Dual Frequency VLBI Monitoring of a Large Sample of Compact Extragalactic Sources at 8 and 32 GHz

Details Dual Frequency VLBI Monitoring of a Large Sample of Compact Extragalactic Sources at 8 and 32 GHz Dual Frequency VLBI Monitoring of a Large Sample of Compact Extragalactic Sources at 8 and 32 GHz

Jan 2012

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21943509j&link_type=abstract

American Astronomical Society, AAS Meeting #219, #435.09

Astronomy and Astrophysics

Astronomy

Scientific paper

We are carrying out regular monitoring of 400+ compact extragalactic sources using large DSN (Deep Space Network) antennas over intercontinental baselines at 8, and 32 GHz simultaneously. This program provides precision astrometric measurements of AGN compact cores, used to maintain the JPL extragalactic reference frame. In addition to astrometric observables, this program has the potential to provide regular flux density measurements at each of these observing frequencies with precision at the level of 10-20%.
Such monitoring of compact radio emission serves as a direct measure of AGN core activity, probing intrinsic jet parameters and providing the opportunity for discriminating between different models of the high-energy emission in these objects by cross-correlating the radio and gamma-ray flux densities. Simultaneous multi-frequency observations will provide high precision spectral information of AGN compact emission regions at the parsec-scale unaffected by the errors often introduced when combining multi-frequency data obtained at different epochs. The spectral index can be used to compare the relativistic electron energy distribution with the photon spectral index seen in gamma-rays. For instance, if Compton up-scattering by the radio synchrotron electron population is the basic process producing the gamma-rays, the spectra in both spectral regions should be directly related.
By providing measurements on both East-West and North-South baselines with large antennas and Gbit/s recording capability, our program can probe sources at the 30 mJy flux limit (10-sigma), potentially increasing the sample to a fainter population of sources. In these regards, our program complements well existing northern and southern hemisphere VLBI monitoring programs, by providing flux measurements at 32 GHz, covering a fainter population sample, and by filling the gap for sources in the [-20:-40] degree declination range. Further, our program also provides additional flexibility for target of opportunity observations.
U.S Government Sponsorship acknowledged. Copyright 2011. All rights reserved.

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