arXiv Analytics

Sign in

arXiv:1807.04250 [astro-ph.GA]AbstractReferencesReviewsResources

Stellar chemo-kinematics of the Cetus dwarf spheroidal galaxy

S. Taibi, G. Battaglia, N. Kacharov, M. Rejkuba, M. Irwin, R. Leaman, M. Zoccali, E. Tolstoy, P. Jablonka

Published 2018-07-11Version 1

In order to minimize environmental effects and gain an insight into the internal mechanisms that shape the properties of the early-type dwarf systems, we study one of the few isolated dwarf spheroidal galaxies (dSphs) of the Local Group (LG): Cetus. We obtained VLT/FORS2 spectra ($R\sim2600$) in the region of the nIR CaII triplet lines for 80 candidate red giant branch stars. The analysis yielded line-of-sight velocities and metallicities ([Fe/H]) for 54 bona fide member stars. The kinematic analysis shows that Cetus is a mainly pressure-supported ($\sigma_v = 11.0_{-1.3}^{+1.6}$ km/s), dark-matter-dominated system ($M_{1/2}/L_V = 23.9_{-8.9}^{+9.7} M_\odot/L_\odot$) with no significant signs of internal rotation. We find Cetus to be a metal-poor system with a significant [Fe/H] spread (median [Fe/H] = -1.71 dex, median-absolute-deviation = 0.49 dex), as expected for its stellar mass. We report the presence of a mild metallicity gradient compatible with those found in other dSphs of the same luminosity; we trace the presence of a stellar population gradient also in the spatial distribution of stars in different evolutionary phases in ancillary SuprimeCam photometric data. There are tentative indications of two chemo-kinematically distinct sub-populations, with the more metal-poor stars showing a hotter kinematics than the metal-richer ones. Furthermore, the photometric dataset reveals the presence of a foreground population that most likely belongs to the Sagittarius stream. This study represents a first comprehensive analysis of Cetus chemo-kinematic properties. Our results add Cetus to the growing scatter in stellar-dark matter halo properties in low-mass galactic systems. The presence of a metallicity gradient akin to those found in similar systems inhabiting different environments may hint at metallicity gradients in LG early-type dwarfs being driven by internal mechanisms.

Related articles: Most relevant | Search more
arXiv:1501.02668 [astro-ph.GA] (Published 2015-01-12)
Metallicity gradients in local field star-forming galaxies: Insights on inflows, outflows, and the coevolution of gas, stars and metals
arXiv:1709.03732 [astro-ph.GA] (Published 2017-09-12)
Medium-resolution Spectroscopy of Red Giant Branch Stars in $ω$ Centauri
Deokkeun An et al.
arXiv:1410.2124 [astro-ph.GA] (Published 2014-10-08)
The Carina Project VII: Towards the breaking of the age-metallicity degeneracy of red giant branch stars using the c_UBI index
M. Monelli et al.