Search

The pure rotational and rovibrational spectra of the ν27 –NH2 torsion of cyclopropylamine (CPA) in the far-infrared region were measured with a high-resolution Fourier transform infrared coupled to a synchrotron. The complex spectra reflect the presence of both trans and gauche conformers. Analysis of the pure rotational spectra (34–64 cm−1) yielded accurate rotational and centrifugal distortion constants of the ground and first two torsional excited states of trans-CPA. The fundamental, hot bands and weak overtones were identified and assigned in the 200–550 cm−1 range. Global analysis of over 19 000 transitions provides accurate energy levels of the torsional polyads up to vT = 3. The torsional levels and their rotational constants were in agreement with the theoretical results from quasiadiabatic channel reaction path Hamiltonian (RPH) calculations, emphasizing the need for molecular-specific theoretical treatments for large amplitude motions. Tunneling components of the torsional fundamental of gauche-CPA were assigned based on the RPH results and symmetry considerations, differing from previous experimental and theoretical work. This comprehensive spectroscopic characterization of CPA is crucial for its potential detection in the interstellar medium as a precursor to complex prebiotic molecules, providing essential data for future astronomical searches and advancing our understanding of nitrogen-containing organic molecules in space. [ABSTRACT FROM AUTHOR]

The rotational dynamics of isocyanogen (CNCN) is studied for its collision with para (p-) and ortho (o-) hydrogen (H2) in the temperature range of 1–100 K. These temperatures correspond to the cold dense molecular clouds in the interstellar medium where molecular hydrogen is the primary collider. An ab initio 4D potential energy surface (PES) is constructed keeping the two molecules under rigid rotor approximation. The PES is generated using the CCSD(T)-F12b/AVTZ level of theory. The 4D PES is further fitted into a neural network (NN) model, which can augment the surface and account for missing data points within spectroscopic accuracy. This NN-fitted PES is then expanded over a bispherical harmonics function to get radial terms, which are expressed into analytic functions. Thereafter, the cross sections (σ) are computed for rotational transitions of CNCN (j → j′) using the close-coupling and centrifugal sudden methods for both p-H2 (jc = 0) and o-H2 (jc = 1) collision till 194 cm−1. In addition, p-H2 (jc = 0, 2) cross sections are also computed using the centrifugal sudden approximation method. The collisional rates are achieved by taking the Boltzmann distribution of σ over the translational energy of H2 till 100 K. Finally, the CNCN–H2 rates are compared to CNCN–He and NCCN–H2 collisional rates. Comparing even and odd transitions for the CNCN–H2 rates show a propensity toward higher rates for even transitions especially for o-H2 collisions considering low-order transitions. [ABSTRACT FROM AUTHOR]

Chloromethane, CH3Cl, is the first organohalogen molecule to be detected in the interstellar medium. Using the recently generated accurate three-dimensional potential energy surface (3D-PES) for the weakly bound CH335Cl–He complex, we deduced that of CH337Cl–He. Both 3D-PESs were incorporated later into dynamical computations code for nuclear motions treatments of each isotopologue colliding with He. We determined the state-to-state (de-)excitation cross sections for transitions among the 105 lowest rotational levels of both ortho-CH335Cl and ortho-CH337Cl (up to jkɛ = 206±). For total energies up to 100 cm−1, we used the quantum close-coupling methodology, and we adopted the coupled state approach for higher energies (up to 2500 cm−1). Rate coefficients for temperatures ranging from 5 to 150 K are then deduced after averaging these cross sections over a Maxwell–Boltzmann velocity distribution. Computations show that isotopic effects are weak, validating the use of collision rates of ortho-CH335Cl for ortho-CH337Cl and vice-versa. However, we expect that our results will be helpful to accurately determine the abundances of these isotopologues in the interstellar medium and, more generally, for understanding the complex and still not fully elucidated chemistry of chlorine containing molecular species there. [ABSTRACT FROM AUTHOR]

Structure determination is necessary to identify unknown organic molecules, such as those in natural products, forensic samples, the interstellar medium, and laboratory syntheses. Rotational spectroscopy enables structure determination by providing accurate 3D information about small organic molecules via their moments of inertia. Using these moments, Kraitchman analysis determines isotopic substitution coordinates, which are the unsigned |x|, |y|, |z| coordinates of all atoms with natural isotopic abundance, including carbon, nitrogen, and oxygen. While unsigned substitution coordinates can verify guesses of structures, the missing +/− signs make it challenging to determine the actual structure from the substitution coordinates alone. To tackle this inverse problem, we develop Kreed (Kraitchman REflection-Equivariant Diffusion), a generative diffusion model that infers a molecule's complete 3D structure from only its molecular formula, moments of inertia, and unsigned substitution coordinates of heavy atoms. Kreed's top-1 predictions identify the correct 3D structure with near-perfect accuracy on large simulated datasets when provided with substitution coordinates of all heavy atoms with natural isotopic abundance. Accuracy decreases as fewer substitution coordinates are provided, but is retained for smaller molecules. On a test set of experimentally measured substitution coordinates gathered from the literature, Kreed predicts the correct all-atom 3D structure in 25 of 33 cases, demonstrating experimental potential for de novo 3D structure determination with rotational spectroscopy. [ABSTRACT FROM AUTHOR]

There is an ongoing debate on the apparent depletion of sulfur in the interstellar medium (ISM) compared to its universal abundance; therefore, the investigation of sulfurous compounds at low temperatures is of utmost importance. This work aims to study thioacetamide, H3C–C(=S)–NH2, in low-temperature inert Ar and para-H2 matrices by IR spectroscopy. The samples have been exposed to various sources of irradiation, such as Lyman-α or laser UV photons as well as energetic electrons. Using different host materials enabled assessing the matrix's impact on precursor decomposition. The response of the molecule to different types of irradiation has also been evaluated. The existence of three main decomposition channels were deduced: formation of (i) CH3, CH4, and HNCS; (ii) H2S and H2C=C=NH; and (iii) NH3 and H2C=C=S. The H3C–CN and H3C–NC isomers of H2C=C=NH could also be identified. Secondary products such as HNC and HCN were also detected in the quantum solid para-H2 in contrast to the more rigid Ar matrix. The listed decomposition products have been observed in the ISM, with the exception of H2C=C=NH and H3C–NC. The results point to the potential sensitivity of the precursor molecule to energetic radiation in space environments. Finally, the findings of this work will serve as a foundation for future irradiation experiments using the astrochemically more relevant pure thioacetamide ice. [ABSTRACT FROM AUTHOR]

