HIGHLIGHTS FROM THE JCMT GROUP ANNUAL REPORT 1993 Nov./1994 Oct.

Receiver B3: The JCMT Group in Ottawa is building Rx B3, a 345 GHz common-user SIS receiver for the JCMT in Hawaii. This facility instrument will provide an order of magnitude improvement over the Rx B3i single-channel lead-alloy SIS receiver delivered to the JCMT in Hawaii in November 1991. The new dual-polarization receiver will use Nb-based SIS mixers with an instantaneous bandwidth of 1.5 GHz. It will provide fully automated tuning and single sideband operation. The project is a collaborative effort with the Rutherford Appleton Laboratory (England) and the Space Research Organization Netherlands (Groningen).

MIDAS project: Hayward is the project leader for the Multi-Input Digital Autocorrelation Spectrometer (MIDAS). It is being developed to accommodate the 345 GHz dual-polarization 4 x 4 focal-plane array receiver currently being designed in the UK for the JCMT. This spectrometer, built in two phases, will be able to process 32 individual IF outputs, each with instantaneous bandwidth of up to 2 GHz.

Upgrades program: Cunningham and Wade are developing an extensive upgrades program for JCMT receivers. This project will ensure that the telescope remains competitive, primarily by upgrading the mixers with SIS devices that are more sensitive and will not require mechanical tuning elements.

Jupiter encounter: Griffin (QMW), Marten (Meudon), Naylor and Tompkins (both at Lethbridge), Davis (Saskatchewan), Matthews, Holland (JAC, Hilo), Han (UH, Manoa) and others used the JCMT to observe the encounter of Comet Shoemaker-Levy 9 with the planet Jupiter in July 1994. Despite the presence of Hurricane Emilia, the JCMT obtained submm spectral observations with both a broad-band FTS (from the Univ. of Saskatchewan) in front of the bolometer, and with the usual spectral line receivers. The HCN J = 3-2 and J = 4-3 lines were detected in about half of the impact sites, and were still observable at the end of 1994 July, and later.

M-type asteroids: Redman, Feldman, and Matthews observed the two largest M-type asteroids, 16 Psyche and 216 Kleopatra, using the JCMT. They confirmed that the emissivities of these largely metallic objects are significantly lower than the emissivities of other asteroids.

Maser line: Thum (IRAM), Tacconi, Harris and Schuster (all MPE) and Matthews made the first successful observations of the H21alpha recombination line from MWC349 with the new MPE high-frequency SIS receiver on the JCMT. This object is the only source in which recombination lines are known to mase. Maser emission had been observed before at lower frequencies; the latest observations at 662 GHz at the JCMT show that the maser emission is present at still higher frequencies. Two main peaks, which appear to arise from the ionized inner boundary of a massive stellar disk, display saturated maser behavior.

Outflows: MacLeod, Avery, Harris and Tacconi (the last two at MPI, Garching) and Schuster (IRAM) have detected at the JCMT strong CO J = 6-5 emission associated with IRAS04368+2557. This CO emission is extended, arising not only in the region of the dense core but also at some of the hot spots out in the outflow lobes. This emission is evidence of shocks generated at the interface between a fast wind and the ambient material.

Dust clouds: Using the JCMT with the UKT14 bolometer and the Aberdeen/QMW polarimeter, Vallee and Bastien (U. de Montreal) observed the extreme-infrared (800 microns) emission from two molecular clouds W75N-IRS and M17-SW, as well as many others. In M17-SW, the magnetic field is perpendicular to the elongation of the cloud. In W75N-IRS, the magnetic field is parallel to the cloud elongation (thus perpendicular to the CO outflow). The last object is thus in contradiction with some predictions in the Pudritz-type models of disks and outflows. Gas clouds: Bell and Matthews detected C3N in the spiral arm gas clouds in the direction of Cas A. This emission is from dense gas clouds, not from diffuse gas clouds.

Contributed by J.P. Vallee.

Semi-annual Meeting of CTAG for JCMT

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Please e-mail any suggestions/comments to Jack Penfold (jpenfold@mtroyal.ab.ca)