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The puzzlingly small CaII triplet absorption in elliptical galaxies

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The puzzlingly small CaII triplet absorption in elliptical galaxies. / Saglia, R. P.; Maraston, C; Thomas, Daniel; Bender, Ralf; Colless, Mattew.

In: The Astrophysical Journal, Vol. 579, No. 1, 01.11.2002, p. L13-L16.

Research output: Contribution to journalArticle

Harvard

Saglia, RP, Maraston, C, Thomas, D, Bender, R & Colless, M 2002, 'The puzzlingly small CaII triplet absorption in elliptical galaxies', The Astrophysical Journal, vol. 579, no. 1, pp. L13-L16.

APA

Saglia, R. P., Maraston, C., Thomas, D., Bender, R., & Colless, M. (2002). The puzzlingly small CaII triplet absorption in elliptical galaxies. The Astrophysical Journal, 579(1), L13-L16.

Vancouver

Saglia RP, Maraston C, Thomas D, Bender R, Colless M. The puzzlingly small CaII triplet absorption in elliptical galaxies. The Astrophysical Journal. 2002 Nov 1;579(1):L13-L16.

Author

Saglia, R. P. ; Maraston, C ; Thomas, Daniel ; Bender, Ralf ; Colless, Mattew. / The puzzlingly small CaII triplet absorption in elliptical galaxies. In: The Astrophysical Journal. 2002 ; Vol. 579, No. 1. pp. L13-L16.

Bibtex

@article{6822d91874fc478db0d394238e73159c,
title = "The puzzlingly small CaII triplet absorption in elliptical galaxies",
abstract = "We measure the central values (within Re/8) of the Ca II triplet line indices CaT* and CaT and the Paschen index PaT at 8600 {\AA} for a 93% complete sample of 75 nearby early-type galaxies with BT < 12 mag and Vgal < 2490 km s-1. We find that the values of CaT* are constant to within 5% over the range of central velocity dispersions 100 km s-1 ≤ σ ≤ 340 km s-1, while the PaT (and CaT) values are mildly anticorrelated with σ. Using simple and composite stellar population models, we show the following: (1) The measured CaT* and CaT are lower than expected from simple stellar population (SSP) models with Salpeter initial mass functions (IMFs) and with metallicities and ages derived from optical Lick (Fe, Mg, and Hβ) indices. Uncertainties in the calibration, the fitting functions, and the SSP modeling taken separately cannot explain the discrepancy. On average, the observed PaT values are within the range allowed by the models and the large uncertainties in the fitting functions. (2) The steepening of the IMF at low masses required to lower the CaT* and CaT indices to the observed values is incompatible with the measured FeH index at 9916 {\AA} and the dynamical mass-to-light ratios of elliptical galaxies. (3) Composite stellar populations with a low-metallicity component reduce the disagreement, but rather artificial metallicity distributions are needed. Another explanation may be that calcium is indeed underabundant in elliptical galaxies.",
keywords = "galaxies : elliptical and lenticular, cD, galaxies : fundamental parameters",
author = "Saglia, {R. P.} and C Maraston and Daniel Thomas and Ralf Bender and Mattew Colless",
year = "2002",
month = nov,
day = "1",
language = "English",
volume = "579",
pages = "L13--L16",
journal = "The Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing",
number = "1",

}

RIS

TY - JOUR

T1 - The puzzlingly small CaII triplet absorption in elliptical galaxies

AU - Saglia, R. P.

AU - Maraston, C

AU - Thomas, Daniel

AU - Bender, Ralf

AU - Colless, Mattew

PY - 2002/11/1

Y1 - 2002/11/1

N2 - We measure the central values (within Re/8) of the Ca II triplet line indices CaT* and CaT and the Paschen index PaT at 8600 Å for a 93% complete sample of 75 nearby early-type galaxies with BT < 12 mag and Vgal < 2490 km s-1. We find that the values of CaT* are constant to within 5% over the range of central velocity dispersions 100 km s-1 ≤ σ ≤ 340 km s-1, while the PaT (and CaT) values are mildly anticorrelated with σ. Using simple and composite stellar population models, we show the following: (1) The measured CaT* and CaT are lower than expected from simple stellar population (SSP) models with Salpeter initial mass functions (IMFs) and with metallicities and ages derived from optical Lick (Fe, Mg, and Hβ) indices. Uncertainties in the calibration, the fitting functions, and the SSP modeling taken separately cannot explain the discrepancy. On average, the observed PaT values are within the range allowed by the models and the large uncertainties in the fitting functions. (2) The steepening of the IMF at low masses required to lower the CaT* and CaT indices to the observed values is incompatible with the measured FeH index at 9916 Å and the dynamical mass-to-light ratios of elliptical galaxies. (3) Composite stellar populations with a low-metallicity component reduce the disagreement, but rather artificial metallicity distributions are needed. Another explanation may be that calcium is indeed underabundant in elliptical galaxies.

AB - We measure the central values (within Re/8) of the Ca II triplet line indices CaT* and CaT and the Paschen index PaT at 8600 Å for a 93% complete sample of 75 nearby early-type galaxies with BT < 12 mag and Vgal < 2490 km s-1. We find that the values of CaT* are constant to within 5% over the range of central velocity dispersions 100 km s-1 ≤ σ ≤ 340 km s-1, while the PaT (and CaT) values are mildly anticorrelated with σ. Using simple and composite stellar population models, we show the following: (1) The measured CaT* and CaT are lower than expected from simple stellar population (SSP) models with Salpeter initial mass functions (IMFs) and with metallicities and ages derived from optical Lick (Fe, Mg, and Hβ) indices. Uncertainties in the calibration, the fitting functions, and the SSP modeling taken separately cannot explain the discrepancy. On average, the observed PaT values are within the range allowed by the models and the large uncertainties in the fitting functions. (2) The steepening of the IMF at low masses required to lower the CaT* and CaT indices to the observed values is incompatible with the measured FeH index at 9916 Å and the dynamical mass-to-light ratios of elliptical galaxies. (3) Composite stellar populations with a low-metallicity component reduce the disagreement, but rather artificial metallicity distributions are needed. Another explanation may be that calcium is indeed underabundant in elliptical galaxies.

KW - galaxies : elliptical and lenticular, cD

KW - galaxies : fundamental parameters

M3 - Article

VL - 579

SP - L13-L16

JO - The Astrophysical Journal

JF - The Astrophysical Journal

SN - 0004-637X

IS - 1

ER -

ID: 1795701