We present new multifrequency Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of the massive [ |$\log _{10}(M_\star /\mathrm{M}_\odot) = 10.3_{-0.2}^{+0.1}$| ], UV-luminous [ |$M_\mathrm{UV} = -21.7 \pm 0.2$| ] |$z=7.31$| galaxy REBELS-25 in Bands 3, 4, 5, and 9. Combining the new observations with previously taken data in Bands 6 and 8, we cover the dust continuum emission of the galaxy in six distinct bands – spanning rest-frame |$50-350\, \mu$| m – enabling simultaneous constraints on its dust mass (⁠|$M_\mathrm{dust}$|⁠), temperature (⁠|$T_\mathrm{dust}$|⁠), and emissivity index (⁠|$\beta _\mathrm{IR}$|⁠) via modified blackbody fitting. Given a fiducial model of optically thin emission, we infer a cold dust temperature of |$T_\mathrm{dust} = 32_{-6}^{+9}\,$|  K and a high dust mass of |$\log _{10}(M_\mathrm{dust}/\mathrm{M}_\odot) = 8.2_{-0.4}^{+0.6}$|⁠ , and moderately optically thick dust does not significantly alter these estimates. If we assume dust production is solely through supernovae (SNe), the inferred dust yield would be high, |$y = 0.7_{-0.4}^{+2.3}\, \mathrm{M}_\odot$| per SN. Consequently, we argue grain growth in the interstellar medium of REBELS-25 also contributes to its dust build-up. This is supported by the steep dust emissivity index |$\beta _\mathrm{IR} = 2.5 \pm 0.4$| we measure for REBELS-25, as well as by its high stellar mass, dense interstellar medium, and metal-rich nature. Our results suggest that constraining the dust emissivity indices of high-redshift galaxies is important not only to mitigate systematic uncertainties in their dust masses and obscured star formation rates, but also to assess if dust properties evolve across cosmic time. We present an efficient observing set-up to do so with ALMA, combining observations of the peak and Rayleigh–Jeans tail of the dust emission. [ABSTRACT FROM AUTHOR]

Reconstructing the intrinsic Ly  |$\alpha$| line flux from high- z QSOs can place constraints on the neutral hydrogen content of the intergalactic medium during reionization. There are now |$\gtrsim 10$| different Ly  |$\alpha$| reconstruction pipelines using different methodologies to predict the Ly  |$\alpha$| line flux from correlations with the spectral information redwards of Ly  |$\alpha$|⁠. However, there have been few attempts to directly compare the performance of these pipelines. Therefore, we devised a blind QSO challenge to compare these reconstruction pipelines on a uniform set of objects. Each author was provided de-identified, observed rest-frame QSO spectra with spectral information only redwards of 1260 Å rest-frame to ensure unbiased reconstruction. We constructed two samples of 30 QSOs, from X-Shooter and Sloan Digital Sky Survey (SDSS) both spanning |$3.5\lt z\lt 4.5$|⁠. Importantly, the purpose of this comparison study was not to champion a single, best-performing reconstruction pipeline but rather to explore the relative performance of these pipelines over a range of QSOs with broad observational characteristics to infer general trends. In summary, we find machine-learning approaches in general provide the strongest 'best guesses' but underestimate the accompanying statistical uncertainty, although these can be recalibrated, while pipelines that decompose the spectral information, for example principal component or factor analysis, generally perform better at predicting the Ly  |$\alpha$| profile. Further, we found that reconstruction pipelines trained on SDSS QSOs performed similarly on average for both the X-Shooter and SDSS samples indicating no discernible biases owing to differences in the observational characteristics of the training set or QSO being reconstructed, although the recovered distributions of reconstructions for X-Shooter were broader likely due to an increased fraction of outliers. [ABSTRACT FROM AUTHOR]

We present a new suite of late-end reionization simulations performed with aton-he , a revised version of the GPU-based radiative transfer code aton that includes helium. The simulations are able to reproduce the Ly  |$\alpha$| flux distribution of the E-XQR-30 sample of QSO absorption spectra at |$5 \lesssim z \lesssim 6.2$|⁠ , and show that a large variety of reionization models are consistent with these data. We explore a range of variations in source models and in the early-stage evolution of reionization. Our fiducial reionization history has a mid-point of reionization at |$z = 6.5$|⁠ , but we also explore an 'Early' reionization history with a mid-point at |$z = 7.5$| and an 'Extremely Early' reionization history with a mid-point at |$z = 9.5$|⁠. Haloes massive enough to host observed Ly  |$\alpha$| emitters are highly biased. The fraction of such haloes embedded in ionized bubbles that are large enough to allow high Ly  |$\alpha$| transmission becomes close to unity much before the volume filling factor of ionized regions. For our fiducial reionization history this happens at |$z = 8$|⁠ , probably too late to be consistent with the detection by JWST of abundant Ly  |$\alpha$| emission out to |$z = 11$|⁠. A reionization history in our 'Early' model or perhaps even our 'Extremely Early' model may be required, suggesting a Thomson scattering optical depth in tension with that reported by Planck, but consistent with recent suggestions of a significantly higher value. [ABSTRACT FROM AUTHOR]

