Details

Autor(en) / Beteiligte

• Youakim, K
• Starkenburg, E
• Martin, N F
• Matijevič, G
• Aguado, D S
• Allende Prieto, C
• Arentsen, A
• Bonifacio, P
• Carlberg, R G
• González Hernández, J I
• Hill, V
• Kordopatis, G
• Lardo, C
• Navarro, J F
• Jablonka, P
• Sánchez Janssen, R
• Sestito, F
• Thomas, G F
• Venn, K

Titel

The Pristine Survey – VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2020-03, Vol.492 (4), p.4986-5002

Ort / Verlag

United Kingdom: Oxford University Press

Erscheinungsjahr

2020

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• ABSTRACT The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ($ \rm [Fe/H] \lt -3$), and currently consists of over 4 million FGK-type stars over a sky area of $\sim 2500\, \mathrm{deg}^2$. We focus our analysis on a subsample of ∼80 000 main-sequence turn-off stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at $ \rm [Fe/H] =-1.6$, and a slope of Δ(LogN)/$\Delta \rm [Fe/H] = 1.0 \pm 0.1$ in the metallicity range of $-3.4\; \lt\; \rm [Fe/H]\; \lt -2.5$. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low-latitude field in the anticentre direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for $ \rm [Fe/H]\; \lt\; -2.5$ and 1.5 for $ \rm [Fe/H]\; \lt\; -3$, suggesting that the lack of low-metallicity globular clusters in the Milky Way is not due simply to statistical undersampling.