Rest-frame far-ultraviolet to far-infrared view of Lyman break galaxies at z=3: Templates and dust attenuation

Álvarez Márquez, J., Burgarella, D., Buat, V., Illbert, O., Pérez González, P. G. 2019. Rest-frame far-ultraviolet to far-infrared view of Lyman break galaxies at z=3: Templates and dust attenuation. Astronomy and Astrophysics 630 DOI: 10.1051/0004-6361/201935719

This work explores, from a statistical point of view, the rest-frame far-ultraviolet (FUV) to far-infrared (FIR) emission of a population of Lyman-break galaxies (LBGs) at z similar to 3 that cannot be individually detected from current FIR observations.

Methods. We performed a stacking analysis over a sample of similar to 17 000 LBGs at redshift 2.5 < z < 3.5 in the COSMOS field. The sample is binned as a function of UV luminosity (L-FUV), UV continuum slope (beta(UV)), and stellar mass (M-*), and then stacked at optical (BVriz bands), near-infrared (YJHK(s) bands), IRAC (3.6, 4.5, 5.6, and 8.0 mu m), MIPS (24 mu m), PACS (100 and 160 mu m), SPIRE (250, 350, and 500 mu m), and AzTEC (1.1 mm) observations. We obtained 30 rest-frame FUV-to-FIR spectral energy distributions (SEDs) of LBGs at z similar to 3, and analyzed these with the CIGALE SED-fitting analysis code. We were able to derive fully consistent physical parameters, that is, M-*, beta(UV), L-FUV, L-IR, A(FUV), star formation rate, and the slope of the dust attenuation law; we built a semiempirical library of 30 rest-frame FUV-to-FIR stacked LBG SEDs as functions of L-FUV, beta(UV), and M-*.

Results. We used the so-called IR-excess (IRX equivalent to L-IR/L-FUV) to investigate the dust attenuation as a function of beta(UV) and M-*. Our LBGs, averaged as a function of beta(UV), follow the well-known IRX-beta(UV) calibration of local starburst galaxies. Stacks as a function of M-* follow the IRX-M-* relationship presented in the literature at high M-* (log(M-* [M-circle dot]) > 10). However, a large dispersion is shown in the IRX-beta(UV) and IRX-M-* planes, in which the beta(UV) and M-* are combined to average the sample. Additionally, the SED-fitting analysis results provide a diversity of dust attenuation curve along the LBG sample, and their slopes are well correlated with M-*. Steeper dust attenuation curves than Calzetti’s are favored in low stellar mass LBGs (log(M-* [M-circle dot]) < 10.25), while grayer dust attenuation curves are favored in high stellar mass LBGs (log(M-* [M-circle dot]) > 10.25). We also demonstrate that the slope of the dust attenuation curves is one of the main drivers that shapes the IRX-beta(UV) plane.

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