Integrated spectra extraction based on signal-to-noise optimization using integral field spectroscopy

¹ Centro de Astrobiología (CSIC-INTA), Ctra de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
e-mail: frosales@cantab.net
² Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
e-mail: arribas@cab.inta-csic.es; colina@cab.inta-csic.es

Received: 27 July 2011
Accepted: 22 December 2011

Abstract

Aims. We explore the potential of a method to extract high signal-to-noise (S/N) integrated spectra of particular physical and/or morphological regions of a two-dimensional field using integral field spectroscopy (IFS) observations by applying an optimization procedure based on either continuum (stellar) or line (nebular) emission features.

Methods. The optimization method is applied to a set of IFS VLT-VIMOS observations of (U)LIRG galaxies. We describe the advantages of the optimization by comparing the results with a fixed-aperture, single-spectrum case, and by implementing some statistical tests.

Results. We demonstrate that the S/N of the IFS optimized integrated spectra is significantly higher than for the single-aperture unprocessed case. In some cases, the optimization based on the emission lines allows to characterize some of the source properties more reliably than with standard integration methods. We are able to clearly retrieve the weak continuum features, hence more precisely constrain the properties of the unresolved stellar population. The most suitable method for integrating spectra over (part of) the field-of-view ultimately depends on the science case, and may involve a trade off among the different variables (e.g. S/N, probe area, spatial resolution, etc.). we therefore provide an iterative user-friendly and versatile IDL algorithm that, in addition to the above-mentioned method, allows the user to spatially integrate spectra following more standard procedures. Our procedure is made available to the community as part of the PINGSoft IFS software package.