Stellar populations in local star-forming galaxies -- I. Data and modelling procedure

Abstract

We present an analysis of the integrated properties of the stellar populations in the Universidad Complutense de Madrid (UCM) Survey of Hα-selected galaxies. In this paper, the first of a series, we describe in detail the techniques developed to model star-forming galaxies using a mixture of stellar populations, and taking into account the observational uncertainties. We assume a recent burst of star formation superimposed on a more evolved population. The effects of the nebular continuum, line emission and dust attenuation are taken into account. We also test different model assumptions including the choice of specific evolutionary synthesis model, initial mass function, star formation scenario and the treatment of dust extinction. Quantitative tests are applied to determine how well these models fit our multi-wavelength observations for the UCM sample. Our observations span the optical and near infrared, including both photometric and spectroscopic data. Our results indicate that extinction plays a key role in this kind of studies, revealing that low-and high-obscured objects may require very different extinction laws and must be treated differently. We also demonstrate that the UCM Survey galaxies are best described by a short burst of star formation occurring within a quiescent galaxy, rather than by continuous star formation. A detailed discussion on the inferred parameters, such as the age, burst strength, metallicity, star formation rate, extinction and total stellar mass for individual objects, is presented in paper II of this series.

horizon-AGN virtual observatory – 2. Template-free estimates of galaxy properties from colours

“…Because Horizon-AGN maximum spatial resolution is at best 1 pkpc, the impact on the inter-stellar medium (ISM) of any process occurring at smaller scale is averaged through the sub-grid recipes. These recipes have been iteratively improved in order to reproduce as well as possible the statistical distribution of integrated galaxy properties throughout cosmic time (in Horizon-AGN such a progress can be tracked through Dubois et al 2012Dubois et al , 2014Park et al 2019). However, they might fail to some extent at reproducing ISM in-homogeneity and clumpiness.…”

“…These estimates usually come from the analysis of the spectral energy distribution (SED) or the E-mail: iary@caltech.edu high-resolution spectrum of galaxies, relying on the correlation between specific wavelengths and physical property: for example H α emission and star formation (Kennicutt 1998) or ∼ 2µm light and stellar mass (Madau et al 1998). In the past two decades data from multi-wavelength photometry and spectroscopic surveys have become abundant, so fitting galaxy templates to observed SED and spectra has become the standard method to perform this analysis (among the pioneering studies: Arnouts et al 1999;Bell & de Jong 2000;Bolzonella et al 2000;Gavazzi et al 2002;Pérez-González et al 2003;Fontana et al 2004;Gallazzi et al 2005). Galaxy parameters are usually derived from the maximum-likelihood template (Bolzonella et al 2000) or from the full probability distribution function (PDF) of the template set (Benítez 2000).…”

The Hα Galaxy Survey

“…The mean redshift of the galaxies is approximately 0.02, thus the derived A(Hα) values will be predominantly for the central regions. There are significant uncertainties in line fluxes for weak-lined galaxies due to the 0.3 nm correction applied to compensate for photospheric absorption underlying both Hα and Hβ lines (Pérez-González et al 2003). As a result, the analysis presented below was done twice; once for all galaxies with relevant data, and then including only galaxies with Hβ EW greater than 1 nm and Hα EW greater than 6 nm, for which the absorption-correction uncertainties will be minimised.…”

Stellar Masses of Luminous Compact Blue Galaxies at Redshifts [CLC][ITAL]z[/ITAL][/CLC] = 0.4–1.2

“…The main uncertainty in the inferred stellar masses arises from the age of the stellar population (Rix & Rieke 1993). Instead of using Ha to constrain the strength and age of a young burst (Gil de Paz et al 2000;Ö stlin et al 2001;Pérez-González et al 2003a, 2003b, an alternative approach when studying galaxies at higher redshifts is to use rest-frame far-UV fluxes (Brinchmann & Ellis 2000, hereafter BE00;Papovich, Dickinson, & Ferguson 2001). Here we use a modified version of the method described in BE00 to estimate the stellar masses of a sample of LCBGs at intermediate redshift.…”