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Recent measurements of primary and secondary CR spectra, their arrival directions, and our improved knowledge of the magnetic field geometry around the heliosphere allow us to set a bound on the distance beyond which a puzzling 10-TeV "bump" and certain related spectral features cannot originate. The sharpness of the spectral breaks associated with the bump, the abrupt change of the CR intensity across the local magnetic equator (90 ° pitch angle), and the similarity between the primary and secondary CR spectral patterns point to a local reacceleration of the bump particles out of the background CRs. We argue that, owing to a steep preexisting CR spectrum, a nearby shock may generate such a bump by boosting particle rigidity by a mere factor of ∼ 1.5 in the range below 50 TV. Reaccelerated particles below ∼ 0.5 TV are convected with the interstellar medium flow and do not reach the Sun. The particles above this rigidity then form the bump. This single universal process is responsible for the observed spectral features of all CR nuclei, primary and secondary, in the rigidity range below 100 TV. We propose that one viable candidate is the system of shocks associated with ∊ Eridani star at 3.2 pc of the Sun, which is well aligned with the direction of the local magnetic field. Other shocks, such as old supernova shells, may produce a similar effect. We provide a simple formula that reproduces the spectra of all CR species with only three parameters uniquely derived from the CR proton data. We show how our formalism predicts helium, boron, carbon, oxygen, and iron spectra, for which accurate data in GV-TV range exist. Our model thus unifies all the CR spectral features observed below 50 TV. [ABSTRACT FROM AUTHOR]

Understanding the physical processes involved in the propagation of cosmic rays in the intergalactic media is one of the biggest problems in astrophysics today. It is an important topic because one first tries to identify the sources and later to understand the physical processes that occur when the particles are accelerated to ultra-high energies (E > 10 18 eV). And because cosmic rays are charged particles, they are deflected in the existing magnetic fields as they propagate to Earth, making it very difficult to correlate their direction of arrival with astrophysical sources. Moreover, cosmic rays consist mainly of atomic nuclei interacting with the cosmic microwave background (CMB) and the extragalactic background light (EBL) during their propagation, and a significant part of their energy is consumed in these processes (for a proton with E ∼ 10 21 eV, its energy is approximately halved over a distance of 20 Mpc). In this article, we describe the main processes between background photons and ultrahigh-energy cosmic rays. We have also used the equations for comparison with the most commonly used programme in this field to illustrate the physical processes addressed. We conclude that the result of the equations leads to well-established results in the field, such as the importance of EBL for the process of photodesintegration (Allard, 2012). [ABSTRACT FROM AUTHOR]

We present ionization structures of IC 2003, a planetary nebula with [WR] central star, using a 1-D dusty photo-ionization code: "CLOUDY 17.03". The photo-ionization model is constrained by archival UV emission line fluxes, medium-resolution optical spectroscopy, IRAS 25 μ m flux, absolute H β flux, and the mean angular size of the nearly spherical optical nebula. To constrain the carbon abundance and the effect of photo-electric heating in the ionized gas, we used UV emission lines. We considered an amorphous carbon dust grain with MRN and KMH size distributions to address the importance of photo-electric heating in the ionized nebula. We show that KMH grain size distribution with quantum dust heating reproduces the observations quite well. We construct the ionization structures of different elements at their different ionization stages in the nebula. We derive the physical properties of the planetary nebula and its chemical composition, as well as the parameters of its central star. The estimated nebular dust-to-gas mass ratio is 2.37 × 10 - 3 , and the enhanced photo-electric heating yielded by small dust grains is 9.4 % of the total heating. We considered the H-poor model atmosphere for the central star; the effective temperature of the central star is 177 kK, the specific gravity log(g) is 6, and its luminosity ( L ∗ ) is 6425 L ⊙ . The derived central star parameters plotted on stellar evolutionary tracks correspond to a central star mass of 0.636 M ⊙ and to a progenitor mass of 3.26 M ⊙ . [ABSTRACT FROM AUTHOR]

The D/H ratio in astrophysical environments has instigated the scientists for at least 50 years. The wide range of values in the interstellar medium (ISM) from 10e to 7 to 10e-1 have usually been claimed to be due to small zero-point energy differences between reactants and products involving D and H (mainly at low temperatures). Here, we present a new source of deuteration processes in the ISM clouds as a result of cosmic ray irradiation. As a study object, we consider a typical molecular clump under the presence of incoming cosmic rays simulated computationally. The calculations were performed employing the Monte Carlo toolkit GEANT4 code (considering hadronic physics) and considering mainly the proton and alpha component of the incoming cosmic rays from the ISM (the dominant ones for the production of secondary protons and deuterons). The results suggest an increasing D/H ratio as function of time in the central part of molecular clumps (<200 AU) with the largest deuteration in the central region of the cloud, and a bump in the D/H ratio around 2–10 AU (which becomes more pronounced for clouds with larger timescales; > 10 Myrs). The results also show that for timescales between 10 and 100 Myrs the central part of the cloud has D/H around 6-16e-3, a value compatible with the observed D/H in some interstellar clouds. This work adds a new piece to the D/H puzzle of the ISM and might also help to explain the D/H ratio measured in different objects inside the Solar system. [ABSTRACT FROM AUTHOR]

We report the detection of a γ -ray bubble spanning at least 100 deg 2 in ultra-high energy (UHE) up to a few PeV in the direction of the star-forming region Cygnus X, implying the presence super PeVatron(s) accelerating protons to at least 10 PeV. A log-parabola form with the photon index Γ (E) = (2.71 ± 0.02) + (0.11 ± 0.02) × log 10 (E / 10 TeV) is found fitting the gamma-ray energy spectrum of the bubble well. UHE sources, "hot spots" correlated with very massive molecular clouds, and a quasi-spherical amorphous γ -ray emitter with a sharp central brightening are observed in the bubble. In the core of ∼ 0.5 ° , spatially associating with a region containing massive OB association (Cygnus OB2) and a microquasar (Cygnus X-3), as well as previously reported multi-TeV sources, an enhanced concentration of UHE γ -rays is observed with 2 photons at energies above 1 PeV. The general feature of the bubble, the morphology, and the energy spectrum, are reasonably reproduced by the assumption of a particle accelerator in the core, continuously injecting protons into the ambient medium. [ABSTRACT FROM AUTHOR]

Our understanding of the formation and interaction processes of astronomical structures in the Universe and in galaxies has significantly expanded due to recent progress in improving the quality of observations, brought about by the emergence of new telescopes. Such processes are associated with the release of a significant amount of energy and may influence our vital activities. One example of energy flow release is magnetic storms, which are associated with processes occurring on the Sun. Such storms lead to disruptions of communication facilities, impact people, and can cause satellite and aircraft failures. There are objects in both near and deep space that are much more powerful than our star. In such objects, enormous energy flows are generated and released in the form of space jets. These energy flows occur in quasars, black holes, protostars, and during supernova explosions of types Ia, Ib, Ic, and II. During a supernova explosion, an immense amount of energy is released in the form of energy and high-energy particles. Such processes can have a significant impact on the safety of space flights. In this paper, the processes of formation of stellar systems within a turbulent interstellar medium are considered. This process is the result of complex processes that occur in the interstellar medium and denser gas formations – molecular clouds. At the same time, there are nonlinear interactions between turbulence and gravity, collisions between molecular clouds, interactions with shock waves, and so on. Supersonic turbulence is one of the main reasons for the formation of dynamic prestellar structures. The evolution of superdense substances formation begins when they gather in turbulent flows or are formed by supersonic collisions between molecular clouds. This process continues until these areas reach prestellar density. Depending on various factors, these superdense formations can either collapse and form new star systems or disintegrate, returning the substance to the interstellar medium. Until recently, the prevailing opinion was that a significant portions of molecular clouds were not gravitationally bound. Conclusions about this were made based on the virial theorem, which expresses the relationship between gravitational and kinetic energy. However, recent studies have refuted this. In this paper, the results of a simulation carried out to study the collision of large ellipsoidal and spherical molecular clouds in a three-dimensional setting. The simulation was conducted on high-resolution grids and utilized the adaptive mesh refinement (AMR) method. • Morphological analysis of supersonic turbulence arising from the collision of spherical and prolate molecular clouds. • Modeling processes leading to the possible formation of new stellar systems. • Study of complex shock wave loading leading to the emergence of supersonic turbulence, Kelvin-Helmholtz instability and the formation of clumps. • Comparison of Chandrasekhar's analytical and numerical solution for an prolate molecular cloud. [ABSTRACT FROM AUTHOR]

