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Abstract

The lowest luminosity ( L) Milky Way satellite galaxies represent the extreme lower limit of the galaxy luminosity function. These ultra-faint dwarfs are the oldest, most dark matter–dominated, most metal-poor, and least chemically evolved stellar systems known. They therefore provide unique windows into the formation of the first galaxies and the behavior of dark matter on small scales. In this review, we summarize the discovery of ultra-faint dwarfs in the Sloan Digital Sky Survey in 2005 and the subsequent observational and theoretical progress in understanding their nature and origin. We describe their stellar kinematics, chemical abundance patterns, structural properties, stellar populations, orbits, and luminosity function, as well as what can be learned from each type of measurement. We conclude the following:

  • ▪  In most cases, the stellar velocity dispersions of ultra-faint dwarfs are robust against systematic uncertainties such as binary stars and foreground contamination.
  • ▪  The chemical abundance patterns of stars in ultra-faint dwarfs require two sources of -process elements, one of which can likely be attributed to neutron star mergers.
  • ▪  Even under conservative assumptions, only a small fraction of ultra-faint dwarfs may have suffered significant tidal stripping of their stellar components.
  • ▪  Determining the properties of the faintest dwarfs out to the virial radius of the Milky Way will require very large investments of observing time with future telescopes.
Finally, we offer a look forward at the observations that will be possible with future facilities as the push toward a complete census of the Local Group dwarf galaxy population continues.

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2019-08-18
2024-04-17
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Literature Cited

