SIMBAD references

We present observations of pseudo-bulges in S0 and spiral galaxies using imaging data taken with the Spitzer Infrared Array Camera. We have used 2D bulge-disc-bar decomposition to determine structural parameters of 185 S0 galaxies and 31 nearby spiral galaxies. Using the Sérsic index and the position on the Kormendy diagram to classify their bulges as either classical or pseudo, we find that 25 S0s (14 per cent) and 24 spirals (77 per cent) host pseudo-bulges. The fraction of pseudo-bulges we find in spiral galaxies is consistent with previous results obtained with optical data and show that the evolution of a large fraction of spirals is governed by secular processes rather than by major mergers. We find that the bulge effective radius is correlated with the disc scale length for pseudo-bulges of S0s and spirals, as expected for secular formation of bulges from disc instabilities, though the discs in S0s are significantly smaller than those in spirals. We show that early-type pseudo-bulge hosting spirals can transform to pseudo-bulge hosting S0s by simple gas stripping. However, simple gas stripping mechanism is not sufficient to transform the late-type pseudo-bulge hosting spirals into pseudo-bulge hosting S0s.