Astronomy and Astrophysics – Astronomy
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21642007m&link_type=abstract
American Astronomical Society, AAS Meeting #216, #420.07; Bulletin of the American Astronomical Society, Vol. 41, p.832
Astronomy and Astrophysics
Astronomy
Scientific paper
We report on the results of VLBI observations of two gigahertz-peaked spectrum sources, 1321+410 and 0026+346, at five frequencies bracketing the spectral peaks. By comparing the three lower-frequency flux-density maps with extrapolations of the high frequency spectra we obtained maps of the optical depths as a function of frequency.
The morphologies of the optical depth maps of 1321+410, at all frequencies, are strikingly uniform, consistent with there being a foreground screen of absorbing gas. We also find that the flux densities across the map fit free-free absorption spectra within the uncertainties. The required free-free optical depths are satisfied with reasonable gas parameters (ne 4000 cm-3, T 104 K, and L 1 pc). We conclude that the case for free-free absorption in 1321+410 is strong.
In 0026+346, there is a compact feature with an inverted spectrum at the highest frequencies which we take to be the core. The optical depth maps, even excluding the possible core component, exhibit a noticeable amount of structure, but the morphology does not correlate with that in the flux-density maps, as would be expected if the absorption was due to synchrotron self-absorption. Additionally, the spectra (except at the core component) are consistent with free-free absorption, to within the uncertainties, and require column depths about one half of that in 1321+410. We conclude that free-free absorption by a relatively thin amount of gas with structure apparent on the scale of our maps in 0026+346 is likely, although the case is weaker than in 1321+410.
This research was supported by an award from the Research Corporation, a NASA NY Space Grant, and by a Booth-Ferris Research Fellowship. The VLBA is operated by the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
Marr Jonathan M.
Perry Thomas M.
Read J. W.
Taylor Greg B.
No associations
LandOfFree
A Case For Free-free Absorption In The GPS Sources 1321+410 And 0026+346 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Case For Free-free Absorption In The GPS Sources 1321+410 And 0026+346, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Case For Free-free Absorption In The GPS Sources 1321+410 And 0026+346 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1891482