2018MNRAS.479.5343K

Query : 2018MNRAS.479.5343K

2018MNRAS.479.5343K - Mon. Not. R. Astron. Soc., 479, 5343-5361 (2018/October-0)

Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge.

KOPOSOV S.E., WALKER M.G., BELOKUROV V., CASEY A.R., GERINGER-SAMETH A., MACKEY D., DA COSTA G., ERKAL D., JETHWA P., MATEO M., OLSZEWSKI E.W. and BAILEY J.I.

Abstract (from CDS):

We report the discovery of a nearby dwarf galaxy in the constellation of Hydrus, between the Large (LMC) and the Small Magellanic Clouds (SMC). Hydrus 1 is a mildly elliptical ultrafaint system with luminosity MV ∼ -4.7 and size 53 ± 3 pc, located 28 kpc from the Sun and 24 kpc from the LMC. From spectroscopy of ∼30 member stars, we measure a velocity dispersion of 2.7 ± 0.5 km s–1 and find tentative evidence for a radial velocity gradient consistent with 3 km s–1 rotation. Hydrus 1's velocity dispersion indicates that the system is dark matter dominated, but its dynamical mass-to-light ratio M/L=66+29–20 is significantly smaller than typical for ultrafaint dwarfs at similar luminosity. The kinematics and spatial position of Hydrus 1 make it a very plausible member of the family of satellites brought into the Milky Way by the Magellanic Clouds. While Hydrus 1's proximity and well-measured kinematics make it a promising target for dark matter annihilation searches, we find no evidence for significant gamma-ray emission from Hydrus 1. The new dwarf is a metal-poor galaxy with a mean metallicity [Fe/H]=-2.5 and [Fe/H] standard deviation of 0.4 dex, similar to other systems of similar luminosity. α abundances of Hyi 1 members indicate that star formation was extended, lasting between 0.1 and 1 Gyr, with self-enrichment dominated by supernova Ia. The dwarf also hosts a highly carbon-enhanced extremely metal-poor star with [Fe/H]∼-3.2 and [C/Fe] ∼ +3.0.

Abstract Copyright: © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): stars: general - globular clusters: general - Galaxy: halo - galaxies: dwarf - Local Group - Magellanic Clouds

VizieR on-line data: <Available at CDS (J/MNRAS/479/5343): table2.dat>

Nomenclature: NAME Hydrus I = NAME Hyi I. Table 2: [KWB2018] NNN N=139 among (Nos 1-235).

