Neutral Hydrogen Column Density Research Articles

The JWST-PRIMAL archival survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-alpha absorption and emission of ~ 600 galaxies at z = 5:0 - 13:4

One of the surprising early findings with has been the discovery of a strong ``roll-over'' or a softening of the absorption edge of in a large number of galaxies at \(z 6\), in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as strong cumulative damped absorption (DLA) wings from high column densities of neutral atomic hydrogen ( signifying major gas accretion events in the formation of these galaxies. To explore this new phenomenon systematically, we assembled the PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 584 galaxies at $z=5.0-13.4$, designed to study the physical properties and gas in and around galaxies during the reionization epoch. We characterized this benchmark sample in full and spectroscopically derived the galaxy redshifts, metallicities, star formation rates, and ultraviolet (UV) slopes. We defined a new diagnostic, the damping parameter to measure and quantify the net effect of emission strength, the fraction in the intergalactic medium, or the local column density for each source. The survey is based on the spectroscopic DAWN Archive (DJA-Spec). We describe DJA-Spec in this paper, detailing the reduction methods, the post-processing steps, and basic analysis tools. All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories. We find that the fraction of galaxies showing strong integrated DLAs with $N_ HI $ only increases slightly from $ 60<!PCT!>$ at $z 6$ up to $ 65-90<!PCT!>$ at $z>8$. Similarly, the prevalence and prominence of emission is found to increase with decreasing redshift, in qualitative agreement with previous observational results. Strong emitters (LAEs) are predominantly found to be associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties, but predominantly at high redshifts and low metallicities. Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine gas accretion. At $z=8-10$, this gas gradually cools and forms into stars that ionize their local surroundings, forming large ionized bubbles and producing strong observed emission at $z<8$.

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.

Search of extended emission from HESS J1702-420 with eROSITA

is a peculiar TeV complex with a morphology changing from a diffuse source ( at $ 2$ TeV to a point-like one ( at $ 10$ TeV energies. The morphology and spectral properties of could be understood in terms of (diffusive) hadronic or leptonic models in which the observed TeV emission arises correpondingly from proton-proton or IC-radiation of relativistic particles present in the region. In this work, we perform searches of the X-ray counterpart of the source originating from the synchrotron emission of the primary or secondary relativistic electrons produced within leptonic or hadronic models. Such an emission can be extended and remain beyond the detection capabilities of narrow field-of-view instruments such as We utilised the publicly available first-6-months eROSITA dataset (DR1) fully covering the selected analysis region of $&gt;5^ around We discuss biases connected to variable plasma temperature or neutral hydrogen column density in the region and present results based on the background modelling approach. The performed analysis does not allow us to detect the extended X-ray counterpart of of $0.07^ sizes. The derived upper limits are significantly higher than the expected hadronic model flux of the X-ray counterpart. For the leptonic model, the derived limits indicate the magnetic field in the region $B We argue that further advances in the diffuse X-ray counterpart searches could be achieved with either next-generation missions or Msec-long observational campaigns using currently operating instruments.

Discovery of a damped Ly α absorber in the circumnuclear zone of the FeLoBAL quasar SDSS J083942.11+380526.3

ABSTRACT SDSS J083942.11+380526.3 ($z=2.315$) is an iron low-ionization broad absorption lines quasar that exhibits visible Balmer absorption lines (H $\alpha$), implying a significant $n=2$ population. The quasar also shows an array of absorption lines, including O i, Ni ii, Fe ii, Mg ii, Al iii to C iv, and N v. The high-ionization absorption lines such as C iv and Si iv are revealed by slightly blueshifted broad absorption lines troughs. The resonance doublets such as Mg ii and Al iii are saturated but did not reached zero intensity which indicates that the broad-line region (BLR) is partially covered. Overall, however, the absorption is predominantly from low-ionization Fe ii lines, emitted from ground and excited states up to at least 3.814 eV. This implies that the absorbing gas spans the hydrogen ionization front and extends into the partially ionized zone where neutral hydrogen is certainly present. Notably, the hydrogen line spectrum of the quasar shows no signature of expected Ly $\alpha$ absorption. Instead, the line spectrum shows an unusual Ly $\alpha$ emission characterized by a fully filled emission line spectrum which is a composite of a strong narrow core superposed on a weak broad base. Taking into account the effect of partial covering to BLR, we have extracted a strong Damped Ly α systems (DLA) trough in Ly $\alpha$ emission region. To fit the spectrum, we performed photoionized model calculations and compared them to the observations. We found that photoionization modelling using cloudy can successfully reproduce the main characteristics of the quasar spectrum, and the predicted neutral hydrogen column density arising from the clouds responsible for the low-ionization absorption provides a good match to the extracted DLA trough. This indicates that both the DLA and the low-ionization absorption arise from the same medium that is roughly collocated with the dusty torus.

