The inner disk of NGC 253

The stellar and interstellar matter distributions in the luminous Sc galaxy NGC 253 are analyzed using maps of the near-infrared continuum (λ = 1 - 2 μm) and the millimeter CO emission line. The stellar disk traced out in the near-infrared exhibits two components: a nuclear peak of diameter ≡20arcsec(≡300 pc) and an extended, inner disk of diameter ≡360arcsec(≡6 kpc). The 2 μm brightness distribution mapped over the full extent of the inner disk is dominated by a barlike feature at position angle 17° east of the major axis extending to ±120arcsec on opposite sides of the nucleus. The derived abundance of molecular gas in the inner disk exceeds that of H I by a factor of 10 and exhibits a much steeper falloff with radius. The total mass of H2 inside R = 4 kpc is ≡2×109M_sun;, which is ≡7% of the dynamical mass at the same radius.