The James Webb Space Telescope (JWST) opened a new era for the identification of molecular systems in the interstellar medium (ISM) by vibrational features. One group of molecules of increasing interest is cyano-derivatives of aromatic organic molecules, which have already been identified in the ISM on the basis of the analysis of rotational signatures, and so, are plausible candidates for the detection by the JWST. Benzonitrile considered in this work represents a suitable example for the validation of a computational strategy, which can be further applied for different, larger, and not-yet observed molecules. For this purpose, anharmonic simulations of infrared (IR) spectra have been compared with recent FTIR experimental studies. The anharmonic computations using the generalized second-order vibrational perturbation theory (GVPT2) in conjunction with a hybrid force field combining the harmonic part of revDSD-PBEP86-D3/juncc-pVTZ with anharmonic corrections from B3LYP-D3/SNSD show very good agreement with those in the experiment, with a mean error of 11cm-1 for all fundamental transitions overall and only 2cm-1 for the C#GJ N stretching fundamental at 4.49 μm. The inclusion of overtones up to three-quanta transitions also allowed the prediction of spectra in the near-infrared region, which shows distinct features due to C #GJ N overtones at the 2.26 μm and 1.52 μm. The remarkable accuracy of the GVPT2 results opens a pathway for the reliable prediction of spectra for a broader range of cyano-astroCOMs. [ABSTRACT FROM AUTHOR]

During the epoch of reionization (EoR), the 21-cm signal allows direct observation of the neutral hydrogen (H  i) in the intergalactic medium (IGM). In the post-reionization era, this signal instead probes H  i in galaxies, which traces the dark matter density distribution. With new numerical simulations, we investigated the end stages of reionization to elucidate the transition of our Universe into the post-reionization era. Our models are consistent with the latest high-redshift measurements, including ultraviolet (UV) luminosity functions up to redshift |$\simeq$| 8. Notably, these models consistently reproduced the evolution of the UV photon background, which is constrained from Lyman- |$\alpha$| absorption spectra. We studied the dependence of this background on the nature of photon sinks in the IGM, requiring mean free path of UV photons to be |$\sim$| 10 comoving-megaparsecs (cMpc) during the EoR that increases gradually with time during late stages (⁠|$z\lesssim 6$|⁠). Our models revealed that the reionization of the IGM transitioned from an inside-out to an outside-in process when the Universe is less than 0.01 per cent neutral. During this epoch, the 21-cm signal also shifted from probing predominantly the H  i in the IGM to that in galaxies. Furthermore, we identified a statistically significant number of large neutral islands (with sizes up to 40 cMpc) persisting until very late stages (⁠|$5 \lesssim z \lesssim 6$|⁠) that can imprint features in Lyman- |$\alpha$| absorption spectra and also produce a knee-like feature in the 21-cm power spectrum. [ABSTRACT FROM AUTHOR]

Enlightening our understanding of the first galaxies responsible for driving reionization requires detecting the 21-cm signal from neutral hydrogen. Interpreting the wealth of information embedded in this signal requires Bayesian inference. Parameter inference from the 21-cm signal is primarily restricted to the spherically averaged power spectrum (1D PS) owing to its relatively straightforward derivation of an analytic likelihood function enabling traditional Monte Carlo Markov Chain approaches. However, in recent years, simulation-based inference (SBI) has become feasible which removes the necessity of having an analytic likelihood, enabling more complex summary statistics of the 21-cm signal to be used for Bayesian inference. In this work, we use SBI, specifically marginal neural ratio estimation to learn the likelihood-to-evidence ratio with swyft , to explore parameter inference using the cylindrically averaged 2D PS. Since the 21-cm signal is anisotropic, the 2D PS should yield more constraining information compared to the 1D PS which isotropically averages the signal. For this, we consider a mock 1000 h observation of the 21-cm signal using the Square Kilometre Array and compare the performance of the 2D PS relative to the 1D PS. Additionally, we explore two separate foreground mitigation strategies, perfect foreground removal and wedge avoidance. We find the 2D PS outperforms the 1D PS by improving the marginalized uncertainties on individual astrophysical parameters by up to |$\sim 30\!-\!40$|  per cent irrespective of the foreground mitigation strategy. Primarily, these improvements stem from how the 2D PS distinguishes between the transverse, |$k_{\perp }$|⁠ , and redshift-dependent, |$k_{\parallel }$|⁠ , information which enables greater sensitivity to the complex reionization morphology. [ABSTRACT FROM AUTHOR]

Detecting the 21-cm signal at |$z\gtrsim 6$| will reveal insights into the properties of the first galaxies responsible for driving reionization. To extract this information, we perform parameter inference with three-dimensional simulations of the 21-cm signal embedded within a Bayesian inference pipeline. Presently, when performing inference, we must choose which sources of uncertainty to sample and which to hold fixed. Since the astrophysics of galaxies is much more uncertain than that of the underlying halo-mass function (HMF), we typically parametrize and model the former while fixing the latter. However, doing so may bias our inference of the galaxy properties. In this work, we explore the consequences of assuming an incorrect HMF and quantify the relative biases on our inferred astrophysical model parameters when considering the wrong HMF. We then relax this assumption by constructing a generalized five parameter HMF model and simultaneously recover it with our underlying astrophysical model. For this, we use 21cmfast and perform simulation-based inference using marginal neural ratio estimation to learn the likelihood-to-evidence ratio with Swyft. Using a mock 1000-h observation of the 21-cm power spectrum from the forthcoming Square Kilometre Array, conservatively assuming foreground wedge avoidance, we find that assuming the incorrect HMF can bias the recovered astrophysical parameters by up to |$\sim 3{\!-\!}4\sigma$| even when including independent information from observed luminosity functions. Using our generalized HMF model, although we recover our astrophysical parameters with a factor of |$\sim 2{\!-\!}4$| larger marginalized uncertainties, the constraints are unbiased, agnostic to the underlying HMF and therefore more conservative. [ABSTRACT FROM AUTHOR]

Forsterite is a primary constituent of interstellar dust and planetary systems. It is believed to originate from the outflows of oxygen-rich stars and undergo further processing within the interstellar medium through the action of cosmic rays and shocks. Under these harsh conditions, point defects may form, such as MgO Schottky vacancies. These vacancies can then undergo atom reconstruction as part of a chemical process to maintain the system's crystalline structure. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously observed interstellar molecules and are thought to form through gas-phase reactions akin to sooting flames. However, their role and impact on dust stability remain unknown. In this study, we employ an atomistic artificial-intelligence-based method, surrogate machine learning trained directly by density functional theory. Specifically, we utilize gofee (global optimization with first-principles energy expressions) to predict possible reconstructions of MgO vacancies on a crystalline forsterite (010) surface as an important component of interstellar dust and planetary systems. We identify nine possible reconstructions involving the formation of unbound Si and O atoms. We investigate their energy stability and find that the reconstruction of Si–O atoms stabilizes the vacancy by about 0.54 eV. Additionally, if PAHs bind with the unbound O and Si atoms of the vacancy, the vacancy is stabilized by approximately 1.76 eV. We demonstrate that PAHs, along with the reconstruction of unbound atoms on the dust surface, affect the stability of the dust, which might open up avenues for diverse chemistry. [ABSTRACT FROM AUTHOR]

