分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a sample of Ly{\alpha} emitters (LAEs) at $z\approx6.6$ from our spectroscopic survey of high-redshift galaxies using the multi-object spectrograph M2FS on the Magellan Clay telescope. The sample consists of 36 LAEs selected by the narrow-band (NB921) technique over nearly 2 deg$^2$ in the sky. These galaxies generally have high Ly{\alpha} luminosities spanning a range of ${\sim}3\times10^{42}{-}7\times10^{43}$ erg s$^{-1}$, and include some of the most Ly{\alpha}-luminous galaxies known at this redshift. They show a positive correlation between the Ly{\alpha} line width and Ly{\alpha} luminosity, similar to the relation previously found in $z\approx5.7$ LAEs. Based on the spectroscopic sample, we calculate a sophisticated sample completeness correction and derive the Ly{\alpha} luminosity function (LF) at $z\approx6.6$. We detect a density bump at the bright end of the Ly{\alpha} LF that is significantly above the best-fit Schechter function, suggesting that very luminous galaxies tend to reside in overdense regions that have formed large ionized bubbles around them. By comparing with the $z\approx5.7$ Ly{\alpha} LF, we confirm that there is a rapid LF evolution at the faint end, but a lack of evolution at the bright end. The fraction of the neutral hydrogen in the intergalactic medium at $z\approx6.6$ estimated from such a rapid evolution is about $\sim0.3\pm0.1$, supporting a rapid and rather late process of cosmic reionization.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a well-designed sample of more than 1000 type 1 quasars at
$3.50.5$. The
evolution of the QLFs from $z\sim5$ to $3.5$ can be described by a pure density
evolution model ($\propto10^{kz}$) and the parameter $k$ is similar to that at
$5
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shu Wang
Linhua Jiang
Yue Shen
Luis C. Ho
Marianne Vestergaard
Eduardo Banados
Chris J. Willott
Jin Wu
Siwei Zou
Jinyi Yang
Feige Wang
Xiaohui Fan
Xue-Bing Wu
摘要： Broad line regions (BLRs) in high-redshift quasars provide crucial
information of chemical enrichment in the early universe. Here we present a
study of BLR metallicities in 33 quasars at redshift $5.7
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Linhua Jiang
Yuanhang Ning
Xiaohui Fan
Luis C. Ho
Bin Luo
Feige Wang
Jin Wu
Xue-Bing Wu
Jinyi Yang
Zhen-Ya Zheng
摘要： Cosmic (hydrogen) reionization marks one of the major phase transitions of the universe at redshift z >= 6. During this epoch, hydrogen atoms in the intergalactic medium (IGM) were ionized by Lyman continuum (LyC) photons. However, it remains challenging to identify the major sources of the LyC photons responsible for reionization. In particular, individual contributions of quasars (or active galactic nuclei, AGNs) and galaxies are still under debate. Here we construct the far-ultraviolet (far-UV) luminosity function for type 1 quasars at z >= 6 that spans 10 magnitudes (-19 -23 mag that is critical to determine quasars' total LyC photon production but has been barely explored previously. We find that the quasar population can only provide less than 7% (95% confidence level) of the total photons needed to keep the universe ionized at z = 6.0 - 6.6. Our result suggests that galaxies, presumably low-luminosity star-forming systems, are the major sources of hydrogen reionization.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jin Wu
Yue Shen
Linhua Jiang
Eduardo Bañados
Xiaohui Fan
Luis C. Ho
Marianne Vestergaard
Feige Wang
Shu Wang
Xue-Bing Wu
Jinyi Yang
摘要： We study the demographics of z ~ 6 broad-line quasars in the black hole (BH) mass-luminosity plane using a sample of more than 100 quasars at 5.7 10^8.5 M_Sun, with a median 1-sigma uncertainty of ~0.5 dex in abundance. The intrinsic Eddington ratio distribution of M_BH > 10^8.5 M_Sun quasars can be approximated by a mass-dependent Schechter model, with a broad peak around log(L_bol/L_Edd}) ~ -0.9. We also find that, at 4.5 < z < 6, the number densities of more massive BHs tend to decline more rapidly with increasing redshift, contrary to the trend at 2.5 < z < 4.5 reported previously.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jin Wu
Yue Shen
Linhua Jiang
Eduardo Bañados
Xiaohui Fan
Luis C. Ho
Marianne Vestergaard
Feige Wang
Shu Wang
Xue-Bing Wu
Jinyi Yang
摘要： We study the demographics of z ~ 6 broad-line quasars in the black hole (BH) mass-luminosity plane using a sample of more than 100 quasars at 5.7 10^8.5 M_Sun, with a median 1-sigma uncertainty of ~0.5 dex in abundance. The intrinsic Eddington ratio distribution of M_BH > 10^8.5 M_Sun quasars can be approximated by a mass-dependent Schechter model, with a broad peak around log(L_bol/L_Edd}) ~ -0.9. We also find that, at 4.5 < z < 6, the number densities of more massive BHs tend to decline more rapidly with increasing redshift, contrary to the trend at 2.5 < z < 4.5 reported previously.
分类： 工程与技术科学 >> 工程与技术科学其他学科 提交时间： 2023-01-03 合作期刊: 《2022年第三届艺术设计、传播与工程科学研讨会》
摘要： The advent of extended reality (XR) in red tourism is revamping tourist experience. Compare to tour guide service in other-directed travel, the influence of XR technology in self-directed travel on perceived value and behavior intention needs further research. This paper constructs a conceptual model based on the relationship between tourist experience, perceived value and behavior intention. Basic data in the memorial hall in a memorial park dedicated to the Battle of the Xiangjiang River during the Long March were obtained through questionnaire survey. After collecting the data, this paper uses structural equation model to verify the hypotheses. As a result of this analysis, the present study offers the following conclusions: First, self-directed tourist experience has positive influence on knowledge value and experience value. Second,other-directed tourist experience has positive influence on knowledge value and sentimental value. Third, experience value, self-directed tourist experience and other-directed tourist experience has positive influence on behavior intention.
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