Image from the Hubble Space Telescope

Physics Faculty : Nahum Arav; Duncan Farrah; Shunsaku Horiuchi; Sara Petty; John Simonetti
Physics Emeriti Faculty : John Broderick; Brian Dennison
ECE Faculty: Steven W. Ellingson; Cameron Patterson
Research Associates : John “JJ” Cherry; Guilin Liu; Oscar Macias

The astronomical sciences group at Virginia Tech is active in studies of: transient phenomenon at radio wavelength (including possible signature for exploding primordial black holes); influence of super massive black holes on structure formation in the universe, observational studies of quasars and Seyfert galaxies; and the interstellar medium (ISM).

Research facilities we are using include: the Hubble space telescope; the largest ground based optical telescopes (VLT, Subaru and Keck); the Very Large Array (VLA) and the Very Long Baseline Array (VLBA) radio telescopes. We operate our own Spectral Line Imaging Camera (SLIC) in current use for the Virginia Tech Spectral-Line Survey.

Hubble Space Telescope

The Hubble Space Telescope in orbit around the Earth

Arav's s group is working on determining the influence of super massive black holes on structure formation in the universe. They do so by observing outflows emanating from the vicinity of the black holes and determining the physical characteristics of these outflows. In particular, the group is concentrating on measuring the kinetic energy of these winds since this is the single most important parameter in assessing their influence on the galactic and intergalactic environments. The work includes observing such outflow using ground based optical telescopes, measuring the different ions that comprise the outflow and performing photoionization modeling to extract the physical conditions in the outflow.

Arav's s group is also working on the connection between the Ultraviolet and X-ray manifestation of the so called "warm absorbers" in Seyfert galaxies. This is done by acquiring and analyzing Ultraviolet and X-ray spectra of these objects using the Hubble space telescope and the Chandra X-ray satellite. The chemical abundances in these objects is also of great interest to the group.

Horiuchi's group is interested in understanding the process of core-collapse supernovae of massive stars. They do this by focusing on their high-energy signatures, with particular emphasis on neutrino emission. Since neutrinos are weakly interacting, they provide a view of a star's interior -- where most of the action of core collapse is happening. The work involves numerically investigating the core collapse process to predict the expected neutrino signal, as well as investigating the astronomical occurrence rate of supernovae. The group also works closely with the nuclear and particle physics groups to investigate the observable signatures in current and upcoming large underground neutrino detectors.

Horiuchi's group is also interested in using high-energy (MeV and above) neutrinos and gamma rays to study the nature of particle dark matter. The current cosmological paradigm requires that dark matter dominate over "normal" baryonic matter. Dark matter does not fit in the Standard Model of particle physics and must arise from some new beyond-the-standard-model physics. While dark matter particles need to be largely stable, in many theoretical models they can cause faint signatures in the high-energy sky. The group is interested in theoretical models of dark matter, as well as the use of astronomical and satellite data to mine for signatures of dark matter.

Simonetti and Dennison have a long-standing interest in the interstellar radio-wave scattering seen toward extragalactic radio sources. The observation and interpretation of the scattering of radio waves from compact sources provide a unique probe of the structure of the ISM at very small scales. Simonetti has also probed irregularities in the ISM through observations of variations in interstellar Faraday rotation (seen toward extragalactic sources).

Simonetti and Dennison are also currently engaged in an optical survey of ionized interstellar gas seen over the northern hemisphere utilizing a sensitive, wide-field, digital (CCD) camera system equipped with narrow-bandpass filters (e.g., an H-alpha interference filter and a [SII] filter). In addition to the survey, observations are being made of selected fields of special interest. The results bear upon studies of radio wave scattering, general ISM phenomena, and searches for small-scale anisotropies in the microwave background radiation produced in the Big Bang. The Virginia Tech Spectral-Line Survey (VTSS) webpage contains details on the project, discussion of current results, and information on SLIC.

ETA Core Array at PARI
The ETA Core Array at the Pisgah Astronomical Research Institute in North Carolina.

Simonetti, in collaboration with faculty in the Department of Electrical and Computer Engineering (Professors Steve Ellingson and Cameron Patterson), is constructing an antenna array designed to continuously monitor virtually the entire northern sky for short bursts of radio emission (radio transients) from high-energy astrophysical phenomena, potentially including gamma ray bursts, supernovae, mergers of compact objects, the explosion of primordial black holes, and giant pulses from pulsars. The project is call ETA for "Eight-meter-wavelength Transient Array." The array is being constructed at a remote site in western North Carolina. The ETA website contains more details on the project. See also, the following articles:

Simonetti and Ellingson are also official representatives for Virginia Tech on the US Consortium for the Square Kilometer Array (SKA), an international project to design and build a radio telescope for the 21st century.

ETA team photo

The ETA project team:
Profs. Simonetti (standing, left)
Ellingson (standing, right)
and Patterson (seated).
Photo by John McCormick
March 20, 2006.

The VTSS project is funded by the NSF Division of Astronomical Sciences, AST-9319670, AST-9800476, and AST-0098487, and by the Horton Foundation. The ETA project is funded by the NSF Division of Astronomical Sciences, AST-0504677.

Undergraduate Astronomy Minor

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