Spectroscopic Survey Research Articles

DESI Survey Validation Data in the COSMOS/Hyper Suprime-Cam Field: Cool Gas Trace Main-sequence Star-forming Galaxies at the Cosmic Noon

We present the first result in exploring the gaseous halo and galaxy correlation using the Dark Energy Spectroscopic Instrument survey validation data in the Cosmic Evolution Survey (COSMOS) and Hyper Suprime-Cam field. We obtain multiphase gaseous halo properties in the circumgalactic medium by using 115 quasar spectra (signal-to-noise ratio > 3). We detect Mg ii absorption at redshift 0.6 < z < 2.5, C iv absorption at 1.6 < z < 3.6, and H i absorption associated with the Mg ii and C iv. By crossmatching the COSMOS2020 catalog, we identify the Mg ii and C iv host galaxies in 10 quasar fields at 0.9< z < 3.1. We find that within the impact parameter of 250 kpc, a tight correlation is seen between the strong Mg ii equivalent width and the host galaxy star formation rate. The covering fraction f c of the strong Mg ii selected galaxies, which is the ratio of the absorbing galaxy in a certain galaxy population, shows significant evolution in the main-sequence galaxies and marginal evolution in all the galaxy populations within 250 kpc at 0.9 < z < 2.2. The f c increase in the main-sequence galaxies likely suggests the coevolution of strong Mg ii absorbing gas and the main-sequence galaxies at the cosmic noon. Furthermore, Mg ii and C iv absorbing gas is detected out of the galaxy virial radius, tentatively indicating the feedback produced by the star formation and/or the environmental effects.

Galaxy clustering measurements out to redshift z ˜ 8 from Hubble Legacy Fields

ABSTRACT We present a novel approach for measuring the two-point correlation function of galaxies in narrow pencil beam surveys with varying depths. Our methodology is utilized to expand high-redshift galaxy clustering investigations up to z ∼ 8 by analysing a comprehensive sample consisting of Ng = 160 Lyman break galaxy candidates obtained through optical and near-infrared photometric data within the CANDELS GOODS data sets from the Hubble Space Telescope Legacy Fields. For bright sources with MUV &amp;lt; −19.8, we determine a galaxy bias of b = 9.33 ± 4.90 at $\overline{z} = 7.7$ and a correlation length of r0 = 10.74 ± 7.06 $h^{-1}\, \mathrm{Mpc}$. We obtain similar results for the XDF, with a galaxy bias measurement of b = 8.26 ± 3.41 at the same redshift for a slightly fainter sample with a median luminosity of MUV = −18.4. By comparing with dark-matter halo bias and employing abundance matching, we deduce a characteristic halo mass of Mh ∼ 1011.5 M⊙ and a duty cycle close to unity. To validate our approach for variable-depth data sets, we replicate the analysis in a region with near-uniform depth using a standard two-point correlation function estimator, yielding consistent outcomes. Our study not only provides a valuable tool for future utilization in JWST data sets but also suggests that the clustering of early galaxies continues to increase with redshift beyond z ≳ 8, potentially contributing to the existence of protocluster structures observed in early JWST imaging and spectroscopic surveys at z ≳ 8.

The Milky Way Bulge Extra-tidal Star Survey: BH 261 (AL 3)

The Milky Way Bulge extra-tidal star survey is a spectroscopic survey with the goal of identifying stripped globular cluster stars from inner Galaxy clusters. In this way, an indication of the fraction of metal-poor bulge stars that originated from globular clusters can be determined. We observed and analyzed stars in and around BH 261, an understudied globular cluster in the bulge. From seven giants within the tidal radius of the cluster, we measured an average heliocentric radial velocity of 〈RV〉 = −61 ± 2.6 km s−1 with a radial velocity dispersion of 〈σ〉 = 6.1 ± 1.9 km s−1. The large velocity dispersion may have arisen from tidal heating in the cluster’s orbit about the Galactic center, or because BH 261 has a high dynamical mass as well as a high mass-to-light ratio. From spectra of five giants, we measure an average metallicity of 〈[Fe/H]〉 = −1.1 ± 0.2 dex. We also spectroscopically confirm an RR Lyrae star in BH 261, which yields a distance to the cluster of 7.1 ± 0.4 kpc. Stars with 3D velocities and metallicities consistent with BH 261 reaching to ∼0.°5 from the cluster are identified. A handful of these stars are also consistent with the spatial distribution of potential debris from models focusing on the most recent disruption of the cluster.