Simbad objects: 159

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Number of rows : 159
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NAME Magellanic Stream HVC 00 32 -30.0           ~ 1079 1
2 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 12317 1
4 9Y-MST J0223-7941 BLL 02 24 01.3 -79 41 36           ~ 25 0
5 [KWB2018] 110 * 02 25 04.74 -79 14 17.1           ~ 1 0
6 [KWB2018] 114 * 02 25 15.16 -79 15 49.5           ~ 1 0
7 [KWB2018] 131 * 02 25 16.38 -79 26 23.5           ~ 1 0
8 [KWB2018] 112 * 02 25 17.04 -79 14 46.2           ~ 1 0
9 [KWB2018] 113 Pe* 02 25 20.79 -79 15 07.8           ~ 1 0
10 [KWB2018] 111 * 02 25 25.91 -79 14 23.7           ~ 1 0
11 [KWB2018] 108 * 02 25 31.96 -79 17 40.3           ~ 1 0
12 [KWB2018] 137 * 02 25 38.73 -79 22 59.4           ~ 1 0
13 [KWB2018] 105 Pe* 02 25 41.55 -79 15 46.0           ~ 1 0
14 [KWB2018] 107 Pe* 02 25 44.72 -79 17 10.8           ~ 1 0
15 [KWB2018] 142 * 02 26 23.72 -79 23 08.5           ~ 1 0
16 [KWB2018] 139 Pe* 02 26 24.74 -79 26 04.2           ~ 1 0
17 [KWB2018] 126 * 02 26 39.79 -79 15 27.9           ~ 1 0
18 [KWB2018] 144 * 02 26 50.22 -79 19 23.0           ~ 1 0
19 [KWB2018] 92 * 02 26 54.17 -79 27 25.0           ~ 1 0
20 [KWB2018] 125 * 02 27 00.03 -79 14 28.6           ~ 1 0
21 [KWB2018] 94 * 02 27 07.05 -79 25 28.7           ~ 1 0
22 [KWB2018] 93 Pe* 02 27 07.82 -79 25 52.5           ~ 1 0
23 [KWB2018] 128 * 02 27 10.57 -79 15 54.5           ~ 1 0
24 [KWB2018] 124 * 02 27 11.94 -79 12 49.7           ~ 1 0
25 [KWB2018] 98 * 02 27 19.02 -79 23 47.3           ~ 1 0
26 [KWB2018] 130 * 02 27 19.34 -79 16 18.7           ~ 1 0
27 OGLE SMC-RRLYR-6309 RR* 02 27 27.1153703616 -79 20 25.662119676     17.879   17.360 ~ 4 0
28 [KWB2018] 103 * 02 27 28.52 -79 20 00.4           ~ 1 0
29 [KWB2018] 165 Pe* 02 27 37.37 -79 22 13.7           ~ 1 0
30 [KWB2018] 167 * 02 27 39.48 -79 19 39.8           ~ 1 0
31 [KWB2018] 119 Pe* 02 27 42.97 -79 16 04.9           ~ 1 0
32 [KWB2018] 162 * 02 27 43.95 -79 23 40.8           ~ 1 0
33 [KWB2018] 117 * 02 27 47.19 -79 07 37.8           ~ 1 0
34 [KWB2018] 163 * 02 27 48.42 -79 23 20.0           ~ 1 0
35 [KWB2018] 120 * 02 27 48.99 -79 17 30.0           ~ 1 0
36 [KWB2018] 91 * 02 28 00.59 -79 18 35.7           ~ 1 0
37 [KWB2018] 175 * 02 28 01.30 -79 19 39.1           ~ 1 0
38 [KWB2018] 172 Pe* 02 28 05.15 -79 24 28.1           ~ 1 0
39 [KWB2018] 170 Pe* 02 28 05.28 -79 25 45.6           ~ 1 0
40 [KWB2018] 89 * 02 28 07.38 -79 15 15.9           ~ 1 0
41 [KWB2018] 168 * 02 28 08.87 -79 27 02.3           ~ 1 0
42 [KWB2018] 90 * 02 28 09.56 -79 18 06.9           ~ 1 0
43 [KWB2018] 88 Pe* 02 28 11.88 -79 15 12.0           ~ 1 0
44 [KWB2018] 86 Pe* 02 28 17.12 -79 13 50.0           ~ 1 0
45 [KWB2018] 171 Pe* 02 28 20.54 -79 24 34.1           ~ 1 0
46 [KWB2018] 77 Pe* 02 28 21.47 -79 12 25.2           ~ 1 0
47 [KWB2018] 60 * 02 28 22.43 -79 25 38.7           ~ 1 0
48 [KWB2018] 66 * 02 28 25.40 -79 23 05.5           ~ 1 0
49 [KWB2018] 63 * 02 28 30.07 -79 24 57.6           ~ 1 0
50 [KWB2018] 61 Pe* 02 28 32.77 -79 25 30.4           ~ 1 0
51 [KWB2018] 67 * 02 28 33.7261189536 -79 20 09.800071584           ~ 2 0
52 [KWB2018] 64 * 02 28 35.99 -79 23 57.6           ~ 1 0
53 [KWB2018] 74 * 02 28 41.19 -79 20 22.7           ~ 1 0
