The Pristine survey: XXVII. The extremely metal-poor stream C-19 stretches over more than 100 degrees

Abstract

The discovery of the most metal-poor stream, C-19, provides us with a fossil record of a stellar structure born very soon after the Big Bang. In this work, we search for new C-19 members over the whole sky by combining two complementary stream-searching algorithms, STREAMFINDER and StarGO,, and utilizing low-metallicity star samples from the Pristine survey as well as Gaia BP/RP spectro-photometric catalogues. We confirm twelve new members, spread over more than 100${}^{\circ }$, using velocity and metallicity information from a set of spectroscopic follow-up programs that targeted a quasi-complete sample of our bright candidates ($G\lesssim 16.0$). From the updated set of stream members, we confirm that the stream is wide, with a stream width of $\sim 200$ pc, and dynamically hot, with a derived velocity dispersion of $10.9_{-1.5}^{+2.1}$ km/s. The tension remains between these quantities and a purely baryonic scenario in which the relatively low-mass stream (even updated to a few $10^4{M}_{\odot }$) stems from a globular cluster progenitor, as suggested by its chemical abundances. Some heating mechanism, such as preheating of the cluster in its own dark matter halo or through interactions with halo sub-structures appears necessary to explain the tension. The impact of binaries on the measured dispersion also remains unknown. Detailed elemental abundances of more stream members as well as multi-epoch radial velocities from spectroscopic observations are therefore crucial to fully understand the nature and past history of the most metal-poor stream of the Milky Way.

A&A in press

References in corpus (28)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• A systematic variation of the stellar initial mass function in early-type galaxies
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Gaia Data Release 3 Properties and validation of the radial velocities
• Modern stellar spectroscopy caveats
• An excess of massive stars in the local 30 Doradus starburst
• Gaia Data Release 3: Analysis of the Gaia BP/RP spectra using the General Stellar Parameterizer from Photometry
• The updated BaSTI stellar evolution models and isochrones: II. alpha-enhanced calculations
• Gaia Data Release 3: External calibration of BP/RP low-resolution spectroscopic data
• Charting the Galactic acceleration field I. A search for stellar streams with Gaia DR2 and EDR3 with follow-up from ESPaDOnS and UVES
• Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
• Internal calibration of Gaia BP/RP low-resolution spectra
• Gaps in globular cluster streams: giant molecular clouds can cause them too
• $S^5$: The Orbital and Chemical Properties of One Dozen Stellar Streams
• A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5
• A luminous and young galaxy at z=12.33 revealed by a JWST/MIRI detection of Hα and [OIII]
• A stellar stream remnant of a globular cluster below the metallicity floor
• Beyond spectroscopy. I. Metallicities, distances, and age estimates for over twenty million stars from SMSS DR2 and Gaia EDR3
• The tidal remnant of an unusually metal-poor globular cluster
• Probing the nature of dark matter with accreted globular cluster streams
• Detection of Strong Epicyclic Density Spikes in the GD-1 Stellar Stream. An Absence of Evidence for the Influence of Dark Matter Subhalos?
• The Pristine survey -- XXIII. Data Release 1 and an all-sky metallicity catalogue based on Gaia DR3 BP/RP spectro-photometry
• The Pristine survey -- XVI. The metallicity of 26 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3
• The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO
• Impact of initial mass functions on the dynamical channel of gravitational wave sources
• The Pristine survey -- XVII. The C-19 stream is dynamically hot and more extended than previously thought
• The Pristine survey XVIII: C-19: Tidal debris of a dark matter-dominated globular cluster?
• The Pristine survey: XXV. The very metal-poor Galaxy: Chemodynamics through the follow-up of the Pristine-Gaia synthetic catalogue

Cited by in corpus (2)

• HR-GO II: chemical abundances of low-$E$ retrograde dynamically-tagged-groups: Revealing Thamnos as a very metal-poor substructure
• A test of Ca ii H & K photometry for isolating massive globular clusters below the metallicity floor