Reconstructing Filaments around Galaxy Clusters from Spectroscopic Surveys using Machine Learning

Next-generation surveys such as the WEAVE Wide-Field Cluster Survey will soon give astronomers an unprecedented opportunity to study cosmic web structure and filamentary populations around clusters. Analysis of classical methods of extracting the cosmic web from simulated 2D projections has revealed significant incompleteness and contamination. In this note, we present the first results from a random forest trained and tested on the dark-matter simulation MDPL2. Our algorithm improves the precision of filament classification by 11% and decreases the structural reconstruction error by 43% compared to the previously published method.

Parameter Estimation for Open Clusters using an Artificial Neural Network with a QuadTree-based Feature Extractor

With the unprecedented increase in the number of known star clusters, quick and modern tools are needed for their analysis. In this work, we develop an artificial neural network (ANN) trained on synthetic clusters to estimate the age, metallicity, extinction, and distance of Gaia open clusters. We implement a novel technique to extract features from the color–magnitude diagram of clusters by means of the QuadTree tool, and we adopt a multiband approach. We obtain reliable parameters for ∼5400 clusters. We demonstrate the effectiveness of our methodology in accurately determining crucial parameters of Gaia open clusters by performing a comprehensive scientific validation. In particular, with our analysis we have been able to reproduce the Galactic metallicity gradient as it is observed by high-resolution spectroscopic surveys. This demonstrates that our method reliably extracts information on metallicity from color–magnitude diagrams (CMDs) of stellar clusters. For the sample of clusters studied, we find an intriguing systematic older age compared to previous analyses present in the literature. This work introduces a novel approach to feature extraction using a QuadTree algorithm, effectively tracing sequences in CMDs despite photometric errors and outliers. The adoption of ANNs, rather than convolutional neural networks, maintains the full positional information and improves performance, while also demonstrating the potential for deriving cluster parameters from simultaneous analysis of multiple photometric bands, beneficial for upcoming telescopes like the Vera Rubin Observatory. The implementation of ANN tools with robust isochrone fit techniques could provide further improvements in the quest for open cluster parameters.

DESI mock challenge: constructing DESI galaxy catalogues based on FastPM simulations

ABSTRACT Together with larger spectroscopic surveys such as the Dark Energy Spectroscopic Instrument (DESI), the precision of large-scale structure studies and thus the constraints on the cosmological parameters are rapidly improving. Therefore, one must build realistic simulations and robust covariance matrices. We build galaxy catalogues by applying a halo occupation distribution (HOD) model upon the FastPM simulations, such that the resulting galaxy clustering reproduces high-resolution N-body simulations. While the resolution and halo finder are different from the reference simulations, we reproduce the reference galaxy two-point clustering measurements – monopole and quadrupole – to a precision required by the DESI Year 1 emission line galaxy sample down to non-linear scales, i.e. $k\lt 0.5\, h\, \mathrm{Mpc}^{-1}$ or $s\gt 10\, \mathrm{Mpc}\, h^{-1}$. Furthermore, we compute covariance matrices based on the resulting FastPM galaxy clustering – monopole and quadrupole. We study for the first time the effect of fitting on Fourier conjugate (e.g. power spectrum) on the covariance matrix of the Fourier counterpart (e.g. correlation function). We estimate the uncertainties of the two parameters of a simple clustering model and observe a maximum variation of 20 per cent for the different covariance matrices. Nevertheless, for most studied scales the scatter is between 2 and 10 per cent. Consequently, using the current pipeline we can precisely reproduce the clustering of N-body simulations and the resulting covariance matrices provide robust uncertainty estimations against HOD fitting scenarios. We expect our methodology will be useful for the coming DESI data analyses and their extension for other studies.

Observational Studies of r- and s-Process Elements for Milky Way Stars

Elements heavier than iron-group are produced by rapid and slow neutron-capture processes (r-process and s-process) in the universe. The site of the processes and history of the enrichment in the Milky Way Galaxy have been studied by spectroscopic observations of stars with different ages and population (Galactic disks, halo etc.). The abundance studies of neutron-capture elements for Milky Way stars, including our long-term observational efforts using the spectroscopic survey telescope LAMOST and the 8.2m Subaru Telescope are reviewed. This article covers the observational results on the abundance distributions of heavy elements (Sr, Ba and Eu), and elemental abundance patterns of r- and s-process enhanced stars.

