CI and CO in nearby galaxy centers: the bright galaxies NGC1068 (M77), NGC2146, NGC3079, NGC4826 (M64), and NGC7469

摘要

Maps and measurements of the J=1-0, J=2-1, J=3-2, J=4-3 12CO, the J=1-0,J=2-1, and J=3-2 13CO lines in the central arcminute squared of NGC1068,NGC2146, NGC3079, NGC4826, and NGC7469, as well as 492 GHz [CI] maps in threeof these are used to model the circumnuclear molecular gas in these galaxies.In all five objects, the bright CO concentrations mapped have line intensitiesthat require two distinct gas components for satisfactory fits. The physicalcondition of the molecular gas differs from galaxy to galaxy. High kinetictemperatures of 125-150 K occur in NGC2146 and NGC3079. Very high densities of0.3-1.0 x 10**5 cm**-3 occur in NGC2146, NGC3079, and NGC7469. The CO to H2conversion factor X is typically an order of magnitude less than the `standard'value in the Solar Neighborhood. The molecular gas is constrained within radiibetween 0.9 and 1.5 kpc from the nuclei. Within these radii, H2 masses aretypically 1.2-2.5 x 10**8 M(sun). The exception is the (relatively nearby)merger NGC4826 with R=0.3 kpc, and M = 3 x 10**7 M(sun). In all five galaxies,the H2 mass is typically about one per cent of the dynamical mass in the sameregion.