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arXiv 2203.09153astro-ph.GAastro-ph.CO
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UV 2175 π衰减凸点及其与z~2处PAH发射的相关性

The UV 2175Å Attenuation Bump and its Correlation with PAH Emission at z~2

Irene Shivaei, Leindert Boogaard, Tanio Díaz-Santos, Andrew Battisti, Jarle Brinchmann, Elisabete da Cunha, Michael Maseda, Jorryt Matthee, Ana Monreal-Ibero, T… 展开作者

Irene Shivaei, Leindert Boogaard, Tanio Díaz-Santos, Andrew Battisti, Jarle Brinchmann, Elisabete da Cunha, Michael Maseda, Jorryt Matthee, Ana Monreal-Ibero, Themiya Nanayakkara, Gergö Popping, Alba Vidal-García, Peter M. Weilbacher

摘要:

紫外线凸点是一个以2175 ° C为中心的广泛吸收特征,可以在一些星系的衰减/消光曲线中看到,但其起源并不为人所知。在这里,我们使用了86个恒星形成星系的样本,z=1.7-2.7与深静止帧紫外光谱从MUSE HUDF调查研究之间的联系,观察到的UV 2175 μ m凸点的强度和斯皮策/MIPS 24微米测光,这在我们的样本探测中红外多环芳烃(PAH)发射的红移范围约6-8微米。该样本具有强大的光谱红移,由典型的主序星星系组成,其恒星质量(log(Mstar/Msun)~ 8.5-10.7)和恒星形成率(SFR; SFR ~ 1-100 Msun/yr)范围很广。MIPS检测的镓具有强烈的紫外线颠簸,除了那些质量加权年龄小于约1.5亿年的镓。我们发现,在固定的恒星质量,紫外颠簸的振幅不随SFR的变化,但在固定的SFR的质量增加。紫外线的颠簸幅度和PAH的强度(定义为中红外辐射归一化的SFR)是高度相关的,两者也与恒星质量密切相关。我们将这些相关性解释为质量-金属丰度关系的结果,使得在低金属丰度下PAH发射由于PAH分子的丰度较低而较弱。如果PAH载体是额外紫外吸收的主要来源,则预期在低质量/金属丰度下,基础平滑衰减曲线顶部的2175 μ m隆起特征较弱或完全不存在。

英文摘要:

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.

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