Steward/NOAO Joint Colloquium Series

Dr. Jannuzi's current research activities are mainly in two areas: 1) studies of the properties of the inter-galactic medium and the gaseous content of the Universe as probes of the formation and evolution of structure in the Universe, and 2) studies of galaxies and large scale structure at redshifts between one and four as traced by the distribution of individual, groups, and clusters of galaxies. I also continue to be involved in studies of various classes of active galaxies.

Professor George Rieke led the development of the MIPS instrument for Spitzer and now leads the science team of the Mid-Infrared Instrument for JWST. His current science is focused on the capabilities of these instruments. The MIPS instrument team has documented the incidence, properties, and evolution of planetary debris disks around nearby stars. Debris disks are perhaps the best way to study planetary system evolution after a system emerges from its protoplanetary disk. The team has also demonstrated that nearly half of the active active nuclei in distant galaxies are missing in deep X-ray catalogs, but can be identified through infrared observations. Rieke's plans for JWST investigations include imaging nearby debris disks to understand how their structures are sculpted by planet systems and to study the interplay between AGN and host galaxy star formation.

Dr. Agueros' primary research interest is in observational stellar astronomy. "Broadly speaking, I work on two different groups of objects. One is ordinary stars, typically less massive than the Sun, which are using the conversion of hydrogen into helium in their cores to prevent gravitational collapse. Surprisingly little is known about how the basic properties of these stars evolve after they reach an age of a few hundred million years -- at which point they are still toddlers, since very low-mass stars can live tens of billions of years, and even the (relatively massive) Sun is expect to live about ten billion years! I am therefore measuring and comparing stellar rotation and magnetic activity in a number of stellar clusters of different ages. These so-called open clusters have homogeneous, single-aged populations that are the key for calibrating the relationship between stellar age, rotation, and activity."

Recognizing 11 graduating seniors for their research: Scott Adams, Tiara Cottam, Michael Eskew, Kevin Hardegree-Ullman, Marita Morris, David Schenck, Louis Scuderi, Jennifer Sierchio, Tuguldur Sukhbold, Jake Turner, Antonio Villarreal.

A memorial to Victor Blanco who died on March 8, 2011. Dr. Blanco was a Puerto Rican astronomer who in 1959 discovered "Blanco 1", a galactic cluster.

Dr. Badenes is a Research Fellow at Tel-Aviv University and the Weizmann Institute of Science in Israel. At TAU, he works at the Department of Astrophysics. At WIS, he is a member of the Experimental Astrophysics Group. His research focuses on Type Ia supernova explosions, their binary progenitor systems, and the supernova remnants (SNRs) that they leave behind.

Professor Bieging specializes in molecular spectroscopic studies of stellar mass loss from red giants and planetary nebulae using radio and IR telescopes and molecular and atomic spectroscopy of interstellar clouds, with emphasis on processes leading to star formation. He is the recipient of the 6th Leon and Pauline Blitzer Award for Excellence in Teaching of Physics and Related Science.

The aim of Dr. Wyatt's research is to understand how planetary systems form and evolve. It involves both theoretical and observational studies of extrasolar planetary systems, as well as of our own solar system. The main strength of my research is in the development of models of the physical and dynamical evolution of circumstellar material and their application to the interpretation of circumstellar disk observations. Past highlights of my work include linking clumps seen Vega’s dust disk to resonant trapping by an unseen Neptune-like planet in this system (Wyatt 2003), the discovery of a spatially resolved Kuiper Belt around the star eta Corvi (Wyatt et al. 2005), and modeling disk collisional evolution showing that the rare systems with hot dust are undergoing transient events, perhaps akin to the solar system’s period of Late Heavy Bombardment (Wyatt et al. 2007a), although the debris disks of most stars are evolving in quasi steady-state (Wyatt et al. 2007b). I wrote a review of debris disk evolution for ARAA (Wyatt 2008), which is a good introduction to this topic.

Dr. Howell is a member of the Kepler Science Team and specializes in research on variable and binary stars, CCD detectors and instrumentation , and ultra-high precision photometry. He developed the practice of differential photometry using CCDs and has applied the technique to ground-based exo-planet transit detections obtaining, to date, the highest precision photometry yet achieved. Dr. Howell is involved in educational outreach programs, especially those involving multi-wavelength astronomy, using ground-based and space based telescopes.

Dr. Lawrence is Regius Professor of Astronomy. His research interests: Active Galactic Nuclei, Observational Cosmology, the Virtual Observatory PI for UK Infrared Deep Sky Survey (UKIDSS) Project Leader for AstroGrid.