  1. Abazajian KN, Keeley RE 2016. Phys. Rev. D 93:083514
  2. Abbott TMC, Abdalla FB, Allam S 2018. Ap. J. Suppl. 239:18
  3. Adén D, Feltzing S, Koch A 2009. Astron. Astrophys. 506:1147–68
  4. Ahnen ML, Ansoldi S, Antonelli LA 2018. J. Cosmol. Astropart. Phys. 3:009
  5. Albert A, Anderson B, Bechtol K 2017. Ap. J. 834:110
  6. Archambault S, Archer A, Benbow W 2017. Phys. Rev. D 95:082001
  7. Audouze J, Tinsley BM 1976. Annu. Rev. Astron. Astrophys. 14:43–79
  8. Banerjee P, Qian YZ, Heger A 2018. MNRAS 480:4963–68
  9. Barger KA, Haffner LM, Wakker BP 2012. Ap. J. 761:145
  10. Battaglia G, Tolstoy E, Helmi A 2006. Astron. Astrophys. 459:423–40
  11. Battaglia G, Tolstoy E, Helmi A 2011. MNRAS 411:1013–34
  12. Bechtol K, Drlica-Wagner A, Balbinot E 2015. Ap. J. 807:50
  13. Beers TC, Flynn K, Gebhardt K 1990. Astron. J. 100:32–46
  14. Behroozi PS, Wechsler RH, Conroy C 2013. Ap. J. 770:57
  15. Bell EF, Slater CT, Martin NF 2011. Ap. J. Lett. 742:L15
  16. Belokurov V, Walker MG, Evans NW 2008. Ap. J. Lett. 686:L83–86
  17. Belokurov V, Walker MG, Evans NW 2009. MNRAS 397:1748–55
  18. Belokurov V, Walker MG, Evans NW 2010. Ap. J. Lett. 712:L103–6
  19. Belokurov V, Zucker DB, Evans NW 2006. Ap. J. Lett. 647:L111–14
  20. Belokurov V, Zucker DB, Evans NW 2007. Ap. J. 654:897–906
  21. Beniamini P, Dvorkin I, Silk J 2018. MNRAS 478:1994–2005
  22. Beniamini P, Hotokezaka K, Piran T 2016a. Ap. J. Lett. 829:L13
  23. Beniamini P, Hotokezaka K, Piran T 2016b. Ap. J. 832:149
  24. Bennet P, Sand DJ, Crnojević D 2017. Ap. J. 850:109
  25. Benson AJ, Frenk CS, Lacey CG 2002. MNRAS 333:177–90
  26. Binney J, Tremaine S 2008. Galactic Dynamics Princeton, NJ: Princeton Univ. Press. 2nd ed.
  27. Bland-Hawthorn J, Karlsson T, Sharma S 2010. Ap. J. 721:582–96
  28. Bland-Hawthorn J, Sutherland R, Webster D 2015. Ap. J. 807:154
  29. Bovill MS, Ricotti M 2009. Ap. J. 693:1859–70
  30. Bovill MS, Ricotti M 2011. Ap. J. 741:17
  31. Boylan-Kolchin M, Weisz DR, Bullock JS, Cooper MC 2016. MNRAS 462:L51–55
  32. Boylan-Kolchin M, Weisz DR, Johnson BD 2015. MNRAS 453:1503–12
  33. Bozek B, Fitts A, Boylan-Kolchin M 2019. MNRAS 483:4086
  34. Brandt TD 2016. Ap. J. Lett. 824:L31
  35. Bromm V, Yoshida N 2011. Annu. Rev. Astron. Astrophys. 49:373–407
  36. Brooks AM, Kuhlen M, Zolotov A, Hooper D 2013. Ap. J. 765:22
  37. Brooks AM, Zolotov A 2014. Ap. J. 786:87
  38. Brown TM, Tumlinson J, Geha M 2012. Ap. J. Lett. 753:L21
  39. Brown TM, Tumlinson J, Geha M 2014. Ap. J. 796:91
  40. Buckley MR, Peter AHG 2018. Phys. Rep. 761:1
  41. Bullock JS, Boylan-Kolchin M 2017. Annu. Rev. Astron. Astrophys. 55:343–87
  42. Bullock JS, Kravtsov AV, Weinberg DH 2000. Ap. J. 539:517–21
  43. Bullock JS, Stewart KR, Kaplinghat M 2010. Ap. J. 717:1043–53
  44. Calabrese E, Spergel DN 2016. MNRAS 460:4397–402
  45. Caldwell N, Walker MG, Mateo M 2017. Ap. J. 839:20
  46. Cannon RD, Hawarden TG, Tritton SB 1977. MNRAS 180:81P–82P
  47. Carlin JL, Grillmair CJ, Muñoz RR 2009. Ap. J. Lett. 702:L9–13