The Lyman-limit photon mean free path at the end of late reionization in the Sherwood–Relics simulations

ABSTRACT Recent evidence supporting reionization ending at redshift $z \lesssim 6$ includes the rapid redshift evolution of the mean free path, $\lambda _{\rm mfp}$, for Lyman-limit photons through the intergalactic medium (IGM) at $5\lt z\lt 6$. Here, we investigate $\lambda _{\rm mfp}$ predicted by the Sherwood–Relics suite of hybrid radiation hydrodynamical simulations. Simulations with comoving volumes of $40^{3}\, h^{-3}\rm \, cMpc^{3}$ ($160^{3}\, h^{-3}\rm \, cMpc^{3}$), calibrated to match the observed Ly $\alpha$ forest transmission with a late end to reionization at $z\lt 6$, are consistent with recent $\lambda _{\rm mfp}$ measurements at $z\lt 5.9$, and are $1.2\sigma$ ($1.8\sigma$) above the highest redshift $\lambda _{\rm mfp}$ measurement at $z=5.93$. The majority of the Lyman-limit opacity at the end of reionization is attributable to highly ionized Ly $\alpha$ forest absorbers with neutral hydrogen column densities $N_{\rm HI} \leq 10^{16}$–$10^{17}\rm \, cm^{-2}$. Resolving these systems is critical for capturing the redshift evolution of $\lambda _{\rm mfp}$ during the final stages of reionization. After reionization completes, overdense gas will reduce $\lambda _{\rm mfp}$ by up to 20 per cent around haloes with masses $M_{\rm h}\sim 10^{9}$–$10^{11}h^{-1}\, {\rm M}_{\odot }$, but during reionization ionized bubbles will instead boost $\lambda _{\rm mfp}$ around haloes by up to an order of magnitude when the IGM is as much as 90 per cent neutral by volume. This effect will play an important role in the visibility of Ly $\alpha$ emitting galaxies at $z\gtrsim 10$ discovered with JWST.

Circumnuclear Gas of a Quasar in Absorption and Emission Lines

We present a detailed analysis of the unusual absorption- and emission-line spectrum of the quasar SDSS J074850.39+442439.0 (hereafter J0748+4424) at a redshift of z = 2.18. The archival SDSS optical spectrum is abundant in narrow absorption lines (NALs) originating from mostly singly ionized iron, nickel, and silicon ions at both ground and excited levels. With the aid of the photoionization simulations, we find that these NALs can be reasonably well reproduced by a homogeneous gas slab with a neutral hydrogen column density of 1021.6–1021.9 cm−2 and a number density of 106.0–106.6 cm−3 illuminated by the quasar central engine with an ionization parameter of 10−2.8–10−2.1. We infer the gas is located at a distance of ∼30–130 pc from the black hole. This circumnuclear gas can reveal itself in emission lines of a width of ∼1000 km s−1. Such intermediate-width emission lines (IELs) are indeed dominant in the observed Lyα emission, as the Lyα broad emission line (BEL) is mostly eaten up by the expected damped Lyα absorption (DLA). The IELs, though rather weak, are also detected in Hα and [O iii] emission lines. The IEL intensities largely agree with the predicted values by the simplified photoionization models using the parameters derived from the absorption lines and a covering fraction of 10%. The intrinsic DLA in J0748+4424, while itself contains abundant information on the circumnuclear environment, may serve as a “natural coronagraph” at the line of sight, exposing the IELs that are otherwise overwhelmed by the BELs.