54 [KWB2018] 154 Pe* 02 28 46.10 -79 12 40.8           ~ 1 0
55 [KWB2018] 68 Pe* 02 28 47.97 -79 26 36.3           ~ 1 0
56 [KWB2018] 153 Pe* 02 28 52.58 -79 10 41.6           ~ 1 0
57 [KWB2018] 160 * 02 28 53.03 -79 16 47.4           ~ 1 0
58 [KWB2018] 70 * 02 28 56.67 -79 23 01.8           ~ 1 0
59 [KWB2018] 159 * 02 28 58.58 -79 16 31.6           ~ 1 0
60 [KWB2018] 75 Pe* 02 28 59.56 -79 19 55.5           ~ 1 0
61 [KWB2018] 69 Pe* 02 28 59.64 -79 25 25.3           ~ 1 0
62 [KWB2018] 156 * 02 28 59.91 -79 14 16.7           ~ 1 0
63 [KWB2018] 72 Pe* 02 29 01.22 -79 21 21.4           ~ 1 0
64 [KWB2018] 155 * 02 29 02.47 -79 12 57.5           ~ 1 0
65 [KWB2018] 71 Pe* 02 29 03.77 -79 21 45.0           ~ 1 0
66 [KWB2018] 31 * 02 29 07.45 -79 25 44.7           ~ 1 0
67 [KWB2018] 147 Pe* 02 29 09.69 -79 12 37.3           ~ 1 0
68 [KWB2018] 151 Pe* 02 29 11.05 -79 17 57.7           ~ 1 0
69 [KWB2018] 146 Pe* 02 29 12.28 -79 11 21.5           ~ 1 0
70 [KWB2018] 34 Pe* 02 29 13.03 -79 20 20.7           ~ 1 0
71 [KWB2018] 145 * 02 29 15.31 -79 07 22.3           ~ 1 0
72 [KWB2018] 149 Pe* 02 29 16.41 -79 16 03.6           ~ 1 0
73 [KWB2018] 33 * 02 29 23.97 -79 21 05.1           ~ 1 0
74 [KWB2018] 150 Pe* 02 29 26.67 -79 17 11.9           ~ 1 0
75 [KWB2018] 152 Pe* 02 29 28.63 -79 18 20.0           ~ 1 0
76 [KWB2018] 32 Pe* 02 29 28.88 -79 23 59.9           ~ 1 0
77 [KWB2018] 39 * 02 29 31.52 -79 19 58.6           ~ 1 0
78 NAME Hydrus I G 02 29 33.4 -79 18 32           ~ 80 0
79 [KWB2018] 188 Pe* 02 29 35.06 -79 17 26.3           ~ 1 0
80 [KWB2018] 185 Pe* 02 29 40.65 -79 12 49.7           ~ 1 0
81 [KWB2018] 180 * 02 29 43.06 -79 16 44.5           ~ 1 0
82 OGLE SMC-RRLYR-6316 RR* 02 29 43.9140525288 -79 16 38.318234520     18.003   17.353 ~ 7 0
83 [KWB2018] 37 * 02 29 46.37 -79 24 57.3           ~ 1 0
84 [KWB2018] 40 * 02 29 49.53 -79 19 50.1           ~ 1 0
85 [KWB2018] 177 * 02 29 51.46 -79 11 37.5           ~ 1 0
86 [KWB2018] 38 * 02 29 52.71 -79 22 53.9           ~ 1 0
87 [KWB2018] 182 Pe* 02 29 55.76 -79 18 18.2           ~ 1 0
88 [KWB2018] 176 * 02 30 03.27 -79 09 51.9           ~ 1 0
89 [KWB2018] 195 * 02 30 04.53 -79 20 52.6           ~ 1 0
90 [KWB2018] 54 * 02 30 05.31 -79 10 08.7           ~ 1 0
91 [KWB2018] 192 * 02 30 09.72 -79 25 53.7           ~ 1 0
92 [KWB2018] 59 Pe* 02 30 17.82 -79 17 29.8           ~ 1 0
93 [KWB2018] 55 * 02 30 23.17 -79 10 12.7           ~ 1 0
94 [KWB2018] 201 * 02 30 23.30 -79 24 48.1           ~ 1 0
95 [KWB2018] 199 Pe* 02 30 24.49 -79 25 28.7           ~ 1 0
96 [KWB2018] 203 Pe* 02 30 29.69 -79 22 39.5           ~ 1 0
97 [KWB2018] 202 Pe* 02 30 31.95 -79 23 54.3           ~ 1 0
98 [KWB2018] 52 Pe* 02 30 33.47 -79 18 04.1           ~ 1 0
99 [KWB2018] 46 * 02 30 36.93 -79 11 52.6           ~ 1 0
100 [KWB2018] 49 Pe* 02 30 37.60 -79 14 51.8           ~ 1 0
101 [KWB2018] 51 * 02 30 38.83 -79 17 57.5           ~ 1 0
102 [KWB2018] 206 * 02 30 40.79 -79 19 29.8           ~ 1 0
103 [KWB2018] 205 * 02 30 44.98 -79 21 21.8           ~ 1 0
104 [KWB2018] 200 * 02 30 45.25 -79 24 57.2           ~ 1 0
105 [KWB2018] 2 * 02 30 45.5624341512 -79 21 36.146023056           ~ 2 0
106 [KWB2018] 5 Pe* 02 30 46.5587728992 -79 20 55.834989360           ~ 2 0
107 [KWB2018] 7 * 02 30 46.79 -79 19 47.9           ~ 1 0