Fast Radio Bursts (FRBs) are extra-galactic origin milli-second duration bright radio bursts. Theoretically, FRBs may produce optical counterparts with durations from milliseconds to hours. The FRB optical counterparts may be detectable in future large field telescopes, including the China Space Station Telescope (CSST), the 2.5-meter Wide Field Survey Telescope (WFST) lead by the University of Science and Technology of China (USTC) and the Purple Mountain Observatory (PMO), and the Earth 2.0 (ET). The fast radio burst optical counterparts are grouped into millisecond time-scale optical counterparts, hourly time-scale optical counterparts, and optical afterglow for our study. The first two can be generated by the high-energy extension of the radio radiation of fast radio bursts and the inverse Compton scattering of high-energy electrons. The event rates highly depend on the optical-to-radio flux ratio η ν. For millisecond duration optical counterparts, the detection rate of WFST, CSST, and ET can reach hundreds per year in an ideal case. If η ν ∼ 10 − 3 , the corresponding annual detection rates of WFST and CSST are in the order of 1, and the annual detection rate of ET is 19.5. For the hourly timescale optical counterparts, ideally, the age of the supernova remnant is 5 years, η ν is about 10 − 6 , and the annual detection rates are above 100. The X-ray counterpart of FRB 200428 indicates that FRBs may produce relativistic outflow, which will interact with the interstellar medium to produce optical afterglows. Combined with the standard afterglow model, the detectability of optical afterglow is explored with a simulation of fast radio bursts following the redshift and energy distribution from the literature. With a total energy-radio energy ratio similar to FRB 200428, (ζ = 10 5), the estimated annual detection rates of CSST, WFST, and ET are 1.3, 1.0, and 67, respectively. [ABSTRACT FROM AUTHOR]

The magnification effect provided by gravitational lensing overcomes the limitations of current observation instruments, allowing researchers to study faint objects at high redshift (z ≈ 4). Over the last decades, the sample of strong lenses has been mostly confined to optical bands. With the advent of (sub)millimeter wide field extragalactic surveys, about 200 strong lenses have been discovered in (sub)millimeter bands. Observations with high resolution and sensitivity from ALMA, NOEMA, and SMA, coupled with the flux boost from strong lensing, provide new windows to study galaxies at high redshift. Many works have investigated topics such as star formation, interstellar medium, and dynamic properties. The main objective of this paper is to review the current research status of galaxy-galaxy lensing in (sub)millimeter bands from the perspectives of observation samples, modeling methods, and scientific applications. [ABSTRACT FROM AUTHOR]

The processes occurring in near and far space have a significant impact on the safety of space flights. Processes such as explosions of supernovae and relativistic jets have a particularly great impact. They arise in quasars, black holes, protostars. Often such structures are observed during the formation of new stars. Such jets have a great impact on the safety of space flights. For example, there is currently no radiation shelter on the International Space Station, so astronauts are at serious risk of getting radiation sickness. In addition, the skin of the orbital station modules consists of aluminum, which accumulates secondary radiation. The formation process of new star systems is the result of complex processes that occur in interstellar gas. These processes include nonlinear interactions of turbulence, gravity, collisions of molecular clouds with each other, as well as rotation and several other factors. The evolution of the formation of superdense substance begins from the moment when it gathers in turbulent flows or is formed by supersonic collisions of molecular clouds with each other, or are formed during the intereaction of molecular clouds with supersonic waves, which are formed during the explosions of supernovae, until the moment when these superdense areas reach the prestellar density. Further, depending on several factors, these superdense formations either collapse or disintegrate and return to the interstellar medium. The analysis of observations allows to conclude that a significant part of the molecular clouds is not gravitationally bound. These conclusions are made based on the virial theorem, which expresses the connection between gravitational and kinetic energy. In this paper, a simulation of large molecular clouds collision in a three-dimensional formulation on ultra-high-resolution grids is carried out. Execution of such calculations requires a lot of computer capacity. The paper presents the results of computer modeling of large-scale processes of filament formation and superdense, gravitationally coupled structurally parallel computation clusters with hybrid architecture. Parallel simulation on supercomputers was conducted with author's software, which uses a modified second-order Godunov method of accuracy of the Total Variation Diminishion type. Calculations were conducted on grids that contain more than one billion cells (1024 × 1024 × 1024). The gravitational potential is calculated on graphic processors. To refine the calculations, the method of adaptive refinement of the AMR grid is used. Simulation results are presented for cases of frontal collision of two molecular clouds, which density is distributed along the radius according to certain laws. • The processes of formation of new stellar systems are studied in this work in 3D simulation. • Appearance of clumps and filaments is discussed. • Morphing of high compression clumps set in possible stars formation zone is discussed. • The calculation program is based on a modified scheme of a high order of accuracy. [ABSTRACT FROM AUTHOR]

We conducted a transmission electron microscopy (TEM) study of an unusual oxide-silicate composite presolar grain (F2-8) from the unequilibrated ordinary chondrite Semarkona (LL3.00). The presolar composite grain is relatively large (>1 µm), has an amoeboidal shape, and contains Mg-rich olivine (forsterite), Mg-Al spinel, and Ca-rich pyroxene. The shape and phase assemblage are reminiscent of amoeboid-olivine-aggregates (AOAs) and add to the growing number of TEM observations of presolar refractory inclusion-like (CAIs and AOAs) grains. In addition to the dominant components, F2-8 also contains multiple subgrains, including an alabandite-oldhamite composite grain within the olivine and several magnetite subgrains within the Mg-Al spinel. We argue that the olivine, Mg-Al spinel, and alabandite-oldhamite formed by equilibrium condensation, whereas the Ca-rich pyroxene formed by non-equilibrium condensation, all in an M-type AGB star envelope. On the other hand, the magnetite subgrains are likely the result of aqueous alteration on the Semarkona asteroidal parent body. Additional evidence of secondary processing includes Fe-enrichment in the Mg-Al spinel and olivine, elevated Al contents in the olivine, and beam sensitivity and a modulated structure for the olivine. Compound presolar grains, in particular oxide-silicate AOA-like grains such as F2-8, record condensation conditions over a wide range of temperatures. Additionally, the presence of several different presolar phases in a composite grain can impart information on the relative rates and effects of post-condensation processing in a range of environments, including the interstellar medium, solar nebula, and the host asteroid parent body. For example, the olivine and spinel in F2-8 show evidence of fluid infiltration, but each component reacted in different ways and to different extents. The TEM observations of F2-8 provide insights across the lifetime of the grain from its formation by condensation in an M-type AGB star envelope, its transit through the interstellar medium, and aqueous alteration during its residence on Semarkona's asteroidal parent body. [ABSTRACT FROM AUTHOR]

The LHC beams cannot be polarized. Hence, the implementation of a dense polarized gas target at the LHCb experiment at CERN, to be operated simultaneously with beam–beam collisions, will enable high-energy fixed target interactions to explore a range of spin physics measurements. Using an atomic beam source at the Forschungszentrum Jülich to provide a polarized atomic hydrogen beam, we investigated the properties of a storage cell coated with amorphous carbon. A notable recombination rate, lying between 93 and 100%, and a preservation of polarization during recombination exceeding 74% was observed. We were able to generate H 2 molecules with a nuclear polarization of − 0. 59. Remarkably, no water layer accumulated on the cooled storage cell surface, even over extended periods. Furthermore, we examined the influence of Lyman- α radiation on the recombination rate on carbon, addressing a prominent question in the field of astrophysics. [ABSTRACT FROM AUTHOR]

[Display omitted] Boron nuclei in cosmic rays (CRs) are believed to be mainly produced by the fragmentation of heavier nuclei, such as carbon and oxygen, via collisions with the interstellar matter. Therefore, the boron-to-carbon flux ratio (B/C) and the boron-to-oxygen flux ratio (B/O) are very essential probes of the CR propagation. The energy dependence of the B/C ratio from previous balloon-borne and space-based experiments can be well described by a single power-law up to about 1 TeV/n within uncertainties. This work reports direct measurements of B/C and B/O in the energy range from 10 GeV/n to 5.6 TeV/n with 6 years of data collected by the Dark Matter Particle Explorer, with high statistics and well controlled systematic uncertainties. The energy dependence of both the B/C and B/O ratios can be well fitted by a broken power-law model rather than a single power-law model, suggesting the existence in both flux ratios of a spectral hardening at about 100 GeV/n. The significance of the break is about 5.6 σ and 6.9 σ for the GEANT4 simulation, and 4.4 σ and 6.9 σ for the alternative FLUKA simulation, for B/C and B/O, respectively. These results deviate from the predictions of conventional turbulence theories of the interstellar medium (ISM), which point toward a change of turbulence properties of the ISM at different scales or novel propagation effects of CRs, and should be properly incorporated in the indirect detection of dark matter via anti-matter particles. [ABSTRACT FROM AUTHOR]

