Access to Astronomical Catalogues

← Click to display the menu
J/AJ/134/321        Hδ line in globular clusters      (Prochaska+, 2007)

Hδ in the integrated light of galaxies: what are we actually measuring? Prochaska L.C., Rose J.A., Caldwell N., Castilho B.V., Concannon K., Harding P., Morrison H., Schiavon R.P. <Astron. J., 134, 321-333 (2007)> =2007AJ....134..321P (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Spectroscopy ; Abundances Keywords: galaxies: abundances - galaxies: evolution - galaxies: stellar content Abstract: We present a cautionary study exploring the reliability of the Hδ line in the integrated spectra of galaxies for determining galaxy ages. Our database consists of the observed integrated spectra of ∼120 early-type galaxies, 7 metal-rich globular clusters in M31 and the Galactic globular cluster 47 Tuc, and the open cluster M67. We have measured Hδ using index definitions designed to assess contamination from the CN molecule in and around Hδ by choosing combinations of bandpasses that both avoid and include a region of CN molecular lines redward of Hδ. We find systematic differences in the ages derived from Hδ measurements among the various definitions when extracting ages from Hδ in old stellar populations with enhanced CN bands due to nonsolar abundance ratios. We propose that neighboring CN lines have a strong effect on pseudocontinuum and central bandpass levels. For stellar populations that have nonsolar abundance ratios in C and/or N, population synthesis models that do not account for abundance ratio variations cannot accurately reproduce the CN 4216Å band, which leads to a corresponding inaccuracy in reproducing the various Hδ indices. Hence, caution must be used when extracting galaxy ages from the Hδ line in old stellar populations with significant nonsolar abundance ratios. Description: The observational data used in this paper consist of integrated spectra of 119 early-type galaxies, 7 metal-rich globular clusters in M31, the open cluster M67, and the Galactic globular cluster 47 Tucanae. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 76 16 Index definitions table2.dat 121 128 Index measurements and error
See also: J/ApJS/94/687 : Old stellar populations. V. (Worthey+, 1994) J/ApJS/111/377 : Hγ + Hδ absorption features (Worthey+ 1997) J/A+A/326/1069 : Abundances in globular clusters (Russell 1997) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Index Abbreviated index name 8- 20 A13 --- Name Index name 22- 29 F8.3 0.1nm bp1 Lower bound of central bandpass 30 A1 --- --- [-] 31- 38 F8.3 0.1nm bp2 Upper bound of central bandpass 40- 47 F8.3 0.1nm cont1 Lower bound of pseudo-continuum 48 A1 --- --- [-] 49- 56 F8.3 0.1nm cont2 Upper bound of pseudo-continuum 59- 66 F8.3 0.1nm Bcont1 ? Lower bound of second pseudo-continuum 67 A1 --- --- [-] 68- 75 F8.3 0.1nm Bcont2 ? Upper bound of second pseudo-continuum 76 A1 --- Ref [ab] Reference of index (1)
Note (1): Note as follows: a = Bandpass definitions are from Worthey & Ottaviani, 1997, Cat. J/ApJS/111/377 b = Bandpass definitions are from Worthey et al., 1994, Cat. J/ApJS/94/687
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 5 A5 --- Type Source location (1) 7- 15 A9 --- Name Source name 17- 21 F5.2 --- HdAb Hdelta_A_b index (2) 23- 26 F4.2 --- e_HdAb 1σ error in hdAb 28- 32 F5.2 --- HdA Hdelta_A_ index (2) 34- 37 F4.2 --- e_HdA 1σ error in HdA 39- 43 F5.2 --- HdAr Hdelta_A_r index (2) 45- 48 F4.2 --- e_HdAr 1σ error in HdAr 50- 54 F5.2 --- HdFb Hdelta_F_b index (2) 56- 59 F4.2 --- e_HdFb 1σ error in HdFb 61- 65 F5.2 --- HdF Hdelta_F_ index (2) 67- 70 F4.2 --- e_HdF 1σ error in HdF 72- 76 F5.2 --- HdFr Hdelta_F_r index (2) 78- 81 F4.2 --- e_HdFr 1σ error in HdFr 83- 86 F4.2 --- Hbb Hbeta_b_ index (2) 88- 91 F4.2 --- e_Hbb 1σ error in Hbb 93- 96 F4.2 --- Hb Hbeta index (2) 98-101 F4.2 --- e_Hb 1σ error in Hb 103-106 F4.2 --- Hbr Hbeta_r_ index (2) 108-111 F4.2 --- e_Hbr 1σ error in Hbr 113-116 F4.2 --- Fe4383 Fe4383 index (2) 118-121 F4.2 --- e_Fe4383 1σ error in Fe4383
Note (1): Source location is abbreviated as: Gal = Milky Way M31 = M31 Globular Clusters CRC03 = Early Type Galaxies in Caldwell, Rose, & Concannon (2003AJ....125.2891C) Note (2): as defined in table1
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 26-Aug-2009
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

catalogue service

© UDS/CNRS

Contact