Hubble Space Telescope optical-near-infrared colors of nearby R-1/4 and exponential bulges

We have analyzed V, H, and J Hubble Space Telescope (HST) images for a samp le of early- to late-type spiral galaxies and have reported elsewhere the s tatistical frequency of R-1/4-law and exponential bulges in our sample as a function of Hubble type and the frequency of occurrence and structural pro perties of the resolved central nuclei hosted by intermediate- to late-type bulges and disks (see references in the text). Here we use these data to s how the following : 1. The V - H color distribution of the R-1/4 bulge peaks around [V - H] sim ilar to 1.3, with a sigma Delta (V - H) similar to 0.1 mag. Assuming a sola r metallicity, these values correspond to stellar ages of approximate to 6 +/- 3 Gyr. In contrast, the V - H color distribution of the exponential bul ges peaks at [V - H similar to 0.9] and has a sigma Delta (V - H) similar t o 0.4 mag. This likely implies significantly smaller ages and/or lower meta llicities for (a significant fraction of the stars in) the exponential bulg es compared to the R-1/4-law spheroids. 2. Most of the central nuclei hosted by the exponential bulges have V - H a nd J - H colors that are compatible with relatively unobscured stellar popu lations. Assuming no or little dust effects, ages greater than or similar t o1 Gyr are suggested for these nuclei, which in turn imply masses of about a few 10(6) to a few 10(7) M., i.e., sufficient to dissolve progenitor bars with masses consistent with those inferred for the exponential bulges by t heir luminosities. 3. While different bulge-nucleus pairs cover a large range of V - H colors, each bulge-nucleus pair has quite similar V - H colors and thus possibly s imilar stellar populations. The HST photometric analysis suggests that exponential-type bulge formation is taking place in the local universe and that this process is consistent with being the outcome of secular evolution processes within the disks. The structures that are currently formed inside the disks are quite dissimilar from the old elliptical-like spheroids that are hosted by the early-type d isks.