A Possible Evolutionary Connection between Active Galactic Nuclei and Starbursts in LINERs

Our analysis of the two magnitude-limited samples of LINERs suggests a correlation between LFIR/LB, or f(25 μm)/f(60 μm), and Hubble-type index at greater than 99.99% significance level. As LFIR/LB and f(25 μm)/f(60 μm) are considered to be indicators of star formation activity and active galactic nuclei (AGN) activity, respectively, our results suggest that LINERs with higher AGN activity may have a lower star formation contribution. The ones with highest AGN activity and lowest star formation contributions are elliptical galaxies. All well-studied type 1 LINERs belong to this group. On the other hand, LINERs with higher star formation activity present lower AGN contributions. We find all well-studied type 2 LINERs in this parameter space. Most LINERs having inner ring structures belong to this group. Statistics with other indicators of star formation or AGN activity (a nuclear mass-to-light ratio at the H band and the ratio of X-ray to UV power) provide further evidence for such a trend. We have seen that along with the evolution of galaxies from late-type spiral galaxies to early-type ones and up to elliptical galaxies, the intensity of AGN activity increases with decreasing star formation contributions. The above analyses may suggest a possible connection between the host galaxies and nuclear activities, and it might also indicate a possible evolutionary connection between AGNs and starbursts in LINERs.