John E. Carlstrom

Velocity structure of the Orion-IRc2 SiO maser: evidence for an 80 AU diameter circumstellar disk

Les positions relatives des caracteristiques du maser SiO a 86 GHz en direction de la source Orion-IRc2 ont ete mesurees avec le reseau millimetrique Hat Creek. Lemission maser apparait originaire dun anneau de diametre 0.15″. Un modele simple de lemission maser emanant dun disque rotatif en expansion est capable de reproduire la structure des vitesses observee de lanneau

Absolute positions of SiO masers

The absolute radio positions of the v = 1, J = 2-1 SiO masers toward nine stars have been measured with typical position uncertainties of + or - 0.15 arcsec. The stars include the IR source IRc2 in Orion and R Aqr. The maser positions are compared with astrometrically determined stellar positions. For six of the stars, the stellar and maser positions differ by less than 0.35 arcsec. For VY CMa, the optical position is displaced by 1.1 arcsec from the maser. 47 refs.

Aperture Synthesis Maps of HCN, HCO+, CO, and 3 mm Continuum Toward M82

The Hat Creek millimeter interferometer was used to map emission from the J = 1 → 0 transitions of HCN, HCO+, and CO, and from 3 mm continuum toward the starburst galaxy M82. These are the first aperture synthesis maps of extragalactic thermal emission from molecules other than CO.

VLBI structure of 3C 84 at 89 GHz

The results of 89 GHz VLBI observations of 3C 84 at five epochs between 1981 and 1985 are reported. The observations are interpreted in terms of a slowly evolving core-halo model. The observational results pertaining to evolution of the flare, the compact core, the 1984 flare, the jet, and hot spot are discussed. The core is identified with the nucleus of NGC 1275. 19 references.

Evolution of the sub-milliarcsecond nucleus of 3C 84 at 100 GHz

VLBI observations of 3C 84 at 3 mm indicate that the narrow jet detected in 1985 has evolved into a resolved component, 0.2 x 0.1 pc, separated from the nucleus by 0.2 pc. The position angle of the new component is close to that of the 1985 jet but differs from that of the 5 pc scale structure seen at lower frequencies. An unresolved nuclear source, less than 0.05 pc in size, has decayed monotonically from 14 Jy in 1982 to less than 0.5 Jy in 1987, corresponding to the decay in total flux density which followed a millimeter-wave outburst in 1980. The changes in source structure can be understood in terms of the diffusion of high-energy electrons with synchrotron lifetimes of about 2 yr from the radio nucleus into the halo. 10 references.