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

Nidever, D. L.; Olsen, Knut; Choi, Yumi; de Boer, Thomas J. L.; Blum, Robert D.; Bell, Eric F.; Zaritsky, Dennis; Martin, Nicolas F.; Saha, Abhijit; Conn, Blair C.; Besla, Gurtina; van der Marel, Roeland P.; Noël, Noelia E. D.; Monachesi, Antonela; Stringfellow, Guy S.; Massana, Pol; Cioni, Maria-Rosa L.; Gallart, C.; Monelli, M.; Martinez-Delgado, David; Muñoz, Ricardo R.; Majewski, Steven R.; Vivas, A. Katherina; Walker, Alistair R.; Kaleida, Catherine; Chu, You-Hua
Referencia bibliográfica

The Astrophysical Journal, Volume 874, Issue 2, article id. 118, 10 pp. (2019).

Fecha de publicación:
4
2019
Número de autores
26
Número de autores del IAC
2
Número de citas
40
Número de citas referidas
38
Descripción
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.
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