Examinando por Autor "Hatziminaoglou, Evanthia"

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Extinction in the 11.2 mu m PAH band and the low L-11.2/L-IR in ULIRGs
(Oxford Academics: Blackwell Publishing, 2020-08-05) Hernández Caballero, A.; Spoon, H. W. W.; Alonso Herrero, A.; Hatziminaoglou, Evanthia; Magdis, Georgios E.; Pérez González, P. G.; Pereira Santaella, M.; Arribas, S.; Cortzen, I.; Labiano, Á.; Piqueras, J.; Rigopoulou, D.; National Aeronautics and Space Administration (NASA); Agencia Estatal de Investigación (AEI); Villum Fonden; Danish National Research Foundation (DNRF); Comunidad de Madrid; 0000-0002-4872-2294; 0000-0001-9197-7623; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present a method for recovering the intrinsic (extinction-corrected) luminosity of the 11.2 mu m PAH band in galaxy spectra. Using 105 high S/N Spitzer/IRS spectra of star-forming galaxies, we show that the equivalent width ratio of the 12.7 and 11.2 mu m PAH bands is independent on the optical depth (tau), with small dispersion (similar to 5 percent) indicative of a nearly constant intrinsic flux ratio R-int = (f(12.7)/f(11.2))(int) = 0.377 +/- 0.020. Conversely, the observed flux ratio, R-obs = (f(12.7)/f(11.2))(obs), strongly correlates with the silicate strength (S-sil) confirming that differences in R-obs reflect variation in tau. The relation between R-obs and S-sil reproduces predictions for the Galactic Centre extinction law but disagrees with other laws. We calibrate the total extinction affecting the 11.2 mu m PAH from R-obs, which we apply to another sample of 215 galaxies with accurate measurements of the total infrared luminosity (L-IR) to investigate the impact of extinction on L-11.2/L-IR. Correlation between L-11.2/L-IR and R-obs independently on L-IR suggests that increased extinction explains the well-known decrease in the average L-11.2/L-IR at high L-IR. The extinction-corrected L-11.2 is proportional to L-IR in the range L-IR = 10(9)-10(13) L-circle dot. These results consolidate L-11.2 as a robust tracer of star formation in galaxies.