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Title: Dust scattering and the radiation pressure force in the M82 superwind

Radiation pressure on dust grains may be an important physical mechanism driving galaxy-wide superwinds in rapidly star-forming galaxies. We calculate the combined dust and gas Eddington ratio (Γ) for the archetypal superwind of M82. By combining archival Galaxy Evolution Explorer data, a standard dust model, Monte Carlo dust scattering calculations, and the Herschel map of the dust surface density distribution, the observed far-UV/near-UV surface brightness in the outflow constrains both the total UV luminosity escaping from the starburst along its minor axis (L {sub *,UV}) and the flux-mean opacity, thus allowing a calculation of Γ. We find that L {sub *,UV} ≈ (1-6) × 10{sup 42} erg s{sup –1}, ∼2-12 times greater than the UV luminosity observed from our line of sight. On a scale of 1-3 kpc above the plane of M82, we find that Γ ∼ 0.01-0.06. On smaller scales (∼0.25-0.5 kpc), where the enclosed mass decreases, our calculation of L {sub *,UV} implies that Γ ∼ 0.1 with factor of few uncertainties. Within the starburst itself, we estimate the single-scattering Eddington ratio to be of order unity. Thus, although radiation pressure is weak compared to gravity on kpc scales above the plane of M82, it may yetmore » be important in launching the observed outflow. We discuss the primary uncertainties in our calculation, the sensitivity of Γ to the dust grain size distribution, and the time evolution of the wind following M82's recent starburst episodes.« less
Authors:
; ;  [1]
  1. Department of Astronomy and Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States)
Publication Date:
OSTI Identifier:
22342001
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; COMPARATIVE EVALUATIONS; DENSITY; DISTRIBUTION; DUSTS; EVOLUTION; GALAXIES; GRAIN SIZE; GRAVITATION; LAUNCHING; LUMINOSITY; MASS; MONTE CARLO METHOD; OPACITY; RADIATION PRESSURE; SCATTERING; SENSITIVITY; STARS; SURFACES