论文标题
早期星系星际介质中的速度分散
Velocity dispersion in the interstellar medium of early galaxies
论文作者
论文摘要
我们研究了由[CII] $158μ\ rm {M} $线排放所追踪的回离（EOR）时期星系（EOR）中星系的视线速度分散的结构。我们的实验室是Serra Suite的一部分，是模拟的原型Lyman-Break Galaxy“ Freesia”。当Freesia处于非常活跃的组装阶段时，分析包括红移范围6 <z <8。我们使用[CII]高光谱数据立方体构建了三个动态不同的进化阶段（Z = 7.4时的螺旋磁盘，Z = 8.0的合并，在Z = 6.5时的磁盘）构建速度分散图。我们发现，以高空间分辨率为0.005英寸（$ \ simeq 30 pc $），发光度加权的平均速度分散体为$σ_{\ rm {\ rm {cii}} $ 〜2388 km/s，其价值最高，具有高度结构的干扰阶段。 CII} $涂抹效应取决于特定的星系结构。 $ v _ {\ rm c}/σ$ 〜7与z = 2-3个星系相似。 σ_ {\ rm sfr} $之间的关系相对平坦，价格为$ 0.02 <σ_{\ rm sfr}/{{\ rm m} _ {\ odot}} \ Mathrm {yrm {yr}^{yr}^{ - 1} { - 1} { - 1} {\ Mathrm Kpc} {\ Mathrm Kpc} {分析关系$σ\proptoσ_{\ rm sfr}^{5/7} $。
We study the structure of spatially resolved, line-of-sight velocity dispersion for galaxies in the Epoch of Reionization (EoR) traced by [CII] $158μ\rm{m}$ line emission. Our laboratory is a simulated prototypical Lyman-break galaxy, "Freesia", part of the SERRA suite. The analysis encompasses the redshift range 6 < z < 8, when Freesia is in a very active assembling phase. We build velocity dispersion maps for three dynamically distinct evolutionary stages (Spiral Disk at z=7.4, Merger at z=8.0, and Disturbed Disk at z=6.5) using [CII] hyperspectral data cubes. We find that, at a high spatial resolution of 0.005" ($\simeq 30 pc$), the luminosity-weighted average velocity dispersion is $σ_{\rm{CII}}$~23-38 km/s with the highest value belonging to the highly-structured Disturbed Disk stage. Low resolution observations tend to overestimate $σ_{\rm CII}$ values due to beam smearing effects that depend on the specific galaxy structure. For an angular resolution of 0.02" (0.1"), the average velocity dispersion is 16-34% (52-115%) larger than the actual one. The [CII] emitting gas in Freesia has a Toomre parameter $\mathcal{Q}$~0.2 and a rotational-to-dispersion ratio of $v_{\rm c}/σ$~ 7 similar to that observed in z=2-3 galaxies. The primary energy source for the velocity dispersion is due to gravitational processes, such as merging/accretion events; energy input from stellar feedback is generally subdominant (< 10%). Finally, we find that the resolved $σ_{\rm{CII}} - Σ_{\rm SFR}$ relation is relatively flat for $0.02<Σ_{\rm SFR}/{{\rm M}_{\odot}} \mathrm{yr}^{-1} {\mathrm kpc}^{-2} < 30$, with the majority of data lying on the derived analytical relation $σ\propto Σ_{\rm SFR}^{5/7}$. At high SFR, the increased contribution from stellar feedback steepens the relation, and $σ_{\rm{CII}}$ rises slightly.