  48. Carlin JL, Sand DJ 2018. Ap. J. 865:7
  49. Carlin JL, Sand DJ, Price P 2016. Ap. J. Lett. 828:L5
  50. Chabrier G 2003. Publ. Astron. Soc. Pac. 115:763–95
  51. Chiboucas K, Jacobs BA, Tully RB, Karachentsev ID 2013. Astron. J. 146:126
  52. Chiboucas K, Karachentsev ID, Tully RB 2009. Astron. J. 137:3009–37
  53. Chiti A, Frebel A, Ji AP 2018. Ap. J. 857:74
  54. Chornock R, Berger E, Kasen D 2017. Ap. J. Lett. 848:L19
  55. Cohen JG, Christlieb N, Thompson I 2013. Ap. J. 778:56
  56. Collins MLM, Tollerud EJ, Sand DJ 2017. MNRAS 467:573–85
  57. Conn AR, Ibata RA, Lewis GF 2012. Ap. J. 758:11
  58. Conn BC, Jerjen H, Kim D, Schirmer M 2018. Ap. J. 852:68
  59. Cowperthwaite PS, Berger E, Villar VA 2017. Ap. J. Lett. 848:L17
  60. Crnojević D, Sand DJ, Spekkens K 2016a. Ap. J. 823:19
  61. Crnojević D, Sand DJ, Zaritsky D 2016b. Ap. J. Lett. 824:L14
  62. Danieli S, van Dokkum P, Conroy C 2018. Ap. J. 856:69
  63. de Jong JTA, Harris J, Coleman MG 2008. Ap. J. 680:1112–19
  64. Deason AJ, Wetzel AR, Garrison-Kimmel S, Belokurov V 2015. MNRAS 453:3568–74
  65. Dey A, Schlegel DJ, Lang D 2018. Astron. J. Submitted. arXiv:1804.08657
  66. Di Cintio A, Brook CB, Macciò AV 2014. MNRAS 437:415–23
  67. D'Onghia E, Lake G 2008. Ap. J. Lett. 686:L61
  68. Drlica-Wagner A, Bechtol K, Allam S 2016. Ap. J. Lett. 833:L5
  69. Drlica-Wagner A, Bechtol K, Rykoff ES 2015. Ap. J. 813:109
  70. Drout MR, Piro AL, Shappee BJ 2017. Science 358:1570–74
    [Google Scholar]
  71. Erkal D, Li TS, Koposov SE 2018. MNRAS 481:3148
  72. Errani R, Peñarrubia J, Walker MG 2018. MNRAS 481:5073
  73. Feltzing S, Eriksson K, Kleyna J, Wilkinson MI 2009. Astron. Astrophys. 508:L1–4
  74. Fillingham SP, Cooper MC, Boylan-Kolchin M 2018. MNRAS 477:4491–98
  75. Fillingham SP, Cooper MC, Pace AB 2016. MNRAS 463:1916–28
  76. Fillingham SP, Cooper MC, Wheeler C 2015. MNRAS 454:2039–49
  77. Fitts A, Boylan-Kolchin M, Elbert OD 2017. MNRAS 471:3547–62
  78. François P, Monaco L, Bonifacio P 2016. Astron. Astrophys. 588:A7
  79. Frebel A, Bromm V 2012. Ap. J. 759:115
  80. Frebel A, Norris JE 2015. Annu. Rev. Astron. Astrophys. 53:631–88
  81. Frebel A, Norris JE, Gilmore G, Wyse RFG 2016. Ap. J. 826:110
  82. Frebel A, Simon JD, Geha M, Willman B 2010. Ap. J. 708:560–83
  83. Frebel A, Simon JD, Kirby EN 2014. Ap. J. 786:74
  84. Fritz TK, Battaglia G, Pawlowski MS 2018a. Astron. Astrophys. 619:A103
  85. Fritz TK, Lokken M, Kallivayalil N 2018b. Ap. J. 860:164
  86. Gaia Collab, Helmi A, van Leeuwen F 2018. Astron. Astrophys. 616:A12
  87. Garrison-Kimmel S, Hopkins PF, Wetzel A 2018. MNRAS Submitted. arXiv:1806.04143
  88. Garrison-Kimmel S, Wetzel A, Bullock JS 2017. MNRAS 471:1709–27
  89. Geha M, Blanton MR, Yan R, Tinker JL 2012. Ap. J. 757:85
  90. Geha M, Brown TM, Tumlinson J 2013. Ap. J. 771:29
  91. Geha M, Willman B, Simon JD 2009. Ap. J. 692:1464–75
  92. Gennaro M, Geha M, Tchernyshyov K 2018a. Ap. J. 863:38
