Investigating the Origins of Spiral Structure in Disk Galaxies through a Multiwavelength Study

Ryan Miller, Daniel Kennefick, Julia Kennefick, Mohamed Shameer Abdeen, Erik Monson, Rafael T. Eufrasio, Douglas W. Shields, Benjamin L. Davis

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The density-wave theory of spiral structure proposes that star formation occurs in or near a spiral-shaped region of higher density that rotates rigidly within the galactic disk at a fixed pattern speed. In most interpretations of this theory, newborn stars move downstream of this position as they come into view, forming a downstream spiral which is tighter, with a smaller pitch angle than that of the density wave itself. Rival theories, including theories which see spiral arms as essentially transient structures, may demand that pitch angle should not depend on wavelength. We measure the pitch angle of a large sample of galaxies at several wavelengths associated with star formation or very young stars (8.0 μm, H-α line and 151 nm in the far-UV) and show that they all have the same pitch angle, which is larger than the pitch angle measured for the same galaxies at optical and near-infrared wavelengths. Our measurements in the B band and at 3.6 μm have unambiguously tighter spirals than the star-forming wavelengths. In addition we have measured in the u band, which seems to fall midway between these two extremes. Thus, our results are consistent with a region of enhanced stellar light situated downstream of a star-forming region.

    Original languageEnglish (US)
    Article number177
    JournalAstrophysical Journal
    Volume874
    Issue number2
    DOIs
    StatePublished - Apr 1 2019

    Keywords

    • galaxies: evolution
    • galaxies: formation
    • galaxies: fundamental parameters
    • galaxies: spiral
    • galaxies: star formation
    • galaxies: structure

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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