Photometric scaling relations are studied for S0 galaxies and compared with those obtained for spirals .
New two-dimensional multi-component decompositions are presented for 122 early-type disk galaxies , using deep K _ { s } -band images .
Combining them with our previous decompositions , the final sample consists of 175 galaxies ( Near-Infrared Survey of S0s , NIRS0S : 117 S0s + 22 S0/a and 36 Sa galaxies ) .
As a comparison sample we use the Ohio State University Bright Spiral Galaxy Survey ( OSUBSGS ) of nearly 200 spirals , for which similar multi-component decompositions have previously been made by us .
The improved statistics , deep images , and the homogeneous decomposition method used , allows us to re-evaluate the parameters of the bulges and disks .
For spirals we largely confirm previous results , which are compared with those obtained for S0s .
Our main results are as follows .
( 1 ) Important scaling relations are present , indicating that the formative processes of bulges and disks in S0s are coupled ( e.g . M _ { K } ^ { o } ( disk ) = 0.63 M _ { K } ^ { o } ( bulge ) - 9.3 ) , like has been found previously for spirals ( for OSUBSGS spirals M _ { K } ^ { o } ( disk ) = 0.38 M _ { K } ^ { o } ( bulge ) - 15.5 ; the rms deviation from these relations is 0.5 mag , for S0s and spirals ) .
( 2 ) We obtain median r _ { eff } / h _ { r } \sim 0.20 , 0.15 and 0.10 for S0 , S0/a-Sa and Sab-Sc galaxies , respectively : these values are smaller than predicted by simulation models in which bulges are formed by galaxy mergers .
( 3 ) The properties of bulges of S0s are different from the elliptical galaxies , which is manifested in the M _ { K } ^ { o } ( bulge ) vs r _ { eff } relation , in the photometric plane ( \mu _ { 0 } , n , r _ { eff } ) , and to some extent also in the Kormendy relation ( < \mu > _ { eff } vs r _ { eff } ) .
The bulges of S0s are similar to bulges of spirals with M _ { K } ^ { o } ( bulge ) < - 20 mag .
Some S0s have small bulges , but their properties are not compatible with the idea that they could evolve to dwarfs by galaxy harassment .
( 4 ) The relative bulge flux ( B / T ) for S0s covers the full range found in the Hubble sequence , even with 13 \% having B / T < 0.15 , typical for late-type spirals .
( 5 ) The values and relations of the parameters of the disks ( h _ { r } ^ { o } , M _ { K } ^ { o } ( disk ) , \mu _ { o } ( 0 ) ) of the S0 galaxies in NIRS0S are similar to those obtained for spirals in the OSUBSGS .
Overall , our results support the view that spiral galaxies with bulges brighter than - 20 mag in the K -band can evolve directly into S0s , due to stripping of gas followed by truncated star formation .