Dr. Crystal Brogan (NRAO)

Low Frequency VLA Survey of the Inner Galactic Plane - Dr. Crystal Brogan Colloquium

ATNF Marsfield Lecture Theatre

Abstract

Low frequency observations of the Galactic plane are an essential tool to explore the environments of two energetically important constituents of the Galactic medium: supernova remnants and HII
regions. I am engaged, together with my collaborators Namir Kassim
(NRL), Joe Lazio (NRL), Bryan Gaensler (CfA) and several graduate
students, in a project to utilize the 74 and 330 MHz systems (fields
of view ~11 degrees and ~3 degrees, respectively) at the Very Large
Array (VLA) to image the inner Galactic plane at low frequencies.
This project is proceeding on two fronts: (1) Survey the inner
Galactic plane from l=-15 to +55 degrees, |b|= 5 degrees at 74 MHz
with ~60 arcsec resolution in order to constrain the low energy end of
SNR spectral energy distributions, and explore the low density ionized
ISM via free-free absorption; and (2) Mosaic the plane at
330 MHz from l=+5 to +19 degrees, |b|= 1 degree with high
resolution (~ 20 arcsec) and surface brightness sensitivity (rms ~5
mJy/beam). This survey will be used to find new SNRs, probe the
radial temperature profile of HII regions, and determine the extent of
HII region halos. For both the 74 and 330 MHz surveys we have already
obtained more than half of the data, and expect to observe the rest
over the course of the next year. The resulting images from these
projects will improve upon existing surveys below 500 MHz by several
orders of magnitude in both resolution and sensitivity and will
approach the same level as existing cm wavelength surveys. In this
talk I will present some of our recent results including the first VLA
high resolution, high sensitivity image of the Galactic center at 74
MHz, spatially resolved free-free absorption toward a number of known
SNRs, and several new SNR candidates.