A Dwarf Disrupting -- Andromeda XXVII and the North West Stream

Abstract

We present a kinematic and spectroscopic analysis of 38 red giant branch stars, in 7 fields, spanning the dwarf spheroidal galaxy Andromeda XXVII and the upper segment of the North West Stream. Both features are located in the outer halo of the Andromeda galaxy at a projected radius of 50-80 kpc, with the stream extending for $\sim$3${}^{\circ }$ on the sky. Our data is obtained as part of the PAndAS survey and enables us to confirm that Andromeda XXVII's heliocentric distance is 827 $\pm$ 47 kpc and spectroscopic metallicity is -2.1${}_{-0.5}^{+0.4}$. We also re-derive Andromeda XXVII's kinematic properties, measuring a systemic velocity = -526.1${}_{-11.0}^{+10.0}${\kms} and a velocity dispersion that we find to be non-Gaussian but for which we derive a formal value of 27.0${}_{-3.9}^{+2.2}${\kms}. In the upper segment of the North West Stream we measure mean values for the metallicity = -1.8$\pm$0.4, systemic velocity = -519.4 $\pm$4.0{\kms} and velocity dispersion = 10.0$\pm$4.0{\kms}. We also detect a velocity gradient of 1.7$\pm$0.3 {\kms} kpc${}^{-1}$ on an infall trajectory towards M31. With a similar gradient, acting in the same direction, in the lower segment we suggest that the North West Stream is not a single structure. As the properties of the upper segment of the North West Stream and Andromeda XXVII are consistent within ~90\% confidence limits, it is likely that the two are related and plausible that Andromeda XXVII is the progenitor of this stream.