Probing Cosmology with Baryon Acoustic Oscillations Using Gravitational Waves

The third-generation (3G) gravitational wave (GW) detectors such as the Einstein Telescope or Cosmic Explorer are expected to play an important role in cosmology. With the help of 3G detectors, we will be able to probe large-scale structure features such as baryon acoustic oscillations (BAO), galaxy bias, etc. We explore the possibility to do precision cosmology, with the 3G GW detectors by measuring the angular BAO scale using localization volumes of compact binary merger events. Through simulations, we show that with a 3G detector network, by probing the angular BAO scale using purely GW observations, we can constrain the Hubble constant for the standard model of cosmology (ΛCDM) with 90% credible regions as . When combined with BAO measurements from galaxy surveys, we show that it can be used to constrain various models of cosmology such as parameterized models for dark energy equations of state. We also show how cosmological constraints using BAO measurements from GW observations in the 3G era will complement the same from spectroscopic surveys.

Supernova Remnants in the Irregular Galaxy NGC 4449

The nearby irregular galaxy NGC 4449 has a star formation rate of ∼0.4M ☉ yr−1 and should host of order 70 supernova remnants (SNRs) younger than 20,000 yr, a typical age for SNRs expanding into an interstellar medium (ISM) with a density of 1 cm−3 to reach the radiative phase. We have carried out an optical imaging and spectroscopic survey in an attempt to identify these SNRs. This task is challenging because diffuse gas with elevated ratios of [S ii]:Hα is omnipresent in NGC 4449, causing confusion when using this common diagnostic for SNRs. Using narrowband interference-filter images, we first identified 49 objects that have elevated [S ii]:Hα ratios compared to nearby H ii regions. Using Gemini-N and GMOS, we then obtained high-resolution spectra of 30 of these SNR candidates, 25 of which have [S ii]:Hα ratios greater than 0.5. Of these, 15 nebulae are almost certainly SNRs, based on a combination of characteristics: higher [O i]:Hα ratios and broader line widths than observed from H ii regions. The remainder are good candidates as well, but need additional confirmation. Surprisingly, despite having superior imaging and spectroscopic data sets to examine, we are unable to confirm most of the candidates suggested by Leonidaki et al. While NGC 4449 is likely an extreme case because of the high surface brightness and elevated [S ii]:Hα ratio of diffuse gas, it highlights the need for sensitive high-resolution optical spectroscopy, or high spatial resolution radio or X-ray observations that can ensure accurate SNR identifications in external galaxies.

Investigating APOKASC Red Giant Stars with Abnormal Carbon-to-nitrogen Ratios

The success of galactic archeology and the reconstruction of the formation history of our Galaxy relies critically on precise ages for large populations of stars. For evolved stars in the red clump and red giant branch, the carbon-to-nitrogen ratio ([C/N]) has recently been identified as a powerful diagnostic of mass and age that can be applied to stellar samples from spectroscopic surveys such as Sloan Digital Sky Survey/APOGEE. Here, we show that at least 10% of red clump stars and red giant branch stars deviate from the standard relationship between [C/N] and mass. We use the APOGEE–Kepler (APOKASC) overlap sample to show that binary interactions are responsible for the majority of these outliers and that stars with indicators of current or previous binarity should be excluded from galactic archeology analyses that rely on [C/N] abundances to infer stellar masses. We also show that the Data Release 14 APOGEE analysis overestimates the surface gravities for even moderately rotating giants (vsini > 2 km s−1).

Modified gravity and massive neutrinos: constraints from the full shape analysis of BOSS galaxies and forecasts for Stage IV surveys

