Extinction in the 11.2 mu m PAH band and the low L-11.2/L-IR in ULIRGs
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Extinction in the 11.2 mu m PAH band and the low L-11.2/L-IR in ULIRGs. / Hernan-Caballero, Antonio; Spoon, Henrik W. W.; Alonso-Herrero, Almudena; Hatziminaoglou, Evanthia; Magdis, Georgios E.; Perez-Gonzalez, Pablo G.; Pereira-Santaella, Miguel; Arribas, Santiago; Cortzen, Isabella; Labiano, Alvaro; Piqueras, Javier; Rigopoulou, Dimitra.
I: Monthly Notices of the Royal Astronomical Society, Bind 497, Nr. 4, 05.08.2020, s. 4614-4625.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Extinction in the 11.2 mu m PAH band and the low L-11.2/L-IR in ULIRGs
AU - Hernan-Caballero, Antonio
AU - Spoon, Henrik W. W.
AU - Alonso-Herrero, Almudena
AU - Hatziminaoglou, Evanthia
AU - Magdis, Georgios E.
AU - Perez-Gonzalez, Pablo G.
AU - Pereira-Santaella, Miguel
AU - Arribas, Santiago
AU - Cortzen, Isabella
AU - Labiano, Alvaro
AU - Piqueras, Javier
AU - Rigopoulou, Dimitra
PY - 2020/8/5
Y1 - 2020/8/5
N2 - 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.
AB - 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.
KW - dust
KW - extinction
KW - galaxies: ISM
KW - galaxies: star formation
KW - infrared: galaxies
KW - infrared: ISM
KW - POLYCYCLIC-AROMATIC-HYDROCARBON
KW - ACTIVE GALACTIC NUCLEI
KW - STAR-FORMATION RATES
KW - INFRARED-EMISSION
KW - MIDINFRARED SPECTROSCOPY
KW - INTERSTELLAR DUST
KW - GALAXIES
KW - FEATURES
KW - DISTRIBUTIONS
KW - SPECTROGRAPH
U2 - 10.1093/mnras/staa2282
DO - 10.1093/mnras/staa2282
M3 - Journal article
VL - 497
SP - 4614
EP - 4625
JO - Royal Astronomical Society. Monthly Notices
JF - Royal Astronomical Society. Monthly Notices
SN - 0035-8711
IS - 4
ER -
ID: 252295213