《做作》(20231026出书)一周论文导读
时间:2024-11-17 03:04:42 出处:焦点阅读(143)
编译 | 冯维维
Nature,做作周论 Volume 622 Issue 7984, 26 October 2023
《做作》第622卷,7984期,出书2023年10月26日
?文导
天体物理学Astrophysics
Confirmation and refutation of very luminous galaxies in the early Universe
韦布望远镜审核到早期宇宙璀璨星系
▲ 作者:Pablo Arrabal Haro, Mark Dickinson, Steven L. Finkelstein, Jeyhan S. Kartaltepe, Callum T. Donnan, Denis Burgarella, Jorge A. Zavala, etc.
▲ 链接:
https://www.nature.com/articles/s41586-023-06521-7
▲ 摘要 :
在宇宙历史的最后5亿年里 ,第一批恒星以及星系组成,做作周论给宇宙播下了重元素,出书并最终重新电离了星系间介质。文导詹姆斯·韦布太空望远镜审核发现了使人惊惶的做作周论大批早期恒星组成星系候选者 ,凭证多波段光度法估量,出书其距离(红移 ,文导z)大到z≈16,做作周论远超JWST以前的出书限度 。
尽管这样的文导光度红移艰深为安妥的,但它们可能蒙受简并以及无意偶尔的做作周论苦难性过错。需要光谱丈量来验证这些源头 ,出书并坚贞地量化可能约束星系组成模子以及宇宙学的文导物理特色。
钻研者揭示了韦布光谱,证明了两个颇为璀璨的星系的红移为z>11 ,并证明了另一个候选星系的红移为z≈16 ,而非此前以为的z = 4.9,它们具备不艰深的星云线发射以及灰尘变红的组合 ,与更遥远天体的颜色相似。
这些服从增强了早期快捷组成颇为璀璨星系的证据,同时也夸张了光谱验证的需要性。大批璀璨的早期星系或者表明之后星系组成模子的缺陷 ,或者与个别以为在前期建树的物理性子(如恒星初始品质函数)的倾向。
▲ Abstract :
During the first 500 million years of cosmic history, the first stars and galaxies formed, seeding the Universe with heavy elements and eventually reionizing the intergalactic medium Observations with the James Webb Space Telescope (JWST) have uncovered a surprisingly high abundance of candidates for early star-forming galaxies, with distances (redshifts, z), estimated from multiband photometry, as large as z?≈?16, far beyond pre-JWST limits. Although such photometric redshifts are generally robust, they can suffer from degeneracies and occasionally catastrophic errors. Spectroscopic measurements are required to validate these sources and to reliably quantify physical properties that can constrain galaxy formation models and cosmology. Here we present JWST spectroscopy that confirms redshifts for two very luminous galaxies with z > 11, and also demonstrates that another candidate with suggested z ≈ 16 instead has z = 4.9, with an unusual combination of nebular line emission and dust reddening that mimics the colours expected for much more distant objects. These results reinforce evidence for the early, rapid formation of remarkably luminous galaxies while also highlighting the necessity of spectroscopic verification. The large abundance of bright, early galaxies may indicate shortcomings in current galaxy formation models or deviations from physical properties (such as the stellar initial mass function) that are generally believed to hold at later times.
Geophysical evidence for an enriched molten silicate layer above Mars’s core
火核外层存在丰硕熔融硅酸盐层
▲ 作者:Henri Samuel, Mélanie Drilleau, Attilio Rivoldini, Zongbo Xu, Quancheng Huang, Rapha?l F. Garcia, Vedran Leki?, Jessica C. E. Irving, James Badro, Philippe H. Lognonné, James A. D. Connolly, Taichi Kawamura, Tamara Gudkova & William B. Banerdt
▲ 链接 :
https://www.nature.com/articles/s41586-023-06601-8
▲ 摘要 :
在火星上探测到的深反射S波判断出火核的巨细为1830±40km,但这需要的轻元素含量与试验岩石学的限度不相容。
一种假如是火星地幔的成份是平均的,这与最近丈量到的沿中间-地幔领土衍射的颇为飞快转达的P波不不同 。
另一种假如是 ,火星的地幔是不屈均的 ,这是早期岩浆陆地凝妄想成一个富含铁以及产热元素的基底层的服从。这种富集导致在岩心上方组成熔融硅酸盐层 ,由部份熔融层拆穿困绕 。
钻研表明这种妄想与所有地球物理数据兼容 ,特意是(1)深反射以及衍射地幔地震相位;(2)地震频率上的弱剪切衰减;(3)火星在火卫一潮汐上的耗散性子 。
在这个场景中 ,火核的巨细为1650±20km,象征着其密度为6.5 g cm?3,比从前的估量大5%~8%,而且可能用比从前所需的更少、更少的合金轻元始终声名 ,其数目与试验以及宇宙化学的限度相不同 。最后 ,层状地幔妄想需要外部源来发生记着实火星地壳中的磁信号。
▲ Abstract:
The detection of deep reflected S waves on Mars inferred a core size of 1,830 ± 40 km, requiring light-element contents that are incompatible with experimental petrological constraints. This estimate assumes a compositionally homogeneous Martian mantle, at odds with recent measurements of anomalously slow propagating P waves diffracted along the core–mantle boundary. An alternative hypothesis is that Mars’s mantle is heterogeneous as a consequence of an early magma ocean that solidified to form a basal layer enriched in iron and heat-producing elements. Such enrichment results in the formation of a molten silicate layer above the core, overlain by a partially molten layer. Here we show that this structure is compatible with all geophysical data, notably (1) deep reflected and diffracted mantle seismic phases, (2) weak shear attenuation at seismic frequency and (3) Mars’s dissipative nature at Phobos tides. The core size in this scenario is 1,650 ± 20 km, implying a density of 6.5 g cm?3, 5–8% larger than previous seismic estimates, and can be explained by fewer, and less abundant, alloying light elements than previously required, in amounts compatible with experimental and cosmochemical constraints. Finally, the layered mantle structure requires external sources to generate the magnetic signatures recorded in Mars’s crust.
物理学Physics
A superconducting nanowire single-photon camera with 400,000 pixels
40万像素的超导纳米线单光子相机
▲ 作者:B. G. Oripov, D. S. Rampini, J. Allmaras, M. D. Shaw, S. W. Nam, B. Korzh & A. N. McCaughan
▲ 链接:
https://www.nature.com/articles/s41586-023-06550-2
▲ 摘要 :
以前50年,超导探测器的普遍运用为探测单薄的电磁信号提供了卓越的锐敏度以及速率 。这些探测器可能在颇为低的温度下使命,发生最小的过剩噪音 ,是测试非部份性子 、钻研暗物资、绘制早期宇宙以及实施量子合计以及通讯的事实抉择 。
可是 ,尽管它们具备吸引人的特色,但当初尚未大规模的超导相机——纵然是最大的演示也从未逾越20,000像素