We constrain the growth index γ by performing a full-shape analysis of the power spectrum multipoles measured from the BOSS DR12 data. We adopt a theoretical model based on the Effective Field theory of the Large Scale Structure (EFTofLSS) and focus on two different cosmologies: γCDM and γνCDM, where we also vary the total neutrino mass. We explore different choices for the priors on the primordial amplitude As and spectral index ns , finding that informative priors are necessary to alleviate degeneracies between the parameters and avoid strong projection effects in the posterior distributions. Our tightest constraints are obtained with 3σ Planck priors on As and ns : we obtain γ = 0.647 ± 0.085 for γCDM and γ = 0.612+0.075 -0.090, Mν < 0.30 for γνCDM at 68% c.l., in both cases ∼ 1σ consistent with the ΛCDM prediction γ ≃ 0.55. Additionally, we produce forecasts for a Stage-IV spectroscopic galaxy survey, focusing on a DESI-like sample. We fit synthetic data-vectors for three different galaxy samples generated at three different redshift bins, both individually and jointly. Focusing on the constraining power of the Large Scale Structure alone, we find that forthcoming data can give an improvement of up to ∼ 85% in the measurement of γ with respect to the BOSS dataset when no CMB priors are imposed. On the other hand, we find the neutrino mass constraints to be only marginally better than the current ones, with future data able to put an upper limit of Mν < 0.27 eV. This result can be improved with the inclusion of Planck priors on the primordial parameters, which yield Mν < 0.18 eV.

Fast production of cosmological emulators in modified gravity: the matter power spectrum

We test the convergence of fast simulations based on the COmoving Lagrangian Acceleration (COLA) method for predictions of the matter power spectrum, specialising our analysis in the redshift range 1 ≤ z ≤ 1.65, relevant to high-redshift spectroscopic galaxy surveys. We then focus on the enhancement of the matter power spectrum in modified gravity (MG), the boost factor, using the Dvali-Gabadadze-Porrati (DGP) theory as a test case but developing a general approach that can be applied to other MG theories. After identifying the minimal simulation requirements for accurate DGP boost factors, we design and produce a COLA simulation suite that we use to train a neural network emulator for the DGP boost factor. Using MG-AREPO simulations as a reference, we estimate the emulator accuracy to be of ∼ 3% up to k = 5 h Mpc-1 at 0 ≤ z ≤ 2. We make the emulator publicly available at: https://github.com/BartolomeoF/nDGPemu.

Testing external photoevaporation in the σ-Orionis cluster with spectroscopy and disk mass measurements (Corrigendum)

{The evolution of protoplanetary disks is regulated by an interplay of several processes, either internal to the system or related to the environment. As most of the stars and planets, including our own Solar System, have formed in massive stellar clusters that contain OB-type stars, studying the effects of UV radiation on disk evolution is of paramount importance.} % aims heading (mandatory) {Here we test the impact of external photoevaporation on the evolution of disks in the mid-age ($sim$3--5 Myr) $sigma$-Orionis cluster by conducting the first combined large-scale UV to IR spectroscopic and mm-continuum survey of this region.} % methods heading (mandatory) {We study a sample of 50 targets located at increasing distances from the central, massive OB system $sigma$-Ori. We combine new spectra obtained with VLT/X-Shooter, used to measure mass accretion rates and stellar masses, with new and previously published ALMA measurements of disk dust and gas fluxes and masses.} % results heading (mandatory) {We confirm the previously found decrease of $M_{rm dust}$ in the inner $sim$0.5 pc of the cluster, and discover an additional dependence with the stellar host mass. The disks around the more massive stars ($ge$ 0.4msun) and located in the inner part ($&lt;$ 0.5 pc) of the cluster have $M_{rm dust}$ about an order of magnitude lower than the more distant ones, in contrast to the rather flat $M_{rm dust}$ distribution as a function of the projected separation from $sigma$-Ori, for the disks around the lowest-mass stars in the sample. About half of the sample is located in the region of the $dot{M}_{rm acc}$ vs $M_{rm disk}$ expected by models of external photoevaporation, i.e. showing shorter disk lifetimes than expected for their ages. The shorter disk lifetimes is observed for all targets with projected separation from $sigma$-Ori $&lt;$ 0.5 pc, proving that the presence of a massive stellar system affects disk evolution. } % conclusions heading (optional), leave it empty if necessary {External photoevaporation is a viable mechanism to explain the observed shorter disk lifetimes and lower $M_{rm dust}$ in the inner $sim$0.5 pc of the $sigma$-Orionis cluster, where the effects of this process are more pronounced. Follow-up observations of the low stellar mass targets are crucial to constrain disk dispersion time scales in the cluster and to confirm the dependence of the external photoevaporation process with stellar host mass. This work confirms that the effects of external photoevaporation are significant down to at least impinging radiation as low as $sim 10^{4}$ G$_0$. }

