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Centro de Astrofísica da Universidade do Porto

Star formation in the local Universe from the CALIFA sample
I. Calibrating the SFR using integral field spectroscopy data

C. Catalán-Torrecilla, A. Gil de Paz, A. Castillo-Morales, J. Iglésias-Páramo, S. F. Sánchez, R. C Kennicutt, P. Pérez-González, R. A. Marino, C. J. Walcher, B. Husemann, R. García-Benito, D. Mast, R. M. González Delgado, J. C. Muñoz-Mateos, J. Bland-Hawthorn, D. J. Bomans, A. del Olmo, L. Galbany, J. M. Gomes, C. Kehrig, Á. R. López-Sánchez, M. A. Mendoza, A. Monreal-Ibero, M. Pérez Torres, P. Sánchez-Blázquez, J. M. Vílchez, and the CALIFA collaboration

Resumo

Context. The star formation rate (SFR) is one of the main parameters used to analyze the evolution of galaxies through time. The need for recovering the light reprocessed by dust commonly requires the use of low spatial resolution far-infrared data. Recombination line luminosities provide an alternative, although uncertain dust-extinction corrections based on narrowband imaging or long-slit spectroscopy have traditionally posed a limit to their applicability. Integral field spectroscopy (IFS) is clearly the way to overcome this kind of limitation.
Aims. We obtain integrated Hα, ultraviolet (UV) and infrared (IR)-based SFR measurements for 272 galaxies from the CALIFA survey at 0.005 <z< 0.03 using single-band and hybrid tracers. We aim to determine whether the extinction-corrected Hα luminosities provide a good measure of the SFR and to shed light on the origin of the discrepancies between tracers. Updated calibrations referred to Hα are provided. The well-defined selection criteria and large statistics allow us to carry out this analysis globally and split by properties, including stellar mass and morphological type.
Methods. We derive integrated, extinction-corrected Hα fluxes from CALIFA, UV surface and asymptotic photometry from GALEX and integrated WISE 22 μm and IRAS fluxes.
Results. We find that the extinction-corrected Hα luminosity agrees with the hybrid updated SFR estimators based on either UV or Hα plus IR luminosity over the full range of SFRs (0.0320 M yr-1). The coefficient that weights the amount of energy produced by newly-born stars that is reprocessed by dust on the hybrid tracers, aIR, shows a large dispersion. However, this coefficient does not became increasingly small at high attenuations, as expected if significant highly-obscured Hα emission were missed, i.e., after a Balmer decrement-based attenuation correction is applied. Lenticulars, early-type spirals, and type-2 AGN host galaxies show smaller coefficients because of the contribution of optical photons and AGN to dust heating.
Conclusions. In the local Universe, the Hα luminosity derived from IFS observations can be used to measure SFR, at least in statistically-significant, optically-selected galaxy samples, once stellar continuum absorption and dust attenuation effects are accounted for. The analysis of the SFR calibrations by galaxies properties could potentially be used by other works to study the impact of different selection criteria in the SFR values derived, and to disentangle selection effects from other physically motivated differences, such as environmental or evolutionary effects.

Palavras chave
galaxies: star formation - galaxies: spiral - galaxies: evolution - techniques: photometric - techniques: spectroscopic

Astronomy and Astrophysics
Volume 584, Página A87
dezembro 2015

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Instituto de Astrofísica e Ciências do Espaço

O Instituto de Astrofísica e Ciências do Espaço é (IA) é uma nova, mas muito aguardada, estrutura de investigação com uma dimensão nacional. Ele concretiza uma visão ousada, mas realizável para o desenvolvimento da Astronomia, Astrofísica e Ciências Espaciais em Portugal, aproveitando ao máximo e realizando plenamente o potencial criado pela participação nacional na Agência Espacial Europeia (ESA) e no Observatório Europeu do Sul (ESO). O IA é o resultado da fusão entre as duas unidades de investigação mais proeminentes no campo em Portugal: o Centro de Astrofísica da Universidade do Porto (CAUP) e o Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL). Atualmente, engloba mais de dois terços de todos os investigadores ativos em Ciências Espaciais em Portugal, e é responsável por uma fração ainda maior da produtividade nacional em revistas internacionais ISI na área de Ciências Espaciais. Esta é a área científica com maior fator de impacto relativo (1,65 vezes acima da média internacional) e o campo com o maior número médio de citações por artigo para Portugal.

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