Constraining the Temperature-density Relation of the Inter-galactic Medium from Analytically Modeling Lyα Forest Absorbers

The absorption by neutral hydrogen in the intergalactic medium (IGM) produces the Lyα forest in the spectra of quasars. The Lyα forest absorbers have a broad distribution of neutral hydrogen column density N H I and Doppler b parameter. The narrowest Lyα absorption lines (of lowest b) with neutral hydrogen column density above ∼1013cm−2 are dominated by thermal broadening, which can be used to constrain the thermal state of the IGM. Here we constrain the temperature-density relation of the IGM at 1.6 < z < 3.6 by using N H I and b parameters measured from 24 high-resolution and high-signal-to-noise quasar spectra and by employing an analytic model to model the N H I-dependent low-b cutoff in the b distribution. In each N H I bin, the b cutoff is estimated using two methods, one non-parametric method from computing the cumulative b distribution and a parametric method from fitting the full b distribution. We find that the IGM temperature T 0 at the mean gas density shows a peak of ∼1.5 × 104 K at z ∼ 2.7–2.9. At redshift higher than this, the index γ approximately remains constant, and it starts to increase toward lower redshifts. The evolution in both parameters is in good agreement with constraints from completely different approaches, which signals that He ii reionization completes around z ∼ 3.

Measurement of AGN dust extinction based on the near-infrared flux variability of WISE data

ABSTRACT We present the measurement of the line-of-sight extinction of the dusty torus for a large number of obscured active galactic nuclei (AGNs) based on the reddening of the colour of the variable flux component in near-infrared (NIR) wavelengths. We collected long-term monitoring data by Wide-field Infrared Survey Explorer (WISE) for 513 local AGNs catalogued by the Swift/BAT AGN Spectroscopic Survey (BASS) and found that the multi-epoch NIR flux data in two different bands (WISE W1 and W2) are tightly correlated for more than 90 per cent of the targets. The flux variation gradient (FVG) in the W1 and W2 bands was derived by applying linear regression analysis, and we reported that those for unobscured AGNs fall in a relatively narrow range, whereas those for obscured AGNs are distributed in a redder and broader range. The AGN’s line-of-sight dust extinction (AV) is calculated using the amount of the reddening in the FVG and is compared with the neutral hydrogen column density (NH) of the BASS catalogue. We found that the NH/AV ratios of obscured AGNs are greater than those of the Galactic diffuse interstellar medium (ISM) and are distributed with a large scatter by at most two orders of magnitude. Furthermore, we found that the lower envelope of the NH/AV of obscured AGNs is comparable to the Galactic diffuse ISM. These properties of the NH/AV can be explained by increase in the NH attributed to the dust-free gas clouds covering the line of sight in the broad-line region.

Metal Lines Associated with the Lyα Forest from eBOSS Data

We investigate the metal species associated with the Lyα forest in eBOSS quasar spectra. Metal absorption lines are revealed in stacked spectra from cross-correlating the selected Lyα absorbers in the forest and the flux fluctuation field. Up to 13 metal species are identified as being associated with relatively strong Lyα absorbers (those with flux fluctuations − 1.0 < δ Lyα < − 0.6 and with a neutral hydrogen column density of ∼ 1015−16 cm−2) over the absorber redshift range of 2 < z abs < 4. The column densities of these species decrease toward higher redshift and for weaker Lyα absorbers. From modeling the column densities of various species, we find that the column density pattern suggests contributions from multiple gas components, both in the circumgalactic medium (CGM) and the intergalactic medium (IGM). While the low-ionization species (e.g., C ii, Si ii, and Mg ii) can be explained by high-density, cool gas (T ∼ 104 K) from the CGM, the high-ionization species may reside in low-density or high-temperature gas in the IGM. The measurements provide inputs for modeling the metal contamination in the Lyα forest baryon acoustic oscillation measurements. Comparisons with metal absorptions in high-resolution quasar spectra and hydrodynamic galaxy formation simulations can further elucidate the physical conditions of these Lyα absorbers.

