[论文解读] The $z \gtrsim 9$ galaxy UV luminosity function from the JWST Advanced Deep Extragalactic Survey: insights into early galaxy evolution and reionization

Lily Whitler, Daniel P. Stark+25 more|arXiv (Cornell University)|Jan 2, 2025

Astronomy and Astrophysical Research被引用 4

一句话总结

论文利用 JWST/JADES 在 z>9 时段推导原框架 rest-frame UV 光度函数，达到 Muv ~ -17，并发现明亮端超额与微弱端斜率陡峭，对早期星系演化与再电离具有意义。

ABSTRACT

The high-redshift UV luminosity function provides important insights into the evolution of early galaxies. JWST has revealed an unexpectedly large population of bright ($M_\mathrm{UV} \lesssim -20$) galaxies at $z\gtrsim10$, implying fundamental changes in the star forming properties of galaxies at increasingly early times. However, constraining the fainter population ($M_\mathrm{UV} \gtrsim -18$) has been more challenging. In this work, we present the $z\gtrsim9$ UV luminosity function from the JWST Advanced Deep Extragalactic Survey. We calculate the UV luminosity function from several hundred $z\gtrsim9$ galaxy candidates that reach UV luminosities of $M_\mathrm{UV}\sim-17$ in redshift bins of $z\sim9-12$ (309 candidates) and $z\sim12-16$ (63 candidates). We search for candidates at $z\sim16-22.5$ and find none. We also estimate the $z\sim14-16$ luminosity function from the $z\geq14$ subset of the $z\sim12-16$ sample. Consistent with other measurements, we find an excess of bright galaxies that is in tension with many theoretical models, especially at $z\gtrsim12$. However, we also find high number densities at $-18\lesssim M_\mathrm{UV} \lesssim-17$, suggesting that there is a larger population of faint galaxies than expected, as well as bright ones. From our parametric fits for the luminosity function, we find steep faint end slopes of $-2.5\lesssimα\lesssim-2.3$, suggesting a large population of faint ($M_\mathrm{UV} \gtrsim -17$) galaxies. Combined, the high normalization and steep faint end slope of the luminosity function could imply that the reionization process is appreciably underway as early as $z=10$.

研究动机与目标

• 使用 JWST/NIRCam 成像（来自 JADES）约束 z>9 的 rest-frame UV 光度函数。
• 探测微弱端区间至 Muv ~ -17，以理解完整的星系族群。
• 评估 UV 光密度随红移的演化及其对宇宙再电离的影响。
• 将观测结果与理论星系形成模型比较，找出矛盾与可能解释。
• 基于 LF 测量，描述再电离过程正在展开的红shift 区间。

提出的方法

• 在 F115W、F150W 和 F200W 的光度失效（dropout）选择，以识别 z~9-17 的星系候选体。
• BEAGLE 光谱能量分布拟合，以推导光度学红移与概率性红移后验。
• 使用八个 JWST/NIRCam 滤镜（F090W–F444W）构建 rest-frame UV 光度测量并计算 LF。
• 在 z~9-12 和 z~12-16 的红移区间计算 UV 光度函数，并在 z>16 处给出上限。
• 估计随红移变化的 rest-UV 光密度演化。
• 结合深度与调查面积的变化来约束 LF 的微弱端。

Figure 1: The F200W footprint of the imaging used in this work. The colorbar shows the $5\sigma$ depth of F200W measured as described in Section 2.2 , where darker grey corresponds to deeper depths. The shallowest region with F200W exposure time of $<5000$ s primarily falls in GOODS-N and has typica

实验结果

研究问题

• RQ1 z~9-12 与 z~12-16 的 rest-frame UV 光度函数形状与归一化是多少？
• RQ2 是否存在与理论模型相比的 z>12 明亮星系超额，这对早期恒星形成意味着什么？
• RQ3 z>9 的 UV LF 的微弱端斜率（alpha）是多少，微弱星系是否主导 UV 光密度？
• RQ4 UV 光密度向更高红shift 的演化如何，对宇宙再电离时间线有何含义？

主要发现

• 在 z>12 的明亮星系存在超额，与许多理论模型相矛盾。
• -18 ≲ Muv ≲ -17 的高数密度，表明存在相当数量的微弱星系群体。
• 参数拟合得到陡峭的微弱端斜率：-2.5 ≲ α ≲ -2.3，表明许多微弱星系（Muv ≳ -17）。
• 结合高归一化与陡峭的微弱端斜率，暗示再电离可能在 z ≈ 10 时就已在进行。
• 在 z~16-22.5 未发现候选体，给出这些红移区间 UV LF 的上限。
• z>9 的结果与明亮星系在 z~13 之前呈现缓慢演化的一致性，并指示对 UV 光密度贡献的星系光度范围较广。

Figure 2: The distributions of observed F277W apparent magnitudes and rest-UV slopes, $\beta$ , of our dropout samples. To measure UV slopes, we fit a power law of the form $f_{\lambda}\propto\lambda^{\beta}$ to three wide filters expected to probe the rest-frame UV; see Section 4 for details. We sh