Michel Fich

The rotation curve of the Milky Way to 2 R(0)

A unified analysis of the Galactic rotation curve is presented using H I CO, and spectrophotometric data obtained in the northern hemisphere are used to determine the rotation curve from R = 3-17 kpc. A number of different functional forms are examined to fit the data, and the errors and uncertainties that go into its determination are discussed. The results are compared with nine recent studies of the rotation curve, and specific recommendations are made on the choice of curves to use in kinematic studies and mass modeling. 36 refs.

Abundances in H II regions at the edge of the Galaxy

Optical spectra, supplemented by some observations of radio recombination lines, have been used to estimate the abundances of helium, oxygen, nitrogen, sulfur, and argon in 18 H II regions in the outer Galaxy. Assuming that R0 (the distance from the center of the Galaxy to the sun) is 8.5 kpc, these H II regions are located between 11.5 and 17.9 kpc from the Galactic center and include many of the most distant (from the center) H II regions known in our Galaxy. The single most striking result of these observations is the apparent high nitrogen abundances in the H II regions at the outer edge of the visible disk of the Galaxy. 40 refs.

The New Milky Way

Our understanding of the large-scale structure of the Milky Way has undergone considerable revision during the past few years. The Galaxy is larger and much more massive than was previously supposed; the newly discovered mass consists of nonluminous matter which is likely to be the dominant form of matter in the universe. New analyses of the atomic hydrogen gas show that the disk of the Galaxy is about twice as extended as was previously thought. Beyond the sun, the gas is concentrated in large-scale, coherent spiral arms indicative of a regular four-armed spiral pattern. The outer edge of the disk has a remarkable scalloping.

Millimeter and submillimeter continuum emission from early-type galaxies

Twenty-two early-type galaxies that were detected by IRAS have been searched for continuum emission at millimeter and submillimeter wavelengths using the James Clerk Maxwell Telescope (JCMT). IRAS was relatively insensitive to cold dust that emits primarily at these longer wavelengths. In this first survey we were able to detect or achieve useful limits on the emission from 14 of the 22 galaxies observed. From these data we estimate upper limits on the dust temperature and lower limits on the mass of dust within the JCMT beam. These results are compared with H I and CO data and with the blue luminosities of the galaxies. The results are consistent with a model where the dust-to-gas ratio is similar to the Galactic one, and the amount of cold dust is an order of magnitude greater than the amount of warm dust (as is also seen in our Galaxy)

Continuum emission at 1 millimeter from the elliptical galaxy NGC 205

The nucleus of NGC 205 has been detected in the continuum at 1.1 mm with a flux of 21 + or - 5 mJy within the central 18 arcsec of the galaxy. This is the first detection of thermal emission from dust grains at millimeter wavelengths from an elliptical galaxy. Combining this measurement with IRAS and optical fluxes suggests that the dust temperature lies between 19 and 26 K and the dust mass between 1 solar mass and 3000 solar masses. These limits depend strongly on the dust emissivity. 26 refs.

A CO Survey of 372 Optical HII Regions

It has been known for some time that the best place to find CO is toward HII regions. Nevertheless, there has been no unbiased survey of CO toward HII regions on even a limited basis. To ameliorate this situation, we have attempted to survey all of the optical HII regions accessible with northern hemisphere millimeter wave radiotelescopes. The initial motivation was to get as many points as possible in order to determine the Galactic rotation curve. We have subsequently found that the information contained in our survey has some inherent interest as has already been shown by Fich, Treffers and Blitz (1982). A catalogue of the results is on press in the Astrophysical Journal Supplement Series (Blitz, Fich and Stark,1981).