Multiple observations now suggest that the hydrogen reionization may have ended well below redshift six. While there has previously been no conclusive proof of extended neutral islands in the |$z \lt 6$| intergalactic medium, it is possible that such islands give rise to the giant Ly  |$\alpha$| absorption troughs seen in the spectra of high-redshift quasars. Here, we present evidence that the deepest and longest known Ly  |$\alpha$| trough at |$z \,\lt\, 6$|⁠ , towards ULAS J0148 + 0600 (J0148), is associated with damping wing absorption. The evidence comes from a window of strong Ly  |$\alpha$| transmission at the edge of the J0148 proximity zone. We show that the relatively smooth profile of this transmission window is highly unlikely to arise from resonant absorption alone, but is consistent with the presence of a damping wing. We further argue that the damping wing is unlikely to arise from a compact source due to the lack of associated metal lines, and is more likely to arise from an extended neutral island associated with the giant Ly  |$\alpha$| trough. We investigate the physical conditions that may give rise to the strong transmission window, and speculate that it may signal an usually deep void, nearby ionizing sources, and/or the recent passage of an ionization front. [ABSTRACT FROM AUTHOR]

We study the radio continuum emission of four galaxies experiencing ram-pressure stripping in four clusters of the Shapley Supercluster at redshift |$z\sim 0.05$|⁠. Multiband (235–1367 MHz) radio data, complemented by integral-field spectroscopy, allow us to detect and analyse in detail the non-thermal component both in the galaxy discs and the radio continuum tails. Three galaxies present radio continuum tails that are tens of kiloparsecs long. By deriving the radio spectral index in the inner and outer tails and comparing our findings with the distribution of the extraplanar ionized gas and the results of N -body/hydrodynamical simulations, we demonstrate that these tails are caused by the ram pressure, which, together with the ionized gas, sweeps the magnetic field from the galaxy discs. We suggest that the radio continuum emission in these tails can be differently powered by (i) in situ star formation, (ii) relativistic electrons stripped from the disc, and (iii) shock excitation or a combination of them. All the ram-pressure-stripped galaxies are found in environments where cluster–cluster interactions occurred and/or are ongoing, thus strongly supporting the thesis that cluster and group collisions and mergers may locally increase the ram pressure and trigger hydrodynamical interactions between the intracluster medium and the interstellar medium of galaxies. [ABSTRACT FROM AUTHOR]

We studied the physical conditions in the local interstellar medium (ISM) and at high redshift by fitting observed column densities of CO and H2 rotational levels and C  i fine-structure levels using photodissociation models calculated with the Meudon PDR code. We analysed CO absorption systems in 28 sight lines in the local ISM and seven damped Lyman-α absorption systems at high redshift, covering |$N({\rm H_2})=10^{19}\!-\!10^{21.5}\,{\rm cm}^{-2}$| and |$N({\rm CO})=10^{13}\!-\!10^{18}\,{\rm cm}^{-2}$|⁠. We constructed a method to accurately calculate CO excitation, incorporating the effects of photon trapping. Our findings indicate that in the local ISM, CO excitation is primarily driven by collisions and excitation due to the CMB radiation. We demonstrated that an increase in CO excitation observed near |$N({\rm CO})\simeq 10^{15}~{\rm cm^{-2}}$|⁠ , is attributed to an increase in gas densities from |${\simeq}100\,{\rm cm}^{-3}$| to |${\simeq}300\!-\!1000\,{\rm cm}^{-3}$|⁠. CO absorption systems in the local ISM are characterized by a gas number density of about 10–1000 cm−3, a kinetic temperature of 10–100 K, and an intensity of external UV field ranging from 0.1 to 10 units of Mathis field. Compared to the average gas probed by C  i absorption, the gas detected in CO is denser and colder, while the external UV field remains nearly constant. We observed a negative correlation between the kinetic temperature and both N (CO) and N (H2), with power-law slopes of |$-0.21\pm 0.02$| and |$-0.65\pm 0.05$|⁠ , respectively. At the same time, the gas number density exhibits a positive correlation with N (CO) and N (H2) with slopes of |$0.38\pm 0.02$| and |$1.15\pm 0.05$|⁠ , respectively. [ABSTRACT FROM AUTHOR]

Small-scale winds driven from accretion discs surrounding active galactic nuclei (AGN) are expected to launch kpc-scale outflows into their host galaxies. However, the ways in which the structure of the interstellar medium (ISM) affects the multiphase content and impact of the outflow remain uncertain. We present a series of numerical experiments featuring a realistic small-scale AGN wind with velocity |$5\times 10^3 \!-\! 10^4\rm {\ km\ s^{-1}}$| interacting with an isolated galaxy disc with a manually controlled clumpy ISM, followed at sub-pc resolution. Our simulations are performed with arepo and probe a wide range of AGN luminosities (⁠|$L_{\rm {AGN}}{=} 10^{43-47}\rm {\ erg\ s^{-1}}$|⁠) and ISM substructures. In homogeneous discs, the AGN wind sweeps up an outflowing, cooling shell, where the emerging cold phase dominates the mass and kinetic energy budgets, reaching a momentum flux |$\dot{p} \approx 7\ L/c$|⁠. However, when the ISM is clumpy, outflow properties are profoundly different. They contain small, long-lived (⁠|$\gtrsim 5\ \rm {Myr}$|⁠), cold (⁠|$T{\lesssim }10^{4.5}{\rm {\ K}}$|⁠) cloudlets entrained in the faster, hot outflow phase, which are only present in the outflow if radiative cooling is included in the simulation. While the cold phase dominates the mass of the outflow, most of the kinetic luminosity is now carried by a tenuous, hot phase with |$T \gtrsim 10^7 \, \rm K$|⁠. While the hot phases reach momentum fluxes |$\dot{p} \approx (1 - 5)\ L/c$|⁠ , energy-driven bubbles couple to the cold phase inefficiently, producing modest momentum fluxes |$\dot{p} \lesssim L/c$| in the fast-outflowing cold gas. These low momentum fluxes could lead to the outflows being misclassified as momentum-driven using common observational diagnostics. We also show predictions for scaling relations between outflow properties and AGN luminosity and discuss the challenges in constraining outflow driving mechanisms and kinetic coupling efficiencies using observed quantities. [ABSTRACT FROM AUTHOR]