We report 3He and 4He concentrations in 57 sediment samples from the southeast Indian Ocean where 60Fe excesses were previously identified in a subset of the same samples (Wallner et al., 2016). The coupled 60Fe-3He data allow further evaluation of two competing hypotheses: (1) a nearby supernova (SN) showered Earth with exotic radionuclides such as 60Fe during the last 3 million years, or (2) 60Fe in terrestrial archives was generated by reactions of galactic cosmic rays (GCRs) on micrometeorite grains that were irradiated for hundreds of millions of years in the interstellar medium, where 3He production by GCRs is larger than the solar wind 3He flux. Piston core ELT49-53 sediments show no correlation between 3He and 60Fe, and sedimentary 3He appears to be dominated by the presence of interplanetary dust particles (IDPs). Because 3He is not supplied in significant amounts by SN ejecta, the absence of a 3He-60Fe correlation provides additional, although circumstantial evidence for the supernova hypothesis. Large uncertainties in the relatively small number of sediment 60Fe measurements currently limit a firmer conclusion. The extraterrestrial 3He accumulation rate in ELT49-53 from 3.2 to 1.7 Ma was 0.88 ± 0.26 × 10−12 cm3 STP/g/kyr, similar to IDP 3He flux estimates from previous sedimentary and ice core records that span both shorter and longer time scales. 4He and 60Fe accumulation rates during this time interval were 0.11 ± 0.04 × 10−6 cm3 STP/cm2/kyr and 1.9 ± 0.5 × 104 atoms/cm2/kyr. Bulk sediment [4He] is strongly anti-correlated with sediment CaCO 3 content, evidence for modulation of the terrigenous and cosmic sedimentary fractions primarily by changes in biogenic carbonate deposition. Although the dominant terrigenous source has not been uniquely identified at the Indian Ocean deposition site, it resembles eolian material from the continental interior of Australia, and shows a narrow range of 3He/4He (from 2 to 4 × 10−8, 0.015–0.030 R A) over the last ∼3 Myrs. [ABSTRACT FROM AUTHOR]

We take a phenomenological approach in a minimal model to understand the spectral intensity of secondary cosmic-ray particles like positrons, antiprotons, Lithium, Beryllium and Boron. Our analysis shows that cosmic rays at ∼ GeV energies pass through a significant amount of matter in regions surrounding the sources. This grammage decreases with increasing cosmic-ray energy and becomes negligible beyond ∼ 100 GeV. During the subsequent propagation in the interstellar medium cosmic rays of all energies up to ∼ 10 5 GeV/ n pass through about 1–2 g cm−2 of matter before leaking into the intergalactic medium. It is in the interstellar medium that the bulk of the positrons and antiprotons are generated. Also cosmic-ray nuclei like C, N, and O at all energies generate additional amounts of Li, Be and B nuclei with a spectrum similar to those of C, O etc. The implications of these findings of the minimal model to the observations of gamma rays and also the importance of spatial and temporal discreteness of cosmic-ray sources for modeling cosmic-ray propagation are briefly pointed out. [ABSTRACT FROM AUTHOR]

Carbonaceous chondrites contain a diverse suite of more or less soluble compounds, including polycyclic aromatic hydrocarbons (PAHs). These compounds are structured around two or more fused benzene rings, and have shown to be detected in various astrophysical environments. The origin of PAHs in carbonaceous chondrites is debated: they may originate from the interstellar medium (ISM) and thus potentially carry information on accretion processes. Alternatively, they may have formed or transformed during secondary processes on parent bodies and thus carry information about aqueous alteration conditions. Here, we investigate the nature, quantity, and isotopic composition of free PAHs in three recently recovered CM chondrites having experienced substantial and distinct degrees of alteration: the CM2.2 Aguas Zarcas, the CM2.0 Mukundpura and the CM1/2 Kolang. All the CMs investigated contain PAHs, with sizes ranging from 2 (naphthalene) to 5 cycles (benzopyrene). The concentration of PAHs is not correlated to the degree of alteration and larger PAHs are also the most depleted in 13C, suggesting an interstellar origin. Yet, the abundance of alkylated PAHs appears correlated to the degree of alteration and all the extracted PAHs are D-depleted, pointing towards hydrogen exchange with water having occurred during aqueous alteration. These combined results suggest that PAHs in CCs likely carry information on both accretion and alteration processes. [ABSTRACT FROM AUTHOR]

The provenance of GEMS (glass with embedded metal and sulfides) in cometary type interplanetary dust particles is investigated using analytical scanning transmission electron microscopy and secondary ion mass spectrometry. We review the current state of knowledge and closely examine the densities, elemental compositions and distributions, iron oxidation states, and isotopic compositions of a subset of GEMS in chondritic porous interplanetary dust. We find that GEMS are underdense with estimated densities that are 35–65% of compositionally equivalent crystalline aggregates. GEMS low densities result in a lower contribution to the bulk compositions of IDPs than has been assumed based on their volume fraction. We also find that element/Si ratios, assumed to be primary (indigenous), are instead perturbed by contamination and secondary alteration, including pulse heating during atmospheric entry. Fe in pyrrhotite inclusions was oxidized and Mg, S, Ca, and Fe were depleted relative to lithophile Al and Si, resulting in reduction in element/Si ratios. Because they trap outgassing elements, Fe-rich oxide rims that formed on the surface of GEMS are serendipitous "witness plates" to the changes in composition that accompany atmospheric entry. As a result of alteration, GEMS elemental compositions cannot reliably inform about their provenance. Except for highly anomalous oxygen isotope ratios measured in some large GEMS grains that indicate a contribution from circumstellar dust, oxygen isotope compositions are generally poor indicators of provenance. Prior work indicates that most GEMS fall close to the terrestrial oxygen isotope composition, which, however, does not exclude a presolar interstellar origin. Nitrogen isotopic compositions are more diagnostic. Elevated 15N/14N ratios indicate that GEMS accreted in conjunction with formation of organic matter by ion–molecule reactions in a cold (<50 K) presolar environment like the extreme outer nebula or interstellar medium. Considering all observations, we conclude that GEMS are most likely processed interstellar silicates. [ABSTRACT FROM AUTHOR]

Our understanding on the role of amorphous carbon in the interstellar medium to form complex structures, such as carbon nanotube/graphene/fullerene, is limited to date. We have investigated how shocks may induce physico-chemical transformation in amorphous carbon by subjecting samples of carbon nanopowder to high-temperature shocks, ∼7300 K, in a hydrogen-free environment for about 2 ms using a shock tube. The shock conditions achieved in the laboratory mimics low velocity interstellar shocks. Post shock samples were analyzed using Raman Spectroscopy and High Resolution – Transmission Electron Microscopy. We have found compelling evidence for the formation of carbon nanotube, graphene, and various other carbon nanostructures induced by the shock. Our results show that shocks in the interstellar medium can provide important chemical pathways to the formation of fullerenes and suggests that other carbonaceous structures may be present as well. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic Hydrocarbons are present in the universe in varied forms and are extensively studied over the years to account for the complex natured Aromatic Infrared Bands (AIBs). As an abundant element in the interstellar medium, nitrogen may substitute carbon atoms in the aromatic rings of PAHs to form Polycyclic Aromatic Nitrogen Heterocyclic (PANH) molecules. These PANH molecules can have new emission features and may contribute to some of the AIBs. Extreme conditions of the ISM may support PAH and/or PANH molecules in the formation of their cationic or anionic forms to further explain the AIBs. The present work reports DFT study of PANH molecules and their ionized variants and discusses their IR spectroscopic features in the 6–10 μm region. [ABSTRACT FROM AUTHOR]