Dr. Oey's research group, Feedback Activity in Nearby Galaxies (FANG), focuses on this massive star feedback to the interstellar and intergalactic medium, on local, global, and cosmic scales. Radiative feedback: HII nebulae and photoionized gas; Chemical feedback: Enrichment processes and galactic chemical evolution; Kinematic feedback: Supernova-driven superbubbles and galactic superwinds; and Massive stars and clusters

The cores of massive stars collapse to protoneutron stars, forming, at core bounce, a hydrodynamic shock that initially travels outward in mass and radius, but soon stalls, needing revival by the supernova mechanism. If the latter lacks efficacy, the protoneutron star may reach its maximum mass before an explosion is launched, leading to a second stage of gravitational collapse that results in the formation of a black hole. Under special, yet to be determined conditions, a black hole -- accretion torus system may form in such failing supernovae and act as the central engine of a long gamma-ray burst. I present results from new 1.5D (spherical symmetry plus rotation) simulations that show the systematics of black hole formation with progenitor mass, metallicity, rotation, and nuclear EOS, and lead to new theoretical constraints on the birth spin of black holes. I go on to present the first 3D simulations of black hole forming core collapse events that track the evolution from the onset of collapse, through the protoneutron star phase and protoneutron star collapse to multiple tens of milliseconds after the appearance of the black hole horizon. March 21, 2011.

Rachel Mandelbaum is with the Dept. of Astrophysical Sciences, Princeton University. Her main area of research is weak gravitational lensing, the very small perturbations in the shapes of distant source galaxies due to massive foreground galaxies/clusters. There are many useful applications of weak lensing due to the fact that it is sensitive to the full matter density projected along the line of sight, regardless of whether that matter is luminous (i.e., visible through a telescope) or not (the mysterious dark matter). I am interested in applications of lensing both to the study of large-scale structure and to galaxy formation, and also using lensing to answer these questions in combination with other probes such as clustering measures.

Dr. Krumholz's research focuses on star formation and the interstellar medium. "The big questions I hope to answer are what sets the global rate of star formation in gas clouds and galaxies? What determines the mass distribution of newly-formed stars? What processes control the formation of the most massive stars, which are the dominant source of luminosity in the universe? How long do star-forming clouds live, and what ultimately destroys them? I try to answer these questions using a mixture of analytic investigations and numerical simulations."

Dr. Frebel is currently a Clay Postdoctoral Fellow at the Harvard-Smithsonian Center for Astrophysics, Cambridge, MA. She is interested in searching for the oldest stars in our Milky Way Galaxy and small dwarf galaxies surrounding the Milky Way. By studying these stars, we can learn details about the nature of the early Universe shortly after the Big Bang when the first stars and galaxies began to form. Employing the the worlds largest optical telescopes we identify old stars by means of their chemically primitive nature. These so-called "metal-poor" stars contain only tiny amounts of heavy elements ("metals") that are heavier than hydrogen and helium. They formed before the Universe was significantly enriched in chemical elements, as we know it today. Hence, the oldest stars in the Milky Way are stellar fossils and make possible to reconstruct the chemical evolution of the Galaxy from the earliest times until today.

Dr. McQuinn is a theoretical physicist interested in astrophysics and cosmology. I specialize in the study of the stuff between galaxies (which constitutes the majority of the mass in the Universe). In particular, he studies the properties of this matter and its evolution from the infant Universe up until today. He is also interested in the nature of the first galaxies, the large-scale structure of the Universe, the properties of the dark matter, and radiative transfer algorithms. He is currently an Einstein Postdoctoral Fellow at the University of California, Berkeley in the Astrophysics Department. I received a Ph.D. from Harvard University in May 2009, and a B.S. in physics and math from Stanford University in June 2004.

Dr. McKee's research focuses on the theory of physical processes in the interstellar medium, the diffuse gas between the stars. How do stars form out of this tenuous gas, and what effect do the stars have back on the interstellar medium? Jerry Ostriker and I developed the three-phase model of the interstellar medium, which has been widely used to organize and interpret observations of the diffuse interstellar medium. With my colleagues and students, I have worked on the theory of the evaporation of clouds by both hot gas and ionizing radiation, the evolution of supernova remnants and stellar wind bubbles, the structure and emission spectrum of interstellar shocks, the evolution of interstellar dust grains, the structure of molecular clouds, and on the theory of active galactic nuclei, particularly the study of reverberation mapping and of Compton-heated coronae and winds above accretion disks. I am currently concentrating on the theory of star formation, including the formation of the first stars. My students and I use both analytic and numerical techniques to address these problems. Richard Klein and I have established the Berkeley Astrophysical Fluid Dynamics Group to develop the technique of adaptive mesh refinement for numerical simulations of astrophysical fluid dynamics, particularly star formation.

Ramesh Narayan is Thomas Dudley Cabot Professor of the Natural Sciences, Harvard University. His research interests are: Gravitational lensing; accretion disks; black holes; gamma-ray bursts.

