Transatlantic VLBI observations at 129 GHz and 147 GHz

In the IRAM Newsletter of August 2001 (No. 49) we have reported on the 2 mm (147 GHz) VLBI experiment made in March and April 2001 on the 3100 km long baseline between the Metsähovi 14-m telescope (MET, Finland) and the IRAM 30-m telescope on Pico Veleta (PV, Spain). We detected the sources 3C279 and 3C273 with a signal-to-noise ratio of SNR $\sim$ 10. The angular resolution (mainly in North-South direction) was $\sim$ 140 $\mu$arcsec (see A&A 2002, 390, L 19). The success of this observation stimulated a test observation on longer transatlantic baselines, reviving for this purpose the Kitt Peak (KP) telescope for VLBI observations and equipping the Heinrich Hertz Telescope (HHT) with a 2 mm receiver, a VLBI terminal, and a maser. Last but not least, a crew had to be collected to run the observations at the 5 participating observatories.

In April 2002, the teams of the Haystack Observatory (USA), the Steward Observatory (USA), NRAO-Tucson (USA), the MPIfR (Germany), the Onsala and SEST Observatory (Sweden and Chile), the Metsähovi Observatory (SF), and IRAM have made VLBI observations at 129 GHz between KP - HHT - PV and at 147 GHz between KP - HHT - SEST - MET - PV. The observations at 129 GHz concentrated on SiO maser line emission, the 147 GHz observation on continuum emission from AGNs. The maser VYCMa was detected on the 200 km long baseline between KP- HHT, the sources 3C 279, 3C 273 and NRAO150 (marginal) were detected on the 8500 km long baseline between KP - HHT - PV with SNRs of 10 to 40. 3C 279 was again detected between MET - PV, while unfortunately no fringes were found to SEST. The highest angular resolution, though only in the direction East-West of the USA and Europe baseline, is 18 $\mu$arcsec. At present the data are being completely reduced for publication. First results were presented at the 6th EVN Symposium held in Bonn, June 2002 (see the conference proceedings). A colourful press release can be found on the MPIfR website (Fig. 3).

Albert GREVE,
on behalf of the international VLBI team.

  

Figure 3: World map with mm wavelength telescopes from: MPIfR Press Information 07/02(1), 12-July-2002