Astronomy and Astrophysics – Astrophysics
Scientific paper
Feb 1982
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982apj...253...70b&link_type=abstract
Astrophysical Journal, Part 1, vol. 253, Feb. 1, 1982, p. 70-85.
Astronomy and Astrophysics
Astrophysics
73
Galactic Rotation, Mass Distribution, Mass To Light Ratios, Spiral Galaxies, Astronomical Photometry, Galactic Radiation, Isophotes, Luminous Intensity, Stellar Mass
Scientific paper
For a sample of 21 Sc galaxies ranging from very low to very high luminosity, we have previously presented rotational velocities across ∼83% of the galaxy isophotal radius, R25. We now analyze the mass distributions for this same sample, and show that for all galaxies, the mass distribution has a single unique form, when the masses are each scaled by a mass scale length, Rm. Unlike luminosity scale lengths which are larger for more luminous (larger) galaxies, mass scale lengths are smaller for galaxies of high luminosity. As normalized here (the radius encompassing a mass of 1010 Msun), Rm is near 4 kpc for a low luminosity Sc and is near 1.5 kpc for a high luminosity Sc. A low luminosity Sc contains a single mass scale length, a high luminosity Sc contains many tens of scale lengths within its isophotal radius. At similar multiples of their scale lengths, all Sc's have equal interior masses.
The form of the characteristic mass curve implies that rotation curves are still rising slightly at radii of many scale lengths, V ∝ r0.1 or r0.2, and local density falls off slower than 1/r2 (ρ ∝ r-1.7). We conclude that the rotational velocities remain high at large nuclear distances due to the presence of significant nonluminous mass at large radii.
Correlations between integral mass, luminosity, mass scale length, isophotal radius, and velocity at the isophotal radius are determined and discussed. The correlation of luminosity with V(R25)) is as steep as that found in the infrared. The ratio of mass to luminosity interior to the isophotal radius is independent of luminosity and equals 3.0 ± 0.3 for Sc galaxies.
Burstein David
Ford Kent Jr. W.
Rubin Vera Cooper
Thonnard N. .
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