We present the systematic exploration of various potential energy surfaces for systems with C6H6-x (x = 0, 1, 2, or 3) empirical formula using an automatic search approach. The primary objective of this study is to identify reaction pathways that lead to the creation of benzene, o-benzyne, and other rings. These pathways initiate with a barrierless recombination reaction and involve subsequent isomerization reactions with submerged transition states until the final product is reached. The reported reaction profiles are consistent with the existing conditions in the interstellar medium if the hot complex formed can cool down through radiative relaxation. Recent studies on the deactivation of polyaromatic hydrocarbons (PAHs) support the possibility of these reactions taking place. The C6-membered rings are considered precursors of PAHs, and our focus is on identifying pathways originating from the barrierless recombination of reactive molecules known to exist in the interstellar medium, with potential implications in other environments. [ABSTRACT FROM AUTHOR]

Gas-phase abundance ratios between C2H4O2 isomers methyl formate (MF), glycolaldehyde (GA), and acetic acid (AA) are typically on the order of 100:10:1 in star-forming regions. However, an unexplained divergence from this neat relationship was recently observed toward a collection of sources in the massive protocluster NGC 6334I; some sources exhibited extreme MF:GA ratios, producing a bimodal behavior between different sources, while the MF:AA ratio remained stable. Here, we use a three-phase gas-grain hot-core chemical model to study the effects of a large parameter space on the simulated C2H4O2 abundances. A combination of high gas densities and long timescales during ice-mantle desorption (∼125–160 K) appears to be the physical cause of the high MF:GA ratios. The main chemical mechanism for GA destruction occurring under these conditions is the rapid adsorption and reaction of atomic H with GA on the ice surfaces before it has time to desorb. The different binding energies of MF and GA on water ice are crucial to the selectivity of the surface destruction mechanism; individual MF molecules rapidly escape the surface when exposed by water loss, while GA lingers and is destroyed by H. Moderately elevated cosmic-ray ionization rates can increase absolute levels of "complex organic molecule" (COM) production in the ices and increase the MF:GA ratio, but extreme values are destructive for gas-phase COMs. We speculate that the high densities required for extreme MF:GA ratios could be evidence of COM emission dominated by COMs desorbing within a circumstellar disk. [ABSTRACT FROM AUTHOR]

We report the detection of Lyman-continuum (LyC) photons from a massive interacting system at z = 1.097 in the Hubble Ultra Deep Field. The LyC detection is made in the far-ultraviolet F154W band of the UVIT telescope on board AstroSat. Both JWST and Hubble Space Telescope (HST) imaging of the system reveal signs that it is a likely merger. In particular, high-resolution imaging in the JWST bands reveals an infrared-luminous object within the system that is faint in the bluer HST bands. The ionized gas kinematics from the MUSE-UDF data supports the merger hypothesis. We estimate that the entire system is leaking more than 8% of its ionizing photons to the intergalactic medium. The spectral-energy-distribution-derived stellar masses of the two components indicate that this is a major merger with a mass ratio of 1.13 ± 0.37. This detection hints at the potential contribution of massive interacting systems at higher redshifts, when major mergers were more frequent, to the ionizing budget of the Universe. [ABSTRACT FROM AUTHOR]

The chemistry of phosphorus (31P) in space is particularly significant due to the key role it plays in biochemistry on Earth. Utilising radio and infrared spectroscopic observations, several key phosphorus-containing molecules have been detected in interstellar clouds, circumstellar shells, and even extragalactic sources. Among these, phosphorus nitride (PN) was the first P-bearing molecule detected in space, and still is the species detected in the largest number of sources. Phosphorus oxide (PO) and phosphine (PH3) were also crucial species due to their role both in chemical networks and in forming biogenic compounds. The still limited high-angular resolution observations performed so far are shading light on the geometrical distribution of these molecules, which represent crucial insights on their formation processes. Observations have also highlighted the challenges and complexities associated with detecting and understanding phosphorus chemistry in space, owing to the low elemental abundance of P relative to other elements. This review article provides a state-of-art picture of the observational results obtained so far on phosphorus compounds in the interstellar medium. Special attention is given to star- forming regions, and to their implications for our understanding of prebiotic chemistry and the potential for life beyond Earth. Our knowledge of the dominant formation and destruction pathways of the most abundant species has improved, but critical questions remain open, among which: what is (are) the main phosphorus carrier(s) in space? Upcoming new facilities are expected to contribute significantly to this field, offering opportunities to both detect new phosphorus-bearing molecules and enlarge the number of sources in which the chemistry of P can be studied. The synergy between observations, theoretical models, laboratory experiments, and computational chemistry is mandatory to significantly progress in our comprehension of the chemistry of this important but poorly studied chemical element. [ABSTRACT FROM AUTHOR]

Ice mantles play a crucial role in shaping the astrochemical inventory of molecules during star and planet formation. Small-scale molecular processes have a profound impact on large-scale astronomical evolution. The areas of solid-state laboratory astrophysics and computational chemistry involve the study of these processes. We review laboratory efforts in ice spectroscopy, methodological advances and challenges, and laboratory and computational studies of ice physics and ice chemistry. We place the last of these in context with ice evolution from clouds to disks. Three takeaway messages from this review are: Laboratory and computational studies allow interpretation of astronomical ice spectra in terms of identification, ice morphology, and local environmental conditions as well as the formation of the involved chemical compounds. A detailed understanding of the underlying processes is needed to build reliable astrochemical models to make predictions about abundances in space. The relative importance of the different ice processes studied in the laboratory and computationally changes during the process of star and planet formation. [ABSTRACT FROM AUTHOR]

