SMASH 1: a very faint globular cluster disrupting in the outer reaches of the LMC?

Abstract

We present the discovery of a very faint stellar system, SMASH 1, that is potentially a satellite of the Large Magellanic Cloud. Found within the Survey of the MAgellanic Stellar History (SMASH), SMASH 1 is a compact ($r_h=9.1_{-3.4}^{+5.9}$ pc) and very low luminosity (M_V = -1.0 +/- 0.9, $L_V=10^{2.3+/-0.4}$ Lsun) stellar system that is revealed by its sparsely populated main sequence and a handful of red-giant-branch candidate member stars. The photometric properties of these stars are compatible with a metal-poor ([Fe/H]=-2.2) and old (13 Gyr) isochrone located at a distance modulus of ~18.8, i.e. a distance of ~57 kpc. Situated at 11.3${}^{\circ }$ from the LMC in projection, its 3-dimensional distance from the Cloud is ~13 kpc, consistent with a connection to the LMC, whose tidal radius is at least 16 kpc. Although the nature of SMASH 1 remains uncertain, its compactness favors it being a stellar cluster and hence dark-matter free. If this is the case, its dynamical tidal radius is only <19 pc at this distance from the LMC, and smaller than the system's extent on the sky. Its low luminosity and apparent high ellipticity ($\epsilon =0.62_{-0.21}^{+0.17}$) with its major axis pointing toward the LMC may well be the tell-tale sign of its imminent tidal demise.

arXiv comment7 pages, 4 figures, 1 table. Accepted for publication in ApJL. v2: corrected figure 4 in which rh for globular clusters were miscalculated. The updated figure reflect the published version of the paper

References in corpus (36)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• On the variation of the Initial Mass Function
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• Eight Ultra-faint Galaxy Candidates Discovered in Year Two of the Dark Energy Survey
• A comprehensive Maximum Likelihood analysis of the structural properties of faint Milky Way satellites
• The Luminosity Function of the Milky Way Satellites
• Third-Epoch Magellanic Cloud Proper Motions II: The Large Magellanic Cloud Rotation Field in Three Dimensions
• Sagittarius II, Draco II and Laevens 3: three new Milky Way satellites discovered in the Pan-STARRS 1 3pi Survey
• The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater
• Segue 2: A Prototype of the Population of Satellites of Satellites
• A general catalogue of extended objects in the Magellanic System
• Big fish, small fish: Two New Ultra-Faint Satellites of the Milky Way
• Magellanic Cloud Structure from Near-IR Surveys II: Star Count Maps and the Intrinsic Elongation of the LMC
• Stellar Kinematics and Metallicities in the Ultra-Faint Dwarf Galaxy Reticulum II
• A Magellanic Origin of the DES Dwarfs
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• Horologium II: a Second Ultra-faint Milky Way Satellite in the Horologium Constellation
• Spectroscopic Confirmation of the Dwarf Galaxies Hydra II and Pisces II and the Globular Cluster Laevens 1
• The discovery of two extremely low luminosity Milky Way globular clusters
• A Hero's Dark Horse: Discovery of an Ultra-Faint Milky Way Satellite in Pegasus
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• ATLAS lifts the Cup: Discovery of a New Milky Way satellite in Crater
• Discovery of a Faint Outer Halo Milky Way Star Cluster in the Southern Sky
• Magellan/M2FS Spectroscopy of the Reticulum 2 Dwarf Spheroidal Galaxy
• Discovery of a Large Stellar Periphery Around the Small Magellanic Cloud
• The Progenitors of the Milky Way Stellar Halo: Big Bricks Favoured over Little Bricks
• Digging deeper into the Southern skies: a compact Milky-Way companion discovered in first-year Dark Energy Survey data
• The Discovery of an Ultra-Faint Star Cluster in the Constellation of Ursa Minor
• Metallicities, Age--Metallicity relationships, and Kinematics of Red Giant Branch Stars in the Outer Disk of the Large Magellanic Cloud
• TriAnd and its Siblings: Satellites of Satellites in the Milky Way Halo
• Physical properties of star clusters in the outer LMC as observed by the Dark Energy Survey
• On a possible origin for the lack of old star clusters in the Small Magellanic Cloud
• Satellite Dwarf Galaxies in a Hierarchical Universe: Infall Histories, Group Preprocessing, and Reionization

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