摘要
威廉·赫歇尔(William Herschel)在1800年首次观测到了太阳光中的红外辐射.在肉眼可见的世界外还存在其他形式的能量,这一发现在人类对于宇宙的认知过程中具有里程碑式的意义.由于地球大气中的水汽对于红外信号的吸收,要可靠地探测到宇宙中的红外辐射,特别是中远红外辐射,必须利用空间红外望远镜.尘埃遮蔽导致的消光——红化,和宇宙膨胀带来的多普勒效应——红移,使得红外成为观测更远、更暗、更年老星系的不二之选,也是研究宇宙起源,特别是宇宙早期星系形成的最佳和唯一途径.
Infrared observatories have been the key to our exploration of the distant universe,given the fact that star light from the early universe is redshifted to the infrared and these bands are immune to dust reddening.In the past 50 years or so,the advancement in space-based infrared telescopes has led to discoveries and systematic confirmation of high-redshift galaxies,including ultra-luminous infrared galaxies(ULIRGs)and active galactic nuclei(AGNs),which have significantly improved our understanding of galaxy formation and evolution at the high-redshift universe.Since its launch at the end of 2021,James Webb Space Telescope(JWST),as the most advanced space astronomical telescope available,has significantly pushed our frontier in the exploration of the origin of the universe with its unprecedented image resolution,deep fields,and the critical spectral coverage in the near-and mid-infrared wavelengths.Our understanding of galaxy formation and evolution in the early universe has greatly advanced with JWST’s new observations.One important breakthrough is the continuous new records for the earliest galaxies detected and confirmed.The Lyman-break method is commonly employed to search for high-redshift galaxies.This method is based on the prominent Lyman-break feature in star-forming galaxies,which results in a significant jump from the bluer to redder bands.Several deep surveys in the nearand mid-infrared bands have taken advantage of this method to select galaxy candidates in the early universe.With followup spectroscopical observations,JWST has identified and confirmed multiple galaxies with redshifts exceeding 10,including the record-breaking redshift 14 galaxies JADES-GS-z14-0 and JADES-GS-z14-1.These findings indicate that large-scale star formation activities already happened only a few hundred million years after the Big Bang.The maturity of these galaxies far exceeded model predictions,posing a challenge to existing theories of galaxy formation and the time for cosmic ionization.In addition to the discovery of high-redshift galaxies,JWST has also revealed the existence of supermassive black holes in the early universe by spectral confirmations.For example,the highly excited spectral emission lines detected in the GN-z11 galaxy suggest the possibility of active accretion of supermassive black holes(SMBHs),which is“over-massive”compared to their host galaxies,as compared to the local SMBH-host mass relations.A population of similar“over-massive”SMBHs has been identified with JWST in the early universe at z>4.This poses concerns to the current pictures on the co-evolution of black holes and their host galaxies,where the two should grow in sync with each other.Different black hole seeding mechanisms have been proposed to explain the observed black hole and host mass ratios.Looking ahead,with the release of more infrared data and the discovery of fainter galaxies at a high redshift,more breakthroughs are expected in the study of dark matter,initial conditions for star formation,co-evolution of black holes and galaxies,and the structure of the early universe.Upcoming infrared observations will further enrich our understanding of the origin of the universe and the formation and evolution of early galaxies,and promote the in-depth development of galaxy formation and evolution theories and simulations.
作者
戴昱
Yu Dai(National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China)
出处
《科学通报》
北大核心
2025年第24期4165-4172,共8页
Chinese Science Bulletin
关键词
红外辐射
空间红外望远镜
威廉赫歇尔
宇宙早期星系
infrared astronomy
galaxy formation
supermassive black holes
high-redshift
Lyman-break galaxy
space telescope