108 [KWB2018] 3 * 02 30 49.4752025016 -79 21 20.568222612           ~ 2 0
109 [KWB2018] 216 Pe* 02 30 52.09 -79 10 25.4           ~ 1 0
110 [KWB2018] 6 * 02 30 53.4035981208 -79 20 04.387336008           ~ 2 0
111 [KWB2018] 215 * 02 30 56.29 -79 09 58.6           ~ 1 0
112 [KWB2018] 4 Pe* 02 30 57.6538852128 -79 21 15.624087228           ~ 2 0
113 [KWB2018] 12 Pe* 02 31 01.13 -79 20 56.4           ~ 1 0
114 [KWB2018] 221 Pe* 02 31 02.36 -79 18 36.6           ~ 1 0
115 [KWB2018] 15 * 02 31 05.15 -79 19 21.2           ~ 1 0
116 [KWB2018] 220 * 02 31 06.34 -79 18 21.7           ~ 1 0
117 [KWB2018] 10 Pe* 02 31 11.5403795496 -79 24 24.040693944           ~ 2 0
118 [KWB2018] 217 Pe* 02 31 13.49 -79 12 07.8           ~ 1 0
119 [KWB2018] 14 Pe* 02 31 15.21 -79 19 44.9           ~ 1 0
120 [KWB2018] 210 Pe* 02 31 16.53 -79 15 41.8           ~ 1 0
121 [KWB2018] 219 Pe* 02 31 16.72 -79 17 22.9           ~ 1 0
122 [KWB2018] 11 Pe* 02 31 20.1245071416 -79 23 06.490735188           ~ 2 0
123 [KWB2018] 207 Pe* 02 31 29.79 -79 13 30.9           ~ 1 0
124 [KWB2018] 209 Pe* 02 31 30.29 -79 14 12.7           ~ 1 0
125 [KWB2018] 212 * 02 31 30.48 -79 16 20.1           ~ 1 0
126 [KWB2018] 225 Pe* 02 31 31.55 -79 20 48.2           ~ 1 0
127 [KWB2018] 226 Pe* 02 31 36.46 -79 20 06.0           ~ 1 0
128 [KWB2018] 222 Pe* 02 31 36.77 -79 23 49.4           ~ 1 0
129 [KWB2018] 228 * 02 31 38.26 -79 19 25.2           ~ 1 0
130 [KWB2018] 27 * 02 31 43.26 -79 15 17.8           ~ 1 0
131 [KWB2018] 23 * 02 31 44.30 -79 10 54.9           ~ 1 0
132 [KWB2018] 25 * 02 31 45.63 -79 11 49.6           ~ 1 0
133 [KWB2018] 29 * 02 31 46.65 -79 18 17.7           ~ 1 0
134 [KWB2018] 30 Pe* 02 31 48.36 -79 18 51.2           ~ 1 0
135 [KWB2018] 28 * 02 31 50.40 -79 16 22.9           ~ 1 0
136 [KWB2018] 24 * 02 31 52.94 -79 11 36.1           ~ 1 0
137 [KWB2018] 26 Pe* 02 31 55.62 -79 14 18.5           ~ 1 0
138 [KWB2018] 16 * 02 32 05.13 -79 11 44.2           ~ 1 0
139 [KWB2018] 231 * 02 32 05.68 -79 22 28.4           ~ 1 0
140 [KWB2018] 17 * 02 32 20.41 -79 13 18.8           ~ 1 0
141 [KWB2018] 22 * 02 32 21.22 -79 18 34.6           ~ 1 0
142 OGLE SMC-RRLYR-6325 RR* 02 32 30.3806488104 -79 27 27.097882956     17.986   17.314 ~ 9 0
143 [KWB2018] 233 * 02 32 32.74 -79 20 40.7           ~ 1 0
144 [KWB2018] 232 * 02 32 36.59 -79 21 22.3           ~ 1 0
145 [KWB2018] 235 Pe* 02 32 36.92 -79 20 27.4           ~ 1 0
146 [KWB2018] 20 * 02 32 39.18 -79 16 39.8           ~ 1 0
147 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7988 0
148 NAME Magellanic Bridge HI 03 11 -77.5           ~ 522 1
149 NAME Reticulum II G 03 35 42.1 -54 02 57           ~ 375 0
150 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
151 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 517 1
152 NAME Crater Cluster GlC 11 36 16.20 -10 52 38.8           ~ 117 1
153 NAME Crater II Dwarf Galaxy G 11 49 14 -18 24.8           ~ 176 0
154 NAME Hydra II G 12 21 42.1 -31 59 07           ~ 118 0
155 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 491 0
156 Z 318-18 G 15 09 08.0 +67 13 21   13.60 10.6     ~ 1459 0
157 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 16269 0
158 NAME Sagittarius II Gl? 19 52 40.5 -22 04 05           ~ 97 0
159 NAME Local Group GrG ~ ~           ~ 9325 0

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