Lyman-alpha Research Articles

Testing Lyα Emitters and Lyman-break Galaxies as Tracers of Large-scale Structures at High Redshifts

We test whether Lyα emitters (LAEs) and Lyman-break galaxies (LBGs) can be good tracers of high-z large-scale structures, using the Horizon Run 5 cosmological hydrodynamical simulation. We identify LAEs using the Lyα emission line luminosity and its equivalent width, and LBGs using the broadband magnitudes at z ∼ 2.4, 3.1, and 4.5. We first compare the spatial distributions of LAEs, LBGs, all galaxies, and dark matter around the filamentary structures defined by dark matter. The comparison shows that both LAEs and LBGs are more concentrated toward the dark matter filaments than dark matter. We also find an empirical fitting formula for the vertical density profile of filaments as a binomial power-law relation of the distance to the filaments. We then compare the spatial distributions of the samples around the filaments defined by themselves. LAEs and LBGs are again more concentrated toward their filaments than dark matter. We also find the overall consistency between filamentary structures defined by LAEs, LBGs, and dark matter, with the median spatial offsets that are smaller than the mean separation of the sample. These results support the idea that the LAEs and LBGs could be good tracers of large-scale structures of dark matter at high redshifts.

The ALMA-CRISTAL survey

Massive star-forming galaxies in the high-redshift universe host large reservoirs of cold gas in their circumgalactic medium (CGM). Traditionally, these reservoirs have been linked to diffuse H I Lyman-α (Lyα) emission extending beyond ≈10 kpc scales. In recent years, millimeter and submillimeter observations have started to identify even colder gas in the CGM through molecular and/or atomic tracers such as the [C II] 158 μm transition. In this context, we studied the well-known J1000+0234 system at z = 4.54 that hosts a massive dusty star-forming galaxy (DSFG), a UV-bright companion, and a Lyα blob. We combined new ALMA [C II] line observations taken by the CRISTAL survey with data from previous programs targeting the J1000+0234 system, and achieved a deep view into a DSFG and its rich environment at a 0″​​​. 2 = 1.3 kpc resolution. We identified an elongated [C II]-emitting structure with a projected size of 15 kpc stemming from the bright DSFG at the center of the field, with no clear counterpart at any other wavelength. The plume is oriented ≈40° away from the minor axis of the DSFG, and shows significant spatial variation of its spectral parameters. In particular, the [C II] emission shifts from 180 km s−1 to 400 km s−1 between the bottom and top of the plume, relative to the DSFG’s systemic velocity. At the same time, the line width starts at 400 − 600 km s−1 but narrows down to 190 km s−1 at the top end of the plume. We discuss four possible scenarios to interpret the [C II] plume: a conical outflow, a cold accretion stream, ram pressure stripping, and gravitational interactions. While we cannot strongly rule out any of these with the available data, we disfavor the ram pressure stripping scenario due to the requirement of special hydrodynamic conditions.

SOHO SWAN Lyα Models Supporting LRO LAMP: 2008–2023

The Lunar Reconnaissance Orbiter Lyman-Alpha Mapping Project (LAMP) has been mapping the Moon since its launch in 2009. Faint ultraviolet illumination of the lunar dark side includes light from stars and from hydrogen Lyα emissions, mostly attributed to sunlight scattered by hydrogen atoms near the Sun with a smaller contribution from the whole Galaxy. Models of the lunar illumination by time-dependent Lyα photons have allowed the LAMP team to map polar shadowed craters suspected of harboring water ice and other volatiles. This paper describes the model that provides daily all-sky Lyα maps tuned by comparisons with all-sky Lyα maps from the SOlar and Heliospheric Observatory Solar Wind ANisotropy Experiment stationed at the Sun–Earth L1 point.