  93. Gennaro M, Tchernyshyov K, Brown TM 2018b. Ap. J. 855:20
  94. Gilmore G, Norris JE, Monaco L 2013. Ap. J. 763:61
  95. Grcevich J, Putman ME 2009. Ap. J. 696:385–95
  96. Grillmair CJ 2006. Ap. J. Lett. 645:L37–40
  97. Grillmair CJ 2009. Ap. J. 693:1118–27
  98. Hansen TT, Andersen J, Nordström B 2016. Astron. Astrophys. 586:A160
  99. Hansen TT, Simon JD, Marshall JL 2017. Ap. J. 838:44
  100. Hargis JR, Willman B, Peter AHG 2014. Ap. J. Lett. 795:L13
  101. Hargreaves JC, Gilmore G, Annan JD 1996. MNRAS 279:108–20
  102. Harrington RG, Wilson AG 1950. Publ. Astron. Soc. Pac. 62:118–20
  103. Harris WE 1996. Astron. J. 112:1487
  104. Hilker M, Richtler T 2000. Astron. Astrophys. 362:895–909
  105. Homma D, Chiba M, Okamoto S 2016. Ap. J. 832:21
  106. Homma D, Chiba M, Okamoto S 2018. Publ. Astron. Soc. Jpn. 70:S18
  107. Hopp U, Schulte-Ladbeck RE, Kerp J 2003. MNRAS 339:33–43
  108. Ibata R, Martin NF, Irwin M 2007. Ap. J. 671:1591–623
  109. Illingworth G 1976. Ap. J. 204:73–93
  110. Irwin MJ, Belokurov V, Evans NW 2007. Ap. J. Lett. 656:L13–16
  111. Irwin MJ, Bunclark PS, Bridgeland MT, McMahon RG 1990. MNRAS 244:16P–19P
  112. Irwin MJ, Ferguson AMN, Huxor AP 2008. Ap. J. Lett. 676:L17
  113. Ishigaki MN, Aoki W, Arimoto N, Okamoto S 2014. Astron. Astrophys. 562:A146
  114. Jang IS, Lee MG 2014. Ap. J. Lett. 795:L6
  115. Jeltema T, Profumo S 2016. MNRAS 458:3592–96
  116. Jeon M, Besla G, Bromm V 2017. Ap. J. 848:85
  117. Jeon M, Bromm V, Pawlik AH, Milosavljević M 2015. MNRAS 452:1152–70
  118. Jethwa P, Erkal D, Belokurov V 2016. MNRAS 461:2212–33
  119. Jethwa P, Erkal D, Belokurov V 2018. MNRAS 473:2060–83
  120. Ji AP, Frebel A, Bromm V 2015. MNRAS 454:659–74
  121. Ji AP, Frebel A, Chiti A, Simon JD 2016a. Nature 531:610–13
  122. Ji AP, Frebel A, Simon JD, Chiti A 2016b. Ap. J. 830:93
  123. Ji AP, Frebel A, Simon JD, Geha M 2016c. Ap. J. 817:41
  124. Ji AP, Simon JD, Frebel A 2019. Ap. J. 870:83
  125. Kallivayalil N, Sales L, Zivick P 2018. Ap. J. 867:19
  126. Kallivayalil N, Wetzel AR, Simon JD 2015. arXiv:1503.01785
  127. Karlsson T, Bromm V, Bland-Hawthorn J 2013. Rev. Mod. Phys. 85:809–48
  128. Kasliwal MM, Nakar E, Singer LP 2017. Science 358:1559–65
    [Google Scholar]
  129. Kennedy R, Frenk C, Cole S, Benson A 2014. MNRAS 442:2487–95
  130. Kim D, Jerjen H 2015. Ap. J. Lett. 808:L39
  131. Kim D, Jerjen H, Mackey D 2015a. Ap. J. Lett. 804:L44
  132. Kim D, Jerjen H, Milone AP 2015b. Ap. J. 803:63
  133. Kim SY, Peter AHG, Hargis JR 2018. Phys. Rev. Lett. 121:211302
  134. King IR 1966. Astron. J. 71:64
  135. Kirby EN, Boylan-Kolchin M, Cohen JG 2013a. Ap. J. 770:16
  136. Kirby EN, Cohen JG, Guhathakurta P 2013b. Ap. J. 779:102
  137. Kirby EN, Cohen JG, Simon JD, Guhathakurta P 2015. Ap. J. Lett. 814:L7
  138. Kirby EN, Cohen JG, Simon JD 2017. Ap. J. 838:83
  139. Kirby EN, Guhathakurta P, Bolte M 2009. Ap. J. 705:328–46
  140. Kirby EN, Lanfranchi GA, Simon JD 2011. Ap. J. 727:78
  141. Kirby EN, Martin CL, Finlator K 2011. Ap. J. Lett. 742:L25