Predicting interloper fraction with graph neural networks

Upcoming emission-line spectroscopic surveys, such as Euclid and the Roman Space Telescope, will be affected by systematic effects due to the presence of interlopers: galaxies whose redshift and distance from us are miscalculated due to line confusion in their emission spectra. Particularly pernicious are interlopers involving the confusion between two lines with close emitted wavelengths, like Hβ emitters confused as [O iii], since those are strongly spatially correlated with the target galaxies. They introduce a particular pattern in the 3D distribution of the observed galaxy catalog that can shift the position of the BAO peak in the galaxy correlation function and bias any cosmological analysis performed with that sample. Here we present a novel method to predict the fraction of interlopers in a galaxy catalog, using Graph Neural Networks (GNNs) to learn the posterior distribution of the interloper fraction while marginalizing over cosmology and galaxy bias. The method is developed using simulations with halos acting as a proxy for galaxies. The GNN can infer the mean and standard deviation of the posterior distribution of interloper fraction using small-scale information that is usually not considered in cosmological analyses. The injection of large-scale information into the graph as a global attribute improves the performance of the GNN when marginalizing over cosmology.

Line-of-sight structure of troughs identified in Subaru Hyper Suprime-Cam Year 3 weak lensing mass maps

ABSTRACT We perform the weak lensing mass mapping analysis to identify troughs, which are defined as local minima in the mass map. Since weak lensing probes the projected matter distribution along the line of sight, these troughs can be produced by single or multiple voids projected along the line of sight. To scrutinize the origins of the weak lensing troughs, we systematically investigate the line-of-sight structure of troughs selected from the latest Subaru Hyper Suprime-Cam (HSC) Year 3 weak lensing data covering $433.48 \, \mathrm{deg}^2$. From a curved sky mass map constructed with the HSC data, we identify 15 troughs with the signal-to-noise ratio higher than 5.7 and address their line-of-sight density structure utilizing redshift distributions of two galaxy samples, photometric luminous red galaxies observed by HSC and spectroscopic galaxies detected by Baryon Oscillation Spectroscopic Survey. While most weak lensing signals due to the troughs are explained by multiple voids aligned along the line of sight, we find that two of the 15 troughs potentially originate from single voids at redshift ∼0.3. The single void interpretation appears to be consistent with our three-dimensional mass mapping analysis. We argue that single voids can indeed reproduce observed weak lensing signals at the troughs if these voids are not spherical but are highly elongated along the line-of-sight direction.

Spectroscopic survey of higher-lying states of Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} meson family

In this work, we investigate the complete spectroscopy of the Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} mesons, with a special focus on the consideration of the unquenched effects. To account for such effects, we employ the modified Godfrey–Isgur model and introduce a screening potential. The resulting mass spectrum of the concerned higher Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} states is then presented, showing significant deviations after considering the unquenched effects. This emphasizes the importance of considering the unquenched effects when studying of the higher Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} mesons. Furthermore, we determine the corresponding spatial wave functions of these Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} mesons, which have practical applications in subsequent studies of their decays. These decays include two-body Okuba–Zweig–Iizuka allowed strong decays, dipion transitions between Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} mesons, radiative decays, and some typical weak decays. With the ongoing high-luminosity upgrade of the Large Hadron Collider, we expect the discovery of additional Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} states in the near future. The knowledge gained from the mass spectrum and the different decay modes will undoubtedly provide valuable insights for future experimental explorations of these higher Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c$$\\end{document} mesons.

A Spectroscopic Survey of Lyα Emitters and Lyα Luminosity Function at Redshifts 3.7 and 4.8

We present a spectroscopic survey of Lyα emitters (LAEs) at z ∼ 3.7 and z ∼ 4.8. The LAEs are selected using the narrowband technique based on the combination of deep narrowband and broadband imaging data in two deep fields, and then spectroscopically confirmed with the MMT multifiber spectrograph Hectospec. The sample consists of 71 LAEs at z ∼ 3.7 and 69 LAEs at z ∼ 4.8 over ∼1.5 deg2, making it one of the largest spectroscopically confirmed samples of LAEs at the two redshifts. Their Lyα luminosities are measured using the secure redshifts and deep photometric data, and span a range of ∼1042.5–1043.6 erg s−1, so these LAEs represent the most luminous galaxies at the redshifts in terms of Lyα luminosity. We estimate and correct sample incompletenesses and derive reliable Lyα luminosity function (LFs) at z ∼ 3.7 and 4.8 based on the two spectroscopic samples. We find that our Lyα LFs are roughly consistent (within a factor of 2−3) with previous measurements at similar redshifts that were derived from either photometric samples or spectroscopic samples. By comparing with previous studies in different redshifts, we find that the Lyα LFs decrease mildly from z ∼ 3.1 to z ∼ 5.7, supporting the previous claim of the slow LF evolution between z ∼ 2 and z ∼ 6. At z > 5.7, the LF declines rapidly toward higher redshift, partly due to the effect of cosmic reionization.

