Lick indices

Lick indices calculations. More...

Classes
class	cphot::LickIndex
	Define a Lick Index similarily to a Filter object. More...
class	cphot::LickLibrary
	Collection of Lick indices. More...

Functions
DMatrix	cphot::reduce_resolution (const DMatrix &w, const DMatrix &flux, double fwhm0, double sigma_floor)
	Adapt the resolution of the spectra to match the lick definitions. More...

Detailed Description

Lick indices calculations.

This package provides function to compute spectral indices.

We provide a collection of many common indices. The Lick system of spectral line indices is one of the most commonly used methods of determining ages and metallicities of unresolved (integrated light) stellar populations.

The calibration of the Lick/ IDS system is complicated because the original Lick spectra were not flux calibrated, so there are usually systematic effects due to differences in continuum shape. Proper calibration involves observing many of the original Lick/IDS standard stars and deriving offsets to the standard system.

references:

• Worthey G., Faber S. M., Gonzalez J. J., Burstein D., 1994, ApJS, 94, 687
• Worthey G., Ottaviani D. L., 1997, ApJS, 111, 377
• Puzia et al. 2002
• Zhang, Li & Han 2005, http://arxiv.org/abs/astro-ph/0508634v1

Note

In Vazdekis et al. (2010), we propose a new Line Index System, hereafter LIS, with three new spectral resolutions at which to measure the Lick indices. Note that this new system should not be restricted to the Lick set of indices in a flux calibrated system. In fact, LIS can be used for any index in the literature (e.g., for the Rose (1984) indices), including newly defined indices (e.g., Cervantes & Vazdekis 2009). The LIS system is defined for 3 different spectral resolutions which are best suited for the following astrophysical cases:

• LIS-5.0AA: globular clusters
• LIS-8.4AA: low and intermediate-mass galaxies
• LIS-14.0AA: massive galaxies Conversions to transform the data from the Lick/IDS system to LIS can be found with discussion of indices and information in Johansson, Thomas & Maraston (2010) http://wwwmpa.mpa-garching.mpg.de/~jonasj/milesff/milesff.pdf

Function Documentation

reduce_resolution()

DMatrix cphot::reduce_resolution	(	const DMatrix &	w,
		const DMatrix &	flux,
		double	fwhm0,
		double	sigma_floor
	)

Adapt the resolution of the spectra to match the lick definitions.

Lick definitions have different resolution elements as function of wavelength. These definition are hard-coded in this function

Parameters

w	wavelength definition in Angstrom
flux	spectra to convert
fwhm0	initial broadening in the spectra fi
sigma_floor	minimal dispersion to consider

Returns

flux_red reduced spectra

Definition at line 67 of file licks.hpp.