  142. Kirby EN, Simon JD, Cohen JG 2015. Ap. J. 810:56
  143. Kirby EN, Simon JD, Geha M 2008. Ap. J. Lett. 685:L43–46
  144. Kleyna J, Wilkinson MI, Evans NW 2002. MNRAS 330:792–806
  145. Kleyna JT, Geller MJ, Kenyon SJ, Kurtz MJ 1997. Astron. J. 113:624–33
  146. Kleyna JT, Wilkinson MI, Evans NW, Gilmore G 2005. Ap. J. Lett. 630:L141–44
  147. Klypin A, Kravtsov AV, Valenzuela O, Prada F 1999. Ap. J. 522:82–92
  148. Koch A, Feltzing S, Adén D, Matteucci F 2013. Astron. Astrophys. 554:A5
  149. Koch A, Hansen T, Feltzing S, Wilkinson MI 2014. Ap. J. 780:91
  150. Koch A, McWilliam A, Grebel EK 2008. Ap. J. Lett. 688:L13–16
  151. Koch A, Wilkinson MI, Kleyna JT 2009. Ap. J. 690:453–62
  152. Komiya Y, Shigeyama T 2016. Ap. J. 830:76
  153. Koposov S, Belokurov V, Evans NW 2008. Ap. J. 686:279–91
  154. Koposov SE, Belokurov V, Torrealba G, Evans NW 2015a. Ap. J. 805:130
  155. Koposov SE, Casey AR, Belokurov V 2015b. Ap. J. 811:62
  156. Koposov SE, Gilmore G, Walker MG 2011. Ap. J. 736:146
  157. Koposov SE, Walker MG, Belokurov V 2018. MNRAS 479:5343–61
  158. Kroupa P 2001. MNRAS 322:231–46
  159. Laevens BPM, Martin NF, Bernard EJ 2015a. Ap. J. 813:44
  160. Laevens BPM, Martin NF, Ibata RA 2015b. Ap. J. Lett. 802:L18
  161. Lai DK, Lee YS, Bolte M 2011. Ap. J. 738:51
  162. Lee DM, Johnston KV, Tumlinson J 2013a. Ap. J. 774:103
  163. Lee MG, Jang IS, Beaton R 2017a. Ap. J. Lett. 835:L27
  164. Lee YS, Beers TC, Kim YK 2017b. Ap. J. 836:91
  165. Lee YS, Beers TC, Masseron T 2013b. Astron. J. 146:132
  166. Lee YW, Joo JM, Sohn YJ 1999. Nature 402:55–57
  167. Li TS, Simon JD, Kuehn K 2018a. Ap. J. 866:22
  168. Li TS, Simon JD, Pace AB 2018b. Ap. J. 857:145
  169. Li YS, De Lucia G, Helmi A 2010. MNRAS 401:2036–52
  170. Lindegren L, Hernández J, Bombrun A 2018. Astron. Astrophys. 616:A2
  171. Livermore RC, Finkelstein SL, Lotz JM 2017. Ap. J. 835:113
  172. LSST Sci. Collab, Abell PA, Allison J 2009. arXiv:0912.0201
  173. MAGIC Collab, Ahnen ML, Ansoldi S 2016. J. Cosmol. Astropart. Phys. 2:039
  174. Majewski SR, Beaton RL, Patterson RJ 2007. Ap. J. Lett. 670:L9–12
  175. Majewski SR, Patterson RJ, Dinescu DI 2000. Proceedings of the 35th Liège International Astrophysical Colloquim: The Galactic Halo: From Globular Clusters to Field Stars 35 A Noels, P Magain, D Caro, E Jehin, G Parmentier, AA Thoul619–22 Liège, Belg.: Inst. Astrophys. Geophys. Liège
  176. Martin NF, de Jong JTA, Rix HW 2008. Ap. J. 684:1075–92
  177. Martin NF, Geha M, Ibata RA 2016a. MNRAS 458:L59–63
  178. Martin NF, Ibata RA, Chapman SC 2007. MNRAS 380:281–300
  179. Martin NF, Ibata RA, Collins MLM 2016b. Ap. J. 818:40
  180. Martin NF, Ibata RA, Irwin MJ 2006. MNRAS 371:1983–91
  181. Martin NF, Ibata RA, Lewis GF 2016c. Ap. J. 833:167
  182. Martin NF, McConnachie AW, Irwin M 2009. Ap. J. 705:758–65
  183. Martin NF, Nidever DL, Besla G 2015. Ap. J. Lett. 804:L5
  184. Martin NF, Schlafly EF, Slater CT 2013a. Ap. J. Lett. 779:L10