Measuring the thermal and ionization state of the low-z IGM using likelihood free inference

ABSTRACT We present a new approach to measure the power-law temperature density relationship $T=T_0 (\rho/ \bar{\rho })^{\gamma -1}$ and the UV background photoionization rate $\Gamma _{{{{\rm H\, {\small I}}}}{}}$ of the intergalactic medium (IGM) based on the Voigt profile decomposition of the Ly α forest into a set of discrete absorption lines with Doppler parameter b and the neutral hydrogen column density $N_{\rm H\, {\small I}}$. Previous work demonstrated that the shape of the $b-N_{{{{\rm H\, {\small I}}}}{}}$ distribution is sensitive to the IGM thermal parameters T0 and γ, whereas our new inference algorithm also takes into account the normalization of the distribution, i.e. the line-density dN/dz, and we demonstrate that precise constraints can also be obtained on $\Gamma _{{{{\rm H\, {\small I}}}}{}}$. We use density-estimation likelihood-free inference (DELFI) to emulate the dependence of the $b-N_{{{{\rm H\, {\small I}}}}{}}$ distribution on IGM parameters trained on an ensemble of 624 nyx hydrodynamical simulations at z = 0.1, which we combine with a Gaussian process emulator of the normalization. To demonstrate the efficacy of this approach, we generate hundreds of realizations of realistic mock HST/COS data sets, each comprising 34 quasar sightlines, and forward model the noise and resolution to match the real data. We use this large ensemble of mocks to extensively test our inference and empirically demonstrate that our posterior distributions are robust. Our analysis shows that by applying our new approach to existing Ly α forest spectra at z ≃ 0.1, one can measure the thermal and ionization state of the IGM with very high precision ($\sigma _{\log T_0} \sim 0.08$ dex, σγ ∼ 0.06, and $\sigma _{\log \Gamma _{{{{\rm H\, {\small I}}}}{}}} \sim 0.07$ dex).

Discovery of three new near-pristine absorption clouds at z = 2.6–4.4

ABSTRACT We report the discovery of three new ‘near-pristine’ Lyman limit systems (LLSs), with metallicities ≈1/1000 solar, at redshifts 2.6, 3.8, and 4.0, with a targeted survey at the Keck Observatory. High-resolution echelle spectra of eight candidates yielded precise column densities of hydrogen and weak, but clearly detected, metal lines in seven LLSs; we previously reported the one remaining, apparently metal-free LLS, to have metallicity &amp;lt;1/10 000 solar. Robust photoionization modelling provides metallicities [Si/H] = −3.05 to −2.94, with 0.26 dex uncertainties (95 per cent confidence) for three LLSs, and $\textrm {[Si/H]} \gtrsim -2.5$ for the remaining four. Previous simulations suggest that near-pristine LLSs could be the remnants of PopIII supernovae, so comparing their detailed metal abundances with nucleosynthetic yields from supernovae models is an important goal. Unfortunately, at most two different metals were detected in each new system, despite their neutral hydrogen column densities ($10^{19.2}\textrm {--}10^{19.4}\, \textrm {cm}^{-2}$) being two orders of magnitude larger than the two previous, serendipitously discovered near-pristine LLSs. Nevertheless, the success of this first targeted survey for near-pristine systems demonstrates the prospect that a much larger, future survey could identify clear observational signatures of PopIII stars. With a well-understood selection function, such a survey would also yield the number density of near-pristine absorbers that, via comparison to future simulations, could reveal the origin(s) of these rare systems.

Resolving the H I in damped Lyman α systems that power star formation.

Reservoirs of dense atomic gas (primarily hydrogen) contain approximately 90 per cent of the neutral gas at a redshift of 3, and contribute to between 2 and 3 per cent of the total baryons in the Universe1-4. These 'damped Lyman α systems'-so called because they absorb Lyman α photons within and from background sources-have been studied for decades, but only through absorption lines present in the spectra of background quasars and γ-ray bursts5-10. Such pencil beams do not constrain the physical extent of the systems. Here we report integral-field spectroscopy of a bright, gravitationally lensed galaxy at a redshift of 2.7 with two foreground damped Lyman α systems. These systems are greater than 238 kiloparsecs squared in extent, with column densities of neutral hydrogen varying by more than an order of magnitude on scales of less than 3 kiloparsecs. The mean column densities are between 1020.46 and 1020.84 centimetres squared and the total masses are greater than 5.5 × 108-1.4 × 109 times the mass of the Sun, showing that they contain the necessary fuel for the next generation of star formation, consistent with relatively massive, low-luminosity primeval galaxies at redshifts greater than 2.

