Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 1979
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1979aj.....84.1181g&link_type=abstract
Astronomical Journal, vol. 84, Aug. 1979, p. 1181-1188.
Astronomy and Astrophysics
Astronomy
148
Emission Spectra, Galactic Rotation, Galactic Structure, H Lines, Brightness Temperature, Galactic Nuclei, Hubble Diagram, Oort Cloud, Tangents, Velocity Measurement
Scientific paper
Sensitive 21-cm H I line data for the Galaxy at galactocentric distances greater and less than that of the sun are reexamined. The following Galactic rotation parameters are derived: a solar galactocentric distance of 8.5 + or - 0.5 kpc, a local circular velocity of 220 + or - 10 km/s, an Oort constant A of 13 + or - 2 km/s per kpc, and an Oort constant B of -13 + or - 2 km/s per kpc. It is found that the rotation curve is flat at about 220 km/s between 4 and 25 kpc and probably well beyond. An H I mass of about 2 billion solar masses is estimated for the Galaxy, along with a luminosity of 17 billion suns and a Hubble type of Sbc II. It is concluded that the total mass of the Galaxy is around 1 trillion solar masses and mostly in unseen form and that the total extent of the Galaxy is about 90 kpc, which puts the Magellanic Clouds within its halo.
Gunn James E.
Knapp Gillan R.
Tremaine Scott D.
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