Astrophysics and Cosmology

The members of the Astronomy and Astrophysics group are among the leaders of their chosen areas of research. We are one of the largest astrophysics groups within a physics department in the country. The research conducted in our group is interwoven and dynamic, with six complementary focus areas.

Supernovae are the explosions of dying stars. But in their death they give clues to the size and fate of the universe. Source: Hubblesite.org
Supernovae are the explosions of dying stars. But in their death they give clues to the size and fate of the universe. Source: Hubblesite.org

Our group is among the top few internationally in supernova research. Baron and Kilic are interested in the systematics of how supernovae explode and what kinds of stars lead to different supernovae. Baron studies the spectra of the expanding supernova atmosphere to determine physical conditions and chemical abundances in the ejecta. Kilic observes compact binary star systems that may lead to supernovae explosions. Some of these binary systems are among the strongest gravitational wave sources known. Dai studies the populations of gamma-ray bursts and their jet breaks. We have set up a “supernova spectrum repository” - a Web site at which any astronomer can view all of the supernova spectra that we gather from observers. This makes us the “headquarters” of supernova spectra.

Galaxy HUDF-JD2 From the Hubble Ultra Deep Field. Source: Hubblesite.org
Galaxy HUDF-JD2 From the Hubble Ultra Deep Field. Source: Hubblesite.org

Cosmological research in our group is anchored in observational data and aims at gaining a deep understanding of our universe.

Dai uses galaxy clusters to study the distribution of dark matter, the baryon fraction in clusters, and dark energy. Baron studies the use of supernovae as distance indicators to remote galaxies to determine the age, size and fate of the universe. Baron also studies the systematic uncertainties of using supernovae as cosmological probes. Munshi uses cosmological simulations to study galaxy formation and constrain the nature of dark matter.

Extragalactic astronomy focuses on the chemical and dynamical evolution on a vast scale.

Dust Disk Around a Black Hole in Galaxy NGC 7052 Source: Hubblesite.org
Dust Disk Around a Black Hole in Galaxy NGC 7052 Source: Hubblesite.org

Dai and Leighly study Active Galactic Nuclei. The ultimate power source for Active Galactic Nuclei is thought to be accretion onto a supermassive blackhole. Their extensive program involves observations in the X-ray, optical, and infrared, and also theoretical modeling. Leighly studies the fundamental properties (covering fractions and column densities) of quasar outflows. Dai uses gravitational lensing to map the quasar accretion disk structure. Munshi studies how galaxies form and evolve using cosmological galaxy formation simulations that leverage supercomputers hosted at NASA and the NSF.

Extrasolar planets and circumstellar disks are studied by two of our faculty. Wisniewski uses multi-wavelength observational techniques, using ground- and space-based facilities, to investigate the structure, evolution, and origin of circumstellar disks. He studies spatially resolved images of protoplanetary and debris disks to search for morphological indicators for the presence of young exoplanets in these systems. Kilic studies the chemical composition of Earth-like planets around evolved stars by observing the remnants of such planets, debris disks.

Nucleosynthesis occurs through out a star's life as well as in its death. It is the key to understanding stellar evolution.
Nucleosynthesis occurs throughout a star’s life as well as in its death. It is the key to understanding stellar evolution.

When stars in the 1-8 solar mass range reach the end of their evolution, they shed outer portions of their atmospheres. The dying star left behind shrinks and gets hotter, and UV light from it causes the outer ring of gas to glow. This “planetary nebula” makes it relatively easy to study the chemical makeup of the gas. This image of NGC 7293, the Helix Nebula, was taken by Reginald Dufour of Rice University, using a CCD camera. Henry studies the chemical abundances of a variety of emission line objects with the goal of understanding stellar production rates and subsequent cosmic accumulation of elements such as C, N, O, Ne, S, and Ar. Kilic studies the chemical composition of Earth-like planets around evolved stars by observing the remnants of such planets, debris disks. Kilic uses white dwarf cosmochronology to measure the ages of the oldest stars in the Galactic disk and halo and to set limits on the age of the universe.

Observational astronomy is the solid foundation that supports all of our research.

