2018MNRAS.479.5343K


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.12CEST12:18:39

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

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

Status at CDS : Large table(s) will be appraised for possible ingestion in VizieR.

Simbad objects: 20

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Number of rows : 20

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME Magellanic Stream HVC 00 32 -30.0           ~ 846 1
2 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11306 1
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9790 1
4 9Y-MST J0223-7941 BLL 02 24 01.3 -79 41 36           ~ 12 0
5 NAME Hydrus I G 02 29 33.4 -79 18 32           ~ 27 0
6 OGLE SMC-RRLYR-6316 RR* 02 29 43.9123779390 -79 16 38.318331275     18.003   17.353 ~ 5 0
7 OGLE SMC-RRLYR-6325 RR* 02 32 30.3806348453 -79 27 27.099155968     17.986   17.314 ~ 5 0
8 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5932 1
9 NAME Magellanic Bridge HI 03 11 -77.5           ~ 365 1
10 NAME Reticulum II G 03 35 42.1 -54 02 57           ~ 208 0
11 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15352 1
12 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 378 1
13 NAME Crater Cluster GlC 11 36 16.20 -10 52 38.8           ~ 66 1
14 NAME Crater II Dwarf Galaxy G 11 49 14 -18 24.8           ~ 76 0
15 NAME Hydra II G 12 21 42.1 -31 59 07           ~ 64 0
16 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 358 0
17 NAME UMi Galaxy G 15 09 11.34 +67 12 51.7   13.60 10.6     ~ 1214 0
18 NAME Galactic Center gam 17 45 39.60213 -29 00 22.0000           ~ 12176 0
19 NAME Laevens 5 Gl? 19 52 40.5 -22 04 05           ~ 39 0
20 NAME Local Group GrG ~ ~           ~ 7260 0

    Equat.    Gal    SGal    Ecl

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