it has moved well beyond its initial goals both scientifically and technically," says Anneila Sargent (MS '67, PhD '78, both degrees in astronomy), the Ira S. Bowen Professor of Astronomy at Caltech and the first director of CARMA.

On April 3, CARMA probed the skies for the last time. The project ceased operations and its telescopes will be repurposed and integrated into other survey projects.

Here is a look back at some of CARMA's most significant discoveries and contributions to the field of astronomy.

Planet formation


Dalmation Drawing

These CARMA images highlight the range of morphologies observed in circumstellar disks, which may indicate that the disks are in different stages in the planet formation process, or that they are evolving along distinct pathways. The bottom row highlights the disk around the star LkCa 15, where CARMA detected a 40 AU diameter inner hole. The two-color Keck image (bottom right) reveals an infrared source along the inner edge of this hole. The infrared luminosity is consistent with a 6M Jupiter planet, which may have cleared the hole.
Credit: CARMA

Newly formed stars are surrounded by a rotating disk of gas and dust, known as a circumstellar disk. These disks provide the building materials for planetary systems like our own solar system, and can contain important clues about the planet formation process.

During its operation, CARMA imaged disks around dozens of young stars such as RY Tau and DG Tau. The observations revealed that circumstellar disks often are larger in size than our solar system and contain enough material to form Jupiter-size planets. Interestingly, these disks exhibit a variety of morphologies, and scientists think the different shapes reflect different stages or pathways of the planet formation process.

CARMA also helped gather evidence that supported planet formation theories by capturing some of the first images of gaps in circumstellar disks. According to conventional wisdom, planets can form in disks when stars are as young as half a million years old. Computer models show that if these so-called protoplanets are the size of Jupiter or larger, they should carve out gaps or holes in the rings through gravitational interactions with the disk material. In 2012, the team of OVRO executive director John Carpenter reported using CARMA to observe one such gap in the disk surrounding the young star LkCa 15. Observations by the Keck Observatory in Hawaii revealed an infrared source along the inner edge of the gap that was consistent with a planet that has six times the mass of Jupiter.

"Until ALMA"—the Atacama Large Millimeter/submillimeter Array in Chile, a billion-dollar international collaboration involving the United States, Europe, and Japan—"came along, CARMA produced the highest-resolution images of circumstellar disks at millimeter wavelengths," says Carpenter.

Star formation


Dalmation Drawing

A color image of the Whirlpool galaxy M51 from the Hubble Space Telescope (HST). A three composite of images taken at wavelengths of 4350 Angstroms (blue), 5550 Angstroms (green), and 6580 Angstroms (red). Bright regions in the red color are the regions of recent massive star formation, where ultraviolet photons from the massive stars ionize the surrounding gas which radiates the hydrogen recombination line emission. Dark lanes run along spiral arms, indicating the location where the dense interstellar medium is abundant.
Credit: Jin Koda

Stars form in "clouds" of gas, consisting primarily of molecular hydrogen, that contain as much as a million times the mass of the sun. "We do not understand yet how the diffuse molecular gas distributed over large scales flows to the small dense regions that ultimately form stars," Carpenter says.

Magnetic fields may play a key role in the star formation process, but obtaining observations of these fields, especially on small scales, is challenging. Using CARMA, astronomers were able to chart the direction of the magnetic field in the dense material that surrounds newly formed protostars by mapping the polarized thermal radiation from dust grains in molecular clouds. A CARMA survey of the polarized dust emission from 29 sources showed that magnetic fields in the dense gas are randomly aligned with outflowing gas entrained by jets from the protostars.

If the outflows emerge along the rotation axes of circumstellar disks, as has been observed in a few cases, the results suggest that, contrary to theoretical expectations, the circumstellar disks are not aligned with the fields in the dense gas from which they formed. "We don't know the punch line—are magnetic fields critical in the star formation process or not?—because, as always, the observations just raise more questions," Carpenter admits. "But the CARMA observations are pointing the direction for further observations with ALMA."

Molecular gas in galaxies


Dalmation Drawing

CARMA was used to image molecular gas in the nearby Andromeda galaxy. All stars form in dense clouds of molecular gas and thus to understand star formation it is important to analyze the properties of molecular clouds.
Credit: Andreas Schruba

The molecular gas in galaxies is the raw material for star formation. "Being able to study how much gas there is in a galaxy, how it's converted to stars, and at what rate is very important for understanding how galaxies evolve over time," Carpenter says.

By resolving the molecular gas reservoirs in local galaxies and measuring the mass of gas in distant galaxies that existed when the cosmos was a fraction of its current age, CARMA made fundamental contributions to understanding the processes that shape the observable universe.

For example, CARMA revealed the evolution, in the spiral galaxy M51, of giant molecular clouds (GMCs) driven by large-scale galactic structure and dynamics. CARMA was used to show that giant molecular clouds grow through coalescence and then break up into smaller clouds that may again come together in the future. Furthermore, the process can occur multiple times over a cloud's lifetime. This new picture of molecular cloud evolution is more complex than previous scenarios, which treated the clouds as discrete objects that dissolved back into the atomic interstellar medium after a certain period of time. "CARMA's imaging capability showed the full cycle of GMCs' dynamical evolution for the first time," Carpenter says.

The Milky Way's black hole

CARMA worked as a standalone array, but it was also able to function as part of very-long-baseline interferometry (VLBI), in which astronomical radio signals are gathered from multiple radio telescopes on Earth to create higher-resolution images than is possible with single telescopes working alone.

