2005ApJ...624..714G

We present the results of a single-dish beam-matched survey of the three lowest rotational transitions of CO in a sample of 20 local (D≲70 Mpc) luminous compact blue galaxies (LCBGs). These ~L*, blue, high surface brightness, starbursting galaxies were selected on the same criteria used to define LCBGs at higher redshifts. Our detection rate was 70%, with those galaxies having L_B<7x10⁹ L_☉not detected. We find that the H₂masses of local LCBGs range from 6.6x10⁶ to 2.7x10⁹ M_☉, assuming a Galactic CO-to-H₂conversion factor. Combining these results with our earlier H I survey of the same sample, we find that the ratio of molecular to atomic gas mass is low, typically 5%-10%. Using a large velocity gradient model, we find that the average gas conditions of the entire interstellar medium in local LCBGs are similar to those found in the centers of star-forming regions in our Galaxy and in the nuclear regions of other galaxies. Star formation rates, determined from IRAS fluxes, are a few M_☉/yr, much higher per unit dynamical mass than normal spiral galaxies. If this rate remains constant, the molecular hydrogen depletion timescales are short, ∼10-200 Myr.