The Lyα Nondetection by JWST NIRSpec of a Strong Lyα Emitter at z = 5.66 Confirmed by MUSE

The detections of Lyα emission in galaxies with redshifts above 5 are of utmost importance for constraining the cosmic reionization timeline, yet such detections are usually based on slit spectroscopy. Here we investigate the significant bias induced by slit placement on the estimate of Lyα escape fraction ( fescLyα ) by presenting a galaxy (dubbed A2744-z6Lya) at z = 5.66, where its deep JWST/NIRSpec prism spectroscopy completely misses the strong Lyα emission detected in the MUSE data. A2744-z6Lya exhibits a pronounced UV continuum with an extremely steep spectral slope of β=−2.640−0.008+0.008 , and it has a stellar mass of ∼108.75 M ⊙, a star formation rate of ∼5.95 M ⊙ yr−1, and a gas-phase metallicity of 12+log(O/H)∼7.90 . The observed flux and rest-frame equivalent width of its Lyα from MUSE spectroscopy are 1.2 × 10−16 erg s−1 cm−2 and 75 Å, equivalent to fescLyα=42%±1% . However, its Lyα nondetection from JWST NIRSpec gives a 5σ upper limit of <5%, in stark contrast to that derived from MUSE. To explore the reasons for this bias, we perform spatially resolved stellar population analysis of A2744-z6Lya using the JWST NIRCam and HST imaging data to construct 2D maps of star formation rate, dust extinction, and neutral hydrogen column density. We find that the absence of Lyα in the slit regions probably stems from both the resonance scattering effect of neutral hydrogen and dust extinction. Through analyzing an extreme case in detail, this work highlights the important caveat of inferring fescLyα from slit spectroscopy, particularly when using the JWST multiplexed NIRSpec microshutter assembly.

Ongoing and Fossil Large-scale Outflows Detected in a High-redshift Radio Galaxy: [C ii] Observations of TN J0924-2201 at z = 5.174

We present Atacama Large Millimeter/submillimeter Array observations of the [C ii] 158 μm line and the underlying continuum emission of TN J0924−2201, which is one of the most distant known radio galaxies at z > 5. The [C ii] line and 1 mm continuum emission are detected at the host galaxy. The systemic redshift derived from the [C ii] line is z [C II] = 5.1736 ± 0.0002, indicating that the Lyα line is redshifted by a velocity of 1035 ± 10 km s−1, marking the largest velocity offset between the [C ii] and Lyα lines recorded at z > 5 to date. In the central region of the host galaxy, we identify a redshifted substructure of [C ii] with a velocity of 702 ± 17 km s−1, which is close to the C iv line with a velocity of 500 ± 10 km s−1. The position and the velocity offsets align with a model of an outflowing shell structure, consistent with the large velocity offset of Lyα. The nondetection of [C ii] and dust emission from the three CO(1–0)-detected companions indicates their different nature compared to dwarf galaxies, based on the photodissociation region model. Given their large velocity of ∼1500 km s−1, outflowing molecular clouds induced by the active galactic nucleus are the most plausible interpretation, and they may exceed the escape velocity of a 1013 M ⊙ halo. These results suggest that TN J0924−2201, with ongoing and fossil large-scale outflows, is in a distinctive phase of removing molecular gas from a central massive galaxy in an overdense region in the early Universe. A dusty H i absorber at the host galaxy is an alternative interpretation.

Lyα Emission Line Profiles of Extreme [O iii]- emitting Galaxies at z ≳ 2: Implications for Lyα Visibility in the Reionization Era

JWST observations have recently begun delivering the first samples of Lyα velocity profile measurements at z > 6, opening a new window into the reionization process. Interpretation of z ≳ 6 line profiles is currently stunted by limitations in our knowledge of the intrinsic Lyα profile (before encountering the intergalactic medium (IGM)) of the galaxies that are common at z ≳ 6. To overcome this shortcoming, we have obtained resolved (R ∼ 3900) Lyα spectroscopy of 42 galaxies at z = 2.1–3.4 with similar properties as are seen at z > 6. We quantify a variety of Lyα profile statistics as a function of [O iii]+Hβ equivalent width (EW). Our spectra reveal a new population of z ≃ 2–3 galaxies with large [O iii]+Hβ EWs (>1200 Å) and a large fraction of Lyα flux emerging near the systemic redshift (peak velocity ≃0 km s−1). These spectra indicate that low-density neutral hydrogen channels are able to form in a subset of low-mass galaxies (≲1 × 108 M ⊙) that experience a burst of star formation (sSFR > 100 Gyr−1). Other extreme [O iii] emitters show weaker Lyα that is shifted to higher velocities (≃240 km s−1) with little emission near the line center. We investigate the impact the IGM is likely to have on these intrinsic line profiles in the reionization era, finding that the centrally peaked Lyα emitters should be strongly attenuated at z ≳ 5. We show that these line profiles are particularly sensitive to the impact of resonant scattering from infalling IGM and can be strongly attenuated even when the IGM is highly ionized at z ≃ 5. We compare these expectations against a new database of z ≳ 6.5 galaxies with robust velocity profiles measured with JWST/NIRSpec.

