Circumnuclear pileups of dust and gas in M82

Red Hα and R-band CCD images of the starburst galaxy M82 are compared with corresponding near-infrared [S III] and I-band images and with a smaller Brγ infrared-array image of the central 500 pc. Enhancements in the continuum-subtracted [S III]/Hα flux ratio are evident along a ∼ kpc-long arc that includes the nuclear dust lanes visible at Hα as well as two especially enhanced regions on opposite sides of the bursting nucleus. If interpreted as the consequences of reddening by dust, the [S III]/Hα flux enhancements indicate the presence of obscured ionized gas, much of which is distributed immediately beyond the nuclear 1 kpc