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.
<Astron. Astrophys. 618, A122 (2018)>
=2018A&A...618A.122T 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 (σv=11.0+1.6-1.3km/s),
dark-matter-dominated system
(M1/2/LV=23.9+9.7-8.9M☉/L☉) 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 7700-9500Å. This set-up, combined with the slit
widths of 1", yielded a resolving power of about R∼2600 at 8600Å.
File Summary:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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
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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.
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Acknowledgements:
Salvatore Taibi, staibi(at)iac.es
(End) Patricia Vannier CDS 27-Jul-2018