arXiv comment15 pages, 10 figures

References in corpus (83)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The NumPy array: a structure for efficient numerical computation
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• Dwarf Galaxies of the Local Group
• The observed properties of dwarf galaxies in and around the Local Group
• The Dartmouth Stellar Evolution Database
• The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies
• The large-scale structure of the Universe
• The remnants of galaxy formation from a panoramic survey of the region around M31
• A giant stream of metal-rich stars in the halo of the galaxy M31
• Evidence for Stellar Substructure in the Halo and Outer Disk of M31
• Constraining the Milky Way potential with a 6-D phase-space map of the GD-1 stellar stream
• Dark matter and cosmic structure
• The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream
• Data analysis recipes: Using Markov Chain Monte Carlo
• Galactic Globular Cluster Metallicity Scale from the Calcium Triplet. II. Rankings, Comparisons and Puzzles
• An Orphan in the "Field of Streams"
• Stellar Streams Discovered in the Dark Energy Survey
• The large-scale structure of the halo of the Andromeda Galaxy Part I: global stellar density, morphology and metallicity properties
• The Disruption of the Sagittarius Dwarf Galaxy.
• Four New Stellar Debris Streams in the Galactic Halo
• Uncovering CDM halo substructure with tidal streams
• Detection of a 60 Degree-Long Dwarf Galaxy Debris Stream
• On the accretion origin of a vast extended stellar disk around the Andromeda galaxy
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Precession of the Sagittarius stream
• Analysis and calibration of CaII triplet spectroscopy of Red Giant Branch stars from VLT/FLAMES observations
• A kinematic study of the Andromeda dwarf spheroidal system
• PAndAS' progeny: extending the M31 dwarf galaxy cabal
• The large-scale structure of the halo of the Andromeda galaxy II. Hierarchical structure in the Pan-Andromeda Archaeological Survey
• Taking measure of the Andromeda halo: a kinematic analysis of the giant stream surrounding M31
• A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude (Part II); Distances to the Satellites of M31
• The Streams of the Gaping Abyss: A population of entangled stellar streams surrounding the Inner Galaxy
• Evidence for an accretion origin for the outer halo globular cluster system of M31
• The number and size of subhalo-induced gaps in stellar streams
• The SPLASH Survey: Spectroscopy of 15 M31 Dwarf Spheroidal Satellite Galaxies
• The PAndAS view of the Andromeda satellite system - II. Detailed properties of 23 M31 dwarf spheroidal galaxies
• Dark Matter Sub-Halo Counts via Star Stream Crossings
• Inferring the Andromeda Galaxy's mass from its giant southern stream with Bayesian simulation sampling
• A kinematically selected, metal-poor stellar halo in the outskirts of M31
• Discovery of a New, Polar-Orbiting Debris Stream in the Milky Way Stellar Halo
• The three dimensional structure of the giant stellar stream in Andromeda
• Piercing the Milky Way: an all-sky view of the Orphan Stream
• Constraining the Milky Way Halo Potential with the GD-1 stellar stream
• Dynamics and Stellar Content of the Giant Southern Stream in M31. I. Keck Spectroscopy of Red Giant Stars
• The SPLASH Survey: Internal Kinematics, Chemical Abundances, and Masses of the Andromeda I, II, III, VII, X, and XIV dSphs
• A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey
• Mass modelling of dwarf spheroidal galaxies: the effect of unbound stars from tidal tails and the Milky Way
• Stellar Streams and Clouds in the Galactic Halo
• The outer halo globular cluster system of M31 - II. Kinematics
• The globular cluster NGC 2419: a crucible for theories of gravity
• The PAndAS Field of Streams: stellar structures in the Milky Way halo toward Andromeda and Triangulum
• The Stellar Populations of M31 Halo Substructure
• The SPLASH Survey: A Spectroscopic Portrait of Andromeda's Giant Southern Stream
• Kinematics of Outer Halo Globular Clusters in M31
• A new low mass for the Hercules dSph: the end of a common mass scale for the dwarfs?
• The tidal trail of NGC205?
• A New Giant Stellar Structure in the Outer Halo of M31
• Strangers in the night: Discovery of a dwarf spheroidal galaxy on its first Local Group infall
• A Keck/DEIMOS spectroscopic survey of the faint M31 satellites And IX, And XI, And XII, and And XIII
• PAndAS in the mist: The stellar and gaseous mass within the halos of M31 and M33
• Metallicity Evolution of the Six Most Luminous M31 Dwarf Satellites
• A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales
• The kinematic identification of a thick stellar disc in M31
• Spectroscopy of the three distant Andromedan satellites Cassiopeia III, Lacerta I, and Perseus I
• A spectroscopic survey of Andromeda's Western Shelf
• Young accreted globular clusters in the outer halo of M31
• Constraining the Milky Way Halo Shape Using Thin Streams
• Dynamical evidence for a strong tidal interaction between the Milky Way and its satellite, Leo V
• Resolving the Stellar Outskirts of M31 and M33
• The Hercules satellite: a stellar stream in the Milky Way halo?
• Substructure and Tidal Streams in the Andromeda Galaxy and its Satellites
• Bootes III is a disrupting dwarf galaxy associated with the Styx stellar stream
• Density Variations in the NW Star Stream of M31
• Stellar Stream and Halo Structure in the Andromeda Galaxy From a Subaru/Hyper Suprime-Cam Survey
• Major Substructure in the M31 Outer Halo: the South-West Cloud
• The Andromeda Stream
• The nature of the progenitor of the M31 North-western stream: globular clusters as milestones of its orbit
• Variable Stars and Stellar Populations in Andromeda XXVII: IV. An off-centered, disrupted galaxy

Cited by in corpus (5)

• The PAndAS View of the Andromeda Satellite System. IV Global properties
• On the origin of the asymmetric dwarf galaxy distribution around Andromeda
• Metallicities of Outer Halo M31 Globular Clusters from Integrated Light Calcium-II Triplet Spectroscopy
• One Stream or Two -- Exploring Andromeda's North West Stream
• Properties of the Lower Segment of M31's North West Stream