The Intra-Group/Cluster Light (IGL/ICL) can be used to study the dynamical evolution of galaxy groups and clusters. Hickson Compact Groups (HCGs) have a high density and a low velocity dispersion, providing a unique environment to study galaxies merger and properties of interacting galaxies. It is also a promising target for the study of IGL. The g and r band deep imaging data of HCG 95 were obtained with Chinese Near Object Survey Telescope (CNEOST). The IGL fraction in HCG 95 is measured with model fitting using GALFIT, giving an IGL fraction (defined by the ratio between the IGL luminosity and the group total luminosity) of 3.55% ± 0.38% and 3.78% ± 0.59% in the g and r band, respectively. When applying the surface brightness threshold method, the IGL fraction is 1.9%–10% and 1.5%–10% in the g an r band, respectively. The color of the IGL (g − r = 0.78 ± 0.37) is similar to that of the HCG 95A and HCG 95C in the group (g − r = 0.82 − 0.85), suggesting that it is composed by an old population. It is showed that the IGL in the group may be from the stripped material of interaction between HCG 95A and HCG 95C, with little recent accretion. Combined with the IGL fraction measurements from literatures, we find that the IGL fraction shows no clear correlation with the total mass of groups. A positive correlation is found between the IGL fraction and the early-type galaxies fraction of groups, suggesting that the IGL fraction is linked to the evolutionary stage of a group. [ABSTRACT FROM AUTHOR]

The idea of an "Outer solar system probe: to be aimed away from the Sun in the plane of the ecliptic" dates from a report of the "Simpson Committee" of the Space Science Board of the National Academy of Sciences in March of 1960. After many studies and name changes, what is now known as "Interstellar Probe" has matured as a concept for making new discoveries that can be made in no other way, by going places yet to be explored. The central technical question has always been propulsion with "near-future" capabilities taken as the backdrop for defining the mission requirements. However, the real issue has always been to unite compelling science with engineering and technical reality. With that perspective in mind the Johns Hopkins University Applied Physics Laboratory (APL) has been tasked by the NASA Heliophysics Division to (re-)study the mission and provide a Technical Report to be delivered late 2021 for input to next Solar and Space Physics Decadal Survey. This "pragmatic Interstellar Probe" of the study is a mission through the outer heliosphere and to the nearby "Very Local" interstellar medium (VLISM), uses today's technology to take the first explicit step on the path of interstellar exploration, and can pave the way, scientifically, technically, and programmatically for more ambitious future journeys (and more ambitious science goals). To enforce these goals broadly-based engineering requirements include (1) readiness to launch no later than January 1, 2030; (2) capability to transmit useful scientific data from 1000 au; (3) powered by no more than 600 W (electric) at the beginning of the mission and no more than half of that at mission's end; and, (4) lifetime of no less than 50 years. To travel as far and as fast as possible with available technology, the use of the Space Launch System Block 2 (SLS B2) cargo version is enabling: carrying the spacecraft as well as a 3rd and 4th stage, solar system escape speeds of at least twice that of Voyager 1 (i.e., up to 7.2 au/yr) should be possible. We provide a top-level summary of work accomplished to date, focusing on how the science goals drive and are affected by telecommunication options, guidance and control requirements, trajectory options, and the baseline system architecture and approach. "It isn't about where we are going. It's about the journey out there." • An "Interstellar Probe" has been discussed in depth for almost 60 years. • The results of a four-year long engineering, science, instrumentation, and implementation trade study for NASA are summarized. • "Best" solutions are assessed and compared. • Over 100 mission approaches using NASA's large new SLS super heavy-lift launch vehicle are quantified and assessed. • Implementation costs are estimated and an example cost-loaded implementation schedule is published for an example mission. [ABSTRACT FROM AUTHOR]

We use the results of high resolution numerical simulations to fix the theoretical model of high redshift quasars (QSOs) ionizing and heating neutral gas, and predict the signal characteristics and signal/noise (S/N) ratios for Five-hundred-meter Aperture Spherical Telescope (FAST) to observe the 21 cm radiation around QSO. Our conclusions are summarized as: (1) the 21 cm frequency spectrum under the FAST field has full HII region for the QSO at z = 8 and with luminosity similar to ULAS J1120+0641, while has only a small trough for the QSO at z = 10 and with low luminosity; (2) the effect of Finite Light Travel Time (FLTT) obviously changes the 21 cm frequency spectrum of high redshift QSOs, makes the transition curve at lower frequency much steeper than that at higher frequency; (3) the FAST telescope can observe the 21 cm radiation of high redshift QSO with very high S/N ratio as high as ∼ 12 , thus can identify the HII regions and the FLTT effect. [ABSTRACT FROM AUTHOR]

• New theoretical branching ratio for two-body decay of neutrons is 1.3 %, not 0.0004 %. • In this branch neutron decays into second flavor of hydrogen atoms (SFHA). • 4 types of atomic experiments plus astrophysical observations evidence SFHA existence. • SFHA is practically dark: no emission or absorption of EM radiation except 21 cm line. • Old neutron stars could generate baryonic dark matter in the form of the SFHA. In attempts to resolve the neutron lifetime puzzle, there was suggested a hypothetical decay of neutrons into some unspecified dark matter (DM) particles. Later there were performed studies on how the hypothetical decay of neutrons would affect neutron stars. Recently it was shown that with the allowance for the second solution of Dirac equation for hydrogen atoms, the theoretical branching ratio (BR) for the two-body decay of neutrons (compared to their three-body decay) is amplified by a factor of 3300 from 0.000004. So, the BR becomes about 1.3% in the excellent agreement with the "experimental" BR = (1.15 ± 0.27)% required for reconciling the two distinct experimental values of the neutron lifetime: one from the beam experiments, another from the trap experiments. This meant that the two-body decay of neutrons in the beam experiments (that count only the protons) plays a much more sizable part in the overestimation of the lifetime of neutrons in these experiments than previously thought. Hydrogen atoms corresponding to the second solution of Dirac equations are called the second flavor of hydrogen atoms (SFHA) by the analogy with the flavors of quarks. The existence of the SFHA is evidenced by four different types of atomic/molecular experiments. The primary feature of the SFHA is that due to having only the s-states, they do not emit or absorb the electromagnetic radiation (except for the 21 cm line): they are practically dark. The SFHA became a candidate for a part of DM for the first time after the SFHA-based successful qualitative and quantitative explanation of the perplexing observation by Bowman et al. of the anomalous absorption in the redshifted 21 cm line from the early Universe. In the present paper we analyzed how this neutron decay into the SFHA affects neutron stars. We showed that old neutron stars could very slowly generate the new specific, described in detail baryonic DM in the form of the SFHA. Some old neutron stars would release it into their tiny atmospheres, while some other old neutron stars would release it into the interstellar medium. Besides, mergers of a neutron star with another neutron star or with a black hole, accompanied by the ejection of neutron-rich material, can also lead to the formation of SFHA as the ejecta cools down. This is another interesting aspect of the multi-messenger astronomy focused on studying these mergers through the gravitational waves they generate. These mechanisms of generating new baryonic DM in the universe should have the fundamental importance. We point out the indirect observational evidence of the continuing generation of new baryonic DM. We hope that our results will stimulate a further research in this direction. [ABSTRACT FROM AUTHOR]

The search for the simplest amino acid, glycine (NH2CH2COOH), in the interstellar medium (ISM) has become a never-ending story for astrochemistry and astrophysics researchers because that molecule plays a possible connection between the Universe and the origin of life. In the last forty years, all searches for NH2CH2COOH in the ISM at millimeter and submillimeter wavelengths have failed. Since the detection of NH2CH2COOH in the ISM is extremely difficult, we aime to search for the possible precursors of NH2CH2COOH. Earlier, many laboratory experiments have suggested that methylamine (CH3NH2) plays an important role in the ISM as a possible precursor of NH2CH2COOH. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we identified the rotational emission lines of CH3NH2 towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The column density of CH3NH2 towards the G358.93–0.03 MM1 is estimated to be (1.10 ± 0.31) × 1017 cm−2 with an excitation temperature of 180.8 ± 25.5 K. The fractional abundance of CH3NH2 with respect to H2 towards the G358.93–0.03 MM1 is (8.80 ± 2.60) × 10−8. The column density ratio of CH3NH2 and NH2CN towards G358.93–0.03 MM1 is (1.86 ± 0.95) × 102. The estimated fractional abundance of CH3NH2 towards the G358.93–0.03 MM1 agrees fairly well with the previous three-phase warm-up chemical modelling abundance of CH3NH2. We also discuss the possible formation mechanism of CH3NH2 , and we find that CH3NH2 is most probably formed via the reactions of radical CH3 and radical NH2 on the grain surface of G358.93–0.03 MM1. • We identify the emission lines of CH 3 NH 2 towards G358.93-0.03 MM1 using the ALMA. • CH 3 NH 2 has primary amine, which plays an important role as a precursor of glycine. • We conclude that G358.93–0.03 MM1 is a highly abundant CH 3 NH 2 source in ISM. • CH 3 NH 2 is created via the reaction of radicals CH 3 and NH 2 on the grain surface. [ABSTRACT FROM AUTHOR]