Low-mass bursty galaxies in JADES efficiently produce ionizing photons and could represent the main drivers of reionization

ABSTRACT We use deep imaging from the JWST Advanced Deep Extragalactic Survey (JADES) to study the evolution of the ionizing photon production efficiency, ξion. We estimate ξion for a sample of 677 galaxies at z ∼ 4–9 using NIRCam (Near-Infrared Camera) photometry. Specifically, combinations of the medium and wide bands F335M–F356W and F410M–F444W to constrain emission lines that trace ξion: Hα and [O iii]. Additionally, we use the spectral energy distribution fitting code prospector to fit all available photometry and infer galaxy properties. The flux measurements obtained via photometry are consistent with FRESCO (First Reionisation Epoch Spectroscopic Complete Survey) and NIRSpec-derived fluxes. Moreover, the emission-line-inferred measurements are consistent with the prospector estimates. We also confirm the observed ξion trend with redshift and MUV, and find: log ξion(z, MUV) = (0.05 ± 0.02)z + (0.11 ± 0.02)MUV + (27.33 ± 0.37). We use prospector to investigate correlations of ξion with other galaxy properties. We see a clear correlation between ξion and burstiness in the star formation history of galaxies, given by the ratio of recent to older star formation, where burstiness is more prevalent at lower stellar masses. We also convolve our ξion relations with luminosity functions from the literature, and constant escape fractions of 10 per cent and 20 per cent, to place constraints on the cosmic ionizing photon budget. By combining our results, we find that if our sample is representative of the faint low-mass galaxy population, galaxies with bursty star formation are efficient enough in producing ionizing photons and could be responsible for the reionization of the Universe.

Survey Operations for the Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) survey is a spectroscopic survey of tens of millions of galaxies at 0 < z < 3.5 covering 14,000 sq. deg. of the sky. In its first 1.1 yr of survey operations, it has observed more than 14 million galaxies and 4 million stars. We describe the processes that govern DESI’s observations of the 15,000 fields composing the survey. This includes the planning of each night’s observations in the afternoon; automatic selection of fields to observe during the night; real-time assessment of field completeness on the basis of observing conditions during each exposure; reduction, redshifting, and quality assurance of each field of targets in the morning following observation; and updates to the list of future targets to observe on the basis of these results. We also compare the performance of the survey with historical expectations and find good agreement. Simulations of the weather and of DESI observations using the real field-selection algorithm show good agreement with the actual observations. After accounting for major unplanned shutdowns, the dark time survey is progressing about 7% faster than forecast, which is good agreement given approximations made in the simulations.

New SB1s with Spectroscopic Orbits from LAMOST-LRS

The LAMOST Low-Resolution Spectroscopic (LAMOST-LRS) Survey provides radial velocities of 10 million stars. These observations can be used to identify new single-lined spectroscopic binaries (SB1s) with their preliminary spectroscopic orbits. First, we perform a statistical χ 2 test on a subsample of LAMOST-LRS stars with velocity observations sufficient for the present work to obtain a set of 6852 radial velocity variables. Subsequently, we discard 399 astrophysical variables through crossmatching with variable catalogs, resulting in 1297 SB1 candidates. Finally, in order to reliably identify SB1s among these SB1 candidates, we employ a combination of The joker, rvfit, and Levenberg–Marquardt algorithms to give the best-fit solutions. An SB1 is identified if its orbital solution satisfies the criteria of the goodness-of-fit statistic (F2) < 3.1, the signal significance > 10, and the maximum gap in phase (phase_gap_max) < 0.3. Our final catalog of SB1s contains 255 systems, 168 of which are newly discovered ones. Cross validation results indicate that the determined orbital periods are consistent with periods of external catalogs within 1σ uncertainties. The period–eccentricity diagram illustrates that a majority of short-period binaries have small eccentricities. Furthermore, in comparison to the general sample, the SB1 catalog exhibits a relatively higher ratio of dwarfs than giants and a slightly lower metallicity.