Star-formation histories of local luminous infrared galaxies^⋆,⋆⋆

¹ Centro de Astrobiología (CSIC/INTA), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
e-mail: mpereira@cab.inta-csic.es
² Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, 39005 Santander, Spain
³ Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
⁴ Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁵ Cavendish Laboratory, University of Cambridge 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK
⁶ Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125, USA
⁷ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile

Received: 18 November 2014
Accepted: 16 February 2015

Abstract

We present analysis of the integrated spectral energy distribution (SED) from the ultraviolet (UV) to the far-infrared and Hα of a sample of 29 local systems and individual galaxies with infrared (IR) luminosities between 10¹¹L_⊙ and 10^11.8L_⊙. We combined new narrow-band Hα + [N ii] and broad-band g, r optical imaging taken with the Nordic Optical Telescope (NOT), with archival GALEX, 2MASS, Spitzer, and Herschel data. Their SEDs(photometry and integrated Hα flux) were fitted simultaneously with a modified version of the magphys code using stellar population synthesis models for the UV–near-IR range and thermal emission models for the IR emission taking the energy balance between the absorbed and re-emitted radiation into account. From the SED fits, we derive the star-formation histories (SFH) of these galaxies. For nearly half of them, the star-formation rate appears to be approximately constant during the last few Gyr. In the other half, the current star-formation rate seems to be enhanced by a factor of 3–20 with respect to what occurred ~1 Gyr ago. Objects with constant SFH tend to be more massive than starbursts, and they are compatible with the expected properties of a main-sequence (M-S) galaxy. Likewise, the derived SFHs show that all our objects were M-S galaxies ~1 Gyr ago with stellar masses between 10^10.1 and 10^11.5 M_⊙. We also derived the average extinction (A_v = 0.6−3 mag) and the polycyclic aromatic hydrocarbon luminosity to L_IR ratio (0.03−0.16) from our fits. We combined the A_v with the total IR and Hα luminosities into a diagramthat can be used to identify objects with rapidly changing (increasing or decreasing) SFR during the past 100 Myr.