@article{403c0fcf965240c29644c92ceea96a1c,
title = "Snake in the Clouds: A new nearby dwarf galaxy in the Magellanic bridge",
abstract = "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 kms-1 and find tentative evidence for a radial velocity gradient consistent with 3 kms-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 kinematicsmake it a promising target for darkmatter 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.",
keywords = "Galaxies: dwarf, Galaxy: halo, Globular clusters: general, Local group, Magellanic Clouds, Stars: general",
author = "Koposov, {Sergey E.} and Walker, {Matthew G.} and Vasily Belokurov and Casey, {Andrew R.} and Alex Geringer-Sameth and Dougal Mackey and {Da Costa}, Gary and Denis Erkal and Prashin Jethwa and Mario Mateo and Olszewski, {Edward W.} and Bailey, {John I.}",
note = "Funding Information: This project used data obtained with the DECam, which was constructed by the DES collaboration. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundac¸{\~a}o Carlos Chagas Filho de Amparo {\`a} Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cient{\'i}fico e Tecnol{\'o}gico and the Minist{\'e}rio da Ci{\^e}ncia, Tecnologia e Inovac{\~a}o, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the DES. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones En{\'e}rgeticas, Medioambi-entales y Tecnol{\'o}gicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgen{\"o}ssische Technische Hochschule (ETH) Z{\"u}rich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ci{\`e}ncies de l{\textquoteright}Espai (IEEC/CSIC), the Institut de F{\'i}sica d{\textquoteright}Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig–Maximilians Univer-sit{\"a}t M{\"u}nchen and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, the Ohio State University, the OzDES Membership Consortium the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University. Funding Information: ARC acknowledges support from the Australian Research Council (ARC) through Discovery Project grant DP160100637. DM is supported by an ARC Future Fellowship (FT160100206). DM and GDC acknowledge support from ARC Discovery Project DP150103294. MM acknowledges support from NSF grant AST1312997. MGW acknowledges support from NSF grant AST1412999. E.O. acknowledges support from NSF grant AST1313006. The research leading to these results has received funding from the European Research Council under the European Union{\textquoteright}s Seventh Framework Programme (FP/2007-2013)/ERC grant agreement number 308024. Funding Information: ARC acknowledges support from the Australian Research Council (ARC) through Discovery Project grant DP160100637. DM is supported by an ARC Future Fellowship (FT160100206). DM and GDC acknowledge support from ARC Discovery Project DP150103294. MM acknowledges support from NSF grant AST1312997. MGW acknowledges support from NSF grant AST1312997. E.O. acknowledges support from NSF grant AST1313006. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC grant agreement number 308024. This project used data obtained with the DECam, which was constructed by the DES collaboration. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, theMinistry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas AandM University, Financiadora de Estudos e Projetos, Funda{\c c}{\~a}o Carlos Chagas Filho de Amparo{\`a} Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cient{\'i}fico e Tecnol{\'o}gico and the Minist{\'e}rio da Ci{\^e}ncia, Tecnologia e Inovac{\~a}o, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the DES. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones En{\'e}rgeticas, Medioambientales y Tecnol{\'o}gicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgen{\"o}ssische Technische Hochschule (ETH) Z{\"u}rich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ci{\`e}ncies de l'Espai (IEEC/CSIC), the Institut de F{\'i}sica d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universit{\"a}t M{\"u}nchen and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, the Ohio State University, the OzDES Membership Consortium the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and TexasA and M University. This work hasmade use of data from the European Space Agency mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https:// www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Based on observations at CTIO, National Optical Astronomy Observatory (NOAO Prop. 2016A-0618 and 2017B-0906; PI: D. Mackey), which is operated by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation. Publisher Copyright: {\textcopyright} 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.",
year = "2018",
month = oct,
day = "1",
doi = "10.1093/mnras/sty1772",
language = "English (US)",
volume = "479",
pages = "5343--5361",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",
}