In addition to the selection using 





, we filter our sample of 1083 double-component galaxies. Our aim is to select S0 galaxies for which we can reliably measure the colors of both the bulge and disk components. To this end, we exclude 68 double-component galaxies with unphysical fits:

1.
nbulge pegged at the allowed fit limits (37 galaxies) and


2.
re,bulge or re,disk pegged at the allowed fit limits (31 galaxies).

We also exclude 404 double-component galaxies with unresolved radial parameters:

1.
re,disk is less than 5% larger than re,bulge, since the bulge is defined as the most compact component (134 galaxies), and


2.
re,bulge is smaller than 80% of the PSF half-width at half-maximum in order to recover reliable bulge properties (Gadotti 2009; Meert et al. 2015; 270 galaxies).

Finally, we exclude 142 double-component galaxies for which the separation of the bulge and disk measurements is unreliable:

1.
nbulge  0.6 to exclude bars, which typically have n ∼ 0.5 (Gadotti 2008a, 2008b; 33 galaxies), and


2.
bulge-to-total flux ratio (B/T) lower than 0.2 and larger than 0.8 to exclude galaxies dominated by one component (Meert et al. 2015; 109 galaxies).

The filter causing the exclusion of the largest number of double-component fits is due to the impact of the PSF on the geometrical properties of the bulge, which tends to make the bulge rounder and harder to constrain. The effects of the PSF on the bulge properties have been detected in several previous works (Gadotti 2008a, 2009; Bernardi et al. 2014; Meert et al. 2015). For galaxies with double-component unphysical fits or unreliable bulge/disk separation, the single-component fit is preferable. Galaxies with unresolved radial parameters are not useful for investigating separate bulge and disk properties, but they are still better characterized by a double-component fit. In conclusion, the number of SDSS+ATLAS single-component galaxies is 782 (47%), the number of SDSS+ATLAS reliable double-component galaxies is 469 (28%), and the number of SDSS+ATLAS double-component galaxies with unresolved radial parameters is 404 (25%). For the single-component sample, 388 galaxies are bulge-dominated with Sérsic index n > 2, and 394 are disk-dominated with Sérsic index n  2. For the reliable double-component sample, 418 galaxies are better described by the most complex Sérsic + exponential model, 37 by the simple Sérsic + exponential model, and 14 by the de Vaucouleurs + exponential model. The range in stellar mass of the 469 double-component galaxies is 





. The galaxies with unresolved bulge and disk radial parameters are characterized by a lower galaxy stellar mass and smaller size compared to the double-component galaxies with reliable bulge and disk measurements. The median 





 difference is 0.145 ± 0.037 dex, and the median galaxy size difference, measured as the single-component re, is 0469 ± 0091. Thus, the exclusion of these galaxies limits our study to double-component galaxies that tend to have a large stellar mass and size for which the bulge and disk colors are reliably estimated.
Citation: Gadotti 2008a
Citation function: Uses
Citation: Gadotti 2008a
Citation function: Background