  185. Martin NF, Slater CT, Schlafly EF 2013b. Ap. J. 772:15
  186. Martinez GD, Minor QE, Bullock J 2011. Ap. J. 738:55
  187. Massari D, Helmi A 2018. Astron. Astrophys. 620:A155
  188. Mateo ML 1998. Annu. Rev. Astron. Astrophys. 36:435–506
  189. McConnachie AW 2012. Astron. J. 144:4
  190. McConnachie AW, Côté P 2010. Ap. J. Lett. 722:L209–14
  191. McConnachie AW, Huxor A, Martin NF 2008. Ap. J. 688:1009–20
  192. McConnachie AW, Irwin MJ, Ibata RA 2009. Nature 461:66–69
  193. Minor QE, Martinez G, Bullock J 2010. Ap. J. 721:1142–57
  194. Moe M, Kratter KM, Badenes C 2019. Ap. J. 875:61
  195. Moore B, Ghigna S, Governato F 1999. Ap. J. Lett. 524:L19–22
  196. Moster BP, Naab T, White SDM 2013. MNRAS 428:3121–38
  197. Muñoz RR, Carlin JL, Frinchaboy PM 2006. Ap. J. Lett. 650:L51–54
  198. Muñoz RR, Côté P, Santana FA 2018. Ap. J. 860:66
  199. Muñoz RR, Geha M, Willman B 2010. Astron. J. 140:138–51
  200. Muñoz RR, Majewski SR, Johnston KV 2008. Ap. J. 679:346–72
  201. Munshi F, Brooks AM, Applebaum E 2017.MNRAS. Submitted. arXiv:1705.06286
  202. Nagasawa DQ, Marshall JL, Li TS 2018. Ap. J. 852:99
  203. Najita J, Willman B, Finkbeiner DP 2016.arXiv:1610.01661
  204. Newton O, Cautun M, Jenkins A 2018. MNRAS 479:2853–70
  205. Niederste-Ostholt M, Belokurov V, Evans NW 2009. MNRAS 398:1771–81
  206. Nomoto K, Kobayashi C, Tominaga N 2013. Annu. Rev. Astron. Astrophys. 51:457–509
  207. Norris JE, Gilmore G, Wyse RFG 2010a. Ap. J. Lett. 722:L104–109
  208. Norris JE, Wyse RFG, Gilmore G 2010b. Ap. J. 723:1632–50
  209. Norris JE, Yong D, Gilmore G, Wyse RFG 2010c. Ap. J. 711:350–60
  210. Oh KS, Lin DNC, Aarseth SJ 1995. Ap. J. 442:142–58
  211. Okamoto S, Arimoto N, Yamada Y, Onodera M 2012. Ap. J. 744:96
  212. Olszewski EW, Aaronson M, Hill JM 1995. Astron. J. 110:2120
  213. Olszewski EW, Pryor C, Armandroff TE 1996. Astron. J. 111:750
  214. Oñorbe J, Boylan-Kolchin M, Bullock JS 2015. MNRAS 454:2092–106
  215. Pace AB, Li TS 2019. Ap. J. 875:77
  216. Peñarrubia J, Ludlow AD, Chanamé J, Walker MG 2016. MNRAS 461:L72–76
  217. Peñarrubia J, Navarro JF, McConnachie AW 2008. Ap. J. 673:226–40
  218. Pian E, D'Avanzo P, Benetti S 2017. Nature 551:67–70
  219. Piatek S, Pryor C 1995. Astron. J. 109:1071–85
  220. Placco VM, Frebel A, Beers TC, Stancliffe RJ 2014. Ap. J. 797:21
  221. Plummer HC 1911. MNRAS 71:460–70
  222. Porter TA, Johnson RP, Graham PW 2011. Annu. Rev. Astron. Astrophys. 49:155–94
  223. Putman ME, Bland-Hawthorn J, Veilleux S 2003. Ap. J. 597:948–56
  224. Read JI, Erkal D 2018. MNRAS Submitted. arXiv:1807.07093
  225. Regis M, Richter L, Colafrancesco S 2017. J. Cosmol. Astropart. Phys. 7:025
  226. Richardson JC, Irwin MJ, McConnachie AW 2011. Ap. J. 732:76
  227. Rocha M, Peter AHG, Bullock J 2012. MNRAS 425:231–44
  228. Roderick TA, Jerjen H, Mackey AD, Da Costa GS 2015. Ap. J. 804:134
  229. Rodriguez Wimberly MK, Cooper MC, Fillingham SP 2019. MNRAS 483:4031
  230. Roederer IU 2013. Astron. J. 145:26
