Also see my Research Statement (pdf)
EoR simulation: Furlanetto, Sokasian, and Hernquist, 2004; Dipole element of PAPER-8 in Green Bank
The Precision Array to Probe the Epoch of Reionization (PAPER) is an array designed to work at low frequencies (100 - 200 MHz) to study the Epoch of Reionization. The PI's are Rich Bradley (NRAO NTC), Don Backer (UC Berkeley), and James Aquirre (University of Pennsylvania), and the team is a growing collaboration including members from UVa, NRAO, UCB, UPenn and SKA South Africa.
PAPER will be a wide-field instrument, so it will take advantage of the latest techniques in 3-D imaging with radio interferometers. Its wide bandwidth gives it the advantage of multi-frequency synthesis. PAPER will also have to deal with the refractive effects of a turbulent ionosphere and a complex polarization calibration scheme.
The Epoch of Reionization is the period early in the history of the Universe when the first stars and galaxies formed. The intense ultraviolet light from these systems ionized the neutral atoms in the intergalactic medium. Mapping this will give astronomers a clearer understanding of when and how the first large-scale structures in the Universe formed.
Probing the Ionosphere with PAPER in Green Bank, West Virginia (pdf) by N. Gugliucci et al., Poster at AAS in January 2010
PAPER 8 Station Results by Parsons et al. 2010 (in press)
Don Backer's PAPER page
PAPER Wiki (password access)
Artist's depiction of water masers around the central black hole in NGC 4258,
from work by Greenhill, Hernstein, Moran, Diamond, Inoue, Miyoshi, and Nakai.
The NRAO is engaged in a "key project" to more accurately measure the value of the Hubble constant than ever before. This involves using water megamasers in disks around AGN to determine the geometrical distance to galaxies. This techniques involves search and monitoring with the Green Bank Telescope and high precision astrometry with the Very Long Baseline Array.
Jim Braatz and I conducted a snapshot survey of over 600 galaxies with the GBT, discovering 8 megamasers galaxies, one of which is suitable for the key project. (Braatz & Gugliucci, 2008, ApJ, 678, 1) I am also planning a VLBA follow-up one on particular detection which may have water masers associated with the AGN jet.
Compact Symmetric Objects
CSOs with the VLBA, by Greg Taylor
Compact Symmetric Objects (CSOs) are small (less than 1 kpc in extext) and young (~10^4 years) radio galaxies. These may be a key early link in radio-loud AGN evolution and make excellent probes of the interstellar medium of the host galaxy.
With Greg Taylor, Allison Peck, and Marcello Giroletti, I investigated the morphology, proper motions, and polarization properties of a sample of CSOs. We were able to measure kinematic ages for a number of these objects, determine rotation measures towards two polarized CSOs, and estimate the angle to the line of sight of one CSO candidate.