Research Expertise and Interest

physics, existence and formation of black holes in galactic nuclei, the nature of the power source, the evolution of (ultra)luminous infrared galaxies, gas dynamics, the fueling of active galactic nuclei, the properties evolution of starburst galaxies

Research Description

My research interests are in experimental astrophysics. My research group and I are studying the physical processes and the evolution of active galaxies and in particular of their central regions. One key issue we have been pursuing is the question whether the accretion onto massive black holes, or star formation powers active and luminous galaxies. For instance, in one class of very luminous galaxies we were recently able to demonstrate from mid-infrared spectroscopy on the Infrared Space Observatory (ISO) that enormous bursts of star formation triggered by the collision of galaxies can produce quasar-like luminosities in the infrared. Such galaxies were apparently much more common in the past than in the local Universe. We are also engaged in testing the paradigm that active galactic nuclei indeed all contain massive black holes. In the nucleus of our own Galaxy we were able to show from near-infrared imaging observations of the motions of individual stars in the central few light days that there must be a million solar mass, central black hole. Such key science goals have been driving our experimental program. We have been developing novel instrumentation, mainly in the infrared and submillimeter range, for large ground-based, airborne and space telescopes. We have been developing sensitive infrared spectrometers and imagers across the entire 1-1000mm band. We are active in the area of adaptive optics with laser stars.

Current projects:

We want to push our studies to ever smaller spatial scales and to ever larger distances, reaching galaxies that were formed in the first few billion years after the Big Bang. Using the new generation of 10m class, ground based telescopes (such as the Keck telescope) together with the new techniques of adaptive optics and interferometry, near-infrared imaging and spectroscopy will be able in the next decade to zoom into the innermost cores of nearby active galaxies. Such high resolution techniques will reveal whether central black holes are present, how they are fed and whether/how stars are formed there. At larger distances it will be possible, for example, to study quantitatively the dynamics of colliding/merging galaxies. Mergers are a key process in the formation and evolution of galaxies. Finally the high resolution observations also make possible spatially resolved studies of the first galaxies formed at high redshift. In the next few years we are planning to carry out infrared observations on these subjects (on the Keck and the ESO VLT) on a broad front and in part with instruments that we are now building. We also will push the capability of far-infrared/submillimeter observations.

We are engaged in building a sensitive far-infrared imaging spectrometer for the new SOFIA airborne observatory that will house a 2.5m telescope in a B747 aircraft. With SOFIA it will be possible to study the far-infrared emission of distant star forming galaxies and reveal their activity independent of the effects of dust obscuration that hampers or makes impossible measurements at shorter wavelengths.

Sensitive astronomical measurements require state of the art radiation detectors. We have begun an ambitious program of developing Ga:As photoconductor detectors. Ga:As detectors promise to substantially extend the wavelength cutoff of present Ge detectors into the submillimeter band, and at the same time, they may be developed into monolithic, large pixel size formats. Our development aims at a blocked impurity band device that could be used on SOFIA or future space missions.

In the News

High-powered, but supportive, environment draws students to Nobel winners’ labs

On the morning that University of California, Berkeley, professor Jennifer Doudna won the 2020 Nobel Prize in Chemistry, her first stop after a 7 a.m. press conference and subsequent media interviews was her campus lab in the Innovative Genomics Institute. When she exited the elevator with her family at 10:30 a.m., she was greeted by dozens of graduate students and lab staff, while several dozen current and former lab members joined in via Zoom.

Nobel Prize ceremonies go virtual for Doudna, Genzel

For the first time since World War II, winners of this year’s Nobel Prizes will not be receiving their medals and diplomas from the King of Sweden in Stockholm. The pandemic has forced the Nobel Committees to deliver the medals to recipients at their homes, with just immediate family and consular or embassy officials in attendance.

Disaster looms for gas cloud falling into Milky Way’s central black hole

Astronomers led by UC Berkeley’s Reinhard Genzel, also of the Max Planck Institute in Germany, have observed a cloud of gas several times the mass of Earth approaching the 4.3 million solar-mass black hole at the center of the Milky Way. Theorist Eliot Quataert calculates that the cloud will not survive the encounter, but will be heated and shredded in 2013.

Featured in the Media

Please note: The views and opinions expressed in these articles are those of the authors and do not necessarily reflect the official policy or positions of UC Berkeley.
October 7, 2020
Marina Koren
Not so long ago, scientists couldn't say with much confidence that black holes existed, nor did they know that a giant one sits at the center of our own galaxy. Yesterday, the Nobel Committee recognized decades of black-hole research by awarding its physics prize to three scientists. Half the prize went to Roger Penrose, of the University of Oxford, who showed that black holes could exist, and half went to Reinhard Genzel, of the Max Planck Institute for Extraterrestrial Physics and UC Berkeley, and Andrea Ghez, of UCLA, who provided the most convincing evidence that a particular black hole - the supermassive one at the center of our Milky Way - did indeed exist. For more on this, see our press release at Berkeley News. Stories on this topic have appeared in dozens of sources, including NBC News, The Washington Post, The Wall Street Journal, CNN, NPR, Vox, and The Mercury News.
October 6, 2020
Dennis Overbye and Derrick Bryson Taylor
The Nobel Prize in Physics was awarded to three astrophysicists today for their work on black holes, massive objects that swallow light and everything else forever that falls into their reach. They are Roger Penrose, an Englishman, Reinhard Genzel, a German, and Andrea Ghez, an American. Genzel is a director at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and a professor at the University of California, Berkeley.Working independently, Genzel and Ghez, and their teams, have spent the last decades tracking stars and dust clouds whizzing around the center of our galaxy with telescopes in Chile and Hawaii, trying to see if that dark dusty realm does indeed harbor a black hole. "Their pioneering work has given us the most convincing evidence yet of a supermassive black hole at the center of the Milky Way," the Swedish Academy of Sciences said in its announcement. For more on this, see our press release at Berkeley News. Stories on this topic have appeared in dozens of sources, including NBC News, The Washington Post, The Wall Street Journal, CNN, NPR, Vox, and The Mercury News.
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