Lyα Imaging around the Hyperluminous Dust-obscured Quasar W2246–0526 at z = 4.6

Hot dust-obscured galaxies (hot DOGs) are a population of hyperluminous, heavily obscured quasars discovered by the Wide-field Infrared Survey Explorer all-sky survey at high redshift. Observations suggested the growth of these galaxies may be driven by mergers. Previous environmental studies have statistically shown hot DOGs may reside in dense regions. Here we use the Very Large Telescope narrowband and broadband imaging to search for Lyα emitters (LAEs) in the 6.′8×6.′8 field of the hot DOG W2246−0526 at z = 4.6. W2246−0526 is the most distant hot DOG. We find that there is an overdensity of LAEs in the W2246−0526 field compared with the blank fields. This is direct evidence that this most distant hot DOG is in an overdense environment on the Mpc scale, and the result relates to the merger origin of hot DOGs.

Searching for the imprints of AGN feedback on the Lyman alpha forest around luminous red galaxies

ABSTRACT We explore the potential of using the low-redshift Lyman $\alpha$ (Ly $\alpha$) forest surrounding luminous red galaxies (LRGs) as a tool to constrain active galactic nuclei (AGNs) feedback models. Our analysis is based on snapshots from the Illustris and IllustrisTNG simulations at a redshift of $z=0.1$. These simulations offer an ideal platform for studying the influence of AGN feedback on the gas surrounding galaxies, as they share the same initial conditions and underlying code but incorporate different feedback prescriptions. Both simulations show significant impacts of feedback on the temperature and density of the gas around massive haloes. Following our previous work, we adjusted the UV background in both simulations to align with the observed number density of Ly $\alpha$ lines ($\rm dN/dz$) in the intergalactic medium and study the Ly $\alpha$ forest around massive haloes hosting LRGs, at impact parameters ($r_{\perp }$) ranging from 0.1 to 100 pMpc. Our findings reveal that $\rm dN/dz$, as a function of $r_{\perp }$, is approximately 1.5 to 2 times higher in IllustrisTNG compared to Illustris up to $r_{\perp }$ of $\sim 10$ pMpc. To further assess whether existing data can effectively discern these differences, we search for archival data containing spectra of background quasars probing foreground LRGs. Through a feasibility analysis based on these data, we demonstrate that ${\rm dN/dz} (r_{\perp })$ measurements can distinguish between feedback models of IllustrisTNG and Illustris with a precision exceeding 16$\sigma$. This underscores the potential of ${\rm dN/dz} (r_{\perp })$ measurements around LRGs as a valuable benchmark observation for discriminating between different feedback models.

The rich galactic environment of a H2-absorption-selected quasar

We present the first Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of a quasar featuring a proximate molecular absorption system, SDSS J125917.31+030922.5. The proximate damped Lyα absorption acts as a natural coronagraph, removing the quasar emission over ∼40 Å in wavelength, and allows us to detect extended Lyα emission without the necessity of subtracting the quasar emission. This natural coronagraph permits the investigation of the quasar environment down to its inner regions (r &lt; 20 kpc), where galaxy interactions or feedback processes should have the most noticeable effects. Our observations reveal a dense environment, with a highly asymmetric Lyα emission within 2″ (∼15 kpc), possibly shaped by a companion galaxy, and a southern extension of the nebulae to about 50 kpc, with rotation-like kinematic signature. The width of the Lyα emission is broadest closer to the quasar, indicating perturbed kinematics as expected if interactions and significant gas flows are present. The foreground absorbing system itself is redshifted by ≈400 km/s relative to the background quasar, and therefore is likely arising from gas moving toward the quasar. Finally two additional Lyα emitters are detected with &gt; 10σ significance at 96 and 223 kpc from the quasar, making this field overdense relative to other similar observations of quasars at z ∼ 3. Our results support the hypothesis that quasars with proximate neutral and molecular absorption trace rich environments where galaxy interactions are at play and motivates further studies of H2-selected quasars to shed light on feeding and feedback processes.