The time-dependent wave packet (TDWP) method was applied to investigate the quantum reaction mechanisms of title reaction, obtaining the state-specified (v = 0, j = 0) reaction probability, integral cross sections and rate constants. [Display omitted] • The quantum effect of the title reaction are studied. • The reaction mechanism of title reaction is ruled by the collision energy. • The reaction probability, integral cross sections and rate constants are calculated. • The rate constants agree well with expermental results. The title reaction is thought to be important for the astronomical PO formation, which may contribute to the generation of bioavailable H 3 PO 3. Using quasi-classical trajectory (QCT) method, the state-specified (v = 0, j = 0) rate constant of this reaction was calculated. The comparison with previous temperature-averaged QCT rate constant shows that the effect of ro-vibrational excitation is relatively small below 2000 K. Then, the time-dependent wave packet (TDWP) method was applied to investigate the quantum reaction mechanisms, obtaining the state-specified (v = 0, j = 0) reaction probability, integral cross sections and rate constants. The number of partial waves and the integral interval of collision energy considered were rigorously tested to ensure the convergence of the TDWP rate constant below 2000 K. The TDWP rate constant agrees better to the latest experimental results at 291 to 685 K than those from the two QCT calculations. Also, the TDWP calculations can produce relatively reliable rate constants at 700 to 2000 K, where the Arrhenius formula fitted by experimental results ignores the temperature dependence of the activation energy. The calculated rate constants are helpful for modelling the phosphorus chemistry and determining the abundances of the P-bearing species in interstellar media (ISM). [ABSTRACT FROM AUTHOR]

Detailed modeling of the evolution of neutral hydrogen in the intergalactic medium during the Epoch of Reionization, 5 ≤ z ≤ 20 , is critical in interpreting the cosmological signals from current and upcoming 21-cm experiments such as the Low-Frequency Array (LOFAR) and the Square Kilometre Array (SKA). Numerical radiative transfer codes provide the most physically accurate models of the reionization process. However, they are computationally expensive as they must encompass enormous cosmological volumes while accurately capturing astrophysical processes occurring at small scales (≲ Mpc). Here, we present pyC 2 Ray, an updated version of the massively parallel ray-tracing and chemistry code, C 2 -Ray, which has been extensively employed in reionization simulations. The most time-consuming part of the code is calculating the hydrogen column density along the path of the ionizing photons. Here, we present the Accelerated Short-characteristics Octahedral ray-tracing (ASORA) method, a ray-tracing algorithm specifically designed to run on graphical processing units (GPUs). We include a modern Python interface, allowing easy and customized use of the code without compromising computational efficiency. We test pyC 2 Ray on a series of standard ray-tracing tests and a complete cosmological simulation with volume size (349 Mpc) 3 , mesh size of 25 0 3 and approximately 1 0 6 sources. Compared to the original code, pyC 2 Ray achieves the same results with negligible fractional differences, ∼ 1 0 − 5 , and a speedup factor of two orders of magnitude. Benchmark analysis shows that ASORA takes a few nanoseconds per source per voxel and scales linearly for an increasing number of sources and voxels within the ray-tracing radii. [ABSTRACT FROM AUTHOR]

We introduce the Python program THALAS (TensorFlow Hydrodynamics Analysis for Lyman-Alpha Simulations), which maps baryon fields (baryon density, temperature, and velocity) to Ly α optical depth fields in both real space and redshift space. Unlike previous Ly α 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 Ly α forest inversion problem: given a Ly α 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. [ABSTRACT FROM AUTHOR]

21-cm cosmology provides an exciting opportunity to probe new physics dynamics in the early universe. In particular, a tiny sub-component of dark matter that interacts strongly with the visible sector may cool the gas in the intergalactic medium and significantly alter the expected absorption signal at Cosmic Dawn. However, the information about new physics in this observable is obscured by astrophysical systematic uncertainties. In the absence of a microscopic framework describing the astrophysical sources, these uncertainties can be encoded in a bottom up effective theory for the 21-cm observables in terms of unconstrained astrophysical fluxes. In this paper, we take a first step towards a careful assessment of the degeneracies between new physics effects and the uncertainties in these fluxes. We show that the latter can be constrained by combining measurements of the UV luminosity function, the Planck measurement of the CMB optical depth to reionization, and an upper bound on the unresolved X-ray flux. Leveraging those constraints, we demonstrate how new physics signatures can be disentangled from astrophysical effects. Focusing on the case of millicharged dark matter, we find sharp predictions, with small uncertainties within the viable parameter space.1 [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) act as condensation nuclei for water/ammonia molecules forming icy water clusters. In the context of small aromatic rings, we have theoretically examined complexes of benzonitrile with water/ammonia molecules in order to investigate the photochemical kinetics of the icy grain formation. First, we obtain the structure of energetically stable complexes containing different H-bonding patterns and analyze their effects in the infrared (IR) and vacuum ultraviolet (VUV) spectra, before and after ionization. Second, we evaluate the H-bonding reorientation kinetics of the complexes at low temperatures, which indicates that the process involving water occurs faster than the corresponding process involving ammonia. Finally, the thermal rate constants indicate which configurations are the most likely to be ionized under vacuum ultraviolet (VUV) irradiation. Our results are consistent with what has experimentally been observed for related complexes, and are useful as a starting point to investigate the process of the icy grains formation. This study provides insight into possible subsequent photochemical reactions occurring in the interstellar medium (ISM) or in jet-cooled molecular complexes. [ABSTRACT FROM AUTHOR]

The possibility of interstellar scientific missions, even if only to explore the local Interstellar Medium (ISM), has received increased consideration in recent years. Due to the immense distances involved, an interstellar spacecraft must be capable of autonomous navigation. Many autonomous navigation strategies exist, but nearly all of these depend in some way on star observations and an ability to match these observations to a catalog of known stars. This is generally accomplished by computing and matching a star pattern descriptor that is invariant to changes in the spacecraft attitude. Unlike missions within the Solar System, an interstellar spacecraft will require a catalog that treats stars as 3D points rather than directions. This is problematic, since it has long been known that view invariants do not exist for sets of 3D points—making the classical method (or any modifications thereof) completely ineffectual for star identification in interstellar space. Moreover, other effects for a spacecraft traveling at relativistic speeds – such as stellar aberration and the relativistic Doppler effect – can negatively affect star identification, navigation observability, and sensor design. These challenges of star identification during interstellar flight are discussed and some possible solutions are suggested. Numerical examples are provided for a variety of motivating mission concepts. • Interstellar missions are expected to rely on star observations as part of their navigation system. • Interstellar missions require 3D star catalogs, which represents a departure from conventional star catalogs. • If stars in the galaxy must be modeled as 3D points, there are no pose invariant descriptors that can be used to index star patterns. • We may obtain star pattern invariants by constraining the allowable motion of the interstellar spacecraft. [ABSTRACT FROM AUTHOR]

After the advent of Herschel Space Observatory, there is much progress of the observational studies on the (sub)millimeter ((sub)mm) lines, such as the middle to high- J CO rotational transitions (J = 4–10), multiple H 2 O lines, and fine-structure emissions of atoms (e.g., C, O) and ions (e.g., C + , N +). These lines are important coolants for the interstellar medium (ISM), and thus can be used to investigate the physical conditions and chemical compositions of the ISM, as well as their power sources. In this paper, we first introduce how to investigate the star formation properties (such as the calibration of star formation rate (SFR) and the determination of star formation mode) using different (sub)mm lines. Then we review for the different methods of measuring total molecular mass, and discuss their advantages and caveats. At last we summarize the use of CO (CO spectral line energy distribution (CO SLED) and the ratio of mid- J CO lines to far-infrared continuum) and other lines to diagnose the power source in galaxies. [ABSTRACT FROM AUTHOR]

