标题： 在高红移星系中检测多环芳烃的代理：模拟极强阻尼莱曼-α吸收体 toward QSO SDSS J1143+1420 在 z=2.323 的物理条件 显示英文标题

标题： Detecting PAHs in high-z galaxies in proxy: Modelling physical conditions in an extremely strong damped Lyman-alpha absorber towards QSO SDSS J1143+1420 at z=2.323

摘要： 我们探索了间接方法，在高红移、气体丰富的吸收选择星系中检测多环芳烃（PAHs）。我们研究了在红移z(ESDLA)=2.323时，针对类星体SDSS J1143+1420的光学VLT/X-shooter观测结果，该观测目标是一个中间的极强的Lyman-alpha吸收体（或ESDLA，log(N(HI))>~21.7）。文献研究显示，这个ESDLA包含尘埃和弥漫分子氢的特征，并且由于其与相关星系的近距离空间接近（影响参数，rho=0.6+/-0.3 kpc），而被特别选为我们的研究对象。在沿着这条视线的有限红外（IR）光谱观测中没有直接检测到PAHs的发射。因此，我们使用CLOUDY数值模拟建模来间接探测ESDLA中PAH的存在。我们注意到，为了再现观察到的温暖H2和CI的柱密度，模型中需要包含PAHs。因此，我们通过PAH/H = 10^(-7.046)的丰度间接推断出ESDLA中存在PAHs。我们还通过在吸收体静止框架中由尘埃对类星体光谱的消光建模，测得相对于恒星形成星系的2175 A波长处的突起强度较低（E(bump)~0.03-0.19 mag）。这与通过CLOUDY建模间接获得的低PAH丰度一致。我们的研究强调了使用CLOUDY建模来间接检测高红移气体丰富的吸收选择星系中的PAHs。 显示英文摘要

摘要： We explore indirect methods to detect Polycyclic Aromatic Hydrocarbons (PAHs) in gas-rich, absorption-selected galaxies at high redshift. We look at the optical VLT/X-shooter observations of an intervening, extremely strong damped Lyman-alpha absorber (or ESDLA, with log(N(HI))>~21.7)) towards QSO SDSS J1143+1420 at redshift, z(ESDLA)=2.323. Literature studies have shown that this ESDLA contains signatures of dust and diffuse molecular hydrogen and it was specifically chosen for our study due to its close spatial proximity (impact parameter, rho=0.6+/-0.3 kpc) with its associated galaxy. There is no direct detection of PAHs emission in the limited observations of infrared(IR)-spectra along this sight-line. Hence, we use CLOUDY numerical simulation modelling to indirectly probe the presence of PAH in the ESDLA. We note that PAHs need to be included in the models to reproduce the observed column densities of warm H2 and CI. Thus, we infer the presence of PAHs indirectly in our ESDLA, with an abundance of PAH/H = 10^(-7.046). We also measure a low 2175 A bump strength (E(bump)~0.03-0.19 mag) relative to star-forming galaxies by modelling extinction of QSO spectra by dust at the absorber rest-frame. This is consistent with the low PAH abundance obtained indirectly using CLOUDY modelling. Our study highlights the usage of CLOUDY modelling to indirectly detect PAH in high-redshift gas-rich absorption-selected galaxies.