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2.1. Host Galaxy Properties

LINERs and Seyferts live in virtually identical host galaxies (Fig. 2). The vast majority of both classes occupy bulge-dominated, early-type systems (87% are found in types E-Sbc), which clearly differ from the population of galaxies whose nuclear spectrum indicates photoionization by current star formation (the so-called H II-nuclei), which is dominated by late-type hosts (63% are Sc's and later). The only noticeable difference in the distribution of morphological types of LINERs and Seyferts is that LINERs occupy a higher proportion of ellipticals. Bars exist with roughly the same frequency within the subsample of disk galaxies in both groups.

The similarity in the host galaxy properties of LINERs and Seyferts becomes even more apparent when we examine their absolute magnitude distributions (Fig. 2); they are statistically indistinguishable. Both peak at MBT0 approx -20.5 mag (for H0 = 75 km s-1 Mpc-1), about 0.4 mag brighter than MBT*, the typical absolute magnitude of the field-galaxy luminosity function. The parent galaxies of H II-nuclei, on the other hand, are systematically fainter than the other two groups by ~ 0.5 mag in the median.

Figure 2

Figure 2. Number distribution of morphological types (left) and total absolute blue magnitudes (right) for H II nuclei, all AGNs (LINERs + Seyferts), and LINERs and Seyferts separately. The median of each distribution is marked by an arrow. Adapted from Ho et al. (1997a).

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