The Magellan M2FS spectroscopic survey of high-redshift galaxies: the brightest Lyman-break galaxies at z∼6z \sim 6

We present a study of a sample of 45 spectroscopically confirmed, UV luminous galaxies at $z\sim 6$. They were selected as bright Lyman-break galaxies (LBGs) using deep multi-band optical images in more than 2 deg$^2$ of the sky, and subsequently identified via their strong Ly$\alpha$ emission. The majority of these LBGs span an absolute UV magnitude range from $-22.0$ to $-20.5$ mag with Ly$\alpha$ equivalent width (EW) between $\sim$10 and $\sim$200 \AA, representing the most luminous galaxies at $z\sim 6$ in terms of both UV continuum emission and Ly$\alpha$ line emission. We model the SEDs of 10 LBGs that have deep infrared observations from HST, JWST, and/or Spitzer, and find that they have a wide range of stellar masses and ages. They also have high star-formation rates ranging from a few tens to a few hundreds of Solar mass per year. Five of the LBGs have JWST or HST images and four of them show compact morphology in these images, including one that is roughly consistent with a point source, suggesting that UV luminous galaxies at this redshift are generally compact. The fraction of our photometrically selected LBGs with strong Ly$\alpha$ emission ($\mathrm{EW}>25$ \AA) is about $0.2$, which is consistent with previous results and supports a moderate evolution of the IGM opacity at the end of cosmic reionization. Using deep X-ray images, we do not find evidence of strong AGN activity in these galaxies, but our constraint is loose and we are not able to rule out the possibility of any weak AGN activity.Comment: 19 pages, 11 figures, Accepted for publication in Ap

An H{\alpha} Impression of Ly{\alpha} Galaxies at z≃6z\simeq6 with Deep JWST/NIRCam Imaging

We present a study of seven spectroscopically confirmed Ly{\alpha} emitting galaxies at redshift $z\simeq6$ using the James Webb Space Telescope (JWST) NIRCam images. These galaxies, with a wide range of Ly{\alpha} luminosities, were recently observed in a series of NIRCam broad- and medium-bands. We measure the continuum and H{\alpha} line properties of the galaxies using the combination of the NIRCam photometry and archival Hubble Space Telescope imaging data. We find that galaxies with bluer UV continuum slopes likely have higher escape fractions of Ly{\alpha} photons. We also find that galaxies with higher Ly{\alpha} line emission tend to produce ionizing photons more efficiently. The most Ly{\alpha}-luminous galaxy in the sample has a high ionizing photon production efficiency of log$_{10} \xi_{\rm ion, 0}$ (Hz erg$^{-1}$) > 26. Our results support that Ly{\alpha} galaxies may have served as an important contributor to the cosmic reionization. Blue and bright Ly{\alpha} galaxies are also excellent targets for JWST follow-up spectroscopic observations.Comment: 10 pages, 4 figures, 2 tables, submitted to ApJ

The Magellan M2FS Spectroscopic Survey of High-Redshift Galaxies: A Sample of 260 Lyα\alpha Emitters at Redshift z≈5.7z\approx5.7

We present a spectroscopic survey of Ly$\alpha$ emitters (LAEs) at $z\approx5.7$ using the multi-object spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at $z\approx5.7$. Our sample consists of 260 LAEs and covers a total effective area of more than two square degrees on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Ly$\alpha$ luminosities. We find that these LAEs span a Ly$\alpha$ luminosity range of $\sim 2\times10^{42} - 5\times10^{43}$ erg s$^{-1}$, and include some of the most luminous galaxies known at $z \ge 5.7$ in terms of Ly$\alpha$ luminosity. Most of them have rest-frame equivalent widths between 20 and 300 \r{A}, and more luminous Ly$\alpha$ emission lines tend to have broader line widths. We detect a clear offset of $\sim20$ \r{A} between the observed Ly$\alpha$ wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Ly$\alpha$ in the high-redshift spectra. This sample is being used to study the Ly$\alpha$ luminosity function and galaxy properties at $z\approx5.7$.Comment: 16 pages, 12 figures, 3 tables; Accepted for publication in Ap

Quantifying the Escape of Ly α at z ≈ 5–6: A Census of Ly α Escape Fraction with H α -emitting Galaxies Spectroscopically Confirmed by JWST and VLT/MUSE

