Tidal streams in the Galactic halo: Evidence for the Sagittarius northern stream or traces of a new nearby dwarf galaxy

Abstract

Standard cosmology predicts that dwarfs were the first galaxies to be formed in the Universe and that many of them merge afterwards to form bigger galaxies such as the Milky Way. This process would have left behind traces such as tidal debris or star streams in the outer halo. We report here the detection of a very low density stellar system at 50+/- 10 kpc from the Galactic center that could be related to the merger process. It could form part of the Sagittarius northern stream or, alternatively, could be the trace of a hitherto unknown dwarf galaxy. The dwarf galaxy in Sagittarius, the closest satellite of the Milky Way, is currently being tidally disrupted and is a ``living'' test for galaxy formation theories. The system found here is 60 deg away from the center of the Sagittarius galaxy. If it is really associated with this galaxy, it would confirm predictions of dynamical interaction models indicating that tidal debris from Sagittarius could extend along a stream completely enveloping the Milky Way in a polar orbit.

14 pages, 3 figures, acepted for publication in Astrophysical Journal Letters

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Cited by in corpus (67)

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• Mapping the Galactic Halo VIII: Quantifying substructure
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• Detection of the Main Sequence Turn-off of a Newly Discovered Milky Way Halo Structure in the Triangulum-Andromeda Region
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• Tracing the Sgr Stream with 2MASS. Detection of Stream stars around Outer Halo Globular Clusters
• Spectroscopic Survey of the Galaxy with Gaia II. The expected science yield from the Radial Velocity Spectrometer
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• Hidden depths in the local Universe: The Stellar Stream Legacy Survey
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• Satellite decay in flattened dark matter haloes
• Remnants of Sagittarius Dwarf Spheroidal Galaxy around the young globular cluster Palomar 12
• The Virgo stellar over-density: Mapping the infall of the Sagittarius tidal stream onto the Milky Way disk
• Environmental mechanisms shaping the nature of dwarf spheroidal galaxies; the view of computer simulations
• Selection of Metal-poor Giant Stars Using the Sloan Digital Sky Survey Photometric System
• A search for stellar tidal debris of defunct dwarf galaxies around globular clusters in the inner Galactic halo
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• A Pan-STARRS1 View of the Bifurcated Sagittarius Stream
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• The Sagittarius stream in Gaia eDR3 and the origin of the bifurcations
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• Hubble Space Telescope Proper Motions along the Sagittarius Stream: I. Observations and Results for Stars in Four Fields
• The slowing down of galaxy disks in dissipationless minor mergers
• Exposing Sgr tidal debris behind the Galactic disk with M giants selected in WISE$\cap$2MASS
• Quantifying the Smoothness of the Stellar Halo: A Link to Accretion History
• The southern leading and trailing wraps of the Sagittarius tidal stream around the globular cluster Whiting1
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• Exploring Halo Substructure with Giant Stars III: First Results from the Grid Giant Star Survey and Discovery of a Possible Nearby Sagittarius Tidal Structure in Virgo
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• Prospects for a Dark Matter annihilation signal towards the Sagittarius dwarf galaxy with ground based Cherenkov telescopes
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• Red Supergiants in the Disk of M81: Tracing the Spatial Distribution of Star Formation 25 Million Years in the Past
• The Next Generation Virgo Cluster Survey. XIX. Tomography of Milky Way Substructures in the NGVS Footprint
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• Stellar tidal streams around nearby spiral galaxies with deep imaging from amateur telescopes
• Properties of Stars in the Subaru Deep Field
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