论文标题
缺乏紧凑型星爆的核芳族烃发射：2型Quasar MRK 477
Absence of nuclear polycyclic aromatic hydrocarbon emission from a compact starburst: The case of the type-2 quasar Mrk 477
论文作者
论文摘要
MRK 477是最接近2型类星体（QSO2），距离为163 MPC。这使其成为研究核活动与恒星形成之间相互作用的理想实验室，并具有很大的细节和信噪比。在这封信中，我们介绍了新的中红外（MID-IR）成像和光谱数据，其角度分辨率为0.4 ARCSEC（〜300 pc），使用Gran Telescopio Canarias（GTC）仪器加拿大仪表获得。星系中央〜400 pc的N波段（8-13微米）谱显示[S IV] 10.51微米的发射，但NO 8.6或11.3 micron PAH特征，通常用作最近恒星形成的示踪剂。这与大小约300 pc的核星爆，6 Myr和1.1x10^8 msun的存在形成鲜明对比，这受到了紫外线哈勃太空望远镜观测的约束。考虑到这一点，我们认为，尽管X射线柱密度相对较大，log n_h = 23.5 cm^-2，即使是主要产生11.3微米PAH频段的更弹性的中性分子也很可能在活性核的附近被破坏。这强调了在使用PAH特征作为星系中部区域的恒星形成示踪剂来评估活性银河核反馈的影响时要保持谨慎的重要性。
Mrk 477 is the closest type-2 quasar (QSO2), at a distance of 163 Mpc. This makes it an ideal laboratory for studying the interplay between nuclear activity and star formation with a great level of detail and signal-to-noise. In this Letter we present new mid-infrared (mid-IR) imaging and spectroscopic data with an angular resolution of 0.4 arcsec (~300 pc) obtained with the Gran Telescopio Canarias (GTC) instrument CanariCam. The N-band (8-13 micron) spectrum of the central ~400 pc of the galaxy reveals [S IV]10.51 micron emission, but no 8.6 or 11.3 micron PAH features, which are commonly used as tracers of recent star formation. This is in stark contrast with the presence of a nuclear starburst of ~300 pc in size, an age of 6 Myr, and a mass of 1.1x10^8 Msun, as constrained from ultraviolet Hubble Space Telescope observations. Considering this, we argue that even the more resilient, neutral molecules that mainly produce the 11.3 micron PAH band are most likely being destroyed in the vicinity of the active nucleus despite the relatively large X-ray column density, of log N_H=23.5 cm^-2, and modest X-ray luminosity, of 1.5x10^43 erg/s. This highlights the importance of being cautious when using PAH features as star formation tracers in the central region of galaxies to evaluate the impact of feedback from active galactic nuclei.
