Galactic model parameters of cataclysmic variables: Results from a new absolute magnitude calibration with 2MASS and WISE

Abstract

In order to determine the spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs), a J-band magnitude limited sample of 263 CVs has been established using a newly constructed period-luminosity-colours (PLCs) relation which includes J,Ks and W1-band magnitudes in 2MASS and WISE photometries, and the orbital periods of the systems. This CV sample is assumed to be homogeneous regarding to distances as the new PLCs relation is calibrated with new or re-measured trigonometric parallaxes. Our analysis shows that the scaleheight of CVs is increasing towards shorter periods, although selection effects for the periods shorter than 2.25h dramatically decrease the scaleheight: the scaleheight of the systems increases from 192pc to 326pc as the orbital period decreases from 12 to 2.25h. The z-distribution of all CVs in the sample is well fitted by an exponential function with a scaleheight of 213-10+11pc. However, we suggest that the scaleheight of CVs in the Solar vicinity should be ∼300pc and that the scaleheights derived using the sech2 function should be also considered in the population synthesis models. The space density of CVs in the Solar vicinity is found 5.58(1.35)×10-6pc−3 which is in the range of previously derived space densities and not in agreement with the predictions of the population models. The analysis based on the comparisons of the luminosity function of white dwarfs with the luminosity function of CVs in this study show that the best fits are obtained by dividing the luminosity functions of white dwarfs by a factor of 350–450.