Published in

Oxford University Press (OUP), Monthly Notices of the Royal Astronomical Society, 1(491), p. 356-377, 2019

DOI: 10.1093/mnras/stz2854

Links

Tools

Export citation

Search in Google Scholar

The Pristine Dwarf-Galaxy survey – II. In-depth observational study of the faint Milky Way satellite Sagittarius II

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

Full text: Unavailable

Green circle
Preprint: archiving allowed
Green circle
Postprint: archiving allowed
Green circle
Published version: archiving allowed
Data provided by SHERPA/RoMEO

Abstract

ABSTRACT We present an extensive study of the Sagittarius II (Sgr II) stellar system using MegaCam g and i photometry, narrow-band, metallicity-sensitive calcium H&K doublet photometry and Keck II/DEIMOS multiobject spectroscopy. We derive and refine the Sgr II structural and stellar properties inferred at the time of its discovery. The colour–magnitude diagram implies Sgr II is old (12.0 ± 0.5 Gyr) and metal poor. The CaHK photometry confirms the metal-poor nature of the satellite ([Fe/H] CaHK = −2.32 ± 0.04 dex) and suggests that Sgr II hosts more than one single stellar population ($σ _\mathrm{[FeH]}^\mathrm{CaHK} = 0.11^{+0.05}_{-0.03}$ dex). Using the Ca infrared triplet measured from our highest signal-to-noise spectra, we confirm the metallicity and dispersion inferred from the Pristine photometric metallicities ([Fe/H]spectro = −2.23 ± 0.05 dex, $σ _\mathrm{[Fe/H]}^\mathrm{spectro} = 0.10 ^{+0.06}_{-0.04}$ dex). The velocity dispersion of the system is found to be $σ _{v} = 2.7^{+1.3}_{-1.0} {\rm \, km \,\, s^{-1}}$ after excluding two potential binary stars. Sgr II’s metallicity and absolute magnitude (MV = −5.7 ± 0.1 mag) place the system on the luminosity–metallicity relation of the Milky Way dwarf galaxies despite its small size. The low but resolved metallicity and velocity dispersions paint the picture of a slightly dark-matter-dominated satellite ($M/L = 23.0^{+32.8}_{-23.0}$ M⊙ L$^{-1}_{⊙ }$). Furthermore, using the Gaia Data Release 2, we constrain the orbit of the satellite and find an apocentre of $118.4 ^{+28.4}_{-23.7} {\rm \, kpc}$ and a pericentre of $54.8 ^{+3.3}_{-6.1} {\rm \, kpc}$. The orbit of Sgr II is consistent with the trailing arm of the Sgr stream and indicates that it is possibly a satellite of the Sgr dSph that was tidally stripped from the dwarf’s influence.

Beta version