In this fashion, CARMA has been linked together with the Submillimeter Telescope in Arizona and the James Clerk Maxwell Telescope and Submillimeter Array in Hawaii to paint one of the most detailed pictures to date of the monstrous black hole at the heart of our Milky Way galaxy. The combined observations achieved an angular resolution of 40 microarcseconds—the equivalent of seeing a tennis ball on the moon.

"If you just used CARMA alone, then the best resolution you would get is 0.15 arcseconds. So VLBI improved the resolution by a factor of 3,750," Carpenter says.

Astronomers have used the VLBI technique to successfully detect radio signals emitted from gas orbiting just outside of this supermassive black hole's event horizon, the radius around the black hole where gravity is so strong that even light cannot escape. "These observations measured the size of the emitting region around the black hole and placed constraints on the accretion disk that is feeding the black hole," he explains.

In other work, VLBI observations showed that the black hole at the center of M87, a giant elliptical galaxy, is spinning.

Transients

CARMA also played an important role in following up "transients," objects that unexpectedly burst into existence and then dim and fade equally rapidly (on an astronomical timescale), over periods from seconds to years. Some transients can be attributed to powerful cosmic explosions such as gamma-ray bursts (GRBs) or supernovas, but the mechanisms by which they originate remain unexplained.

"By looking at transients at different wavelengths—and, in particular, looking at them soon after they are discovered—we can understand the progenitors that are causing these bursts," says Carpenter, who notes that CARMA led the field in observations of these events at millimeter wavelengths. Indeed, on April 27, 2013, CARMA detected the millimeter-wavelength emission from the afterglow of GRB 130427A only 18 hours after it first exploded. The CARMA observations revealed a surprise: in addition to the forward-moving shock, there was one moving backward. This "reverse" shock had long been predicted, but never conclusively observed.

Getting data on such unpredictable transient events is difficult at many observatories, because of logistics and the complexity of scheduling. "Targets of opportunity require flexibility on the part of the organization to respond to an event when it happens," says Sterl Phinney (BS '80, astronomy), professor of theoretical astrophysics and executive officer for astronomy and astrophysics at Caltech. "CARMA was excellent for this purpose, because it was so nimble."

Galaxy clusters


Dalmation Drawing

Multi-wavelength view of the redshift z=0.2 cluster MS0735+7421. Left to right: CARMA observations of the SZ effect, X-ray data from Chandra, radio data from the VLA, and a three-color composite of the three. The SZ image reveals a large-scale distortion of the intra-cluster medium coincident with X-ray cavities produced by a massive AGN outflow, an example of the wide dynamic-range, multi-wavelength cluster imaging enabled by CARMA.
Credit: Erik Leitch (University of Chicago, Owens Valley Radio Observatory)

Galaxy clusters are the largest gravitationally bound objects in the universe. CARMA studied galaxy clusters by taking advantage of a phenomenon known as the Sunyaev-Zel'dovich (SZ) effect. The SZ effect results when primordial radiation left over from the Big Bang, known as the cosmic microwave background (CMB), is scattered to higher energies after interacting with the hot ionized gas that permeates galaxy clusters. Using CARMA, astronomers recently confirmed a galaxy cluster candidate at redshifts of 1.75 and 1.9, making them the two most distant clusters for which an SZ effect has been measured.

"CARMA can detect the distortion in the CMB spectrum," Carpenter says. "We've observed over 100 clusters at very good resolution. These data have been very important to calibrating the relation between the SZ signal and the cluster mass, probing the structure of clusters, and helping discover the most distant clusters known in the universe."

Training the next generation

In addition to its many scientific contributions, CARMA also served as an important teaching facility for the next generation of astronomers. About 300 graduate students and postdoctoral researchers have cut their teeth on interferometry astronomy at CARMA over the years. "They were able to get hands-on experience in millimeter-wave astronomy at the observatory, something that is becoming more and more rare these days," Sargent says.

Tom Soifer (BS '68, physics), professor of physics and Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy, notes that many of those trainees now hold prestigious positions at the National Radio Astronomy Observatory (NRAO) or are professors at universities across the country, where they educate future scientists and engineers and help with the North American ALMA effort. "The United States is currently part of a tripartite international collaboration that operates ALMA. Most of the North American ALMA team trained either at CARMA or the Caltech OVRO Millimeter Array, CARMA's precursor," he says.

Looking ahead

Following CARMA's shutdown, the Cedar Flats sites will be restored to prior conditions, and the telescopes will be moved to OVRO. Although the astronomers closest to the observatory find the closure disappointing, Phinney takes a broader view, seeing the shutdown as part of the steady march of progress in astronomy. "CARMA was the cutting edge of high-frequency astronomy for the past decade. Now that mantle has passed to the global facility called ALMA, and Caltech will take on new frontiers."

Indeed, Caltech continues to push the technological frontier of astronomy through other projects. For example, Caltech Assistant Professor of Astronomy Greg Hallinan is leading the effort to build a Long Wavelength Array (LWA) station at OVRO that will instantaneously image the entire viewable sky every few seconds at low-frequency wavelengths to search for radio transients.

The success of CARMA and OVRO, Soifer says, gives him confidence that the LWA will also be successful. "We have a tremendously capable group of scientists and engineers. If anybody can make this challenging enterprise work, they can."

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