Staring at the Shadows of Archaic Galaxies: Damped Lyα and Metal Absorbers Toward a Young z ∼ 6 Weak-line Quasar

We characterize the Lyα halo and absorption systems toward PSO J083+11, a unique z = 6.3401 weak-line quasar, using Gemini Near-infrared Spectrograph, Magellan Folded-port Infrared Echellette, and Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) data. Strong absorptions by hydrogen and several metal lines (e.g., C ii, Mg ii, and O i) are discovered in the spectrum, which indicates the presence of: (i) a proximate subdamped Lyα (sub-DLA) system at z = 6.314 and (ii) a Mg ii absorber at z = 2.2305. To describe the observed damping wing signal, we model the Lyα absorption with a combination of a sub-DLA with the neutral hydrogen column density of and absorption from the intergalactic medium with a neutral fraction of around 10%. The sub-DLA toward PSO J083+11 has an abundance ratio of [C/O] = −0.04 ± 0.33 and metallicity of [O/H] = −2.19 ± 0.44, similar to those of low-redshift metal-poor DLAs. These measurements suggest that the sub-DLA might truncate PSO J083+11’s proximity zone size and complicate the quasar lifetime measurement. However, this quasar shows no sign of a Lyα halo in the MUSE data cube, where the estimated 1σ limit of surface brightness is at an aperture size of 1″, or equivalent to a Lyα luminosity of ≤43.46 erg s−1. This nondetection, while being only weak independent evidence on its own, is at least consistent with a young quasar scenario, as expected for a quasar with a short accretion timescale.

ZELDA: fitting Lyman alpha line profiles using deep learning

ABSTRACT We present zELDA (redshift Estimator for Line profiles of Distant Lyman Alpha emitters), an open source code to fit Lyman α (Ly α) line profiles. The main motivation is to provide the community with an easy to use and fast tool to analyse Ly α line profiles uniformly to improve the understating of Ly α emitting galaxies. zELDA is based on line profiles of the commonly used ‘shell-model’ pre-computed with the full Monte Carlo radiative transfer code LyaRT. Via interpolation between these spectra and the addition of noise, we assemble a suite of realistic Ly α spectra which we use to train a deep neural network.We show that the neural network can predict the model parameters to high accuracy (e.g. ≲ 0.34 dex H i column density for R ∼ 12 000) and thus allows for a significant speedup over existing fitting methods. As a proof of concept, we demonstrate the potential of zELDA by fitting 97 observed Ly α line profiles from the LASD data base. Comparing the fitted value with the measured systemic redshift of these sources, we find that Ly α determines their rest frame Ly α wavelength with a remarkable good accuracy of ∼0.3 Å ($\sim 75\,\, {\rm km\, s}^{-1}$). Comparing the predicted outflow properties and the observed Ly α luminosity and equivalent width, we find several possible trends. For example, we find an anticorrelation between the Ly α luminosity and the outflow neutral hydrogen column density, which might be explained by the radiative transfer process within galaxies.

Multiwavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632 + 057 with NuSTAR, VERITAS, MDM, and Swift

Abstract HESS J0632+057 belongs to a rare subclass of binary systems that emit gamma rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp “primary” peak and broader “secondary” peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between 2019 December and 2020 February, when the orbital phase (ϕ) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multiwavelength spectra data obtained over the four NuSTAR and VERITAS observations, constraining the pulsar spin-down luminosity and the magnetization parameter at the shock. Despite long-term monitoring of the source from 2019 October to 2020 March, the MDM observatory did not detect significant variation in Hα and Hβ line equivalent widths, an expected signature of Be-disk interaction with the pulsar. Furthermore, fitting folded Swift-XRT light-curve data with an intrabinary shock model constrained the orbital parameters, suggesting two orbital phases (at ϕ D = 0.13 and 0.37), where the pulsar crosses the Be-disk, as well as phases for the periastron (ϕ 0 = 0.30) and inferior conjunction (ϕ IFC = 0.75). The broadband X-ray spectra with Swift-XRT and NuSTAR allowed us to measure a higher neutral hydrogen column density at one of the predicted disk-passing phases.

Using Solar Wind Helium to Probe the Structure and Seasonal Variability of the Martian Hydrogen Corona

AbstractWe utilize measurements from instruments on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to investigate singly ionized helium formed by charge exchange between solar wind alpha particles and neutral hydrogen in the region upstream from Mars. We show that the observed helium ion signal varies with solar wind speed and spatial location in a manner consistent with expectations for a charge exchange source. We find that the ratio of singly to doubly ionized helium varies with Martian season, with a peak in the southern summer season. The inferred neutral hydrogen column density and the seasonal variation thereof agree with the results of previous studies based on other measurement techniques. The MAVEN helium ion measurements provide a new method of probing the hydrogen corona, with nearly continuous coverage of the Martian seasonal cycle across the entire mission, enabling study of the interannual variability of the Martian exosphere.

