Astrophysics and Cosmology-Dept of Physics - Carnegie Mellon University

Astrophysics and Cosmology


Rupert Croft
Tiziana Di Matteo

Raphael Flauger

Shirley Ho
Rachel Mandelbaum
Jeffrey Peterson
Hy Trac

Matthew Walker

McWilliams Center for Cosmology:

Group Overview

The research of the CMU Astrophysics and Cosmology group covers a wide range of problems in theoretical, computational, and observational cosmology. These problems include the study of the earliest energy emission in the universe -the Cosmic Background Radiation- to the evolution of galaxies and the formation of large-scale structure. We are part of the worldwide scientific effort to put constraints on the basic cosmological parameters that describe the evolution of the universe. Many of these parameters are expected to be tied down over the next decade using data from the current and planned ground-based and space-based observatories. The analysis of these new data sets is very challenging and will require both the development of highly sophisticated numerical simulations and the application of the latest tools in data-mining, statistics, and computer science. 

Group members have access to data from a variety of major telescopes and space missions, including the Sloan Digital Sky Survey, the Chandra and XMM X-ray satellites, and the Hubble Space Telescope. CMU is a partner in The National Virtual Observatory. CMU also owns a 2m sub-millimeter telescope, Viper, at the South Pole. Computer resources are vital to the success of any modern astrophysics group. The CMU group owns a state-of-the-art Beowulf cluster and has access to the TeraScale facilities of the Pittsburgh Super Computing center.

Recent results include those in strong lensing; weak lensing; the Sunyaev-Zeldovich effect; the X-ray background; numerical simulations; and ``baryon wiggles''. The group has also made preliminary measurements of many of the fundamental cosmological parameters including Hubble's Constant, Omega Matter, Omega Total and sigma-8. The group has major involvements in some of the most exciting projects in cosmology and extra-Galactic astronomy e.g. SDSS-III AND SDSS-IV, LSST, ACT, HSC, and Euclid and is well placed to be a world leader in the race to the underlying cosmological model.

Member Research Thrusts

Rupert Croft’s main research interests are in computational cosmology, involving both simulations and the analysis of large surveys. He primarily focuses on the physics of the intergalactic medium, its use as a probe of cosmology and of galaxy and quasar formation. He is a member of the SDSS-III survey of galaxies and quasar absorption lines which aims to measure dark energy parameters using large scale baryonic oscillatory features as a standard ruler. Croft also works on the interaction between matter and radiation in the intergalactic medium, on the re-ionization of the Universe, and predictions for future 21cm radio observations of this high redshift cosmological frontier. He makes use of the McWilliams Center’s high performance computing facilities, including Warp, the 700 core cluster to perform cosmological hydrodynamic and radiative transfer simulations.

Tiziana Di Matteo is a theorist with expertise in both high energy astrophysics and cosmology. Her recent interests focus on state-of-the-art cosmological simulations of galaxy formation including detailed modeling of the impact of black hold feedback on structure formation. She has consistently been awarded large allocations of time on the largest national computing facilities and also makes use of the computational facilities of the McWilliams Center for Cosmology.

Richard Griffiths' research programs are in space astronomy, especially 'deep surveys' using current earth-orbiting optical and X-ray telescopes, part of the work of observational cosmology. In a 'deep survey' a telescope is pointed at a blank region of sky for about a week, in order to find the faintest and most distant objects that the telescope can detect.  He is currently involved in the results of deep X-ray surveys using the two large X-ray telescopes launched in 1999, the Chandra X-ray Observatory, CXO (NASA) and the XMM-Newton satellite (European Space Agency).  He uses some of the world's largest telescopes to identify the kinds of galaxies which are the greatest producers of X-rays.  Griffiths has also led the Medium Deep Survey, a Key Project using the Hubble Space Telescope, and the largest program of observations ever undertaken with the Hubble.

Shirley Ho is a cosmologist whose interest ranges from theory to observations, and whose research involves both simulations and analysis of large scale structure surveys such as the Sloan Digital Sky Survey III or of the cosmic microwave background data from Planck HFI and LFI.  She primarily works on utilizing the large scale structure and cosmic microwave background to understand the beginning of the universe, the dark components of the universe such as dark energy and dark matter and its lighter but equally elusive contents such as neutrinos and the evaluation of the universe.  Her recent interest focuses on the use of a standard ruler called Baryon Acoustic Oscillations via various large scale structure tracers, such as the 3D clustering tracer of large scale structure.

Rachel Mandelbaum's research interests are predominantly in the areas of observational cosmology and galaxy studies. This work includes the use of weak gravitational lensing and other analysis techniques, with projects that range from development of improved data analysis methods, to actual application of such methods to existing data. Currently, she is focusing on data from the SDSS (including the ongoing SDSS-III), and is working on upcoming surveys including Hyper-SuprimeCam (HSC), LSST, HSC, LSST, and Euclid.

Jeffrey Peterson's group carries out cosmological observations using the 21 cm emission line of neutral hydrogen. The group is involved in projects using existing telescopes to make three dimensional maps of 21 cm emission for redshifts around ten. These maps will be used to study the first stars and their interaction with surrounding gas. The team also designs and builds 21 cm telescopes. In particular, the group is working to build the Cylinder Radio Telescope in Morocco. This 10,000 square meter telescope will map most of the sky at redshifts near one in order to constrain models of Dark Energy.

Hy Trac is a theoretical and computational cosmologist whose scientific interests include cosmic evolution and structure formation. He is actively working on understanding how the first generation of stars and galaxies re-ionize the universe and how the intergalactic medium can be studied using the Lyman alpha forest. As a member of the Atacama Cosmology Telescope (ACT) project, he is studying how galaxy clusters can be discovered through the Sunyaev-Zel'dovich effect. His research also focuses on the development and application of N-body, hydrodynamic, and radiative transfer algorithms.