Dr. Zheng is a YCAA fellow at Yale Center for Astronomy and Astrophysics. Heobtained my PhD in Astronomy at the Ohio State University. Before moving to Yale, he was a postdoc at the Institute for Advanced Study. His main research areas are in cosmology, large-scale structure, galaxy formation and evolution, and Lyman-alpha radiative transfer. He also has broad interests in other fields of astrophysics.Feb. 14, 2011.

Abstract: review how the combination of models that include realistic gas supplies in galaxies, and feedback from massive stars and AGN to maintain those gas reservoirs, have led to huge shifts in our understanding of galaxy formation. In particular, gas-richness may represent the most important determining factor in galaxy evolution through hierarchical mergers, and may resolve a number of decades-old outstanding mysteries. The degree of gas-richness in mergers has dramatic effects on bulge structural properties, stellar populations, mass profiles, and kinematics; models with the appropriate gas content have finally begun to produce realistic galaxies that resolve a number of discrepancies with observations. Evolution in the gas properties of the Universe naturally predicts evolution in the Hubble sequence, giving rise to many of the unique properties of high-redshift galaxies and starbursts. In very gas-rich mergers, expected to occur more and more frequently at high redshifts, gas can qualitatively change the character of mergers, making disks robust to destruction in mergers and explaining the abundance of disks in a Lambda-CDM Universe. Gas-rich mergers also link the brightest starburst and quasar populations with massive galaxies today. I'll close by discussing the next generation of models at the interface between the fields of star formation, AGN, and galaxy formation.

The terminal collision defining the end of accretion leaves an indelible mark on the final physical and dynamical properties of a rocky planet. In our own solar system, giant collisions are invoked to explain the observed variations in bulk compositions, spin orientations, moon systems, and asymmetries in crustal thickness. The range of possible outcomes is even greater in extrasolar planetary systems. I will present advances in experimental techniques and numerical methods to understand the physics of giant collisions. Feb. 7th 2011

Dr. Robertson is currently a Hubble Fellow in the Astronomy Department at the California Institute of Technology. His research interests include theoretical topics related to galaxy formation, dark matter, hydrodynamics, and numerical simulation methodologies. He previously held a Spitzer Fellowship at the Kavli Institute for Cosmological Physics and Enrico Fermi Institute at the University of Chicago. He earned his Ph.D. in Astronomy from Harvard University in 2006, and received a B.S. in Physics and Astronomy at the University of Washington, Seattle in 2001.

Dr. Eliza Kempton graduated from Middlebury College in 2003 with a B.A. in physics, and in 2009 she received her Ph.D. from Harvard University in astronomy. Eliza's research focuses on small extrasolar planets known as super-Earths. These planets are 1 to 10 times more massive than the Earth, and they are currently offering astronomers the first glimpse into "exo"-worlds that may be similar to our own. Eliza models the atmospheres of extrasolar super-Earths to determine aspects such as atmospheric structure and composition. Understanding the atmospheres of extrasolar planets is an important step on the road toward finding a truly Earth-like planet. Jan. 27, 2011.

Black holes form in the early Universe and grow to billions of solar masses as their gravity attracts surrounding matter. This cosmic accretion releases a huge amount of energy, which may quench star formation through so-called “feedback.” Tracing the history of black hole growth out to very high redshifts with multiwavelength surveys, we find that most AGN are heavily obscured and that obscuration is more common in the young Universe and in low-luminosity AGN. By studying the host galaxies of AGN, we see evidence at z~1 that AGN may help quench star formation, even though at z~0 star formation in the local Universe appears to turn off well before AGN reach their peak brightness. Finally, we find an intriguing dependence of AGN activity on host galaxy morphology, which may hint at AGN triggering mechanisms. Jan 24, 2011

Dr. Angel is Director, Steward Observatory Mirror Laboratory, Regents' Professor of Astronomy, and Regents' Professor of Optical Sciences. His major research areas are Research: Adaptive optics, Instrumentation, Extrasolar planets, Telescope design and optical fabrication, Geoengineeering and Concentrating. photovoltaic solar energy

Jeyhan Kartaltepe is currently a sixth year graduate student at the Institute for Astronomy at the University of Hawaii in Honolulu. My thesis research is on the properties of infrared galaxies. Many of these galaxies are interacting or in the process of merging, like the ones shown in the above Hubble Space Telescope image. These galaxies are fondly known as The Mice. My research focuses on the evolution of such galaxies.December 9, 2010

Abstract: The first stars are thought to be extremely luminous and reside in dark matter halos with masses of approximately a million solar masses. I will present results from radiation hydrodynamics simulations that follow the formation of tens of metal-free stars and their impact on high-redshift galaxy formation and reionization. HII regions created by the first stars are a few kiloparsecs in radius, which then overlap with each other and constitute a volume filling fraction of about a quarter at redshift 15. We also find that the first galaxies are enriched up to 1/1000th of solar metallicity, which is sufficient to transition to lower-mass star formation. I will finish by presenting new results that self-consistently follow the transition from Pop III to II star formation for the first time. Dec. 6, 2010.