Exploring the Very Extended Low-surface-brightness Stellar Populations of the Large Magellanic Cloud with SMASH

David L. Nidever, Knut Olsen, Yumi Choi, Thomas J.L.De Boer, Robert D. Blum, Eric F. Bell, Dennis Zaritsky, Nicolas F. Martin, Abhijit Saha, Blair C. Conn, Gurtina Besla, Roeland P.Van Der Marel, Noelia E.D. Noël, Antonela Monachesi, Guy S. Stringfellow, Pol Massana, Maria Rosa L. Cioni, Carme Gallart, Matteo Monelli, David Martinez-DelgadoRicardo R. Munoz, Steven R. Majewski, A. Katherina Vivas, Alistair R. Walker, Catherine Kaleida, You Hua Chu

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


We present the detection of very extended stellar populations around the Large Magellanic Cloud (LMC) out to R ∼ 21°, or ∼18.5 kpc at the LMC distance of 50 kpc, as detected in the Survey of the Magellanic Stellar History (SMASH) performed with the Dark Energy Camera on the NOAO Blanco 4 m Telescope. The deep (g ∼ 24) SMASH color-magnitude diagrams (CMDs) clearly reveal old (∼9 Gyr), metal-poor ([Fe/H] ≈ -0.8 dex) main-sequence stars at a distance of ∼50 kpc. The surface brightness of these detections is extremely low with our most distant detection at Σ g ≈ 34 mag arcsec -2 . The SMASH radial density profile breaks from the inner LMC exponential decline at ∼13°-15°and a second component at larger radii has a shallower slope with power-law index α = -2.2 that contributes ∼0.4% of the LMC's total stellar mass. In addition, the SMASH densities exhibit large scatter around our best-fit model of ∼70% indicating that the envelope of stellar material in the LMC periphery is highly disturbed. We also use data from the NOAO Source catalog to map the LMC main-sequence populations at intermediate radii and detect a steep dropoff in density on the eastern side of the LMC (at R ≈ 8°) as well as an extended structure to the far northeast. These combined results confirm the existence of a very extended, low-density envelope of stellar material with a disturbed shape around the LMC. The exact origin of this structure remains unclear, but the leading options include an accreted halo or tidally stripped outer disk material.

Original languageEnglish (US)
Article number118
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 1 2019


  • Local Group
  • Magellanic Clouds
  • galaxies: dwarf
  • galaxies: halos
  • galaxies: individual (Large Magellanic Cloud)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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