Volume 531, July 2011
|Number of page(s)||4|
|Section||Cosmology (including clusters of galaxies)|
|Published online||31 May 2011|
On Öpik’s distance evaluation method in a cosmological context
Tuorla ObservatoryDepartment of Physics and Astronomy, University of Turku, 21500 Piikkiö, Finland
Received: 9 February 2011
Accepted: 19 April 2011
Aims. Öpik derived the distance to M 31 using its rotation, flux and angular size. We describe his method and its reliance on the mass-to-luminosity ratio M/L in an instructive way and consider it formally within a family of dynamical cosmic distance indicators.
Methods. We consider ways of overcoming the M/d degeneracy in methods where together with the dynamical equation one uses an auxiliary relation M ~ dn to infer the distance d (with examples for n = 0,1,2,3). As a possible deep space analog to Öpik’s method we assess hypothetical Eddington radiators (M/L = M/LEdd).
Results. We describe ways of calibrating Öpik-related methods that do not use directly the angular size and consider their sensitivity to the used local H0. We find, for instance, that when the size-luminosity relation is calibrated using distance-independent reverberation mapping to infer the BLR size, the derived mass M ∝ LαΔλ2 does not depend on H0, whereas the Eddington ratio Lbol/LEdd does (as ∝ H0-2). This is illustrated using very luminous yet quiescent radio quasars at redshifts 0.5–1.6.
Key words: galaxies: distances and redshifts / distance scale
© ESO, 2011
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