2001AJ....121.2483U

We study the characteristics of central star-forming regions of early-type spiral galaxies by optical spectroscopic observations. The sample consists of 13 galaxies which have ratios of far-infrared (FIR) to optical B-band luminosity, log(L_FIR/L_B), larger than the average of this type, -0.5. Strong line emissions are detected around the nucleus, and the line ratios of most regions are H II region-like, except for a few shocked regions. There is no low-ionization nuclear emission-line region (LINER). The [N II] and [S II] lines are somewhat enhanced, compared to the disk H II regions, but the enhancements cannot be attributed to hidden active galactic nuclei (AGNs) and the shock excitation. The median extinction derived from the Hα/Hβ intensity ratio is 1.0 mag in A_V, and the median SFR of our sample galaxies, corrected for extinction, is estimated to be 2 M_☉.yr^–1. Both values are comparable to those of late-type spiral galaxies. We find a correlation that the radii of the central star-forming regions tend to become larger with the turn-over radii of the rotation curves.