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J/MNRAS/446/369  Colour and spectral index from the SLUGGS survey (Usher+, 2015)

The SLUGGS survey: globular cluster stellar population trends from weak absorption lines in stacked spectra. Usher C., Forbes D.A., Brodie J.P., Romanowsky A.J., Strader J., Conroy C., Foster C., Pastorello N., Pota V., Arnold J.A. <Mon. Not. R. Astron. Soc., 446, 369-390 (2015)> =2015MNRAS.446..369U (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Populations, stellar ; Colors ; Magnitudes, absolute ; Spectroscopy ; Surveys Keywords: globular clusters: general - galaxies: abundances - galaxies: star clusters: general - galaxies: stellar content Abstract: As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ∼90 Å-1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations. Description: The SLUGGS survey is an ongoing study of 25 massive, nearby, early-type galaxies and their GC systems using Keck DEIMOS spectroscopy and wide-field imaging from Suprime-Cam (Miyazaki et al. 2002, PASJ, 54, 833) on the Subaru telescope. The spectra were all observed with DEIMOS in multislit mode between 2006 and 2013 with the primary aim of measuring GC radial velocities. Exposure times averaged two hours per slit mask. All observations used a central wavelength of 7800 Å, the 1200 line/mm grating and 1 arcsec slits. This setup yields a resolution of Δλ∼1.5 Å and covers the Na I doublet to CaT wavelength region. In roughly half of the slits, Hα is also covered. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 58 10 Galaxy properties tablea1.dat 201 45 Colour and spectral index measurements of spectra stacked by colour for galaxies tablea2.dat 201 20 Colour and spectral index measurements of spectra stacked by colour for groups
See also: VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) J/MNRAS/355/608 : NGC 4649 (M60) globular clusters (Forbes+, 2004) J/A+A/455/453 : Globular Cluster System of NGC5846 (Chies-Santos+, 2006) J/ApJ/655/144 : ACS Virgo Cluster Survey. XIII. (Mei+, 2007) J/AJ/137/4956 : Globular clusters around NGC 1407 (Romanowsky+, 2009) J/MNRAS/413/813 : ATLAS3D project. I. (Cappellari+, 2011) J/MNRAS/420/37 : NGC 4365 globular clusters (Blom+, 2012) J/MNRAS/426/1475 : CaT in 903 globular clusters (Usher+, 2012) J/MNRAS/428/389 : SLUGGS globular clusters in early-type galaxies (Pota+, 2013) J/MNRAS/436/1172 : Globular Clusters of NGC 4278 in SLUGGS (Usher+, 2013) J/AJ/148/32 : Globular cluster candidates in NGC 3115 (Jennings+, 2014) J/MNRAS/452/2208 : NGC 4473 globular clusters (Alabi+, 2015) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 A3 --- --- [NGC] 4- 7 I4 --- NGC [1407/5846] Host galaxy name 8 A1 --- n_NGC [a] Note on NGC (1) 10- 11 I2 h RAh Simbad Hour of Right Ascension (J2000) 13- 14 I2 min RAm Simbad Minute of Right Ascension (J2000) 16- 21 F6.3 s RAs Simbad Second of Right Ascension (J2000) 23 A1 --- DE- Simbad Sign of the Declination (J2000) 24- 25 I2 deg DEd Simbad Degree of Declination (J2000) 27- 28 I2 arcmin DEm Simbad Arcminute of Declination (J2000) 30- 34 F5.2 arcsec DEs Simbad Arcsecond of Declination (J2000) 36- 39 I4 km/s Vsys Systemic velocity from Cappellari et al. (2011, J/MNRAS/413/813) 41- 44 F4.1 Mpc Dist Distance from Cappellari et al. (2011, J/MNRAS/413/813) (2) 46- 50 F5.1 mag KMag K-band absolute magnitude from Cappellari et al. (2011, J/MNRAS/413/813) (3) 52- 54 I3 --- Spectra Total number of GC spectra 56- 58 I3 --- GC Number of unique GCs with spectra
Note (1): NGC 1407 and NGC 3115 are not part of the Cappellari et al. (2011, J/MNRAS/413/813) sample so their radial velocities were taken from NED while their distances are from Tonry et al. (2001ApJ...546..681T) with the same -0.06 mag distance moduli offset as Cappellari et al. (2011, J/MNRAS/413/813). We assume that NGC 1400 and NGC 1407 are part of the same group and use the mean of their distance moduli for NGC 1407. Their K-band absolute magnitude is also calculated from the 2MASS total K apparent magnitude and the distance in the same manner as Cappellari et al. (2011, J/MNRAS/413/813). Note (2): Based on surface brightness fluctuations (SBF) of Tonry et al. (2001ApJ...546..681T). For NGC 4365, NGC 4473 and NGC 4649, Cappellari et al. (2011, J/MNRAS/413/813) used the SBF distance of Mei et al. (2007, J/ApJ/655/144). Note (3): Calculated from the 2MASS (Skrutskie et al. 2006, Cat. VII/233) total K-band apparent magnitude and the distance in the previous column, corrected for foreground extinction.
