Context.
The intergalactic medium (IGM) is believed to contain the majority of baryons in the universe and to trace the same dark matter structure as galaxies, forming filaments and sheets. Ly
α
...absorbers, which sample the neutral component of the IGM, have been extensively studied at low and high redshift, but the exact relation between Ly
α
absorption, galaxies, and the large-scale structure is observationally not well constrained.
Aims.
In this study, we aim at characterising the relation between Ly
α
absorbers and nearby over-dense cosmological structures (galaxy filaments) at recession velocities Δ
v
≤ 6700 km s
−1
by using archival observational data from various instruments.
Methods.
We analyse 587 intervening Ly
α
absorbers in the spectra of 302 extragalactic background sources obtained with the Cosmic Origins Spectrograph (COS) installed on the
Hubble
Space Telescope (HST). We combine the absorption line information with galaxy data of five local galaxy filaments from the V8k catalogue.
Results.
Along the 91 sightlines that pass close to a filament, we identify 215 (227) Ly
α
absorption systems (components). Among these, 74 Ly
α
systems are aligned in position and velocity with the galaxy filaments, indicating that these absorbers and the galaxies trace the same large-scale structure. The filament-aligned Ly
α
absorbers have a ∼90% higher rate of incidence (d /d
z
= 189 for log
N
(H
I
) ≥ 13.2) and a slightly shallower column density distribution function slope (−
β
= −1.47) relative to the general Ly
α
population at
z
= 0, reflecting the filaments’ matter over-density. The strongest Ly
α
absorbers are preferentially found near galaxies or close to the axis of a filament, although there is substantial scatter in this relation. Our sample of absorbers clusters more strongly around filament axes than a randomly distributed sample would do (as confirmed by a Kolmogorov–Smirnov test), but the clustering signal is less pronounced than for the galaxies in the filaments.
Aims. We investigated the ionisation conditions and distances of Galactic high-velocity clouds (HVCs) in the Galactic halo and beyond in the direction of the Local Group (LG) barycentre and ...anti-barycentre, by studying spectral data of 29 extragalactic background sources obtained with the Cosmic Origins Spectropgraph (COS) installed on the Hubble Space Telescope (HST). Methods. We model column-densities of low, intermediate, and high ions such as Si II, C II, Si III, Si VI, and C IV, and use these data to construct a set of Cloudy ionisation models. Results. In total, we found 69 high-velocity absorption components along the 29 lines of sight. The components in the direction of the LG barycentre span the entire range of studied velocities, 100 ≲ |vLSR| ≲ 400 km s−1, while those in the anti-barycentre sample have velocities up to about 300 km s−1. For 49 components, we infer the gas densities. In the direction of the LG barycentre, the gas densities exhibit a wide range from log nH = −3.96 to −2.55, while in the anti-barycentre direction the densities are systematically higher, log nH > −3.25. The barycentre absorbers can be split into two groups based on their density: a high-density group with log nH > −3.54, which can be affected by the Milky Way radiation field, and a low-density group (log nH ≤ −3.54). The latter has very low thermal pressures of P/k < 7.3 K cm−3. Conclusions. Our study shows that part of the absorbers in the LG barycentre direction trace gas at very low gas densities and thermal pressures. These properties indicate that the absorbers are located beyond the virial radius of the Milky Way. Our study also confirms results from earlier, single-sightline studies, suggesting the presence of a metal-enriched intragroup medium filling the LG near its barycentre.
Human parechoviruses (HPeV) cause symptoms ranging from severe neonatal infections to mild gastrointestinal and respiratory disease. Use of PCR and genotyping has markedly improved the detection rate ...of HPeV but has simultaneously raised questions about the clinical relevance of positive tests. This retrospective study correlates positive HPeV1 or HPeV3 PCR tests in stools from children with their symptoms to determine clinical relevance. Children with HPeV1- or HPeV3-positive stool samples, as detected by real time RT-PCR and direct genotyping, between 2004 and 2008 were selected. Clinical data were retrospectively collected from the patient’s files and results were compared. One hundred and thirty-eight children with positive HPeV1 (n = 112) or HPeV3 (n = 26) stool samples were identified. Significantly more HPeV3-infected children were neonates or infants younger than 6 months of age. Meningitis or sepsis-like illnesses were diagnosed most frequently and were found in significantly younger children. Almost half of HPeV1-infected children had an underlying disease. Mild gastrointestinal disease was seen most frequently in these children. There was no clear correlation between viral load (Ct value) and severity of symptoms. In conclusion, HPeV3 detected by PCR in stool samples is associated with clinically relevant disease. For HPeV1, a positive stool sample is mainly associated with symptoms in children with underlying disease.