Peering into cosmic reionization: Lyα visibility evolution from galaxies at z = 4.5–8.5 with JWST

The resonant scattering interaction between Lyα photons and neutral hydrogen implies that a partially neutral intergalactic medium has the ability to significantly impact the detectability of Lyα emission in galaxies. Thus, the redshift evolution of the Lyα equivalent width distribution of galaxies offers a key observational probe of the degree of ionization during the Epoch of Reionization (EoR). Previous in-depth investigations at z ≥ 7 were limited by ground-based instrument capabilities. We present an extensive study of the evolution of Lyα emission from galaxies at 4.5 &lt; z &lt; 8.5, observed as part of the CEERS and JADES surveys in the JWST NIRSpec/PRISM configuration. The sample consists of 235 galaxies in the redshift range of 4.1 &lt; z &lt; 9.9. We identified 65 of them as Lyα emitters. We first measured the Lyα escape fractions from Lyα to Balmer line flux ratios and explored the correlations with the inferred galaxies’ physical properties, which are similar to those found at lower redshift. We also investigated the possible connection between the escape of Lyα photons and the inferred escape fractions of LyC photons obtained from indirect indicators, finding no secure correlation. We then analyzed the redshift evolution of the Lyα emitter fraction, finding lower average values at z = 5 and 6 compared to previous ground-based observations. At z = 7, the GOODS-S results are aligned with previous findings, whereas the visibility in the EGS field appears to be enhanced. This discrepancy in Lyα visibility between the two fields could potentially be attributed to the presence of early reionized regions in the EGS. Such a broad variance is also expected in the Cosmic Dawn II radiation-hydrodynamical simulation. The average Lyα emitter fraction obtained from the CEERS+JADES data continues to increase from z = 5 to 7, ultimately declining at z = 8. This suggests a scenario in which the ending phase of the EoR is characterized by ∼1 pMpc ionized bubbles around a high fraction of moderately bright galaxies. Finally, we characterize such two ionized regions found in the EGS at z = 7.18 and z = 7.49 by estimating the radius of the ionized bubble that each of the spectroscopically-confirmed members could have created.

Seasonal Variation of Saturn's Lyα Brightness

We examine Saturn’s nonauroral (dayglow) emissions at Lyα observed by the Cassini/Ultraviolet Imaging Spectrograph (UVIS) instrument from 2003 until 2017, to constrain meridional and seasonal trends in the upper atmosphere. We separate viewing geometry effects from trends driven by atmospheric properties, by applying a multivariate regression to the observed emissions. The Lyα dayglow brightnesses depend on the incident solar flux, solar incidence angle, emission angle, and observed latitude. The emissions across latitudes and seasons show a strong dependence with solar incidence angle, typical of resonantly scattered solar flux and consistent with no internal source such as electroglow. We observe a bulge in Lyα brightnesses that shifts with the summer season from the southern to the northern hemisphere. We estimate atomic hydrogen optical depths above the methane homopause level for dayside disk observations (2004–2016) by comparing observed Lyα emissions to a radiative transfer model. We model emissions from resonantly scattered solar flux and a smaller but significant contribution by scattered photons from the interplanetary hydrogen (IPH) background. During the northern summer, inferred hydrogen optical depths steeply decrease with latitude toward the winter hemisphere from a northern hemisphere bulge, as predicted by a 2D seasonal photochemical model. The southern hemisphere mirrors this trend during its summer. However, inferred optical depths show substantially more temporal variation between 2004 and 2016 than predicted by the photochemical model. We benchmark our brightness values by comparing observed IPH Lyα emissions from Cassini/UVIS in 2006 with a model of the IPH emissions. Cassini/UVIS observations agree well with the modeled IPH background.

