J/A+A/618/A122 Cetus dSph stellar chemo-kinematics (Taibi+, 2018) ================================================================================ Stellar chemo-kinematics of the Cetus dwarf spheroidal galaxy. Taibi S., Battaglia G., Kacharov N., Rejkuba M., Irwin M., Leaman R., Zoccali M., Tolstoy E., Jablonka P. =2018A&A...618A.122T (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxies, nearby ; Photometry, UBVRI ; Radial velocities ; Abundances, [Fe/H] ; Spectroscopy Keywords: galaxies: dwarf - Local Group - galaxies: kinematics and dynamics - galaxies: abundances - galaxies: structure - techniques: spectroscopic Abstract: Cetus is an isolated, dwarf spheroidal (dSph) galaxy at a distance of 755kpc. In order to quantify its stellar chemo-kinematical properties, we observed individual red giants branch stars in Cetus with the Very Large Telescope (VLT) FORS2 instrument, in Mask eXchange Unit (MXU) configuration. The kinematic analysis shows that Cetus is a mainly pressure-supported ({sigma}_v_=11.0^+1.6^_-1.3_km/s), dark-matter-dominated system (M_1/2_/L_V_=23.9^+9.7^_-8.9_M_{sun}_/L_{sun}_) with no significant signs of internal rotation. We find Cetus to be a metal-poor system with a significant metallicity spread (median [Fe/H]=-1.71dex, median-absolute-deviation =0.49dex), 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 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. 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 Local Group early-type dwarfs being driven by internal mechanisms. Description: We observed four slitmasks with VLT/FORS2 in the region of the nIR CaII triplet lines for 80 candidate red giant branch (RGB) stars. The temporal baseline spanned a period between 2012 December 11 and 2014 November 23 (UT). We used the 1028z+29 holographic grism in conjunction with the OG590+32 order separation filter, to cover a wavelength range of 7700-9500{AA}. This set-up, combined with the slit widths of 1", yielded a resolving power of about R~2600 at 8600{AA}. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table5.dat 110 83 Properties of the observed VLT/FORS2 targets in Cetus dSph sp/* . 166 Individual fits spectra and error files -------------------------------------------------------------------------------- See also: J/ApJ/669/765 : Chandra X-ray sources in LALA Cetus field (Wang+, 2007) J/ApJ/699/1742 : LCID project. I. Cetus and Tucana variables (Bernard+, 2009) J/ApJ/706/762 : LAEs at z~4.5 in the LALA Cetus field (Wang+, 2009) J/MNRAS/422/89 : Cetus dSph RR Lyrae (Monelli+, 2012) Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 I1 --- Field [1/4] Field number (1) 3- 4 I2 --- Ap Slit aperture (2) 6- 13 F8.6 deg RAdeg Right ascension (J2000) 15- 23 F9.5 deg DEdeg Declination (J2000) 25- 30 F6.3 --- Vmag V-band magnitude 32- 36 F5.3 --- e_Vmag Error on the V-band magnitude 38- 43 F6.3 --- Imag I-band magnitude 45- 49 F5.3 --- e_Imag Error on the I-band magnitude 51- 59 F9.3 km/s HV line-of-sight heliocentric velocity 60- 64 F5.2 km/s e_HV Error on the heliocentric velocity 66- 70 F5.2 [-] [Fe/H] ?=- Metallicity 72- 75 F4.2 [-] e_[Fe/H] ?=- Metallicity error 77- 82 F6.3 pix-1 SNR Signal-to-noise ratio 84 A1 --- Memb [N/Y] Membership 86- 97 A12 --- FileName1 Name of the spectrum file in subdirectory sp 99-110 A12 --- FileName2 Name of the spectrum error file in subdirectory sp -------------------------------------------------------------------------------- Note (1): Fileds number as follows: 1 = Cen 2 = NE 3 = SE 4 = NW Note (2): numbers <30 indicate targets from chip-1, otherwise from chip-2 numbers counted from bottom to top of the CCD. -------------------------------------------------------------------------------- Acknowledgements: Salvatore Taibi, staibi(at)iac.es ================================================================================ (End) Patricia Vannier CDS 27-Jul-2018