The number of offshore wind farms is increasing rapidly, leading to questions about the environmental impact of such farms. In the Netherlands, an extensive monitoring programme is being executed at ...the first offshore wind farm (Offshore Windfarm Egmond aan Zee, OWEZ). This letter compiles the short-term (twoyears) results on a large number of faunal groups obtained so far. Impacts were expected from the new hard substratum, the moving rotor blades, possible underwater noise and the exclusion of fisheries. The results indicate no short-term effects on the benthos in the sandy area between the generators, while the new hard substratum of the monopiles and the scouring protection led to the establishment of new species and new fauna communities. Bivalve recruitment was not impacted by the OWEZ wind farm. Species composition of recruits in OWEZ and the surrounding reference areas is correlated with mud content of the sediment and water depth irrespective the presence of OWEZ. Recruit abundances in OWEZ were correlated with mud content, most likely to be attributed not to the presence of the farm but to the absence of fisheries. The fish community was highly dynamic both in time and space. So far, only minor effects upon fish assemblages especially near the monopiles have been observed. Some fish species, such as cod, seem to find shelter inside the farm. More porpoise clicks were recorded inside the farm than in the reference areas outside the farm. Several bird species seem to avoid the park while others are indifferent or are even attracted. The effects of the wind farm on a highly variable ecosystem are described. Overall, the OWEZ wind farm acts as a new type of habitat with a higher biodiversity of benthic organisms, a possibly increased use of the area by the benthos, fish, marine mammals and some bird species and a decreased use by several other bird species.
This letter compiles the short-term (two years) results on a large number of faunal groups obtained so far. Impacts were expected from the new hard substratum, the moving rotor blades, possible ...underwater noise and the exclusion of fisheries. The results indicate no short-term effects on the benthos in the sandy area between the generators, while the new hard substratum of the monopiles and the scouring protection led to the establishment of new species and new fauna communities. Bivalve recruitment was not impacted by the OWEZ wind farm. Species composition of recruits in OWEZ and the surrounding reference areas is correlated with mud content of the sediment and water depth irrespective the presence of OWEZ. Overall, the OWEZ wind farm acts as a new type of habitat with a higher biodiversity of benthic organisms, a possibly increased use of the area by the benthos, fish, marine mammals and some bird species and a decreased use by several other bird species.
Since summer 2021, the Radio Neutrino Observatory in Greenland (RNO-G) is searching for astrophysical neutrinos at energies Formula omitted PeV by detecting the radio emission from particle showers ...in the ice around Summit Station, Greenland. We present an extensive simulation study that shows how RNO-G will be able to measure the energy of such particle cascades, which will in turn be used to estimate the energy of the incoming neutrino that caused them. The location of the neutrino interaction is determined using the differences in arrival times between channels and the electric field of the radio signal is reconstructed using a novel approach based on Information Field Theory. Based on these properties, the shower energy can be estimated. We show that this method can achieve an uncertainty of 13% on the logarithm of the shower energy after modest quality cuts and estimate how this can constrain the energy of the neutrino. The method presented in this paper is applicable to all similar radio neutrino detectors, such as the proposed radio array of IceCube-Gen2.
Aims. We aim to define a small and large chemical network which can be used for the quantitative simultaneous analysis of molecular emission from the near-IR to the submm. We also aim to revise ...reactions of excited molecular hydrogen, which are not included in UMIST, to provide a homogeneous database for future applications. Methods. We have used the thermo-chemical disk modeling code ProDiMo and a standard T Tauri disk model to evaluate the impact of various chemical networks, reaction rate databases and sets of adsorption energies on a large sample of chemical species and emerging line fluxes from the near-IR to the submm wavelength range. Results. We find large differences in the masses and radial distribution of ice reservoirs when considering freeze-out on bare or polar ice coated grains. Most strongly the ammonia ice mass and the location of the snow line (water) change. As a consequence molecules associated to the ice lines such as N2H+ change their emitting region; none of the line fluxes in the sample considered here changes by more than 25% except CO isotopologues, CN and N2H+ lines. The three-body reaction N+H2+M plays a key role in the formation of water in the outer disk. Besides that, differences between the UMIST 2006 and 2012 database change line fluxes in the sample considered here by less than a factor of two (a subset of low excitation CO and fine structure lines stays even within 25%); exceptions are OH, CN, HCN, HCO+ and N2H+ lines. However, different networks such as OSU and KIDA 2011 lead to pronounced differences in the chemistry inside 100 au and thus affect emission lines from high excitation CO, OH and CN lines. H2 is easily excited at the disk surface and state-to-state reactions enhance the abundance of CH+ and to a lesser extent HCO+. For sub-mm lines of HCN, N2H+ and HCO+, a more complex larger network is recommended. Conclusions. More work is required to consolidate data on key reactions leading to the formation of water, molecular ions such as HCO+ and N2H+ as well as the nitrogen chemistry. This affects many of the key lines used in the interpretation of disk observations. Differential analysis of various disk models using the same chemical input data will be more robust than the interpretation of absolute fluxes.
Over the last 25 years, radiowave detection of neutrino-generated signals, using cold polar ice as the neutrino target, has emerged as perhaps the most promising technique for detection of ...extragalactic ultra-high energy neutrinos (corresponding to neutrino energies in excess of 0.01 Joules, or 1017 electron volts). During the summer of 2021 and in tandem with the initial deployment of the Radio Neutrino Observatory in Greenland (RNO-G), we conducted radioglaciological measurements at Summit Station, Greenland to refine our understanding of the ice target. We report the result of one such measurement, the radio-frequency electric field attenuation length $L_\alpha$. We find an approximately linear dependence of $L_\alpha$ on frequency with the best fit of the average field attenuation for the upper 1500 m of ice: $\langle L_\alpha \rangle = ( ( 1154 \pm 121) - ( 0.81 \pm 0.14) \, ( \nu /{\rm MHz}) ) \,{\rm m}$ for frequencies ν ∈ 145 − 350 MHz.
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