论文标题
11.2微米PAH频段和低L_11.2/L_IR的灭绝
Extinction in the 11.2 micron PAH band and the low L_11.2/L_IR in ULIRGs
论文作者
论文摘要
我们提出了一种恢复星系光谱中11.2微米带的固有（灭绝校正）光度的方法。使用恒星形成星系的105个高S/N SPITZER/IRS光谱，我们表明，12.7和11.2 micron PAH频段的等效宽度比在光学深度上是独立的，〜5％的分散体表示近乎恒定的内部磁通率R_Int =（f_12.7/f_12.7/f_11.11.11.11.2）。相反，观察到的通量比，R_OBS =（F_12.7/F_11.2）_OB与硅酸盐强度（S_SIL）密切相关，证实R_OB的差异反映了光学深度的变化。 R_OB和S_SIL之间的关系再现了银河中心灭绝法的预测，但不同意其他法律。我们校准影响R_OB的11.2微米PAH的总灭绝，我们将其应用于另一个215个星系的样本，具有准确测量总红外发光度（L_IR），以研究灭绝对L_11.2/L_IR的影响。 L_11.2/L_IR与R_OB之间的相关性在L_IR上独立地表明，增加的灭绝解释了高L_IR的平均L_11.2/L_IR的众所周知的减少。灭绝校正的L_11.2与L_IR/L_SUN = 10^9--10^13的L_IR成比例。这些结果将L_11.2合并为星系中恒星形成的强大示踪剂。
We present a method for recovering the intrinsic (extinction-corrected) luminosity of the 11.2 micron 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 micron PAH bands is independent on the optical depth, with small dispersion of ~5% 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 the optical depth. 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 micron 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/L_sun = 10^9--10^13. These results consolidate L_11.2 as a robust tracer of star formation in galaxies.
