3 years ago

Discovery of two neighboring satellites in the Carina constellation with MagLiteS.

R. A. Gruendl, K. Bechtol, K. Kuehn, B. C. Conn, S. E. Koposov, D. J. James, V. Belokurov, M. D. Johnson, S. Allam, J. D. Simon, D. Martinez-Delgado, N. F. Martin, T. S. Li, G. S. Stringfellow, N. E. D. Noël, A. R. Walker, D. L. Tucker, D. L. Nidever, A. K. Vivas, C. Gallart, B. Yanny, N. Kuropatkin, G. Torrealba, K. A. G. Olsen, P. Jethwa, A. Drlica-Wagner

We report the discovery of two ultra-faint satellites in the vicinity of the Large Magellanic Cloud (LMC) in data from the Magellanic Satellites Survey (MagLiteS). Situated 18$^{\circ}$ ($\sim 20$ kpc) from the LMC and separated from each other by only $18^\prime$, Carina~II and III form an intriguing pair. By simultaneously modeling the spatial and the color-magnitude stellar distributions, we find that both Carina~II and Carina~III are likely dwarf galaxies, although this is less clear for Carina~III. There are in fact several obvious differences between the two satellites. While both are well described by an old and metal poor population, Carina~II is located at $\sim 36$ kpc from the Sun, with $M_V\sim-4.5$ and $r_h\sim 90$ pc, and it is further confirmed by the discovery of 3 RR Lyrae at the right distance. In contrast, Carina~III is much more elongated, measured to be fainter ($M_V\sim-2.4$), significantly more compact ($r_h\sim30$ pc), and closer to the Sun, at $\sim 28$ kpc, placing it only 8 kpc away from Car~II. Together with several other systems detected by the Dark Energy Camera, Carina~II and III form a strongly anisotropic cloud of satellites in the vicinity of the Magellanic Clouds.

Publisher URL: http://arxiv.org/abs/1801.07279

DOI: arXiv:1801.07279v1

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