The James Webb Space Telescope provides an unprecedented opportunity for unbiased surveys of Hα-emitting galaxies at z > 4 with the NIRCam's wide-field slitless spectroscopy (WFSS). In this work, we present a census of Lyα escape fraction (f esc,Lyα ) of 165 star-forming galaxies at z = 4.9–6.3, utilizing their Hα emission directly measured from FRESCO NIRCam/WFSS data. We search for Lyα emission of each Hα-emitting galaxy in the Very Large Telescope/MUSE data. The overall f esc,Lyα measured by stacking is 0.090 ± 0.006. We find that f esc,Lyα displays a strong dependence on the observed UV slope (β obs) and E(B − V), such that the bluest galaxies (β obs ∼ −2.5) have the largest escape fractions (f esc,Lyα ≈ 0.6), indicative of the crucial role of dust and gas in modulating the escape of Lyα photons. f esc,Lyα is less well related to other parameters, including the UV luminosity and stellar mass, and the variation in f esc,Lyα with them can be explained by their underlying coupling with E(B − V) or β obs. Our results suggest a tentative decline in f esc,Lyα at z ≳ 5, implying increasing intergalactic medium attenuation toward higher redshift. Furthermore, the dependence of f esc,Lyα on β obs is proportional to that of the ionizing photon escape fraction (f esc,LyC), indicating that the escape of Lyα and ionizing photon may be regulated by similar physical processes. With f esc,Lyα as a proxy to f esc,LyC, we infer that UV-faint (M UV > −16) galaxies contribute >70% of the total ionizing emissivity at z = 5–6. If these relations hold during the epoch of reionization, UV-faint galaxies can contribute the majority of UV photon budget to reionize the Universe

Informative scene decomposition for crowd analysis, comparison and simulation guidance

Crowd simulation is a central topic in several fields including graphics. To achieve high-fidelity simulations, data has been increasingly relied upon for analysis and simulation guidance. However, the information in real-world data is often noisy, mixed and unstructured, making it difficult for effective analysis, therefore has not been fully utilized. With the fast-growing volume of crowd data, such a bottleneck needs to be addressed. In this paper, we propose a new framework which comprehensively tackles this problem. It centers at an unsupervised method for analysis. The method takes as input raw and noisy data with highly mixed multi-dimensional (space, time and dynamics) information, and automatically structure it by learning the correlations among these dimensions. The dimensions together with their correlations fully describe the scene semantics which consists of recurring activity patterns in a scene, manifested as space flows with temporal and dynamics profiles. The effectiveness and robustness of the analysis have been tested on datasets with great variations in volume, duration, environment and crowd dynamics. Based on the analysis, new methods for data visualization, simulation evaluation and simulation guidance are also proposed. Together, our framework establishes a highly automated pipeline from raw data to crowd analysis, comparison and simulation guidance. Extensive experiments and evaluations have been conducted to show the flexibility, versatility and intuitiveness of our framework

A Spectroscopic Survey of Lyα Emitters at z ≈ 3.1 over ∼1.2 Deg(2)

We present a spectroscopic survey of Ly alpha emitters (LAEs) atz 3.1 in the Subaru XMM-Newton Deep Survey Field. This field has deep imaging data in a series of broad and narrow bands, including two adjacent narrow bands NB497 and NB503 that have allowed us to efficiently select LAE candidates atz 3.1. Using spectroscopic observations on MMT Hectospec and Magellan M2FS, we obtained a sample of 166 LAEs atz 3.1 over an effective area of similar to 1.2 deg(2), including 16 previously known LAEs. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We make use of the secure redshifts and multiband data to measure spectral properties such as Ly alpha luminosity and rest-frame UV slope. We derive a robust Ly alpha luminosity function (LF) that spans a luminosity range from similar to 10(42.0)to >10(43.5)erg s(-1). Significant overdense and underdense regions are detected in our sample, but the area coverage is wide enough to largely suppress the effect from such cosmic variance. Our Ly alpha LF is generally consistent with those from previous studies atz similar to 3.1. At the brightest end of the LF, there is a tentative detection of a density excess that is not well described by the Schechter function. The comparison with the LFs at other redshifts suggests that the Ly alpha LF does not show significant evolution at 2 z < 5. Finally, we build the composite spectra of the LAEs and detect the Nv lambda 1239 and Civ lambda lambda 1548,1551 doublet emission lines at significance of similar to 4 sigma, suggesting very hard radiation fields in (some of) these LAEs.National Natural Science Foundation of ChinaThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]