Mercer 5: a probable new globular cluster in the Galactic bulge

A J Longmore, R Kurtev, P W Lucas, D Froebrich, R de Grijs, V D Ivanonv, Thomas Maccarone, J Borissova, L M Ker

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Abstract

We present a detailed study of a dust-obscured Galactic star cluster Mercer 5 ([MCM2005b] 5) in an extremely crowded field in the Milky Way. Near-infrared (near-IR) photometry from United Kingdom Infrared Digital Sky Surveys (UKIDSS) and the Son of ISAAC on the New Technology Telescope (SofI/NTT), combined with near-IR spectroscopy also from SofI, indicates that it is almost certainly a Galactic globular cluster, located at the edge of the Galactic bulge. The cluster suffers ˜9 mag of visual extinction, with strong evidence for an extinction gradient across the cluster. A simulation of the differential reddening in the cluster using empirical data from NGC 6539 (chosen because it had high signal-to-noise ratio data and low field star contamination) as a template mimics the observations extremely well. This simulation and other arguments are used to indicate that the most prominent clump of stars in the colour-magnitude diagrams is a horizontal branch clump. On this basis we conclude
Original languageEnglish
Pages (from-to)465
JournalMonthly Notices of the Royal Astronomical Society
StatePublished - Sep 2011

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    Longmore, A. J., Kurtev, R., Lucas, P. W., Froebrich, D., Grijs, R. D., Ivanonv, V. D., Maccarone, T., Borissova, J., & Ker, L. M. (2011). Mercer 5: a probable new globular cluster in the Galactic bulge. Monthly Notices of the Royal Astronomical Society, 465.