Space VLBI observations of 3C 279 at 1.6 and 5 GHz

Abstract

We present the results of VLBI Space Observatory Program (VSOP) observations of the gamma-ray blazar 3C 279 at 1.6 and 5 GHz from January 1998. The combination of the VSOP and VLBA-only images at these two frequencies maps the jet structure on scales from 1 to 100 mas. A spectral index map was made by combining the VSOP 1.6 GHz image with a matched-resolution VLBA-only image at 5 GHz from our VSOP observation on the following day. The spectral index map shows the core to have a highly inverted spectrum, with some areas having a spectral index approaching the limiting value for synchrotron self-absorbed radiation of +2.5 (S∝να). Gaussian model fits to the VSOP visibilities reveal high brightness temperatures (>1012 K) that are difficult to measure with ground-only arrays. An extensive error analysis was performed on the brightness temperature measurements. Most components did not have measurable brightness temperature upper limits, but lower limits were measured as high as 5×1012 K. This lower limit is sig...