J/ApJ/621/673 Line indices for 124 early-type galaxies (Thomas+, 2005)
The epochs of early-type galaxy formation as a function of environment.
Thomas D., Maraston C., Bender R., De Oliveira C.M.
<Astrophys. J., 621, 673-694 (2005)>
=2005ApJ...621..673T 2005ApJ...621..673T
ADC_Keywords: Abundances ; Velocity dispersion ; Galaxies, spectra ;
Spectroscopy
Keywords: galaxies: abundances - galaxies: elliptical and lenticular, cD -
galaxies: evolution - galaxies: formation - galaxies: stellar content
Abstract:
The aim of this paper is to set constraints on the epochs of
early-type galaxy formation through the "archaeology" of the stellar
populations in local galaxies. Using our models of absorption-line
indices that account for variable abundance ratios, we derive ages,
total metallicities, and element ratios of 124 early-type galaxies in
high- and low-density environments. The data are analyzed by
comparison with mock galaxy samples created through Monte Carlo
simulations taking the typical average observational errors into
account, in order to eliminate artifacts caused by correlated errors.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 87 124 Sample parameters and line indices
table3.dat 45 124 Results for population parameters
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See also:
J/A+A/395/431 : Line-strength indices for 148 early-type galaxies
(Beuing+, 2002)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name
13- 17 F5.1 km/s Sigma Velocity dispersion
19- 22 F4.1 km/s e_Sigma The 1σ error in Sigma
24- 27 F4.2 0.1nm Hb The Hβ line index
29- 32 F4.2 0.1nm e_Hb The 1σ error in Hb
34- 37 F4.2 0.1nm Mgb The Mg b line index
39- 42 F4.2 0.1nm e_Mgb The 1σ error in Mgb
44- 47 F4.2 0.1nm <Fe> The <Fe> line index
49- 52 F4.2 0.1nm e_<Fe> The 1σ error in <Fe>
54- 55 A2 --- Morph Galaxy morphology type
57- 68 A12 --- Den Environmental density (low or high)
70- 77 A8 --- Ref Literature source (1)
79- 87 A9 --- Class Classification by symbol type in Fig. 4 (2)
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Note (1): Sources for the data, defined as follows:
Gonzalez = Gonzales (1993, Ph.D. thesis, Univ. California, Santa Cruz),
Beuing = Beuing et al. (2002, Cat. J/A+A/395/431),
Mehlert = Mehlert et al. (2003, Cat. J/A+A/407/423),
Oliveira = Mendes de Oliveira et al. (in preparation).
Note (2): The symbol types used in Fig. 4 are defined as follows:
circles = linear relationships of age, metallicity, and α/Fe ratio
with velocity dispersion
diamonds = realizations in which 70% of the galaxy's stellar populations
is assumed to form around a look-back time of 2.5Gyr
squares = simulations assuming 1.4Gyr old subcomponents (20% in mass)
triangles = simulations assuming 1.2Gyr old subcomponents (10% in mass)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name
13- 16 F4.1 Gyr Age Stellar population age (1)
18- 20 F3.1 Gyr e_Age 1σ error in Age (2)
22- 26 F5.3 [Sun] [Z/H] Log of the total Z/H abundance (1)
28- 32 F5.3 [Sun] e_[Z/H] The 1σ error in [Z/H] (2)
34- 39 F6.3 [Sun] [a/Fe] Log of the α/Fe abundance (1)
41- 45 F5.3 [Sun] e_[a/Fe] The 1σ error in [a/Fe](2)
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Note (1): The stellar population parameters age, total metallicity [Z/H],
and [a/Fe] abundance ratio are derived from Hβ, Mg b, and <Fe>
(Table 2) using SSP models of Thomas et al. (2003MNRAS.343..279T 2003MNRAS.343..279T)
and Thomas et al. (2004MNRAS.351L..19T 2004MNRAS.351L..19T).
Note (2): Estimated via Monte Carlo simulations (see text).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Marianne Brouty [CDS] 31-Aug-2005