SDSS J003251.30+004345.2 , the SIMBAD biblio

2020ApJ...894...34D - Astrophys. J., 894, 34-34 (2020/May-1)

The metallicity gradient and complex formation history of the outermost halo of the Milky Way.

DIETZ S.E., YOON J., BEERS T.C. and PLACCO V.M.

Abstract (from CDS):

We present an examination of the metallicity distribution function of the outermost stellar halo of the Galaxy based on an analysis of both local (within 4 kpc of the Sun, ∼16,500 stars) and non-local (∼21,700 stars) samples. These samples were compiled using spectroscopic metallicities from the Sloan Digital Sky Survey and photometric metallicities from the SkyMapper Southern Survey. We detect a negative metallicity gradient in the outermost halo (r > 35 kpc from the Galactic center), and find that the frequency of very metal-poor ([Fe/H] < -2.0) stars in the outer-halo region reaches up to ∼60% in our most distant sample, commensurate with previous theoretical predictions. This result provides clear evidence that the outer-halo formed hierarchically. The retrograde stars in the outermost halo exhibit a roughly constant metallicity, which may be linked to the accretion of the Sequoia progenitor. In contrast, prograde stars in the outermost halo exhibit a strong metallicity-distance dependence, indicating that they likely originated from the accretion of galaxies less massive than the Sequoia progenitor galaxy.

Abstract Copyright: © 2020. The American Astronomical Society. All rights reserved.

Journal keyword(s): Milky Way Galaxy - Milky Way evolution - Milky Way formation - Milky Way dynamics - Milky Way stellar halo - Stellar populations - Population II stars - Stellar kinematics - Metallicity - Galaxy structure

VizieR on-line data: <Available at CDS (J/ApJ/894/34): table1.dat table2.dat>

Simbad objects: 24035

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