Cut - off radii of galactic disks

ASTRONOMY AND ASTROPHYSICS Cutoff radii of galactic disks A new statistical study on the truncation of galactic disks Abstract. We present the analysis of a CCD survey of 31 nearby (≤ 110 Mpc) edge-on spiral galaxies. The three-dimensional one-component best fit models provide their disk-scalelengths h and for the first time their disk cutoff radii R co. We confirm for this sample the existence of such sharp truncations, and find a significantly lower mean value of the distance independent ratio R co /h = 2.9 ± 0.7 than the standard value of 4.5 often used in the literature. Our data show no correlation of these parameters with Hubble type, whereas we report a correlation between R co /h and the distance based scalelength in linear units. Compared to the Milky Way we find only lower values of R co /h, explained either by possible selection effects or by the completely different techniques used. We discuss our data in respect to present models for the origin of the cutoff radii, either as a relict of the galaxy formation process , or as an evolutionary phenomenon.