The Pristine survey – XVI. The metallicity of 26 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3

Abstract

We use the photometric metallicities provided by the panoramic Pristine survey to study the veracity and derive the metallicities of the numerous stellar streams found by the application of the STREAMFINDER algorithm to the Gaia EDR3 data. All 26 streams present in Pristine show a clear metallicity distribution function, which provides an independent check of the reality of these structures, supporting the reliability of STREAMFINDER in finding streams and the power of Pristine to measure precise metallicities. We further present 6 candidate structures with coherent phase-space and metallicity signals that are very likely streams. The majority of studied streams are very metal-poor (14 structures with [Fe/H] < −2.0) and include 3 systems with [Fe/H] < −2.9 (C-11, C-19, and C-20). These streams could be the closest debris of low-luminosity dwarf galaxies or may have originated from globular clusters of significantly lower metallicity than any known current Milky Way globular cluster. Our study shows that the promise of the Gaia data for Galactic Archeology studies can be substantially strengthened by quality photometric metallicities, allowing us to peer back into the earliest epochs of the formation of our Galaxy and its stellar halo constituents.

Metallicity Distribution Functions of 13 Ultra-faint Dwarf Galaxy Candidates from Hubble Space Telescope Narrowband Imaging

“…Figure 14, shows the distribution of mean metallicities of our satellites compared to the stellar streams recently characterized by S5 (Li et al 2022) and Pristine (Martin et al 2022). The mean metallicities of our galaxies are centered at 〈[Fe/H]〉 ∼ −2.6 and range from 〈[Fe/H]〉 = −3.0 to 〈[Fe/H]〉 = −2.0.…”

M92 (NGC 6341) Is a Metal-complex Globular Cluster with an Atypical Primordial Population

“…Recently, a stellar stream related to M92 has been discovered (Sollima 2020;Thomas et al 2020;Martin et al 2022). At face value, the stellar stream is dynamically young, and its estimated mass could be as large as ∼10% of the total cluster's mass.…”

Subhalo Spreading of Thin Tidal Star Streams

“…The 70.514 million dark matter particles, each having a mass of 3.518 × 10 4 M ☉ , are assigned a softening of 40 pc. The early-time particle distribution is evolved to 0.8 Gyr at which time the dark matter halos in the simulation were identified using the Amiga Halo Finder code (Gill et al 2004;Knollmann & Knebe 2009) as host dwarf galaxies for a population of highredshift, low-metal-abundance globular clusters, which are the progenitors of most thin streams (Martin et al 2022). Globularcluster-like star particle clusters are constructed using a W = 7 King model (King 1966) with masses randomly drawn from the range (4-20) × 10 4 M ☉ with an N(M) ∝ M −1 distribution.…”