ED-2: a cold but not so narrow stellar stream crossing the Solar neighbourhood

Abstract

ED-2 is a stellar stream identified as a compact group in integrals of motion space in a local sample of halo stars from the third Gaia data release. Here we investigate its nature and possible association with known halo substructures. We explore the current properties of ED-2 members in phase-space, and also analyse the expected distribution via orbit integration. In addition, we study the metallicity of ED-2 using APOGEE DR17 and LAMOST DR8 (and re-calibrated DR3). ED-2 forms a compact group in the $x-z$ (or $R-z$) plane, showing a pancake-like structure as it crosses the Solar neighbourhood. Dynamically it is most similar the globular clusters NGC 3201 and NGC 6101, and the stellar stream Ylgr and Phlegethon. However, its orbit is sufficiently different that none of these objects is likely to be ED-2's progenitor. We also find ED-2 to be quite metal-poor, with all of its stars $[Fe/H]\le -2.42$, with a median $[Fe/H]=-2.60_{-0.21}^{+0.20}$. At this low metallicity, it is unlikely that ED-2 stems from any known globular cluster, instead, ED-2 seems to be in a similar category as the recently discovered Phoenix and C-19 stellar streams. We find that ED-2 members are scattered across the whole sky, which is due to its current orbital phase. We predict that as this object moves to its next apocentre it will acquire an on-sky morphology that is akin to cold stellar streams. Finally, since ED-2 is nearing pericentre, we predict that additional members found below the plane should have large radial velocities, close to $\sim$ 500 km/s in the present-day direction of the globular cluster NGC 6101.

Accepted for publication in A&A; animated Figure 6 available here https://youtu.be/B6UzryhfrHY

References in corpus (25)

• The NumPy array: a structure for efficient numerical computation
• Gaia Early Data Release 3: The astrometric solution
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• Gaia EDR3 view on Galactic globular clusters
• Streams, substructures and the early history of the Milky Way
• Detection of a 63 Degree Cold Stellar Stream in the Sloan Digital Sky Survey
• An Orphan in the "Field of Streams"
• Gaia Early Data Release 3: Summary of the contents and survey properties
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• The Streams of the Gaping Abyss: A population of entangled stellar streams surrounding the Inner Galaxy
• Charting the Galactic acceleration field I. A search for stellar streams with Gaia DR2 and EDR3 with follow-up from ESPaDOnS and UVES
• Dynamical Relics of the Ancient Galactic Halo
• Robust Data-driven Metallicities for 175 Million Stars from Gaia XP Spectra
• Measuring the Mass of the Large Magellanic Cloud with Stellar Streams Observed by $S^5$
• Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
• Gaia Early Data Release 3: The Galactic anticentre
• Orbital Clustering Identifies the Origins of Galactic Stellar Streams
• Fourteen candidate RR Lyrae star streams in the inner Galaxy
• The Gaia DR3 view of dynamical substructure in the stellar halo near the Sun
• NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context
• The tidal remnant of an unusually metal-poor globular cluster
• The Pristine survey -- XVI. The metallicity of 26 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3
• The Milky Way's stellar streams and globular clusters do not align in a Vast Polar Structure
• A chemo-dynamical link between the Gjöll stream and NGC 3201
• New stellar velocity substructures from Gaia DR3 proper motions

Cited by in corpus (7)

• Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry
• Dynamical formation of Gaia BH3 in the progenitor globular cluster of the ED-2 stream
• The 33 M${}_{\odot }$ black hole Gaia BH3 is part of the disrupted ED-2 star cluster
• The Pristine survey: XXV. The very metal-poor Galaxy: Chemodynamics through the follow-up of the Pristine-Gaia synthetic catalogue
• How well can we unravel the accreted constituents of the Milky Way stellar halo? A test on cosmological hydrodynamical simulations
• Nearby stellar substructures in the Galactic halo from DESI Milky Way Survey Year 1 Data Release
• One Stream or Two -- Exploring Andromeda's North West Stream