The brightest galaxies at cosmic dawn
The brightest galaxies at cosmic dawn
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DOI：
10.1093/mnras/stad035
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发表时间：
2023-03-07
影响因子：
4.8
通讯作者：
Treu, Tommaso
中科院分区：
文献类型：
--
作者：
Mason, Charlotte A.;Trenti, Michele;Treu, Tommaso
JWST最近的观测表明，与大多数理论模型相比，有超过10个候选星系。在这里，我们探索了晕形成时间尺度、恒星形成效率和尘埃衰减之间的相互作用如何影响在早期宇宙中观察到的星系的性质和数量密度。为了指导直觉，我们计算了紫外线光度函数(LF)的理论上限，假设恒星形成是100%有效的，光晕中的所有气体都被转化为恒星，星系处于紫外线发射的峰值年龄(类似于10Myr)。这一上限类似于比目前的观测结果大4个数量级，这意味着在兰姆达冷暗物质宇宙学中，与恒星形成没有正式的张力。在一个更真实的模型中，我们使用由扩展的Press-Scheck hter理论得出的晕形成时间尺度的分布作为恒星形成率(SFR)的代理。我们预测，到目前为止，在Z？10观测到的星系主要是那些形成时间尺度最快的星系，因此是最极端的SFR和年轻的年龄。与中值紫外线星等与晕质量的关系相比，这些星系可以被向上散射1.5毫克。这可能在高红移时引入了选择效应，即到目前为止只探测到了最年轻(？0 Myr)、最高恒星形成的星系(特定的SFR？30 Gyr(-1))。此外，我们的模拟表明，UVLF亮端的红移演化受到尘埃衰减积累的很大影响。我们预测，更深入的JWST观测(达到m类似于30)将揭示更多典型的星系，它们具有相对较老的年龄(类似于100 Myr)和较不极端的特定SFR(类似于10 Gyr(-1)，对于类似于-20星系的MUV，z类似于10)。
Recent JWST observations suggest an excess of z ? 10 galaxy candidates abo v e most theoretical models. Here, we explore how the interplay between halo formation time-scales, star formation efficiency, and dust attenuation affects the properties and number densities of galaxies observed in the early Universe. To guide intuition, we calculate the theoretical upper limit on the UV luminosity function (LF), assuming star formation is 100 per cent efficient and all gas in haloes is converted into stars, and that galaxies are at the peak age for UV emission (similar to 10 Myr). This upper limit is similar to 4 orders of magnitude greater than current observations, implying no formal tension with star formation in Lambda cold dark matter cosmology. In a more realistic model, we use the distribution of halo formation time-scales derived from extended Press-Schechter theory as a proxy for star formation rate (SFR). We predict that the galaxies observed so far at z ? 10 are dominated by those with the fastest formation time-scales, and thus most extreme SFRs and young ages. These galaxies can be upscattered by similar to 1.5 mag compared to the median UV magnitude versus halo mass relation. This likely introduces a selection effect at high redshift whereby only the youngest (?0 Myr), most highly star-forming galaxies (specific SFR ? 30 Gyr (-1)) have been detected so far. Furthermore, our modelling suggests that redshift evolution at the bright end of the UV LF is substantially affected by the build-up of dust attenuation. We predict that deeper JWST observations (reaching m similar to 30) will reveal more typical galaxies with relatively older ages ( similar to 100 Myr) and less extreme specific SFRs ( similar to 10 Gyr(-1 )for a MUV similar to -20 galaxy at z similar to 10).