  231. Roederer IU, Kirby EN 2014. MNRAS 440:2665–75
  232. Roederer IU, Mateo M, Bailey III JI 2016. Astron. J. 151:82
  233. Roederer IU, Preston GW, Thompson IB 2014. Astron. J. 147:136
  234. Romano D, Bellazzini M, Starkenburg E, Leaman R 2015. MNRAS 446:4220–31
  235. Ryan-Weber EV, Begum A, Oosterloo T 2008. MNRAS 384:535–40
  236. Safarzadeh M, Ji AP, Dooley GA 2018. MNRAS 476:5006–15
  237. Safarzadeh M, Scannapieco E 2017. MNRAS 471:2088–96
  238. Sakamoto T, Hasegawa T 2006. Ap. J. Lett. 653:L29–32
  239. Sales LV, Navarro JF, Kallivayalil N, Frenk CS 2017. MNRAS 465:1879–88
  240. Salpeter EE 1955. Ap. J. 121:161
  241. Salvadori S, Ferrara A 2009. MNRAS 395:L6–10
  242. Salvadori S, Skúladóttir Á, Tolstoy E 2015. MNRAS 454:1320–31
  243. Sand DJ, Crnojević D, Strader J 2014. Ap. J. Lett. 793:L7
  244. Sand DJ, Seth A, Olszewski EW 2010. Ap. J. 718:530–42
  245. Sand DJ, Strader J, Willman B 2012. Ap. J. 756:79
  246. Santana FA, Muñoz RR, Geha M 2013. Ap. J. 774:106
  247. Sawala T, Frenk CS, Fattahi A 2016. MNRAS 456:85–97
  248. Schechter P 1976. Ap. J. 203:297
  249. Searle L, Sargent WLW 1972. Ap. J. 173:25
  250. Shapley H 1938a. Harv. Coll. Obs. Bull. 908:1–11
    [Google Scholar]
  251. Shapley H 1938b. Nature 142:715–16
  252. Shappee BJ, Simon JD, Drout MR 2017. Science 358:1574–78
    [Google Scholar]
  253. Shen S, Madau P, Conroy C 2014. Ap. J. 792:99
  254. Shipp N, Drlica-Wagner A, Balbinot E 2018. Ap. J. 862:114
  255. Siegel DM, Barnes J, Metzger BD 2019. Nature 569:241
  256. Siegel MH, Shetrone MD, Irwin M 2008. Astron. J. 135:2084–94
  257. Simon JD 2018. Ap. J. 863:89
  258. Simon JD, Blitz L 2002. Ap. J. 574:726–39
  259. Simon JD, Frebel A, McWilliam A 2010. Ap. J. 716:446–52
  260. Simon JD, Geha M 2007. Ap. J. 670:313–31
  261. Simon JD, Geha M, Minor QE 2011. Ap. J. 733:46
  262. Simon JD, Li TS, Drlica-Wagner A 2017. Ap. J. 838:11
  263. Simpson CM, Bryan GL, Johnston KV 2013. MNRAS 432:1989–2011
  264. Slater CT, Bell EF, Martin NF 2011. Ap. J. Lett. 742:L14
  265. Smartt SJ, Chen TW, Jerkstrand A 2017. Nature 551:75–79
  266. Somerville RS 2002. Ap. J. Lett. 572:L23–26
  267. Spekkens K, Mason BS, Aguirre JE, Nhan B 2013. Ap. J. 773:61
  268. Spekkens K, Urbancic N, Mason BS 2014. Ap. J. Lett. 795:L5
  269. Spencer ME, Mateo M, Walker MG 2017. Astron. J. 153:254
  270. Spiniello C, Trager SC, Koopmans LVE, Chen YP 2012. Ap. J. Lett. 753:L32
  271. Spite M, Spite F, François P 2018. Astron. Astrophys. 617:A56
  272. Starkenburg TK, Helmi A, Sales LV 2016. Astron. Astrophys. 595:A56
  273. Strigari LE 2018. Rep. Prog. Phys. 81:056901
    [Google Scholar]
  274. Strigari LE, Bullock JS, Kaplinghat M 2007. Ap. J. Lett. 657:L1–4
  275. Strigari LE, Bullock JS, Kaplinghat M 2008. Nature 454:1096–97
  276. Tinsley BM 1979. Ap. J. 229:1046–56
  277. Tollerud EJ, Bullock JS, Strigari LE, Willman B 2008. Ap. J. 688:277–89
  278. Tolstoy E, Hill V, Tosi M 2009. Annu. Rev. Astron. Astrophys. 47:371–425
