Statistics
Scientific paper
Jun 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...445..559k&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 445, no. 2, p. 559-577
Statistics
119
Astronomical Models, Dark Matter, Galactic Structure, Gravitational Lenses, Kinematics, Density Distribution, Luminosity, Mass Distribution, Mass To Light Ratios, Red Shift
Scientific paper
The radio ring lens MG 1654+134 strongly constrains the structure and mass of the 19 mag lens galaxy at its center. The best-fit effective radius for a de Vaucouleurs model of the lens galaxy is Re = 2.0 sec (1.5 sec is less than Re is less than 3.0 min) marginally consistent with fits to the observed lens galaxy. The B band mass-to-light ratio interior to the ring that the galaxy would have today is (M/L)B = (20.4 +/- 2.8)(fe/1.4)h, where a passively evolving early type galaxy fades by a factor of fe is approximately equal to 1.4 between the lens redshift and the present. This (M/L)B is inconsistent with stellar dynamical models of nearby ellipticals, but it is consistent with estimates from the statistics of gravitational lens numbers and separations. Isothermal models fit the ring with a halo velocity dispersion of sigmaDM = (216 +/- 2) km/s, consistent with the fundamental plane the stellar dynamics of ellipticals in dark matter halos (predicted dispersion (212 +/- 12)(fe/1.4-0.29 km/s), and the statistics of gravitational lenses. This strongly supports the conclusion from lens statistics that early type galaxies do not have constant mass-to-light ratios even on scales comparable to the effective radius. Density distributions with rho varies as (r squared + s squared)(alpha - 3/2) fit the data only in the restricted range 0.9 is less than or approximately alpha is less than or approximately 1.1 where alpha = 1 is an isothermal model. Centrally concentrated models such as the Plummer or modified Hubble models require large, finite core radii (800/h and 600/h pc, respectively) but fail to fit the structure of the ring. Isothermal models only have upper limits of order 100/h pc on the core radius. The major axis of the mass distribution is 7 deg +/- 10 deg from the major axis of the luminosity distribution. The models clearly distinguish between different angular structures for the lens model, and a quadrupole expansion of an elipsoidal density distribution fits the data better than a similar monopole in an external shear.
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