Observations that resolve nearby galaxies into individual regions across multiple phases of the gas–star formation–feedback "matter cycle" have provided a sharp new view of molecular clouds, star-formation efficiencies, timescales for region evolution, and stellar feedback. We synthesize these results, covering aspects relevant to the interpretation of observables, and conclude the following: The observed cloud-scale molecular gas surface density, line width, and internal pressure all reflect the large-scale galactic environment while also appearing mostly consistent with properties of a turbulent medium strongly affected by self-gravity. Cloud-scale data allow for statistical inference of both evolutionary and physical timescales. These suggest a period of cloud collapse on the order of the free-fall or turbulent crossing time (∼10–30 Myr) followed by forming massive stars and subsequent rapid (≲5 Myr) gas clearing after the onset of star formation. The star-formation efficiency per free-fall time is well determined over thousands of individual regions at εff ≈ 0.5−0.3+0.7%. The role of stellar feedback is now measured using multiple observational approaches. The net yield is constrained by the requirement to support the vertical weight of the galaxy disk. Meanwhile, the short gas-clearing timescales suggest a large role for presupernova feedback in cloud disruption. This leaves the supernovae free to exert a large influence on the larger galaxy, including stirring turbulence, launching galactic-scale winds, and carving superbubbles. [ABSTRACT FROM AUTHOR]

Dwarf irregular (dIrr) galaxies are among the most common type of galaxy in the Universe. They typically have gas-rich, low-surface-brightness, metal-poor, and relatively thick disks. Here, we summarize the current state of our knowledge of the interstellar medium (ISM), including atomic, molecular, and ionized gas, along with their dust properties and metals. We also discuss star-formation feedback, gas accretion, and mergers with other dwarfs that connect the ISM to the circumgalactic and intergalactic media. We highlight one of the most persistent mysteries: the nature of pervasive gas that is yet undetected as either molecular or cold hydrogen, the "dark gas." Some highlights include the following: Significant quantities of Hi are in far-outer gas disks. Cold Hi in dIrrs would be molecular in the Milky Way, making the chemical properties of star-forming clouds significantly different. Stellar feedback has a much larger impact in dIrrs than in spiral galaxies. The escape fraction of ionizing photons is significant, making dIrrs a plausible source for reionization in the early Universe. Observations suggest a significantly higher abundance of hydrogen (H2 or cold Hi) associated with CO in star-forming regions than that traced by the CO alone. [ABSTRACT FROM AUTHOR]

The thermal history and structure of the intergalactic medium (IGM) at |$z \ge 4$| is an important boundary condition for reionization, and a key input for studies using the Ly  |$\alpha$| forest to constrain the masses of alternative dark matter candidates. Most such inferences rely on simulations that lack the spatial resolution to fully resolve the hydrodynamic response of IGM filaments and minihaloes to H  i reionization heating. In this letter, we use high-resolution hydrodynamic + radiative transfer simulations to study how these affect the IGM thermal structure. We find that the adiabatic heating and cooling driven by the expansion of initially cold gas filaments and minihaloes sources significant small-scale temperature fluctuations. These likely persist in much of the IGM until |$z \le 4$|⁠. Capturing this effect requires resolving the clumping scale of cold, pre-ionized gas, demanding spatial resolutions of |${\le} 2$|   |$h^{-1}$| kpc. Pre-heating of the IGM by X-rays can slightly reduce the effect. Our preliminary estimate of the effect on the Ly  |$\alpha$| forest finds that, at |$\log (k /[{\rm km^{-1} s}]) = -1.0$|⁠ , the Ly  |$\alpha$| forest flux power (at fixed mean flux) can increase |${\approx} 10~{{\ \rm per\ cent}}$| going from 8 and 2  |$h^{-1}$| kpc resolution at |$z = 4{\!-\!}5$| for gas ionized at |$z \ \lt\ 7$|⁠. These findings motivate more careful analyses of how the effects studied here affect the Ly  |$\alpha$| forest. [ABSTRACT FROM AUTHOR]

Recent quasar absorption line observations suggest that reionization may end as late as |$z \approx 5.3$|⁠. As a means to search for large neutral hydrogen islands at |$z\ \lt\ 6$|⁠ , we revisit long dark gaps in the Ly  |$\beta$| forest in Very Large Telescope/X-Shooter and Keck/Echellette Spectrograph and Imager quasar spectra. We stack the Ly  |$\alpha$| forest corresponding to both edges of these Ly  |$\beta$| dark gaps and identify a damping wing-like extended absorption profile. The average redshift of the stacked forest is |$z=5.8$|⁠. By comparing these observations with reionization simulations, we infer that such a damping wing-like feature can be naturally explained if these gaps are at least partially created by neutral islands. Conversely, simulated dark gaps lacking neutral hydrogen struggle to replicate the observed damping wing features. Furthermore, this damping wing-like profile implies that the volume-averaged neutral hydrogen fraction must be |$\langle x_{\rm H\,{\small {I}}} \rangle \ge 6.1 \pm 3.9~{{\ \rm per\ cent}}$| at |$z = 5.8$|⁠. Our results offer robust evidence that reionization extends below |$z=6$|⁠. [ABSTRACT FROM AUTHOR]

