Detailed study of the Milky Way globular cluster Laevens 3

Nicolas Longeard, Nicolas Martin, Rodrigo A. Ibata, Michelle L.M. Collins, Benjamin P.M. Laevens, Eric Bell, Dougal Mackey

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    9 Citations (Scopus)

    Abstract

    We present a photometric and spectroscopic study of the Milky Way satellite Laevens 3. Using MegaCam/Canada-France-Hawaii Telescope g and i photometry and Keck II/DEIMOS multi-object spectroscopy, we refine the structural and stellar properties of the system. The Laevens 3 colour-magnitude diagram shows that it is quite metal-poor, old (13.0 ± 1.0 Gyr), and at a distance of 61.4 ± 1.0 kpc, partly based on two RR Lyrae stars. The system is faint (MV = −2.8+0023 mag) and compact (rh = 11.4 ± 1.0 pc). From the spectroscopy, we constrain the systemic metallicity ([Fe/H]spectro = −1.8 ± 0.1 dex) but the metallicity and velocity dispersions are both unresolved. Using Gaia DR2, we infer a mean proper motion of (μα, μδ) = (0.51 ± 0.28, −0.83 ± 0.27) mas yr−1, which, combined with the system's radial velocity (〈vr〉 = −70.2 ± 0.5 km s−1), translates into a halo orbit with a pericenter and apocenter of 40.7+51467 and 85.6+175.92 kpc, respectively. Overall, Laevens 3 shares the typical properties of the Milky Way's outer halo globular clusters. Furthermore, we find that this system shows signs of mass segregation that strengthens our conclusion that Laevens 3 is a globular cluster.

    Original languageEnglish
    Pages (from-to)1498-1508
    Number of pages11
    JournalMonthly Notices of the Royal Astronomical Society
    Volume490
    Issue number2
    DOIs
    Publication statusPublished - 1 Dec 2019

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