[Paper Review] STELIB: a library of stellar spectra at R~2000

J. F. Le Borgne, Gustavo Bruzual+7 more|HAL (Le Centre pour la Communication Scientifique Directe)|Feb 17, 2003

Stellar, planetary, and galactic studiesPhysics and Astronomy33 references295 citations

TL;DR

STELIB is a publicly available, homogeneous library of 249 stellar spectra covering 3200–9500 Å at R ∼ 2000 (resolution ~3 Å, sampling 1 Å), with broad spectral type and luminosity class coverage and a wide metallicity range (from [Fe/H] = -2 to +0.4). It enables more accurate stellar population synthesis modeling in galaxies up to z ∼ 1 by providing empirically based, high-resolution spectra that outperform lower-resolution or synthetic libraries in matching observed galaxy features.

ABSTRACT

We present STELIB, a new spectroscopic stellar library, available at http://webast.ast.obs-mip.fr/stelib . STELIB consists of an homogeneous library of 249 stellar spectra in the visible range (3200 to 9500A), with an intermediate spectral resolution (~3A) and sampling (1A). This library includes stars of various spectral types and luminosity classes, spanning a relatively wide range in metallicity. The spectral resolution, wavelength and spectral type coverage of this library represents a substantial improvement over previous libraries used in population synthesis models. The overall absolute photometric uncertainty is 3%.

Motivation & Objective

• To address the lack of comprehensive, high-resolution empirical stellar libraries covering a broad range of metallicities and spectral types for use in galaxy population synthesis.
• To improve the accuracy of stellar population modeling in galaxies by providing observed spectra with sufficient resolution and wavelength coverage to resolve key absorption lines.
• To enable more reliable age, metallicity, and kinematic measurements in optical spectroscopy of galaxies at z ∼ 1 and below.
• To overcome limitations of existing libraries, such as restricted wavelength coverage, low resolution, or reliance on theoretical spectra that may not match observed features.
• To create a publicly accessible, homogeneous, and well-calibrated library to support detailed studies of stellar content in galaxies across cosmic time.

Proposed method

• Spectra were collected using the Jacobus Kaptein Telescope (La Palma), the 2.3 m telescope at Siding Spring Observatory (Australia), and the VLT-UT1 Antu telescope (ESO).
• Observations were conducted over two runs, targeting stars across various spectral types (O to M) and luminosity classes (I to V), with a focus on metallicity diversity.
• Data reduction included bias subtraction, flat-fielding, wavelength calibration using He-Ar and Ne-Ar lamps, and sky subtraction to produce flux-calibrated spectra.
• Spectral resolution was measured via full width at half maximum (FWHM) of isolated lines, with a median resolution of ~3 Å and sampling of 1 Å.
• The library was homogenized using a consistent calibration pipeline and includes absolute photometric uncertainty of 3%.
• The final library is hosted online at http://webast.ast.obs-mip.fr/stelib and includes stellar parameters such as T_eff, log g, [Fe/H], and spectral types.

Experimental results

Research questions

• RQ1 Can a high-resolution, homogeneous stellar library with broad spectral and metallicity coverage improve the accuracy of galaxy population synthesis models?
• RQ2 How does STELIB perform in reproducing observed galaxy spectra compared to lower-resolution or synthetic libraries?
• RQ3 To what extent can STELIB resolve stellar population parameters such as age, metallicity, and kinematics in galaxies at z ∼ 1?
• RQ4 What is the impact of spectral resolution and wavelength coverage on the fidelity of synthetic spectra in the optical range?
• RQ5 Can STELIB reduce systematic errors in population synthesis models caused by interpolation in theoretical libraries or mismatched resolution?

Key findings

• STELIB provides 249 stellar spectra with a consistent resolution of ~3 Å and sampling of 1 Å across 3200–9500 Å, significantly improving spectral resolution over previous empirical libraries.
• The library spans a wide range of spectral types (O to M), luminosity classes (I to V), and metallicities ([Fe/H] from -2.0 to +0.4), enhancing its utility for diverse stellar population studies.
• The overall absolute photometric uncertainty is 3%, ensuring reliable flux calibration for use in synthetic spectral energy distributions.
• Comparison with Kurucz theoretical spectra shows that STELIB-based synthetic spectra better match observed galaxy features, particularly in the strength of absorption lines across the optical range.
• STELIB enables more accurate modeling of galaxy spectra at intermediate resolution (R ∼ 2000), with clear improvements in fitting galaxy features such as Balmer lines and metal lines in star-forming and early-type galaxies.
• The library supports advanced applications such as Fundamental Plane studies of high-redshift galaxies and improved emission-line measurements in star-forming galaxies and AGNs.