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Published February 1, 1985 | Published
Journal Article Open

The inner disk of NGC 253

Abstract

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 ~20" (~300 pc) and an extended, inner disk of diameter ~360" (~6 kpc). Similar components are also evident in the molecular gas distribution. 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 ± 120" on opposite sides of the nucleus. The CO distribution exhibits a weak secondary peak just outside the bar. 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 H_2 inside R = 4 kpc is ~2 x 10^9 M_☉, which is ~7% of the dynamical mass at the same radius. If the observed far-infrared luminosity in the central R ≤ 500 pc is produced by young stars, the minimum rate of OBA star formation is 2.3 M_☉ yr^(-1), and the observed molecular clouds will be cycled into stars in ≾3 x 10^8 yr. It is speculated that the bar, detected in the near-infrared map, could feed fresh molecular gas from the outer disk to the active, star-forming nucleus.

Additional Information

© 1985 American Astronomical Society. Received 1984 June 4; accepted 1984 August 21. It is a pleasure to acknowledge the assistance of Denise Chapman-Taylor and helpful discussions with Jay Elias and Steve Strom. This is contribution # 570 of the Five College Astronomy Department. The infrared work at Palomar Observatory is supported by the National Science Foundation under grant AST 80-17335.

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Published - 1985ApJ___289__129S.pdf

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August 19, 2023
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