Hot, |$\log (T/\mathrm{K})$| |$\sim$| 7.5, gas was recently discovered in the Milky Way in extragalactic sightlines. In order to determine its location, here we present sightlines to Galactic X-ray binaries (XRBs) passing through the Interstellar Medium (ISM). In this pilot study, we investigate absorption features of S |$_{\mathrm{XVI}}$|⁠ , Si |$_{\mathrm{XIV}}$|⁠ , and Ne |$_{\mathrm{X}}$| in the spectra of three XRBs, namely 4U 1735–44, 4U 1820–30, and Cyg X-2, using Chandra High Energy Transmission Grating archival observations. We do not detect any of these lines. We determine the 2 |$\sigma$| upper limit for the equivalent widths of the undetected absorption lines and the column densities of the corresponding ions. We note that the 2 |$\sigma$| upper limits for S |$_{\mathrm{XVI}}$| K |$\alpha$| and Si |$_{\mathrm{XIV}}$| K |$\alpha$| are an order of magnitude smaller than those previously detected in the extragalactic sightlines. Our finding suggests that if any gas at |$\log (T/\mathrm{K})$| |$\gt\ 7$| is present in the Galactic ISM, it is unlikely to be ubiquitous. This is an important result because it implies that S |$_{\mathrm{XVI}}$|⁠ , Si |$_{\mathrm{XIV}}$|⁠ , and Ne |$_{\mathrm{X}}$| absorption detected in extragalactic sightlines is not from the ISM, but is likely from a hot gas phase in the extraplanar region beyond the ISM or in the extended Circumgalactic Medium. [ABSTRACT FROM AUTHOR]

The identification of complex pre-biotic molecules using millimetre and submillimetre telescopes allows us to understand how the basic building blocks of life are formed in the universe. In the interstellar medium, ethylene glycol (⁠|$({\rm CH}_2{\rm OH})_{2}$|⁠) is the simplest sugar alcohol molecule, and it is the reduced alcohol of the simplest sugar-like molecule, glycolaldehyde (⁠|${\rm CH}_{2}{\rm OHCHO}$|⁠). We present the detection of the rotational emission lines of |$aGg^{\prime }$| conformer of ethylene glycol (⁠|$({\rm CH}_2{\rm OH})_{2}$|⁠) towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array. The estimated column density of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| towards the G358.93–0.03 MM1 is (4.5 |$\pm 0.1)\times 10^{16}$| cm |$^{-2}$| with an excitation temperature of 155 |$\pm$| 35 K. The abundance of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with respect to |${\rm H}_{2}$| is (1.4 |$\pm 0.5)\times 10^{-8}$|⁠. Similarly, the abundances of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with respect to |${\rm CH}_{2}{\rm OHCHO}$| and |${\rm CH}_{3}{\rm OH}$| are 3.1 |$\pm$| 0.5 and (6.1 |$\pm 0.3)\times 10^{-3}$|⁠. We compare the estimated abundance of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with the existing three-phase warm-up chemical model abundance of |$({\rm CH}_2{\rm OH})_{2}$|⁠ , and we notice the observed abundance and modelled abundance are nearly similar. We discuss the possible formation pathways of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| towards the hot molecular cores, and we find that |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| is probably created via the recombination of two |${\rm CH}_{2}{\rm OH}$| radicals on the grain surface of G358.93–0.03 MM1. [ABSTRACT FROM AUTHOR]

The recent detection of ethanolamine (EtA, HOCH |$_2$| CH |$_2$| NH |$_2$|⁠), a key component of phospholipids, i.e. the building blocks of cell membranes, in the interstellar medium is in line with an exogenous origin of life-relevant molecules. However, the stability and survivability of EtA molecules under inter/circumstellar and Solar System conditions have yet to be demonstrated. Starting from the assumption that EtA mainly forms on interstellar ice grains, we have systematically exposed EtA, pure and mixed with amorphous water (H |$_2$| O) ice, to electron, ion, and thermal processing, representing 'energetic' mechanisms that are known to induce physicochemical changes within the ice material under controlled laboratory conditions. Using infrared (IR) spectroscopy, we have found that heating of pure EtA ice causes a phase change from amorphous to crystalline at 180 K, and further temperature increase of the ice results in sublimation-induced losses until full desorption occurs at about 225 K. IR and vacuum ultraviolet (VUV) spectra of EtA-containing ices deposited and irradiated at 20 K with 1 keV electrons as well as IR spectra of H |$_2$| O:EtA mixed ice obtained after 1 MeV He |$^+$| ion irradiation have been collected at different doses. The main radiolysis products, including H |$_2$| O, CO, CO |$_2$|⁠ , NH |$_3$|⁠ , and CH |$_3$| OH, have been identified and their formation pathways are discussed. The measured column density of EtA is demonstrated to undergo exponential decay upon electron and ion bombardment. The half-life doses for electron and He |$^+$| ion irradiation of pure EtA and H |$_2$| O:EtA mixed ice are derived to range between |$10.8\!-\!26.3$|  eV/16u. Extrapolating these results to space conditions, we conclude that EtA mixed in H |$_2$| O ice is more stable than in pure form and it should survive throughout the star and planet formation process. [ABSTRACT FROM AUTHOR]

Ram pressure stripping is perhaps the most efficient mechanism for removing gas and quenching galaxies in dense environments, as they move through the intergalactic medium. Extreme examples of on-going ram pressure stripping are known as jellyfish galaxies, characterized by a tail of stripped material that can be directly observed in multiple wavelengths. Using the largest homogeneous broad-band optical jellyfish candidate sample in local clusters known to date, we measure the angle between the direction of the tails visible in the galaxies, and the direction towards the host cluster centre. We find that 33 per cent of the galaxy tails point away from the cluster centre, 18  per cent point towards the cluster centre, and 49  per cent point elsewhere. Moreover, we find stronger signatures of ram pressure stripping happening on galaxies with a tail pointing away and towards the cluster centre, and larger velocity dispersion profiles for galaxies with tails pointing away. These results are consistent with a scenario where ram pressure stripping has a stronger effect for galaxies following radial orbits on first infall. The results also suggest that in many cases, radially infalling galaxies are able to retain their tails after pericenter and continue to experience significant on-going ram pressure stripping. We further constrain the lifespan of the optical tails from the moment they first appear to the moment they disappear, by comparing the observed tail directions with matched N -body simulations through Bayesian parameter estimation. We obtain that galaxy tails appear for the first time at |$\sim 1.16$| R |$_{200}$| and disappear |$\sim 660$| Myr after pericenter. [ABSTRACT FROM AUTHOR]

