The Pristine survey -- XVII. The C-19 stream is dynamically hot and more extended than previously thought

Abstract

The C-19 stream is the most metal poor stellar system ever discovered, with a mean metallicity $[Fe/H]=-3.38\pm 0.06$. Its low metallicity dispersion (${\sigma }_{[Fe/H]}$ $<$ 0.18 at the 95\% confidence level) as well as variations in sodium abundances strongly suggest a globular cluster origin. In this work, we use VLT/UVES spectra of seven C-19 stars to derive more precise velocity measurements for member stars, and to identify two new members with radial velocities and metallicities consistent with the stream's properties. One of these new member stars is located 30 $°$ away from the previously identified body of C-19, implying that the stream is significantly more extended than previously known and that more members likely await discovery. In the main part of C-19, we measure a radial velocity dispersion ${\sigma }_v$ = 6.2${}_{-1.4}^{+2.0}$ km s${}^{-1}$ from nine members, and a stream width of 0.56$°\pm 0.08°$, equivalent to $\sim$158 pc at a heliocentric distance of 18 kpc. These confirm that C-19 is comparatively hotter, dynamically, than other known globular cluster streams and shares the properties of faint dwarf galaxy streams. On the other hand, the variations in the Na abundances of the three newly observed bright member stars, the variations in Mg and Al for two of them, and the normal Ba abundance of the one star where it can be measured provide further evidence for a globular cluster origin. The tension between the dynamical and chemical properties of C-19 suggests that its progenitor experienced a complex birth environment or disruption history.

arXiv comment7 pages, 6 figures, accepted to MNRAS. The C-19 member list is published via https://github.com/zyuan-astro/C-19

References in corpus (44)

• 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
• galpy: A Python Library for Galactic Dynamics
• Gaia Early Data Release 3: The astrometric solution
• Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere
• Gaia Early Data Release 3: Photometric content and validation
• Multiple Stellar Populations in Globular Clusters
• The Origin and Evolution of the Galaxy Mass-Metallicity Relation
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Constraining the Milky Way potential with a 6-D phase-space map of the GD-1 stellar stream
• CH in stellar atmospheres: an extensive linelist
• The Pristine survey I: Mining the Galaxy for the most metal-poor stars
• A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars
• Uncovering CDM halo substructure with tidal streams
• How Lumpy is the Milky Way's Dark Matter Halo?
• Ghostly Tributaries to the Milky Way: Charting the Halo's Stellar Streams with the Gaia DR2 catalogue
• Atomic data for the Gaia-ESO Survey
• Charting the Galactic acceleration field I. A search for stellar streams with Gaia DR2 and EDR3 with follow-up from ESPaDOnS and UVES
• STREAMFINDER I: A New Algorithm for detecting Stellar Streams
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• Gaps in globular cluster streams: giant molecular clouds can cause them too
• $S^5$: The Orbital and Chemical Properties of One Dozen Stellar Streams
• Current velocity data on dwarf galaxy NGC1052-DF2 do not constrain it to lack dark matter
• The Pristine Survey IV: Approaching the Galactic metallicity floor with the discovery of an ultra metal-poor star
• MyGIsFOS: an automated code for parameter determination and detailed abundance analysis in cool stars
• Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream
• Astrophysical tests of atomic data important for stellar Mg abundance determinations
• A NLTE line formation for neutral and singly-ionised titanium in model atmospheres of the reference A-K stars
• A stellar stream remnant of a globular cluster below the metallicity floor
• The tidal remnant of an unusually metal-poor globular cluster
• Influence of inelastic collisions with hydrogen atoms on the non-LTE modelling of Ca I and Ca II lines in late-type stars
• Probing the nature of dark matter with accreted globular cluster streams
• Globular Clusters in a Cosmological N-body Simulation
• The minimum metallicity of globular clusters and its physical origin -- implications for the galaxy mass-metallicity relation and observations of proto-globular clusters at high redshift
• Stellar envelopes of globular clusters embedded in dark mini-haloes
• Even-to-Odd Barium Isotope Ratio in Selected Galactic Halo Stars
• The Density Structure of Simulated Stellar Streams
• Non-LTE Sodium Abundance in Galactic Thick- and Thin-Disk Red Giants
• Velocity Dispersion of the GD-1 Stellar Stream
• Stochastic tidal heating by random interactions with extended substructures
• The Pristine survey II: a sample of bright stars observed with FEROS
• Influence of Inelastic Collisions with Hydrogen Atoms on the Formation of Al I and Si I Lines in Stellar Spectra
• The formation of the Milky Way halo and its dwarf satellites: A NLTE-1D abundance analysis. V. The Sextans galaxy
• Line-of-sight velocity and metallicity measurements of the Palomar 5 tidal stream

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• The Pristine survey XXVIII. Journey to the Galactic outskirts: Mapping the outer halo red giant stars down to the very metal-poor end
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