The Metallicity of HVC Complex C: Observational Evidence for the Accretion of Low-Metallicity Gas onto the Milky Way

Bart P. Wakker, J. Chris Howk, Blair D. Savage, Steve L. Tufte, Ron J. Reynolds, Hugo van Woerden, Ulrich J. Schwarz

    OnderzoeksoutputAcademicpeer review


    We present observations of the (field of the) Seyfert galaxy Mark 290, which probes the high-velocity cloud (HVC) complex C, one of the largest HVCs (Wakker & van Woerden 1991). We find that this object has a metallicity of 0.094+/-0.020^{+0.022}_{-0.019} times solar. A semi-theoretical upper limit of 30 kpc is set to its distance; D. Combined with the observed lower limit of 5 kpc (van Woerden et al. 1998b) this puts complex C in the galactic halo (z=3.5-20 kpc). The total gaseous mass is 2.0 tdex6 (D/5 kpc)^2 M_odot and, depending on whether the space velocity is completely radial or completely vertical, the HVC represents a downward mass flux of 0.036-0.083 (D/5 kpc) M_odot yr^{-1}, or 2.9-6.7 tdex{-3} (D/5 kpc)^{-1} M_odot yr^{-1} kpc^{-2}. These numbers suggest that complex C is unlikely to be part of a Galactic Fountain, but rather represents accreting low-metallicity material. Our results provide the first direct observational evidence for the infall of low-metallicity gas on the Milky Way, required in models of galactic chemical evolution.
    Originele taal-2English
    TitelThe third Stromlo symposium
    Subtitel the Galactic Halo : proceedings of a symposium held at Australian Academy of Science, Canberra, Australia, 17-21 August 1998
    Plaats van productieSan Francisco
    UitgeverijAstronomical Society of the Pacific
    ISBN van geprinte versie1-886733-86-4
    StatusPublished - 1999

    Publicatie series

    Naam Astronomical Society of the Pacific conference series

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