In order to investigate how the growth of galactic bulges progresses 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 radio observations of ^ { 12 } CO ( 1 \rightarrow 0 ) using the Nobeyama Millimeter Array ( with 2–4 kpc spatial resolution ) for two FIR-bright NLS1s , yielding the first detection of their CO emission .
Corresponding molecular–gas masses { M ( H _ { 2 } ) } of ( 1 - 3 ) \times 10 ^ { 9 } { M _ { \odot } } are the 2nd and 4th largest ones among NLS1s .
By estimating dynamical masses and bulge masses { M _ { bulge } } for these two NLS1s using CO channel map and CO line widths , we found { M ( H _ { 2 } ) } amount to 0.13–0.35 of these masses .
Taking account the star formation efficiency ( \sim 0.1 ) , the increase in M _ { bulge } in those NLS1s in the near future ( \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 10 ^ { 7.5 } yr ) is expected not to be a huge fraction ( 1–5 % of the preexisting stars ) .
Bulge growth may have finished before BH growth , or bulge–BH coevolution may proceed with many , occasional discrete events , where one coevolution event produces only a small amount of mass growth of BHs and of bulges .
We also discuss the ratios of star-formation rate–to–gas accretion rate onto BHs , finding that two NLS1s have very small ratios ( \approx 1 ) compared with the { M _ { bulge } } / { M _ { BH } } ratios found in active and inactive galaxies ( \approx 700 ) .
This huge difference suggests either the non-overlapped coevolution , long star formation duration or temporarily high accretion rate during NLS1 phase .