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Title: Discovery of two neighbouring satellites in the Carina constellation with MagLiteS

Abstract

Here, 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.

Authors:
ORCiD logo [1];  [2];  [3];  [4];  [5];  [6];  [7];  [5];  [8];  [7];  [5];  [5];  [9];  [10];  [11];  [12];  [13];  [14];  [5];  [15] more »;  [16];  [6];  [17];  [18]; ORCiD logo [19];  [5] « less
  1. Univ. of Cambridge, Cambridge (United Kingdom); Academia Sinica, Taipei (Taiwan)
  2. Univ. of Cambridge, Cambridge (United Kingdom); Flatiron Institute, New York, NY (United States)
  3. Univ. of Cambridge, Cambridge (United Kingdom); Carnegie Mellon Univ., Pittsburgh, PA (United States)
  4. Large Synoptic Survey Telescope, Tucson, AZ (United States)
  5. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  6. National Optical Astronomy Observatory, Tucson, AZ (United States)
  7. Cerro Tololo Inter-American Observatory, La Serena (Chile)
  8. Univ. of Cambridge, Cambridge (United Kingdom)
  9. Mount Stromlo Observatory, Weston Creek, ACT (Australia)
  10. Instituto de Astrofisica de Canarias, Tenerife (Spain); Univ. de La Laguna, Tenerife (Spain)
  11. Univ. of Illinois, Urbana, IL (United States); National Center for Supercomputing Applications, Urbana, IL (United States)
  12. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  13. National Center for Supercomputing Applications, Urbana, IL (United States)
  14. Australian Astronomical Observatory, North Ryde, NSW (Australia)
  15. Univ. de Strasbourg, Strasbourg (France); Max-Planck-Institut fur Astronomie, Heidelberg (Germany)
  16. Univ. Heidelberg, Heidelberg (Germany)
  17. Univ. of Surrey, Guildford (United Kingdom)
  18. Observatories of the Carnegie Institution for Science, Pasadena, CA (United States)
  19. Univ. of Colorado, Boulder, CO (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1438044
Report Number(s):
arXiv:1801.07279; FERMILAB-PUB-18-156-AE-CD
Journal ID: ISSN 0035-8711; 1671470; TRN: US1900397
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 475; Journal Issue: 4; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Galaxy: halo; galaxies: dwarf; Magellanic Clouds

Citation Formats

Torrealba, G., Belokurov, V., Koposov, S. E., Bechtol, K., Drlica-Wagner, A., Olsen, K. A. G., Vivas, A. K., Yanny, B., Jethwa, P., Walker, A. R., Li, T. S., Allam, S., Conn, B. C., Gallart, C., Gruendl, R. A., James, D. J., Johnson, M. D., Kuehn, K., Kuropatkin, N., Martin, N. F., Martinez-Delgado, D., Nidever, D. L., Noel, N. E. D., Simon, J. D., Stringfellow, G. S., and Tucker, D. L. Discovery of two neighbouring satellites in the Carina constellation with MagLiteS. United States: N. p., 2018. Web. doi:10.1093/mnras/sty170.
Torrealba, G., Belokurov, V., Koposov, S. E., Bechtol, K., Drlica-Wagner, A., Olsen, K. A. G., Vivas, A. K., Yanny, B., Jethwa, P., Walker, A. R., Li, T. S., Allam, S., Conn, B. C., Gallart, C., Gruendl, R. A., James, D. J., Johnson, M. D., Kuehn, K., Kuropatkin, N., Martin, N. F., Martinez-Delgado, D., Nidever, D. L., Noel, N. E. D., Simon, J. D., Stringfellow, G. S., & Tucker, D. L. Discovery of two neighbouring satellites in the Carina constellation with MagLiteS. United States. doi:10.1093/mnras/sty170.
Torrealba, G., Belokurov, V., Koposov, S. E., Bechtol, K., Drlica-Wagner, A., Olsen, K. A. G., Vivas, A. K., Yanny, B., Jethwa, P., Walker, A. R., Li, T. S., Allam, S., Conn, B. C., Gallart, C., Gruendl, R. A., James, D. J., Johnson, M. D., Kuehn, K., Kuropatkin, N., Martin, N. F., Martinez-Delgado, D., Nidever, D. L., Noel, N. E. D., Simon, J. D., Stringfellow, G. S., and Tucker, D. L. Tue . "Discovery of two neighbouring satellites in the Carina constellation with MagLiteS". United States. doi:10.1093/mnras/sty170. https://www.osti.gov/servlets/purl/1438044.
@article{osti_1438044,
title = {Discovery of two neighbouring satellites in the Carina constellation with MagLiteS},
author = {Torrealba, G. and Belokurov, V. and Koposov, S. E. and Bechtol, K. and Drlica-Wagner, A. and Olsen, K. A. G. and Vivas, A. K. and Yanny, B. and Jethwa, P. and Walker, A. R. and Li, T. S. and Allam, S. and Conn, B. C. and Gallart, C. and Gruendl, R. A. and James, D. J. and Johnson, M. D. and Kuehn, K. and Kuropatkin, N. and Martin, N. F. and Martinez-Delgado, D. and Nidever, D. L. and Noel, N. E. D. and Simon, J. D. and Stringfellow, G. S. and Tucker, D. L.},
abstractNote = {Here, 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.},
doi = {10.1093/mnras/sty170},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 4,
volume = 475,
place = {United States},
year = {2018},
month = {1}
}

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Cited by: 24 works
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Figures / Tables:

Figure 1 Figure 1: Stellar overdensity significance versus “local” significance (see main text for details) of MagLiteS candidate detections. Only stars with |b| > 12° and distance to the LMC greater than 10° are used. Blue filled circles show the locations of two known objects in the field of view: Pictor IImore » and KMHK 1762. In this part of the sky, there are also several star clusters: NGC 2808, IC 4499 and E3. However, these are detected with significances in excess of 20 and are omitted in the plot. Other detected overdensities are shown as black points, the new discoveries, Car II and III are shown as red filled circles. There are also a small number of detections associated with data artifacts that are shown in light gray. The red dashed line marks the SL = 6 threshold. Objects with high S but low SL are likely associated with areas in which the variance was underestimated. The region above the red line offers a clean candidate selection.« less

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