The recent experimental identification of aminomethanol (NH 2 CH 2 OH) and its synthesis under simulated interstellar conditions suggests that it may be formed, and thus observable, in the interstellar medium. To aid in its possible detection, this work presents high-level theoretical, anharmonic vibrational and rotational spectroscopic data for the three lowest-energy conformers of NH 2 CH 2 OH. All three conformers fall within 0.80 kcal mol−1 of each other at the CCSD(T)-F12b/cc-pCVTZ-F12 level, with an anharmonic zero-point vibrational energy correction. Additionally, all three conformers are shown to have multiple vibrational frequencies with intensities greater than 100 km mol−1. The most notable of these are the symmetric O-C-N stretch of the lower-energy C 1 conformer at 976.4 cm−1, the C-O stretch of the C s conformer at 964.9 cm−1, and the antisymmetric O-C-N stretch of the higher-energy C 1 conformer at 1099.0 cm−1. While much of the vibrational spectra of the three overlap, these features should help to separate them. Finally, all three conformers have non-zero dipole moments on the order of 1 D, suggesting that they may be observable by rotational spectroscopy, as well. In all cases, the computational data provided herein will help to facilitate future experimental and observational studies on this key molecule in the formation of extraterrestrial amino acids. [Display omitted] [ABSTRACT FROM AUTHOR]

This article presents an investigation into the electron impact ionization of diverse prebiotic molecules that exist within the interstellar medium. Specifically, the molecules under consideration here include ethylene glycol, ethanolamine, glycolonitrile, aminoacetonitrile, acetamide, and glycolaldehyde. These molecules hold the potential to serve as precursor compounds, playing a critical role in the formation of essential building blocks necessary for life's emergence. To understand the chemistry in these regions when such molecules interact with particles like electrons, we require reaction rates and cross sections. In this work, the electron impact ionization cross section is calculated using the robust optical potential approach and the complex scattering potential-ionization cross section method over a wide range of energies from 10 eV to 5000 eV on a fine grid. The incorporation of screening correction in this approach effectively addresses the superimposition of charge densities originating from distinct atoms within each molecule. Additionally, the binary-encounter Bethe ionization cross section is computed to facilitate comparison and validation of the presented data. [Display omitted] • Astrobiologically relevant molecules are studied upon irradiation of electron. • Complex optical potential is used to depict the electron-target interaction. • Ionization cross section of all the molecules are reported for the first time. • Two different theoretical methods CSP-ic and BEB are used for verification. • Screening correction is incorporated to increase accuracy of reported data. [ABSTRACT FROM AUTHOR]

Starlight polarization serves one of the powerful tools to study magnetic fields in the Galactic interstellar medium. Heiles catalogue contains polarization information for 9286 stars, and is by far the biggest. This catalogue has been extensively used to study the magnetic fields. However, the distance parameters of the stars in this catalogue are from photometric observations, and very uncertain. We cross match Heiles catalogue with Gaia Data Release 2 (DR2), and identify 7613 stars using both angular separation and magnitude as constraints. We then obtain precise distances from Gaia DR2 for these stars. For more than 90% of the stars, the relative errors of the new distances are within 20%. Based on the new catalogue, we demonstrate how starlight polarization can probe Galactic magnetic fields. [ABSTRACT FROM AUTHOR]

We present the X-ray analysis of dwarf nova EY Cyg using the 45 ks XMM-Newton observatory archival data obtained in quiescence. We find orbital modulations in X-rays. We simultaneously fitted EPIC pn, MOS1 and MOS2 data using a model for interstellar medium absorption (tbabs) and a multi-temperature plasma emission model with a power-law distribution of temperatures (CEVMKL) as expected from low accretion rate quiescent dwarf novae. The XMM-Newton EPIC spectra of the source yields a maximum temperature kT max ∼ 14.9 - 2.2 + 3.3 keV with an unabsorbed X-ray flux and luminosity of (1.8–2.0) × 10 - 12 ergs−1 cm−1 and (8.7–9.7) × 10 31 ergs−1, respectively, in the energy range 0.1–50 keV. There is 3–4 sigma excess at energies below 0.5 keV, we model the excess using MEKAL , POWERLAW and BBODY models and favor the model MEKAL which is physical. According to previous studies, the secondary in this system is thought to be a K-type star which may radiate in the soft X-ray region. The fit with an additive MEKAL model gives a temperature of kT ∼ 0.1 keV with an unabsorbed X-ray flux and luminosity of (2.7–8.8) × 10 - 14 ergs−1 cm−1 and (1.3–4.2) × 10 30 ergs−1, respectively, for the companion star. Based on the results from the timing and spectral analysis, we highly suggest that the secondary of EY Cyg is a K-type star. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical modeling of the collision process of two molecular clouds (MC). The process of formation and growth of dense clumps and filament is investigated. The density distribution along the MC radius is modeling according to various laws, and the density at the center of molecular clouds also changes. The processes of deformation, fragmentation, and the formation of superdense clumps zones are analyzed. Calculations are carried out according to different scenarios of collision of two spherical clouds that are heterogeneous in size, displacement, and internal distribution. The Euler numerical code created by the authors is used to conduct a numerical experiment on high-performance computers. The appearance of zones with a high degree of compression of the substance during the formation of new clouds and the oscillations arising from this strongly depend on the initial momentum of the colliding molecular clouds. The paper presents an analysis of the redistribution of gas density that occurs during local compression in bow-shock core and outer layers of clouds. The mechanism of substance turbulization, fragmentation, and the creation of dense regions was analyzed and interpreted. Compressions arising in the gas core and wave-like rarefaction in the interstellar medium are interpreted as Kelvin-Helmholtz instability aftereffects. • 3D simulation of molecular clouds collision was done using possible scenarios. • Appearance of clumps and filaments in bow-shock shock layer and core is discussed. • Morphing of high compression clumps set in possible stars formation zone is discussed. [ABSTRACT FROM AUTHOR]

The Galaxy contains a small but quite significant population of highly energetic denizens: supernova remnants with fast shocks, pulsars with powerful winds, intensely-interacting binary systems built from a compact object and a massive star. All of these environments conspire to generate non-thermal populations of particles, and radiation produced by these particles is gradually revealing the methods by which Nature accelerates cosmic rays, as well as the ways in which those cosmic rays escape and diffuse into the interstellar medium. In this talk, we discuss advances in our understanding of these environments and processes provided by recent results from VERITAS, an array of ground-based imaging air-Cherenkov telescopes located at the Whipple Observatory in southern Arizona and sensitive to gamma rays in the energy range from 85 GeV to > 30 TeV. These results include studies of cosmic-ray acceleration in the supernova remnants Cassiopeia A and IC 443, as well as the remarkable Fall 2017 periastron passage of VER J2032+4127, the binary system containing PSR J2032+4127 and the Be star MT91 213 with a 50-year period. [ABSTRACT FROM AUTHOR]

A new three-dimensional potential energy surface of the electronic ground state of the chloronium ion, H 2 Cl + , based on the explicitly correlated coupled cluster method with a triple zeta basis set adapted to this method has been expanded in an analytical representation. This potential energy surface is later incorporated into our home-made Fortran code to compute variationally the vibrational levels, zero-point ground average structural parameters and the rotational constants of the chloronium ion and several isotopologues. Our results show a good agreement with experimental data and that our results will help to detect H 2 Cl + isotopologues in the interstellar medium. [Display omitted] • Potential energy surface of the chloronium cation, H 2 Cl + • Anharmonic vibrational levels and transitions of H 2 Cl + and isotopologues. • Zero-point average structure and rotational constants of H 2 Cl + and isotopologues. [ABSTRACT FROM AUTHOR]

• Determination of the energy difference (ΔE Cis-Trans) between the Cis- and Trans-HONO conformers of nitrous acid. • Relative line intensities for the B-type transitions of pure rotational bands of Trans-HONO and Cis-HONO measured. • Far infrared FTS spectra on SOLEIL. • Line list for HONO in the far infrared region. The first goal of this work is to improve the determination of the energy difference (ΔE Cis-Trans) between the ground vibrational state of the Cis- and Trans-HONO conformers of nitrous acid. For this, high resolution spectra were recorded in the 50–200 cm−1 spectral region at three different temperatures, 240, 270 and 296 K. The relative line intensities for the B-type transitions of pure rotational bands of Trans-HONO and Cis-HONO achieved from our measurements were combined in least squares fit computations to those measured previously by Sironneau et al. [ Sironneau V, Flaud JM, Orphal J, Kleiner I, Chelin P. Absolute line intensities of HONO and DONO in the far-infrared and re-determination of the Energy Difference between the trans- and cis-species of nitrous acid. J Mol Spectrosc 2010;259:100–104 ]. In this way, we can significantly improve the accuracy on the HONO conformer energy difference, with a value for ΔE Cis-Trans = 95.8 ± 9.2 cm−1 compared to SIRΔE Cis-Trans = 99 ± 25 cm−1 in the previous study of Sironneau et al. The second goal is to generate a line list with "absolute" line intensities for the pure rotational bands in the far infrared region of Trans-HONO and Cis-HONO, with both A- and B-type transitions. This new line list proved to be more robust for an improved detection of HONO in astrophysical objects [ Coutens A, Ligterink NFW, Loison JC, Wakelam V, Calcutt H, Drozdovskaya MN, Jørgensen JK, Müller HSP, Van Dishoeck EF, Wampfler SF. The ALMA-PILS survey: First detection of nitrous acid (HONO) in the interstellar medium. Astronomy & Astrophysics 2019;623:L13 ]. Comparison of the ALMA observations of the HONO transitions towards the protostar IRAS16293 B (black) with the model obtained with the JPL line list for T ex = 300 K and N = 1.4 1015 cm−2 blue dashed line) and the one obtained with our new line list for similar parameters (red solid line). [Display omitted] [ABSTRACT FROM AUTHOR]

