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arXiv 1702.06182astro-ph.GA
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从HiZELS到z=2.2的尘埃遮蔽恒星形成和气体的演化

Evolution of Dust-Obscured Star Formation and Gas to z=2.2 from HiZELS

Alasdair Thomson, James Simpson, Ian Smail, Mark Swinbank, Philip Best, David Sobral, James Geach, Edo Ibar, Helen Johnson

摘要:

我们调查的远红外特性的星系选择通过深,窄带成像的H $α$发射线在四个红移片从$z=0.40$-$2.23$ $\sim 1$度$^2$的高红移发射线调查(HiZELS)的一部分。我们使用堆叠的方法在赫歇尔PACS/SPIRE波段,随着$850\,μ$ m成像从SCUBA-2研究H $α$ -发射器的尘埃特性的演变以上的演变特征的光度阈值,$0.2L^\star_{{\rm H}α}(z)$。我们调查的尘埃温度和我们的堆叠样品的远红外光度之间的关系,发现H $α$ -选择识别冷,低- $L_{\rm IR}$星系($T_{\rm dust}\sim 14$ k; $\log[L_{\rm IR}/{\rm L}_\odot]\sim 9.9$)在$z=0.40$,更明亮,温暖的系统($T_{\rm dust}\sim 34$ k; $\log[L_{\rm IR}/{\rm L}_\odot]\sim 11.5$)在$z=2.23$。使用修改后的灰体模型,我们估计的“特征尺寸”的尘埃发射区的HiZELS星系的$\sim 0.5$千秒差距,近一个数量级小于其恒星的连续体的大小,这可能提供clupholism结构的间接证据。最后,我们测量尘埃质量从我们的远红外SEDs随着金属性依赖的气体-尘埃比($δ_{\rm GDR}$),以测量典型的分子气体质量的$\sim 10^{10}$ M $_\odot$这些明亮的H $α$ -发射器。气体耗尽的时间尺度在每个红移都比哈勃时间短,这表明它们的气体库可能来自星系际介质。基于H $α$选择星系的数密度,我们发现典型的恒星形成星系比$0.2L^{\star}_{{\rm H}α}(z)$更亮,宇宙总气体含量的一个重要部分($35\pm10$ %),与最新宇宙学模拟的预测一致。

英文摘要:

We investigate the far-infrared properties of galaxies selected via deep, narrow-band imaging of the H$α$ emission line in four redshift slices from $z=0.40$--$2.23$ over $\sim 1$deg$^2$ as part of the High-redshift Emission Line Survey (HiZELS). We use a stacking approach in the Herschel PACS/SPIRE bands, along with $850\,μ$m imaging from SCUBA-2 to study the evolution of the dust properties of H$α$-emitters selected above an evolving characteristic luminosity threshold, $0.2L^\star_{{\rm H}α}(z)$. We investigate the relationship between the dust temperatures and the far-infrared luminosities of our stacked samples, finding that H$α$-selection identifies cold, low-$L_{\rm IR}$ galaxies ($T_{\rm dust}\sim 14$k; $\log[L_{\rm IR}/{\rm L}_\odot]\sim 9.9$) at $z=0.40$, and more luminous, warmer systems ($T_{\rm dust}\sim 34$k; $\log[L_{\rm IR}/{\rm L}_\odot]\sim 11.5$) at $z=2.23$. Using a modified greybody model, we estimate "characteristic sizes" for the dust-emitting regions of HiZELS galaxies of $\sim 0.5$kpc, nearly an order of magnitude smaller than their stellar continuum sizes, which may provide indirect evidence of clumpy ISM structure. Lastly, we measure the dust masses from our far-IR SEDs along with metallicity-dependent gas-to-dust ratios ($δ_{\rm GDR}$) to measure typical molecular gas masses of $\sim 10^{10}$M$_\odot$ for these bright H$α$-emitters. The gas depletion timescales are shorter than the Hubble time at each redshift, suggesting probable replenishment of their gas reservoirs from the intergalactic medium. Based on the number density of H$α$-selected galaxies, we find that typical star-forming galaxies brighter than $0.2L^{\star}_{{\rm H}α}(z)$ host a significant fraction ($35\pm10$%) of the total gas content of the Universe, consistent with the predictions of the latest cosmological simulations.

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