Upgrade of the Lyman-alpha diagnostic system on DIII-D for main chamber edge neutral studies.

The LLAMA (Lyman Alpha Measurement Apparatus) pinhole camera diagnostic had previously been deployed on DIII-D to measure radial profiles of the Lyman-α (Ly-α) deuterium neutral line brightness across the plasma boundary in the lower chamber to infer neutral deuterium density and ionization rate profiles. This system has recently been upgraded with a new diagnostic head, named ALPACA, that also encloses two pinhole cameras and duplicates the LLAMA views in the upper chamber. Similar to LLAMA, ALPACA provides two times 20 lines of sight, viewing the plasma edge on the inboard and outboard sides with a radial resolution of ∼2.5 cm (FWHM) and an effective time resolution of ∼1 ms that allows for the investigation of inter-ELM dynamics. The extended Ly-α system provides better coverage to study neutrals in experiments with various plasma shapes utilizing both the upper and lower divertors. Furthermore, post-campaign calibration of the LLAMA diagnostic has successfully been demonstrated for the first time. This was facilitated by various upgrades to the calibration set-up and detailed measurements of the emissivity distribution of the Ly-α calibration source using a pinhole collimator. It was found that the sensitivity of the inboard LLAMA pinhole camera was reduced by a factor of 2.0 ± 0.2 over the course of six months of plasma operation in 2021. The upgraded Ly-α system, equipped with improved absolute calibration, will provide key input for neutral fueling and pedestal particle transport studies and for 2D edge transport code validation on the DIII-D tokamak.

A Spectral Atlas of Lyα Emitters at z = 5.7 and z = 6.6

We present two uniformly observed spectroscopic samples of Lyα emitters (LAEs; 127 at z = 5.7 and 82 at z = 6.6), which we use to investigate the evolution of the LAE population at these redshifts. The observations cover a large field (44 deg2) in the North Ecliptic Pole, as well as several smaller fields. We have a small number of exotic LAEs in the samples: double-peaked Lyα profiles; very extended red wings; and one impressive lensed LAE cross. We also find three broad-line active galactic nuclei. We compare the Lyα line width measurements at the two redshifts, finding that the lower-luminosity LAEs show a strong evolution of decreasing line width with increasing redshift, while the high-luminosity LAEs do not, with a transition luminosity of log L(Lyα) ≈ 43.25 erg s−1. Thus, at z = 6.6, the high-luminosity LAEs may be producing large ionized bubbles themselves, or they may be residing in overdense galaxy sites that are producing such bubbles. In order to avoid losses in the red wing, the radius of the ionized bubble must be larger than 1 pMpc. The double-peaked LAEs also require transmission on the blue side. For the four at z = 6.6, we use models to estimate the proximity radii, R a , where the ionizing flux of the galaxy is sufficient to make the surroundings have a low enough neutral fraction to pass the blue light. Since the required R a are large, multiple ionizing sources in the vicinity may be needed.

The MOSDEF-KCWI Survey: Spectral Properties of Lyα Halos around z ∼ 2 Star-forming Galaxies

We present Keck Cosmic Web Imager integral field observations of extended Lyα emission in the circumgalactic medium of 27 typical star-forming galaxies at z ∼ 2, drawn from the Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE) Deep Evolution Field (MOSDEF) survey. Using composite spectra in two bins of star formation rate (SFR), star formation rate surface density (ΣSFR), and other galactic properties, we measure spatial variations in the Lyα profile across three regions in the Lyα halo. We find single-peaked, redshifted profiles are ubiquitous within a central 7 kpc radius region. Further out in the halo (7–14 and 14–21 kpc), the Lyα profile of the resonantly scattered emission exhibits more diversity, either transitioning to a double-peaked profile or remaining single peaked across the halo. We find a shorter scale length of the Lyα halo surface brightness profile for composite halos with faster winds. The composites have a similar average inclination, suggesting those with faster winds clear channels in the interstellar medium (ISM), reducing the fraction of Lyα photons resonantly scattered to large radii. A uniform expanding shell radiative transfer model reproduces the shape but not the normalization of the observed double-peaked Lyα profiles. Models that adopt a more realistic, clumpy ISM are likely needed to reproduce both the shape and normalization of the Lyα profiles.

JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at z = 7–12 Obtained with Lyα Damping Wing Absorptions in 27 Bright Continuum Galaxies

We present volume-averaged neutral hydrogen fractions x H I and ionized bubble radii R b measured with Lyα damping wing absorption of galaxies at the epoch of reionization. We combine JWST/NIRSpec spectra taken by the CEERS, GO-1433, DDT-2750, and JADES programs and obtain a sample containing 27 bright UV-continuum (M UV < −18.5 mag) galaxies at 7 < z < 12. We construct four composite spectra binned by redshift and find the clear evolution of the softening break toward high redshift at rest-frame 1216 Å, suggesting an increase of Lyα damping wing absorption. We estimate Lyα damping wing absorption in the galaxy spectra with realistic templates including Lyα emission and circumgalactic medium absorptions. Assuming the standard inside-out reionization picture having an ionized bubble with radius R b around a galaxy embedded in the intergalactic medium with x H I, we obtain x H I (R b ) values generally increasing (decreasing) from xHI=0.53−0.47+0.18 to 0.92−0.10+0.08 ( logRb=1.67−0.16+0.14 to −0.69−0.24+0.89 comoving Mpc) at redshift 7.12−0.08+0.06 to 9.91−1.15+1.49 . The redshift evolution of x H I indicates a moderately late reionization history consistent with the one previously suggested from the electron scattering of cosmic microwave background and the evolution of UV luminosity function with an escape fraction f esc ∼ 0.2. Our R b measurements suggest that bubble sizes could be up to a few dex larger than the cosmic average values estimated by analytic calculations for a given x H I, while our R b measurements are roughly comparable with the values for merged ionized bubbles around bright galaxies predicted by recent numerical simulations.

The clustering of Lyman Alpha Emitting galaxies at 𝗓=2–3

We measure the clustering of Lyman Alpha Emitting galaxies (LAEs) selected from the One-hundred-square-degree DECam Imaging in Narrowbands (ODIN) survey, with spectroscopic follow-up from Dark Energy Spectroscopic Instrument (DESI). We use DESI spectroscopy to optimize our selection and to constrain the interloper fraction and redshift distribution of our narrow-band selected sources. We select samples of 4000 LAEs at z = 2.45 and 3.1 in 9 sq.deg. centered on the COSMOS field with median Lyα fluxes of ≈ 10-16 erg s-1 cm-2. Covariances and cosmological inferences are obtained from a series of mock catalogs built upon high-resolution N-body simulations that match the footprint, number density, redshift distribution and observed clustering of the sample. We find that both samples have a correlation length of r 0 = 3.0 ± 0.2 h-1 Mpc. Within our fiducial cosmology these correspond to 3D number densities of ≈ 10-3 h3 Mpc-3 and, from our mock catalogs, biases of 1.7 and 2.0 at z = 2.45 and 3.1, respectively. We discuss the implications of these measurements for the use of LAEs as large-scale structure tracers for high-redshift cosmology.

MUSE Analysis of Gas around Galaxies (MAGG) - VI. The cool and enriched gas environment of z≳3 Lyα emitters

We present a novel dataset that extends our view of the cosmic gas around $z 3-4$ Lyalpha emitters (LAEs) in the Muse Analysis of Gas around Galaxies (MAGG) survey by tracing a cool and enriched gas phase through 47 absorbers identified in newly obtained VLT/X-shooter near-infrared quasar spectra. Jointly with the more ionized gas traced by systems and the neutral from previous work, we find that LAEs are distributed inside cosmic structures that contain multiphase gas in composition and temperature. All gas phases are a strong function of the large-scale galaxy environment: the and the strength and kinematics positively correlate with the number of associated galaxies, and it is $ times more likely to detect metal absorbers around groups of LAEs than isolated ones. Exploring the redshift evolution, the covering factor of around groups of LAEs and isolated ones remains approximately constant from $z to $z but the one of around group galaxies drops by $z Adding the cool enriched gas traced by the absorbers to the results that we obtained for the and gas, we put forward a picture in which LAEs lie along gas filaments that contain high column-density systems and are enriched by strong and absorbers. While the gas appears to be more centrally concentrated near LAEs, weaker systems instead trace a more diffuse gas phase extended up to larger distances around the galaxies.