Exploration of the heliosphere and the far reaches of our solar system by the Voyagers and New Horizons and near-Earth observations of the Kuiper Belt and exoplanetary systems have all profoundly changed how we view our own home in space. An Interstellar Probe escaping beyond the solar-system boundaries with new observational techniques would be a bold move in space exploration, enabling detailed, new understanding of the global heliosphere in the context of other astrospheres, further discoveries of unexplored Kuiper Belt Objects, and the first observations of our circumsolar dust disk. These would offer insight into the evolution of the solar system and our understanding of exoplanetary systems. With the power supplies on the Voyagers nearing their end of life, the rapid pace of discovery of exoplanets in other stellar systems, and the evolution in our own understanding brought about by results from the Voyager, Cassini, and Interstellar Boundary Explorer (IBEX) spacecraft, the time is right for looking at the next steps we can make into our stellar neighborhood. The question facing us today is what the appropriate next step - a true first step - is in negotiating the transition from science fiction to engineering reality. The scientific imperatives associated with reaching the near interstellar medium in order to understand our origins and our own current locale in the Milky Way trace to the beginnings of the Space Age, and they have been debated and refined since that time and into the current epoch. The subjects of interstellar travel, interstellar probes, and interstellar "precursor" missions are not new but have lacked traction with policy makers and the scientific community at large because of the states of both scientific knowledge and engineering realities. The next step in reaching to the stars will require the recognition of engineering limits, scientific trades, and scientific compromises, but this is new neither in science nor exploration. Such a step would be an "Interstellar Probe." The time for that step has come. • An "Interstellar Probe" has been discussed in depth for almost 60 years. • NASA requested a study of this mission to prepare for the upcoming Decadal Surveys. • Traditional science goals are re-examined, updated, and expanded. • Approaches to required payload, spacecraft, and analysis methodology are identified. • Three mission approaches using NASA's large new booster and studied and assessed. [ABSTRACT FROM AUTHOR]

• The work provides an ab initio adiabatic potential, permanent dipole moment and static dipole polarizability for the ground state of argonium (ArH +) over a wide range of interatomic distances. • The present results could be useful to estimate the downward cascade radiative transitions as well as the radiative association and dissociative recombination rates for the astronomically important ArH + isotopologues. A high level electronic structure calculation of the Born–Oppenheimer (BO) potential, scalar-relativistic effect and adiabatic correction is performed for the X 1 Σ + ground state of astronomically important isotopologues of the ArH + cation. Particular attention is paid to both short and long distances, where experimental spectroscopic data is not yet available. The BO energy is obtained over a wide range of interatomic distances (R ∈ [0.5, 20] Å) in the framework of multi-reference coupled pair functional (MR-ACPF) and single-reference coupled-cluster (CCSD(T)) methods. The all-electrons basis sets of the def2- n ZVPP (n = 3 , 4) and n ZaPa-NR, aug-cc-pCV n Z (n = 3 − 6) quality are used to monitor energy convergence. The BO energies are corrected for the basis set superposition error (BSSE) via the counterpoise method and are reduced to the complete basis set (CBS) limit using alternative extrapolating schemes. The permanent dipole moment d (R) and static dipole polarizability α (R) are calculated using a finite-field method. The molecular structure parameters coincide with their empirical counterparts for low vibrational levels to within 0.1%. Implementation of the ab initio results to circumscribe our understanding of the chemical networks in interstellar space is discussed. [ABSTRACT FROM AUTHOR]

• The low-lying electronic states of PN+ are calculated with the icMRCI + Q/56 + CV + DK method. • Transition probabilities of dipole allowed transitions of PN+ are presented. • Radiative lifetimes of some excited states are evaluated. • Spin-orbit coupling integrals between low-lying electronic states are computed. • The predissociation of 14Σ − (υ ' = 1)→16Σ+, 14Σ − (υ ' = 15)→16Π and 14Δ (υ ' = 19)→16Π are discussed. The PN+ cation is regarded as a candidate of ions which may exist in the interstellar medium. Accurate transition properties are desired to identify the spectra from astronomical observation. However, transition data of PN+ are relatively limited. In this work, the state-of-the-art ab initio calculations are carried out to investigate the low-lying electronic states of PN+ correlating to two lowest dissociation limits, its transition properties and its spin-orbit couplings. For the X2Σ+ and A2Π states, the calculated spectroscopic constants agree well with previous experimental data. For the other electronic states, the accuracy of the spectroscopic parameters is also ensured by comparing with previous theoretical results. Then, transition probabilities of dipole allowed transition systems are calculated. The radiative lifetimes of vibrational levels for the A2Π, 14Π, 14Δ, 14Σ−, and 24Π states are also evaluated. Such transition data can be used in the identification of PN+ in the laboratory or the interstellar space. Finally, the predissociation of 14Σ− (υ ' = 1)→16Σ+, 14Σ− (υ ' = 15)→16Π and 14Δ (υ '= 19)→16Π are analyzed with the help of spin-orbit coupling integrals. [ABSTRACT FROM AUTHOR]

Astrophysical and cosmogenic neutrinos are produced in the interactions of ultra-high energy cosmic rays. Astrophysical neutrinos originate from the interactions of cosmic ray protons with the matter (pp interactions) or photons (γ p interactions) inside their sources and have energies ranging from TeV to 10 PeV , while cosmogenic neutrinos are produced during cosmic rays propagation in the intergalactic medium through the interaction with cosmic microwave background (CMB) as well as infrared and optical background (IRB) photons and have energies up to 100 EeV. These neutrinos can travel without deflection and reach earth, so the study of this messengers can reveal different characteristics of the cosmic ray sources. In addition to the properties of the sources, the redshift of the sources and the photon background characteristics can also be important in the propagation of cosmic rays. In this paper, first by applying analytical approaches, we calculate the optical depths of UHECR sources (τ) which generate astrophysical neutrinos, and by using the observed fluxes of CR and astrophysical neutrino, we calculate τ 0 min for different CR source spectral indexes. Then, using CRPropa3 code, we simulate the propagation of UHECRs in the extragalactic medium. Taking a reference case, the propagated CR and neutrino flux are obtained for sources with pure proton mass composition, minimum energy of 0.1 EeV to the maximum rigidity of 200 EV, minimum redshift of z min = 0.0007 , maximum redshift of z max = 6 and the Gilmore 2012 IRB background model. Switching the composition to a mixed galactic composition and pure Fe, it is shown that CR and neutrino fluxes are affected by changing the cosmic ray composition. Furthermore, effects of different IRB models and maximum redshift of the sources are investigated. Finally, three source redshift distributions of 3 ⩽ z ≤ 4 , 4 ⩽ z ≤ 5 and 5 ⩽ z ≤ 6 are considered and the changes in spectra are demonstrated. The study of these changes can help us to understand the nature of UHECR sources. [ABSTRACT FROM AUTHOR]