The Cosmic Ultraviolet Baryon Survey (CUBS) – IV. The complex multiphase circumgalactic medium as revealed by partial Lyman limit systems

ABSTRACT We present a detailed study of two partial Lyman limit systems (pLLSs) of neutral hydrogen column density $N_\mathrm{H\, I}\approx (1-3)\times 10^{16}\, \mathrm{cm}^{-2}$ discovered at $z$ = 0.5 in the Cosmic Ultraviolet Baryon Survey (CUBS). Available far-ultraviolet spectra from the Hubble Space Telescope Cosmic Origins Spectrograph and optical echelle spectra from MIKE on the Magellan Telescopes enable a comprehensive ionization analysis of diffuse circumgalactic gas based on resolved kinematics and abundance ratios of atomic species spanning five different ionization stages. These data provide unambiguous evidence of kinematically aligned multiphase gas that masquerades as a single-phase structure and can only be resolved by simultaneous accounting of the full range of observed ionic species. Both systems are resolved into multiple components with inferred α-element abundance varying from [α/H] ≈−0.8 to near solar and densities spanning over two decades from log nH/cm−3 ≈ −2.2 to &amp;lt;−4.3. Available deep galaxy survey data from the CUBS program taken with VLT/MUSE, Magellan/LDSS3-C and Magellan/IMACS reveal that the $z$ = 0.47 system is located 55 kpc from a star-forming galaxy with prominent Balmer absorption of stellar mass ${{M_{\rm star}}}\approx 2\times 10^{10}\, {{M_{\odot}}}$, while the $z$ = 0.54 system resides in an overdense environment of 11 galaxies within 750 kpc in projected distance, with the most massive being a luminous red galaxy of ${{M_{\rm star}}}\approx 2\times 10^{11}\, {{M_{\odot}}}$ at 375 kpc. The study of these two pLLSs adds to an emerging picture of the complex, multiphase circumgalactic gas that varies in chemical abundances and density on small spatial scales in diverse galaxy environments. The inhomogeneous nature of metal enrichment and density revealed in observations must be taken into account in theoretical models of diffuse halo gas.

Laboratory Observation of C and O Emission Lines of the White Dwarf H1504+65-like Atmosphere Model

Abstract White dwarfs play important roles in stellar evolution and help us gauge the age of our galaxy. The white dwarf H1504+65, the hottest known post-asymptotic giant branch star, is peculiar due to its C- and O-rich but He- and H- deficient atmosphere whose composition cannot be well predicted by current stellar evolution models. The analysis of the elemental abundance and the benchmark of stellar atmospheric models depends heavily on spectral data under cosmic conditions, which are currently extremely scarce. We created a well-defined, uniform, relatively large-scale ∼millimeter plasma sample in the laboratory with a temperature and a C/O ratio similar to those of H1504+65’s atmosphere. The emission spectra with high precision in the range of 10–80 nm were obtained and identified according to databases such as NIST and Kelly. A detailed comparison between our emission lines and the Chandra-observed white dwarf H1504+65 atmosphere’s absorption lines was performed. The stongly isolated O VI lines in the range of 10–13 nm are observed in both cases. We observed a wealth of O V lines in the range of 13–14 nm that cannot be well identified or predicted by models due to the weak flux and also probably due to the blending effect of Fe group elements in the Chandra spectrum. Long-wavelength lines ranging from 14 to 80 nm, which are not observed in the Chandra spectrum because of the high interstellar neutral hydrogen column density, show abundant O IV-V, C IV lines, and strong O VI lines. Moreover, the intensities of the lines at 62.973 and 17.216 nm are analyzed to characterize the plasma temperature.