Graduate student Sara Barber on an observing run at the Kitt Peak National Observatory 4m Telescope near Tucson, AZ
Graduate student Sara Barber on an observing run at the Kitt Peak National Observatory 4m Telescope near Tucson, AZ

Our astronomers use ground- and space- based observatories to study supernovae, supernoave progenitors and remnants, Active Galactic Nuclei, galaxy clusters, gravitational wave sources, extrasolar planets, and debris disks. Our group has recently been awarded observing time on the ground-based MDM 2.4m, NASA IRTF 3m, APO 3.5m, KPNO 4m, Hale 5m, MMT 6.5m, Gemini 8m, Subaru 8.2m, Keck 10m, GTC 10.4m, LBT 12m telescopes and the space-based Hubble Space Telescope, Spitzer Space Telescope, XMM-Newton, and the Chandra X-ray Observatory. We use our 16-inch campus telescope for student training and weekly public star parties. Our graduate students host these star parties as well as a weekly journal club.

 

Computational physics studies on our 112 node Xserve cluster, at OU’s OSCER super computer, at Argonne National Laboratory, at the National Energy Research Supercomputer Center (NERSC) in Berkeley and with NSF XSEDE are also ongoing in the areas of supernovae, cosmology, Galactic chemical evolution, active galactic nuclei, and computational galaxy formation. Astronomy continues to be an exciting field with new ideas and new facilities emerging in the coming decade. We welcome the chance to work with motivated and qualified graduate students.

Research Areas

Faculty

Emeritus Faculty

Research Highlight: OU-Apache Point Observatory Partnership

Research Highlight: OU-Apache Point Observatory Partnership

The University of Oklahoma has signed a 3-year lease agreement with the Astrophysical Research Consortium in Sunspot, NM (see the press release), giving its undergraduate students, graduate students, postdocs, and faculty access to research-grade 3.5m and 0.5m telescopes at the Apache Point Observatory. After being trained to use these facilities on-site in NM, OU astronomers will operate these telescopes from their offices in Norman. The agreement will help elevate OU’s astrophysics research profile and provide invaluable educational training to OU students.

Research Highlight: Star Chemistry

Research Highlight: Star Chemistry

The Ring Nebula was formed when a Sun-like star nearing the end of its life ejected part of its atmosphere into the interstellar medium. The nebular gas itself is heated by the UV continuum from the remnant of the original star visible at the center of the Ring. Also shown is a slitless spectrum of the Ring, where an image of the nebula appears at wavelengths of bright nebular emission. Planetary nebulae are useful in Prof. Henry’s research in determining properties of the interstellar medium as well as for studying the evolution of stars like the Sun. Credits: Image, Hubble Heritage Team (NASA); Spectrum: Julie Skinner (former OU Astronomy undergraduate), using the 2.1 meter telescope at KPNO.

Research Highlight: Munshi Galaxy Group

Research Highlight: Munshi Galaxy Group

Prof. Munshi, in collaboration with scientists at Rutgers, Grinnell and UW ran two new computer simulations of Milky Way-mass galaxies and their surroundings. They are the highest resolution simulations ever published of Milky Way-type galaxies. They are cosmological simulations, meaning that they start soon after the Big Bang and model the evolution of galaxies over the entire age of the Universe (almost 14 billion years).  The high resolution allows us to achieve something that no one else has: we are able to model some of the lowest-mass of the Milky Way’s neighboring (“satellite”) galaxies.  In recent years, “ultra-faint” satellites of the Milky Way have been discovered as digital sky surveys come online that can probe to fainter depths than ever before.  While our own Milky Way contains about 100 billion stars and is thousands of lightyears across, ultra-faint galaxies contain a million times fewer stars, with less than 100 thousand stars (even as low as a few hundred stars), and are substantially smaller, spanning tens of lightyears.  Our simulations allow us to begin to model these ultra-faint satellites for the first time around a cosmological simulation of a Milky Way, meaning they provide some of the first predictions for what future surveys will discover. Research in the Munshi Galaxy Group includes utilizing these simulations, dubbed the "DC Justice League" and extremely high resolution simulations of isolated dwarf galaxies (the "MARVEL-ous Dwarfs") to study galaxy formation and constrain the nature of dark matter using galaxies.

These simulations are only achievable by using powerful supercomputers with highly optimized code.  Press release here.  For a visualization of a simulation, click here.

Research Highlight: Active Galactic Nuclei

Research Highlight: Active Galactic Nuclei

Active Galactic Nuclei (AGN) such as the one imaged here by the Hubble Space Telescope, are the most luminous, persistently emitting individual objects in the Universe. They can be seen at the largest distances, and provide a probe of the early Universe after structure formation. Used as a background light, absorption lines in their spectra trace nonluminous matter. They are powered by accretion onto black holes, and are key for understanding black hole demographics and the black hole mass function. Prof. Leighly works to understand how the primary physical parameters for black hole accretion, the black hole mass and accretion rate, manifest themselves in the broad band continuum and line emission from AGN.