Cosmology

Main Content

Questions

What is dark energy? How does it evolve? Is the Cosmological Constant an accurate model for dark energy?
What is dark matter? How does it affect large-scale structure formation?
Are there systematic errors in the extragalactic distance scale and the Hubble Constant?
What is the expansion history of the universe?
How did the first galaxies and quasars form and evolve? What are the observational signatures of these first luminous objects?
How did the stars and galaxies we know today arise from the initial conditions of the Big Bang, and how did the process of Cosmic Reionization unfold?
What are the properties of the supermassive black holes that power the most distant quasars? How did they form at the cosmic dawn?
What is the relationships between supermassive black holes and host galaxies?

Discoveries and Milestones

Don Schneider played a leading role in the development of the Sloan Digital Sky Survey Catalog, which contains over 105,000 spectroscopically-confirmed quasars found during the first two phases of the Sloan Digital Sky Survey (1999-2008).
Yuexing Li has pioneered the numerical modeling of the formation, evolution, and multi-band properties of the most distant galaxies and quasars by combining multi-scale cosmological simulations with multi-wavelength radiative transfer calculations. She has developed essential models of quasar formation, as well as a comprehensive radiative transfer code ART² ,which has a wide range of applications in modeling both continuum and emission lines from galaxies and quasars.
Derek Fox and collaborators discovered the most distant gamma-ray burst at redshift z=8.2, when the Universe was only a few hundred million years old.
Robin Ciardullo pioneered the technique of using the Planetary Nebulae Luminosity Function for extragalactic distance measurements, which is only method that can be applied to all large galaxies within ~ 20 Mpc, regardless of Hubble type or stellar population.
Yuexing Li and Derek Fox organized the conference The First Galaxies, Quasars, and Gamma-Ray Bursts at Penn State in June 2010.

Current Projects

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) will measure dark energy between 1.9<z<3.5 and trace the evolution of the component over much of the history of the universe. The project will also facilitate a large number of other projects, from the measurement of total neutrino mass to the identification of ultra-low metallicity stars in the Milky Way. Drs. Ciardullo, Gronwall, and Schneider are members of the HETDEX team.
Yuexing Li is conducting computational work to investigate the formation of the first quasars, accretion onto black holes, Lyman-alpha emission from high-redshift galaxies, fossils of the first black holes and galaxies in the Milky Way, and large-scale structure formation.
Don Schneider is involved in the Sloan Digital Sky Survey-III and the Large Synoptic Survey Telescope, which will be used to study the high-redshift universe (as well as a variety of other subjects).
Qirong Zhu and Yuexing Li are studying the co-evolution of massive black holes and host galaxies from cosmic dawn to present day using a set of high-resolution, hydrodynamic cosmological simulations.
Shawn Sinawa and Yuexing Li are modeling the observational signatures of the first quasars for JWST and ALMA, using the 3-D radiative transfer code ART².

Student Highlights

John Feldmeier was the first to apply the PNLF method to spiral galaxies. His paper with undergraduates Rachel Kuzio de Naray and Mary Beth Laychak also produced the first robust connection of the Popuation I and Population II distance ladders.
For his undergraduate honors thesis, George Trammell studied the UV/optical properties of the spectral energy distributions of optically-selected quasars based upon data obtained from the GALEX satellite and the Sloan Digital Sky Survey.
As part of his PhD thesis, Jiajian Shen examined the properties of massive black holes that reside in low-redshift active galactic nuclei.
As part of this PhD thesis, Jian Wu studied the Baldwin Effect (the inverse correlation between line strength and continuum luminosity) in a sample of quasars; the data included observations from variety of X-ray and ultraviolet satellites and the Sloan Digital Sky Survey.
For his undergraduate honors thesis, Michael Peth combined optical data taken by the Sloan Digital Sky Survey and infrared observations from the United Kingdom Infrared Digital Sky Survey to create a large catalog of quasars.