Ultradense Gas Tracked by Unshifted Broad Absorption Lines in a Quasar

Abstract We present a detailed analysis of the broad absorption line system in the quasar SDSS J122017.06+454941.1, which are clearly detected in hydrogen Lyman series and metal lines, such as C iv, Si iv, Si iii, Al iii, and C ii, with a similar velocity as that of the broad emission lines. We reliably measured the column densities of H i, Al iii, and C ii, and obtained a low limit to Si iv and Si iii. With the help of the photoionization simulations, we found that the absorption gas has a hydrogen number density n H ≈ 1011.03 cm−3 and a hydrogen column density N H ≈ 1021.0 cm−2, and is exposed to the radiation with an ionization parameter U ≈ 10−1.25, and thus located the absorber at ∼0.3 pc from the central supermassive black hole, remarkably similar to the radius of the broad-line region (BLR; 0.17–0.84 pc as estimated by the luminosity–radius relation) of the quasar. It is likely that our line of sight may happen to intercept the low-column part of the BLR with a high density similar to that of the inferred value of the absorber. We suggest that detection of Al iii absorption line doublet in moderate quality quasar spectra could be a good indicator of dense gases, provided that the neutral hydrogen column density of the absorber is .

The Abell 3391/95 galaxy cluster system

Context.Inferences about dark matter, dark energy, and the missing baryons all depend on the accuracy of our model of large-scale structure evolution. In particular, with cosmological simulations in our model of the Universe, we trace the growth of structure, and visualize the build-up of bigger structures from smaller ones and of gaseous filaments connecting galaxy clusters.Aims.Here we aim to reveal the complexity of the large-scale structure assembly process in great detail and on scales from tens of kiloparsecs up to more than 10 Mpc with new sensitive large-scale observations from the latest generation of instruments. We also aim to compare our findings with expectations from our cosmological model.Methods.We used dedicated SRG/eROSITA performance verification (PV) X-ray, ASKAP/EMU Early Science radio, and DECam optical observations of a ~15 deg2region around the nearby interacting galaxy cluster system A3391/95 to study the warm-hot gas in cluster outskirts and filaments, the surrounding large-scale structure and its formation process, the morphological complexity in the inner parts of the clusters, and the (re-)acceleration of plasma. We also used complementary Sunyaev-Zeldovich (SZ) effect data from thePlancksurvey and custom-made Galactic total (neutral plus molecular) hydrogen column density maps based on the HI4PI and IRAS surveys. We relate the observations to expectations from cosmological hydrodynamic simulations from the Magneticum suite.Results.We trace the irregular morphology of warm and hot gas of the main clusters from their centers out to well beyond their characteristic radii,r200. Between the two main cluster systems, we observe an emission bridge on large scale and with good spatial resolution. This bridge includes a known galaxy group but this can only partially explain the emission. Most gas in the bridge appears hot, but thanks to eROSITA’s unique soft response and large field of view, we discover some tantalizing hints for warm, truly primordial filamentary gas connecting the clusters. Several matter clumps physically surrounding the system are detected. For the “Northern Clump,” we provide evidence that it is falling towards A3391 from the X-ray hot gas morphology and radio lobe structure of its central AGN. Moreover, the shapes of these X-ray and radio structures appear to be formed by gas well beyond the virial radius,r100, of A3391, thereby providing an indirect way of probing the gas in this elusive environment. Many of the extended sources in the field detected by eROSITA are also known clusters or new clusters in the background, including a known SZ cluster at redshiftz= 1. We find roughly an order of magnitude more cluster candidates than the SPT and ACT surveys together in the same area. We discover an emission filament north of the virial radius of A3391 connecting to the Northern Clump. Furthermore, the absorption-corrected eROSITA surface brightness map shows that this emission filament extends south of A3395 and beyond an extended X-ray-emitting object (the “Little Southern Clump”) towards another galaxy cluster, all at the same redshift. The total projected length of this continuous warm-hot emission filament is 15 Mpc, running almost 4 degrees across the entire eROSITA PV observation field. The Northern and Southern Filament are each detected at &gt;4σ. ThePlanckSZ map additionally appears to support the presence of both new filaments. Furthermore, the DECam galaxy density map shows galaxy overdensities in the same regions. Overall, the new datasets provide impressive confirmation of the theoretically expected structure formation processes on the individual system level, including the surrounding warm-hot intergalactic medium distribution; the similarities of features found in a similar system in the Magneticum simulation are striking. Our spatially resolved findings show that baryons indeed reside in large-scale warm-hot gas filaments with a clumpy structure.