Nuclear Bar Catalyzed Star Formation: Co, Co, and Molecular Gas Properties in the Nucleus of Maffei 2

We present 300 resolution maps of CO, its isotopologues, and HCN from in the center of Maffei 2. The J 1⁄4 1Y0 rotational lines of CO, CO, CO and HCN, and the J 1⁄4 2Y1 lines of CO and CO were observed with the Owens Valley Radio Observatory (OVRO) and Berkeley-Illinois-Maryland Association (BIMA) arrays. The lower opacity CO isotopologues give more reliable constraints on H2 column densities and physical conditions than optically thick 12CO. The J 1⁄4 2Y1/1Y0 line ratios of the isotopologues constrain the bulk of the molecular gas to originate in low-excitation, subthermal gas. From large velocity gradient (LVG) modeling, we infer that the central giant molecular clouds (GMCs) have nH2 10 cm 3 and Tk 30 K. Continuum emission at 3.4, 2.7, and 1.4 mm was mapped to determine the distribution and amount of H ii regions and dust. Column densities derived from CO and 1.4 mm dust continuum fluxes indicate the standard Galactic conversion factor overestimates the amount of molecular gas in the center of Maffei 2 by factors of 2Y4. Gas morphology and the clear ‘‘parallelogram’’ in the position-velocity diagram shows that molecular gas orbits within the potential of a nuclear ( 220 pc) bar. The nuclear bar is distinct from the bar that governs the large-scale morphology of Maffei 2. Giant molecular clouds in the nucleus are nonspherical and have large line widths, due to tidal effects. Dense gas and star formation are concentrated at the sites of the x1-x2-orbit intersections of the nuclear bar, suggesting that the starburst is dynamically triggered. Subject headingg s: galaxies: individual (Maffei 2) — galaxies: ISM — galaxies: nuclei — galaxies: starburst — radio lines: galaxies