Abstract Time is arguably the key limiting factor for interstellar exploration. At high speeds, flyby missions to nearby stars by laser propelled wafersats taking 50–100 years would be feasible. Directed energy launch systems could accelerate on the other side also crafts weighing several tons to cruising speeds of the order of 1000 km/s (c/300). At these speeds, superconducting magnetic sails would be able to decelerate the craft by transferring kinetic energy to the protons of the interstellar medium. A tantalizing perspective, which would allow interstellar probes to stop whenever time is not a limiting factor. Prime candidates are in this respect Genesis probes, that is missions aiming to offer terrestrial life new evolutionary pathways on potentially habitable but hitherto barren exoplanets. Genesis missions raise important ethical issues, in particular with regard to planetary protection. Here we argue that exoplanetary and planetary protection differ qualitatively as a result of the vastly different cruising times for payload delivering probes, which are of the order of millennia for interstellar probes, but only of years for solar system bodies. Furthermore we point out that our galaxy may harbor a large number of habitable exoplanets, M-dwarf planets, which could be sterile due to the presence of massive primordial oxygen atmospheres. We believe that the prospect terrestrial life has in our galaxy would shift on a fundamental level in case that the existence of this type of habitable but sterile oxygen planets will be corroborated by future research. It may also explain why our sun is not a M dwarf, the most common star type, but a medium-sized G-class star. Highlights • Directed energy launch systems allow for two types of interstellar missions. • Flyby microprobes targeting alpha-Centauri would gather science data. • Payload delivering probes would be slower, braking magnetically on arrival. • Slow probes could bring uni-cellular life to habitable but sterile M-dwarf planets. • Planetary protection of exoplanets cannot be grounded on utility considerations. [ABSTRACT FROM AUTHOR]

Abstract A Smart Dust is a femto-spacecraft with an external surface coated with electrochromic material, which exploits the solar radiation pressure to produce a propulsive acceleration. As the optical properties of the electrochromic material change upon application of a suitable electric voltage, its propulsive acceleration may be modulated, within some limits, without the use of any propellant. This paper analyzes the optimal trajectories of a Sun-pointing Smart Dust, which provides a propulsive acceleration aligned with the Sun-spacecraft direction. In particular, the paper describes the relative motion of a Smart Dust with respect to a conventional spacecraft (the Mother Ship) that covers a heliocentric circular orbit of given radius. The Smart Dust is required to vary periodically its angular position with respect to the Mother Ship using an optimal (minimum time) strategy. This problem is addressed using an indirect approach and the optimal control law is obtained in a closed-form solution. The results discussed in this paper ensure interesting improvements over existing models from the recent literature, including the possibility of obtaining a generic phasing angle of the Smart Dust and to take into account an optimal number of on-off switchings of the electrochromic control system. Highlights • The paper analyzes the phasing maneuver of a Smart Dust in a circular heliocentric orbit. • The phasing maneuver is studied by evaluating the optimal (minimum) flight time. • The optimization problem is solved using an indirect approach. • The optimal control law is obtained in an analytical form using a lin-earized dynamics. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to assess the feasibility of an interstellar mission to reach the Alpha Centauri star system and delivering scientific data, using current and near-future technology. The mission baseline uses 100 GW of laser power to accelerate a spacecraft of 2750 kg to 5% the speed of light with light sail technology, resulting in a travel time of about a century. This paper explores several aspects of the mission: Possible locations of the laser infrastructure and different sail materials to achieve the required acceleration are discussed. Deceleration using a magnetic sail in the interstellar medium and in the heliosphere of the target star, taking into account mathematical models from Zubrin [6], Freeman [22] and Gros [21], is studied. Potential orbits in the star system are considered for observation and data collection. Finally, a multi-spacecraft mission architecture is presented, as it would allow for the spacecraft to be launched sequentially, thus exploiting the possibility of continuously operating the laser infrastructure. Highlights • Mission architecture to send multiple spacecrafts to Alpha Centauri star system. • Laser sail acceleration and magnetic sail deceleration. • Performance comparison of different light sail materials, on a spacecraft level. • Dependencies between light sail, laser and mission parameters. • Performance analysis of magnetic sails considering different mathematical models. [ABSTRACT FROM AUTHOR]

Highlights • Star formation in molecular clouds has been considered. • Thermal instability along with opacity and molecular cooling. • Negative polytropes result in field stars. • Positive polytropes result in star bursts. Abstract In search of the scenario of the star formation process, fragmentation of molecular clouds has been modelled under two different conditions. In the first case, thermal instability along with an equation of state with negative polytropic indices (n) has been considered which give rise to minimal fragment masses in the range 0.001 M ⊙ to 8.5 M ⊙ for −10 < n < 0, n ≠ − 1. In the second case, an opacity limited fragmentation along with positive polytropic indices is considered which lead to a wide range of minimal fragment masses resulting in field stars, massive stars, and star bursts. This might be due to the effect of opacity which is responsible for slow dissipation of heat in a compressed medium. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we investigate temporal and spatial magnetosphere response to the impact of interplanetary (IP) shocks with different inclinations and speeds on the Earth's magnetosphere. A data set with more than 500 IP shocks is used to identify positive sudden impulse (SI+) events as expressed by the SuperMAG partial ring current index. The SI+ rise time (RT), defined as the time interval between compression onset and maximum SI+ signature, is obtained for each event. We use RT and a model suggested by Takeuchi et al. (2002) to calculate the geoeffective magnetospheric distance (GMD) in the shock propagation direction as a function of shock impact angle and speed for each event. GMD is a generalization of the geoeffective magnetosphere length (GML) suggested by Takeuchi et al. (2002), defined from the subsolar point along the X line toward the tail. We estimate statistical GMD and GML values which are then reported for the first time. We also show that, similarly to well-known results for RT, the highest correlation coefficient for the GMD and impact angle is found for shocks with high speeds and small impact angles, and the faster and more frontal the shock, the smaller the GMD. This result indicates that the magnetospheric response depends heavily on shock impact angle. With these results, we argue that the prediction and forecasting of space weather events, such as those caused by coronal mass ejections, will not be accurately accomplished if the disturbances' angles of impact are not considered as an important parameter within model and observation scheme capabilities. [ABSTRACT FROM AUTHOR]

• Activation energies for the addition of methyl radical (CH 3) to a graphene surface were systematically determined by density functional theory method. • Binding energies between CH 3 and the graphene surface were determined. • Absorption and IR spectrum of methylated graphene were theoretically predicted. • Hyperfine coupling constant of methylated graphene was theoretically predicted. Abstract The interaction and reaction of methyl radical (CH 3) with polycyclic aromatic hydrocarbons (PAHs) have been investigated by means of density functional theory (DFT) to systematically elucidate the binding nature of CH 3 to graphene nanoflakes. PAHs with n = 4–37, where n indicates the number of benzene rings, were chosen as graphene nanoflakes. The activation energies for the addition of CH 3 to the graphene surface were found to be almost constant, with values in the range 13.0–15.0 kcal/mol at the CAM-B3LYP/6-311G(d,p) level, for all PAHs. The binding energies between CH 3 and the graphene surfaces were slightly dependent on the size (n): 1.0–4.2 kcal/mol. The absorption spectra showed that a long tail is generated in the low-energy region after CH 3 addition to the graphene surfaces. The electronic states of the CH 3 -added graphenes were discussed on the basis of theoretical results Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Electromagnetic field fluctuations are arguably among the most fundamental kinetic processes in classical, collisionless plasmas. Considering their two characteristic features, propagation and amplitude modulation, they include such eminent phenomena as waves and instabilities. This work is devoted to an extension of their theoretical understanding with particular emphasis on weakly propagating and aperiodic fluctuations and their spontaneous emission. In this regard, three main results are achieved that contribute to both generic plasma theory as well as astrophysical applications. Firstly, the fluctuation–dissipation theorem for weakly coupled thermal plasmas is generalized to arbitrary values of the complex frequency in order to rid the previous formulations of their restrictions in this respect. Secondly, the spontaneously emitted magnetic field fluctuations in the intergalactic medium are addressed. Due to a recently discovered damped and aperiodic mode, the level of magnetic noise is high enough to have the latter serving as a seed field for further amplification processes like magnetohydrodynamic dynamo action, so this spontaneous emission is of major relevance for cosmic magnetogenesis. Here, it is shown that a highly relativistic electron–positron pair beam can trigger a transition of these damped fluctuations into amplified ones in certain wavenumber ranges, thus allowing for an even higher seed level. It is found that only those fluctuations are accessible to amplification whose wavevectors are perpendicular or at least almost perpendicular to the propagation direction of the beam. Thirdly, the possibilities are investigated to obtain observational evidence for this newly discovered stable branch of the Weibel mode because an empirical confirmation of its existence is still pending today. It is shown that the mode-driven turbulence is incompressible and that, therefore, dispersion measure, rotation measure, and scintillation related techniques are not applicable. The velocity fluctuations generated by the mode, however, are shown to be large enough to qualify line broadening studies as a suitable diagnostic method to detect the mode after all. [ABSTRACT FROM AUTHOR]