PAH发射：JWST/MIRI探测到的$z=0.5-0.8$恒星形成星系和静止星系
PAH emission from star-forming and quiescent galaxies at $z=0.5-0.8$ probed by JWST/MIRI
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中文总结 AI 辅助
利用JWST/MIRI数据，研究发现PAH质量分数在约70%太阳金属丰度处呈双峰快速转变，大质量恒星形成星系PAH丰度更高，而静止星系因淬灭过程PAH被破坏。
中文摘要 AI 辅助
我们利用AstroSat/UVIT、JWST、HST、Herschel和MUSE的多波段数据，研究了GOODS-South天区中224个由MIRI选出的、红移$z=0.5-0.8$的恒星形成星系和静止星系中多环芳烃（PAH）尘埃分子的发射。我们定义了一个观测诊断参数f$_{\rm PAH}$，即JWST/MIRI F1280W波段流量与F770W和F2550W波段流量平均值的比值，并证明该参数通过捕捉我们目标红移处的7.7$\mu$m PAH发射，能有效追踪PAH质量分数（q$_{\rm PAH}$）。我们观察到f$_{\rm PAH}$和q$_{\rm PAH}$均呈现相似性质的双峰分布，这表明星系中PAH的富集经历了一个从贫PAH系统到富PAH系统的快速转变阶段，该转变发生在约70%太阳金属丰度处。对于恒星形成星系（SFGs；即约占总样本的78%），我们发现f$_{\rm PAH}$随恒星质量和静止系FUV光度增加而增大，表明大质量、紫外明亮的星系具有更高的PAH质量分数。然而，大多数大质量静止星系（QGs）的PAH质量分数低于质量相似的SFGs，这表明在淬灭过程中PAH和更小的尘埃颗粒更容易被破坏。在SFGs中，我们观察到f$_{\rm PAH}$与O32发射线比值之间存在反相关关系，表明在强电离星际介质中PAH发生光解离。这种反相关关系，连同f$_{\rm PAH}$与气相金属丰度12+log(O/H)之间的相关性，表明低质量、贫金属的SFGs（在更高红移处越来越常见）拥有更极端的条件，不利于PAH的产生和存活。
英文摘要
We investigate emission from polycyclic aromatic hydrocarbon (PAH) dust molecules in 224 MIRI-selected star-forming and quiescent galaxies at $z=0.5-0.8$ in the GOODS-South field using multi-wavelength data from the AstroSat/UVIT, JWST, HST, Herschel, and MUSE. We define an observed diagnostic parameter, f$_{\rm PAH}$, as the ratio of JWST/MIRI F1280W to the average of F770W and F2550W band fluxes, and demonstrate that it effectively traces the PAH mass fraction (q$_{\rm PAH}$) by capturing 7.7$μ$m PAH emission at our targeted redshift. We observe a bimodal distribution of similar nature in both f$_{\rm PAH}$ and q$_{\rm PAH}$, suggesting that PAH enrichment in galaxies goes through a rapid transition phase from a PAH-poor to a PAH-rich system, at about 70\% solar metallicity. For the star-forming galaxies (SFGs; i.e., $\sim$78\% of the total sample), we find that f$_{\rm PAH}$ increases with stellar mass and rest-frame FUV luminosity, identifying massive, UV-bright galaxies to have higher PAH mass fraction. However, the majority of the massive quiescent galaxies (QGs) show lower PAH mass fraction relative to that of SFGs of similar mass, suggesting PAH and smaller dust grains are more susceptible to destruction during quenching processes. Among SFGs, we observe an anti-correlation between f$_{\rm PAH}$ and the O32 emission line ratio, suggesting PAH photo-dissociation in strongly ionized ISM. This anti-correlation, along with a correlation between f$_{\rm PAH}$ and gas-phase metallicity 12+log(O/H), indicates that low-mass, metal-poor SFGs, which are increasingly common at even higher redshifts, host more extreme conditions less favorable for PAH production and survival.
发表机构
- S. N. Bose National Centre for Basic Sciences（S.N. 玻色基础科学国家中心）
- Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)（中央研究院天文及天文物理研究所）
- East Asian Observatory（东亚天文台）
- Inter-University Centre for Astronomy and Astrophysics（大学间天文学和天体物理学中心）
- IPAC, California Institute of Technology（加州理工学院行星与红外天文中心）
- Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心）
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