Byte-by-byte Description of file: tablea1.dat tablea2.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Group [faint bright] Galaxy group (1) 8- 10 A3 --- --- [NGC] 11- 14 I4 --- NGC [1407/5846]? Host galaxy name 16- 21 F6.4 mag g-i Subaru/Suprime-Cam (g-i) colour index 23- 28 F6.4 mag E_g-i Upper limit uncertainty in g-i 30- 35 F6.4 mag e_g-i Lower limit uncertainty in g-i 37- 43 F7.3 mag iMag Subaru/Suprime-Cam i-band absolute magnitude 45- 49 F5.3 mag E_iMag Upper limit uncertainty in iMag 51- 55 F5.3 mag e_iMag Lower limit uncertainty in iMag 57- 61 F5.3 0.1nm CaT Ca II triplet spectral index strength (Å) 63- 67 F5.3 0.1nm E_CaT Upper limit uncertainty in CaT 69- 73 F5.3 0.1nm e_CaT Lower limit uncertainty in CaT 75- 79 F5.3 0.1nm Fe86 Fe86 spectral index strength (Å) 81- 85 F5.3 0.1nm E_Fe86 Upper limit uncertainty in Fe86 87- 91 F5.3 0.1nm e_Fe86 Lower limit uncertainty in Fe86 93- 97 F5.3 0.1nm Mg88 Mg88 spectral index strength (Å) 99-103 F5.3 0.1nm E_Mg88 Upper limit uncertainty in Mg88 105-109 F5.3 0.1nm e_Mg88 Lower limit uncertainty in Mg88 111-116 F6.3 0.1nm Na82 Na82 spectral index strength (Å) 118-122 F5.3 0.1nm E_Na82 Upper limit uncertainty in Na82 124-128 F5.3 0.1nm e_Na82 Lower limit uncertainty in Na82 130-135 F6.4 --- TiO89 TiO89 spectral index strength 137-142 F6.4 --- E_TiO89 Upper limit uncertainty in TiO89 144-149 F6.4 --- e_TiO89 Lower limit uncertainty in TiO89 151-155 F5.3 0.1nm Halpha Hα spectral index strength (Å) 157-161 F5.3 0.1nm E_Halpha Upper limit uncertainty in Halpha 163-167 F5.3 0.1nm e_Halpha Lower limit uncertainty in Halpha 169-173 F5.3 0.1nm PaT Paschen line spectral index strength (Å) 175-179 F5.3 0.1nm E_PaT Upper limit uncertainty in PaT 181-185 F5.3 0.1nm e_PaT Lower limit uncertainty in PaT 187-191 F5.2 km/s sigma ? Velocity dispersion 193-196 F4.2 km/s E_sigma ? Upper limit uncertainty in sigma 198-201 F4.2 km/s e_sigma ? Lower limit uncertainty in sigma
Note (1): NGC 1407, NGC 4278, NGC 4365 and NGC 4649 are in the bright group; NGC 3115, NGC 3377, NGC 4473 and NGC 4494 are in the faint group.
History: From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 30-Oct-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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