论文标题
UV2175Å衰减凸起及其与Z〜2时PAH排放的相关性
The UV 2175Å Attenuation Bump and its Correlation with PAH Emission at z~2
论文作者
论文摘要
紫外线凹凸是一种以2175Å为中心的广泛吸收特征，在某些星系的衰减/灭绝曲线中可见，但其起源并不众所周知。 Here, we use a sample of 86 star-forming galaxies at z=1.7-2.7 with deep rest-frame UV spectroscopy from the MUSE HUDF Survey to study the connection between the strength of the observed UV 2175Å bump and the Spitzer/MIPS 24 micron photometry, which at the redshift range of our sample probes mid-IR polycyclic aromatic hydrocarbon (PAH) emission at ~6-8 micron.该样品具有稳健的光谱红移，由典型的主要序列星系组成，其恒星质量（log（mstar/msun）〜8.5-10.7）和恒星形成速率（SFRS; SFR 〜1-1-100 msun/yr）。带有MIPS探测的星系具有强烈的紫外线凸起，除了年龄大于150 Myr的大规模加权年龄的星系。我们发现，在固定恒星质量下，紫外凸起幅度不会随SFR而变化，而是在固定SFR处随质量而增加。 UV凸起振幅和PAH强度（定义为由SFR归一化的MID-IR发射）高度相关，并且都与恒星质量密切相关。我们将这些相关性解释为质量金属关系的结果，因此，由于PAH分子的丰度较低，因此在低金属性PAH发射时，PAH发射较弱。如果PAH载体是额外的紫外线吸收的主要来源，则预计在基础平滑衰减曲线顶部的2175Å凹凸特征较弱或完全不存在。
The UV bump is a broad absorption feature centered at 2175Å that is seen in the attenuation/extinction curve of some galaxies, but its origin is not well known. Here, we use a sample of 86 star-forming galaxies at z=1.7-2.7 with deep rest-frame UV spectroscopy from the MUSE HUDF Survey to study the connection between the strength of the observed UV 2175Å bump and the Spitzer/MIPS 24 micron photometry, which at the redshift range of our sample probes mid-IR polycyclic aromatic hydrocarbon (PAH) emission at ~6-8 micron. The sample has robust spectroscopic redshifts and consists of typical main-sequence galaxies with a wide range in stellar mass (log(Mstar/Msun) ~ 8.5-10.7) and star formation rates (SFRs; SFR ~ 1-100 Msun/yr). Galaxies with MIPS detections have strong UV bumps, except for those with mass-weighted ages younger than ~150 Myr. We find that the UV bump amplitude does not change with SFR at fixed stellar mass but increases with mass at fixed SFR. The UV bump amplitude and the PAH strength (defined as mid-IR emission normalized by SFR) are highly correlated and both also correlate strongly with stellar mass. We interpret these correlations as the result of the mass-metallicity relationship, such that at low metallicities PAH emission is weak due to a lower abundance of PAH molecules. The weak or complete absence of the 2175Å bump feature on top of the underlying smooth attenuation curve at low mass/metallicities is then expected if the PAH carriers are the main source of the additional UV absorption.
