Galactic masers and the Milky Way circular velocity

Jo Bovy, David W. Hogg, Hans Walter Rix

    Research output: Contribution to journalArticle

    Abstract

    Masers found in massive star-forming regions can be located precisely in six-dimensional phase space and therefore serve as a tool for studying Milky Way dynamics. The non-random orbital phases at which the masers are found and the sparseness of current samples require modeling. Here, we model the phase-space distribution function of 18 precisely measured Galactic masers, permitting a mean velocity offset and a general velocity dispersion tensor relative to their local standards of rest, and accounting for different pieces of prior information. With priors only on the Sun's distance from the Galactic Center and on its motion with respect to the local standard of rest, the maser data provide a weak constraint on the circular velocity at the Sun of Vc = 246 ± 30 km s-1. Including prior information on the proper motion of Sgr A* leads to Vc = 244 ≈ 13 km s-1. We do not confirm the value of Vc ≈ 254 km s-1 found in more restrictive models. This analysis shows that there is no conflict between recent determinations of Vc from Galactic Center analyses, orbital fitting of the GD-1 stellar stream, and the kinematics of Galactic masers; a combined estimate is Vc = 236 ± 11 km s-1. Apart from the dynamical parameters, we find that masers tend to occur at post-apocenter, circular-velocity-lagging phases of their orbits.

    Original languageEnglish (US)
    Pages (from-to)1704-1709
    Number of pages6
    JournalAstrophysical Journal
    Volume704
    Issue number2
    DOIs
    StatePublished - 2009

    Fingerprint

    masers
    phase velocity
    sun
    kinematics
    orbitals
    proper motion
    massive stars
    modeling
    distribution functions
    tensors
    orbits
    estimates

    Keywords

    • Galaxy: Fundamental parameters
    • Galaxy: Kinematics and dynamics
    • Galaxy: Structure
    • Methods:Statistical

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Galactic masers and the Milky Way circular velocity. / Bovy, Jo; Hogg, David W.; Rix, Hans Walter.

    In: Astrophysical Journal, Vol. 704, No. 2, 2009, p. 1704-1709.

    Research output: Contribution to journalArticle

    Bovy, Jo ; Hogg, David W. ; Rix, Hans Walter. / Galactic masers and the Milky Way circular velocity. In: Astrophysical Journal. 2009 ; Vol. 704, No. 2. pp. 1704-1709.
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