12CO observations on narrow-line Seyfert 1 galaxies

In order to investigate how the growth of galactic bulges is accompanied with the growth of central black holes (BHs), we observed molecular gas (fuel for the coming star formation) in possibly young active galaxies, narrow-line Seyfert 1 galaxies (NLS1s). We present the results of pilot observations of ¹²CO (1→0) line using the Nobeyama Millimeter Array for two FIR-bright NLS1s, ending in the first detection of their CO emission. Corresponding molecular-gas masses M(H₂) of (1−3)×10⁹M_⊙ are the 2nd and 4th largest ones among NLS1s. Together with CO data for other NLS1s (including our sub-kpc observations) and for broad-line Seyfert 1 galaxies (BLS1s), we found that NLS1s and BLS1s contain a similar amount of molecular-gas. We do not see a significant difference in M(H₂)/M_BH ratios and in M(H₂)/M_bulge ratios between NLS1s and BLS1s. The lack of a clear difference in M(H₂) between them indicates either that bulge and BH growth phases are not overlapped or that the duration of star formation is much longer than that of active galaxies.