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arXiv 2305.09714astro-ph.GA
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早期宇宙尘埃性质的经验研究

An empirical study of dust properties at the earliest epochs

Joris Witstok, Gareth C. Jones, Roberto Maiolino, Renske Smit, Raffaella Schneider

AI总结:

本研究分析了17个早期宇宙星系的尘埃连续发射性质,发现尘埃发射率指数在宇宙演化中保持稳定,但高红移星系表现出与亮红外星系相当或更极端的尘埃温度和红外光度,且部分星系的尘埃产量难以仅用超新星解释。

摘要:

我们基于从文献中汇编的17个早期宇宙($4 < z < 8$)星系样本,对其具有充分采样的远红外(FIR)光谱能量分布(SED)中的尘埃连续发射性质进行了经验分析。我们将研究结果置于更广阔的背景中,通过自洽地将其与近邻恒星形成星系、亮红外星系(LIRGs)和类星体样本进行比较。除了两个源之外,我们发现尘埃发射率指数在宇宙时间演化上没有显著变化,在 $z > 4$ 时测得一致的值为 $β_\text{IR} = 1.8 \pm 0.3$,这表明大多数星系的有效尘埃性质并未发生剧烈变化。尽管具有可比的恒星质量,我们发现高红移星系在尘埃温度($T_\text{dust} > 40 \\, \mathrm{K}$)和红外光度($L_\text{IR} > 10^{11} \\, \mathrm{L_\odot}$)方面与 HERUS 样本中的 LIRGs 相似,甚至更为极端。我们发现尘埃温度向高红移方向呈温和演化,尽管 LIRGs 和类星体表现出升高的温度,表明存在更高效和/或额外的加热机制。在数据可用的情况下,我们将恒星质量估计值与推断的尘埃质量进行了比较,这种尘埃质量与温度之间的简并性只能通过良好约束的 SED 来缓解。在仅有一半的情况中,尘埃产量可能仅由超新星解释,有四个源($44\\%$)显著超过了 $M_\text{dust} \approx 0.01 M_*$ 这一高度乐观的产量。我们讨论了这种明显不一致的可能解释,以及高红移星系(包括当前 IR 亮样本)尘埃性质测量中潜在观测偏差。

英文摘要:

We present an empirical analysis of the properties of dust-continuum emission in a sample of 17 galaxies in the early Universe ($4 < z < 8$) with well-sampled far-infrared (FIR) spectral energy distributions (SEDs) compiled from the literature. We place our results into context by self-consistently comparing to samples of nearby star-forming galaxies, luminous infrared galaxies (LIRGs), and quasars. With the exception of two sources, we find no significant evolution in the dust emissivity index across cosmic time, measuring a consistent value of $β_\text{IR} = 1.8 \pm 0.3$ at $z > 4$, suggesting the effective dust properties do not change dramatically for most galaxies. Despite having comparable stellar masses, we find the high-redshift galaxies to be similar to, or even more extreme than, LIRGs in the HERUS sample in terms of dust temperature ($T_\text{dust} > 40 \, \mathrm{K}$) and IR luminosity ($L_\text{IR} > 10^{11} \, \mathrm{L_\odot}$). We find the dust temperature evolves mildly towards high redshift, though the LIRGs and quasars exhibit elevated temperatures indicating a more efficient and/or additional heating mechanism. Where available, we compare stellar-mass estimates to our inferred dust masses, whose degeneracy with dust temperature can only be mitigated with a well-constrained SED. In merely half of the cases the dust yield may be explained by supernovae alone, with four sources ($44\%$) significantly exceeding a highly optimistic yield where $M_\text{dust} \approx 0.01 M_*$. We discuss possible explanations for this apparent inconsistency and potential observational biases in the measurements of the dust properties of high-redshift galaxies, including in the current IR-bright sample.

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