X iv : a st ro - p h / 99 06 15 8 v 1 9 J un 1 99 9 A VLBI and MERLIN Survey of faint , compact radio sources
نویسندگان
چکیده
We present preliminary results from a VLBI survey at λ = 6 cm of a sample of 35 sources with flux densities of 2 – 100 mJy. These sources were selected from the VLA FIRST survey at λ = 20 cm, in a 3 degree field around the bright calibrator 1156+295, simply by imposing S 20 > 10 mJy and θ < 5 arcsec. MERLIN observations at λ6 cm detected 70/127 of these sources with a threshold of 2 mJy at 50 mas resolution and the closest 35 of these to the calibrator were observed with the VLBA+EVN in snapshot mode at λ6 cm. These sources are a mixture of flat and steep-spectrum sources and include: weak flat-spectrum nuclei of large radio galaxies , low power AGN in nearby galaxies and radio quiet quasars. With these short observations, the sensitivity is limited and most appear as either core-jets or simple point sources on the milliarcsec scale. Nonetheless, it is encouraging that with only 10 minutes observation per source, at least 35% of all sources with S 20 > 10 mJy can be detected and imaged with global 6cm VLBI.
منابع مشابه
ar X iv : a st ro - p h / 99 02 09 5 v 1 5 F eb 1 99 9 Radiospectra and Kinematics in Blazars
Broad band spectra of total and compact–scale radio emission from blazars, used in combination with kinematic information inferred from VLBI monitoring programs, can be applied successfully to better constrain the models of compact jets. We discuss here a " hands-on " approach for tying together the kinematic and spectral properties of radio emission from blazars.
متن کاملar X iv : a st ro - p h / 98 06 04 8 v 1 3 J un 1 99 8 MERLIN observations of GRS 1915 + 105 : a progress report
Abstract We present a progress report on MERLIN radio imaging of a radio outburst from GRS 1915+105. The major ejection occurred at the end of a ∼ 20 day ‘plateau’ state, characterised by low/hard X-ray fluxes and a relatively strong flat-spectrum radio component. Apparent superluminal motions have been mapped with unprecedented resolution, and imply higher velocities in the jet than previously...
متن کاملar X iv : a st ro - p h / 99 02 06 2 v 1 4 F eb 1 99 9 SOURCES OF RELATIVISTIC JETS IN THE GALAXY
متن کامل
ar X iv : a st ro - p h / 98 12 05 6 v 1 2 D ec 1 99 8 Differential Astrometry over 15 ◦
We observed the pair of radio sources 1150+812 and 1803+784 in November 1993 with a VLBI array, simultaneously recording at 8.4 and 2.3 GHz. We determined the angular separation between the two sources with submilliarcsecond accuracy by using differential techniques. This result demonstrates the feasibility of high precision differential astrometry for radio sources separated in the sky by almo...
متن کاملar X iv : a st ro - p h / 99 06 08 9 v 1 4 J un 1 99 9 The SW Sextantis stars
I review the observational properties of SW Sex stars. I show that they can be explained by an accretion stream overflowing the disc, combined with an accretion disc wind. I suggest that SW Sex behaviour is caused by episodes of very high mass transfer, which are balanced by VY Scl low states.
متن کامل