TensorFlow Hydrodynamics Analysis for Ly-[formula omitted] Simulations

We introduce the Python program THALAS (TensorFlow Hydrodynamics Analysis for Lyman-Alpha Simulations), which maps baryon fields (baryon density, temperature, and velocity) to Lyα optical depth fields in both real space and redshift space. Unlike previous Lyα codes, THALAS is fully differentiable, enabling a wide variety of potential applications for general analysis of hydrodynamical simulations and cosmological inference. To demonstrate THALAS’s capabilities, we apply it to the Lyα forest inversion problem: given a Lyα optical depth field, we reconstruct the corresponding real-space dark matter density field. Such applications are relevant to both cosmological and three-dimensional tomographic analyses of Lyman Alpha forest data.

On the Nature of the Radio Calibrator and Gamma-Ray Emitting NLS1 Galaxy 3C 286 and Its Multiwavelength Variability

The quasar 3C 286, a well-known calibrator source in radio astronomy, was found to exhibit exceptional multiwavelength properties. Its rich and complex optical emission-line spectrum revealed its narrow-line Seyfert 1 (NLS1) nature. Given its strong radio emission, this makes 3C 286 one of the radio-loudest NLS1 galaxies known to date. 3C 286 is also one of very few known compact steep-spectrum (CSS) sources detected in the gamma-ray regime. Observations in the X-ray regime, rarely carried out so far, revealed evidence for variability, raising the question whether it is driven by the accretion disk or jet. 3C 286 is also well known for its damped Lyman alpha system from an intervening absorber at z = 0.692, triggering a search for the corresponding X-ray absorption along the line-of-sight. Here, we present new observations in the radio, X-ray, optical, and UV bands. The nature of the X-ray variability is addressed. Spectral evidence suggests that it is primarily driven by the accretion disk (not the jet), and the X-ray spectrum is well fit by a powerlaw plus soft excess model. The radio flux density and polarization remain constant at the Effelsberg telescope resolution, reconfirming the use of 3C 286 as radio calibrator. The amount of reddening/absorption along the line-of-sight intrinsic to 3C 286 is rigorously assessed. None is found, validating the derivation of a high Eddington ratio (L/LEdd ∼ 1) and of the very high radio-loudness index of 3C 286. Based on the first deep Chandra image of 3C 286, tentative evidence for hard X-ray emission from the SW radio lobe is reported. A large variety of models for the gamma-ray emission of 3C 286 are briefly discussed.

The Web Epoch of Reionization Lyα Survey (WERLS). I. MOSFIRE Spectroscopy of z ∼ 7–8 Lyα Emitters* *The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the

We present the first results from the Web Epoch of Reionization Lyα Survey (WERLS), a spectroscopic survey of Lyα emission using Keck I/MOSFIRE and LRIS. WERLS targets bright (J < 26) galaxy candidates with photometric redshifts of 5.5 ≲ z ≲ 8 selected from pre-JWST imaging embedded in the Epoch of Reionization (EoR) within three JWST deep fields: CEERS, PRIMER, and COSMOS-Web. Here, we report 11 z ∼ 7–8 Lyα emitters (LAEs; three secure and eight tentative candidates) detected in the first five nights of WERLS MOSFIRE data. We estimate our observed LAE yield is ∼13%, which is broadly consistent with expectations assuming some loss from redshift uncertainty, contamination from sky OH lines, and that the Universe is approximately half-ionized at this epoch, whereby observable Lyα emission is unlikely for galaxies embedded in a neutral intergalactic medium. Our targets are selected to be UV-bright, and span a range of absolute UV magnitudes with −23.1 < M UV < −19.8. With two LAEs detected at z = 7.68, we also consider the possibility of an ionized bubble at this redshift. Future synergistic Keck+JWST efforts will provide a powerful tool for pinpointing beacons of reionization and mapping the large-scale distribution of mass relative to the ionization state of the Universe.