  279. Tolstoy E, Irwin MJ, Helmi A 2004. Ap. J. Lett. 617:L119–22
  280. Torrealba G, Belokurov V, Koposov SE 2018. MNRAS 475:5085–97
  281. Torrealba G, Koposov SE, Belokurov V, Irwin M 2016a. MNRAS 459:2370–78
  282. Torrealba G, Koposov SE, Belokurov V 2016b. MNRAS 463:712–22
  283. Tremonti CA, Heckman TM, Kauffmann G 2004. Ap. J. 613:898–913
  284. van Dokkum PG, Conroy C 2010. Nature 468:940–42
  285. Vargas LC, Geha M, Kirby EN, Simon JD 2013. Ap. J. 767:134
  286. Venn KA, Irwin M, Shetrone MD 2004. Astron. J. 128:1177–95
  287. Venn KA, Starkenburg E, Malo L 2017. MNRAS 466:3741–52
  288. Vincenzo F, Matteucci F, Vattakunnel S, Lanfranchi GA 2014. MNRAS 441:2815–30
  289. Vogt SS, Mateo M, Olszewski EW, Keane MJ 1995. Astron. J. 109:151–63
  290. Walker MG, Mateo M, Olszewski EW 2016. Ap. J. 819:53
  291. Walker MG, Mateo M, Olszewski EW 2009a. Astron. J. 137:3109–38
  292. Walker MG, Mateo M, Olszewski EW 2009b. Ap. J. 704:1274–87
  293. Walsh SM, Jerjen H, Willman B 2007. Ap. J. Lett. 662:L83–86
  294. Walsh SM, Willman B, Jerjen H 2009. Astron. J. 137:450–69
  295. Walsh SM, Willman B, Sand D 2008. Ap. J. 688:245–53
  296. Wang J, Frenk CS, Cooper AP 2013. MNRAS 429:1502–13
  297. Webster D, Bland-Hawthorn J, Sutherland R 2015. Ap. J. Lett. 799:L21
  298. Webster D, Frebel A, Bland-Hawthorn J 2016. Ap. J. 818:80
  299. Webster D, Sutherland R, Bland-Hawthorn J 2014. Ap. J. 796:11
  300. Weinberg DH, Bullock JS, Governato F 2015. PNAS 112:12249–55
    [Google Scholar]
  301. Weisz DR, Boylan-Kolchin M 2017. MNRAS 469:L83–88
  302. Weisz DR, Dolphin AE, Skillman ED 2014. Ap. J. 789:147
  303. Westmeier T, Staveley-Smith L, Calabretta M 2015. MNRAS 453:338–44
  304. Wetzel AR, Hopkins PF, Kim Jh 2016. Ap. J. Lett. 827:L23
  305. Wetzel AR, Tollerud EJ, Weisz DR 2015. Ap. J. Lett. 808:L27
  306. Wheeler C, Oñorbe J, Bullock JS 2015. MNRAS 453:1305–16
  307. Wheeler C, Pace AB, Bullock JS 2017. MNRAS 465:2420–31
  308. Whiting AB, Hau GKT, Irwin M, Verdugo M 2007. Astron. J. 133:715–33
  309. Willman B 2010. Adv. Astron. 2010:285454
    [Google Scholar]
  310. Willman B, Blanton MR, West AA 2005a. Astron. J. 129:2692–700
  311. Willman B, Dalcanton J, Ivezić Ž 2002. Astron. J. 124:2600–6
  312. Willman B, Dalcanton JJ, Martinez-Delgado D 2005b. Ap. J. Lett. 626:L85–88
  313. Willman B, Geha M, Strader J 2011. Astron. J. 142:128
  314. Willman B, Strader J 2012. Astron. J. 144:76
  315. Wilson AG 1955. Publ. Astron. Soc. Pac. 67:27–29
  316. Wise JH, Demchenko VG, Halicek MT 2014. MNRAS 442:2560–79
  317. Wolf J, Martinez GD, Bullock JS 2010. MNRAS 406:1220–37
  318. Yoon J, Beers TC, Dietz S 2018. Ap. J. 861:146
  319. Zucker DB, Belokurov V, Evans NW 2006a. Ap. J. Lett. 643:L103–106
  320. Zucker DB, Belokurov V, Evans NW 2006b. Ap. J. Lett. 650:L41–44
  321. Zucker DB, Kniazev AY, Bell EF 2004. Ap. J. Lett. 612:L121–124
  322. Zucker DB, Kniazev AY, Martínez-Delgado D 2007. Ap. J. Lett. 659:L21–24
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