Making use of the APOGEE DR17 catalogue with high quality data for 143 509 red giant branch stars we explore the strength of different mechanisms that causes a star to radially migrate in the Milky Way stellar disc. At any position in the disc we find stars that are more metal-rich than the local interstellar medium. This is surprising and normally attributed to the migration of these stars after their formation inside their current Galactocentric radius. Such stars are prime candidates for studying the strength of different migratory processes. We specifically select two types of metal-rich stars: (i) super metal-rich stars (⁠|$\mathrm{[Fe/H]}\gt 0.2$|⁠) and (ii) stars that are more metal-rich than their local environment. For both, we explore the distribution of orbital parameters and ages as evidence of their migration history. We find that most super metal-rich stars have experienced some amount of churning as they have orbits with |$R_g\gtrsim 5 \,{\rm kpc}$|⁠. Furthermore, about half of the super metal-rich stars are on non-circular orbits (⁠|$\mathrm{ecc} \gt 0.15$|⁠) and therefore also have experienced blurring. The metallicity of young stars in our sample is generally the same as the metallicity of the interstellar medium, suggesting they have not radially migrated yet. Stars with lower metallicity than the local environment have intermediate to old ages. We further find that super metal-rich stars have approximately the same age distribution at all Galactocentric radii, which suggests that radial migration is a key mechanism responsible for the chemical compositions of stellar populations in the Milky Way. [ABSTRACT FROM AUTHOR]

Measurements of the mean free path of Lyman-continuum photons in the intergalactic medium during the epoch of reionization can help constrain the nature of the sources as well as sinks of hydrogen-ionizing radiation. A recent approach to this measurement has been to utilize composite spectra of multiple quasars at |$z\sim 6$|⁠ , and infer the mean free path after correcting the spectra for the presence of quasar proximity zones. This has revealed not only a steep drop in the mean free path from |$z=5$| to |$z=6$|⁠ , but also potentially a mild tension with reionization simulations. We critically examine such direct measurements of the mean free path for biases due to quasar environment, incomplete reionization, and quasar proximity zones. Using cosmological radiative transfer simulations of reionization combined with one-dimensional radiative transfer calculations of quasar proximity zones, we find that the bias in the mean free path due to overdensities around quasars is minimal at |$z\sim 6$|⁠. Patchiness of reionization at this redshift also does not affect the measurements significantly. Fitting our model to the data results in a mean free path of |$\lambda _{\mathrm{mfp}}=1.49^{+0.47}_{-0.52}$|  pMpc at |$z=6$|⁠ , which is consistent with the recent measurements in the literature, indicating robustness with respect to the modelling of quasar proximity zones. We also compare various ways in which the mean free path has been defined in simulations before the end of reionization. Overall, our finding is that recent measurements of the mean free path appear to be robust relative to several sources of potential bias. [ABSTRACT FROM AUTHOR]

We present deep 1.4–4.8 μ m JWST-NIRCam imaging of the Serpens Main star-forming region and identify 20 candidate protostellar outflows, most with bipolar structure and identified driving sources. The outflow position angles (PAs) are strongly correlated, and they are aligned within ±24° of the major axis of the Serpens filament. These orientations are further aligned with the angular momentum vectors of the two disk shadows in this region. We estimate that the probability of this number of young stars being coaligned if sampled from a uniform PA distribution is 10−4. This in turn suggests that the aligned protostars, which seem to be at similar evolutionary stages based on their outflow dynamics, formed at similar times with a similar spin inherited from a local cloud filament. Further, there is tentative evidence for a systematic change in average PA between the northwestern and southeastern cluster, as well as increased scatter in the PAs of the southeastern protostars. SOFIA-HAWC+ archival dust polarization observations of Serpens Main at 154 and 214 μ m are perpendicular to the dominant jet orientation in the northwestern region in particular. We measure and locate shock knots and edges for all of the outflows and provide an identifying catalog. We suggest that Serpens main is a cluster that formed from an isolated filament and due to its youth retains its primordial outflow alignment. [ABSTRACT FROM AUTHOR]

Aims. We present a new sub-grid model, HYACINTH – HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations – for computing the non-equilibrium abundances of H2 and its carbon-based tracers, namely CO, C, and C+, in cosmological simulations of galaxy formation. Methods. The model accounts for the unresolved density structure in simulations using a variable probability distribution function of sub-grid densities and a temperature-density relation. Included is a simplified chemical network that has been tailored for hydrogen and carbon chemistry within molecular clouds and easily integrated into large-scale simulations with minimal computational overhead. As an example, we applied HYACINTH to a simulated galaxy at redshift z ~ 2.5 in post-processing and compared the resulting abundances with observations. Results. The chemical predictions from HYACINTH are in reasonable agreement with high-resolution molecular-cloud simulations at different metallicities. By post-processing a galaxy simulation with HYACINTH, we reproduced the H I − H2 transition as a function of the hydrogen column density NH for both Milky-Way-like and Large-Magellanic-Cloud-like conditions. We also matched the NCO versus NH2 relation inferred from absorption measurements towards Milky-Way molecular clouds, although most of our post-processed regions occupy the same region as (optically) dark molecular clouds in the NCO – NH2 plane. Column density maps reveal that CO is concentrated in the peaks of the H2 distribution, while atomic carbon more broadly traces the bulk of H2 in our post-processed galaxy. Based on both the column density maps and the surface density profiles oŕ the different gas species in the post-processed galaxy, we find that C+ maintains a substantially high surŕace density out to ~10 kpc as opposed to other components that exhibit a higher central concentration. This is similar to the extended [C II] emission ŕound in some recent observations at high redshifts. [ABSTRACT FROM AUTHOR]

The intergalactic medium in the vicinity of galaxy protoclusters are interesting testbeds to study complex baryonic effects such as gravitational shocks and feedback. Here, we utilize hydrodynamical simulations from the SIMBA and The Three Hundred suites to study the mechanisms influencing large-scale Lyman- |$\alpha$| transmission in |$2\lt z\lt 2.5$| protoclusters. We focus on the matter overdensity-Lyman- |$\alpha$| transmission relation |$(\delta _m-\delta _F)$| on Megaparsec-scales in these protoclusters, which is hypothesized to be sensitive to the feedback implementations. The lower density regions represented by the SIMBA-100 cosmological volume trace the power-law |$\delta _m-\delta _F$| relationship often known as the fluctuating Gunn–Peterson approximation. This trend is continued into higher density regions covered by simulations that implement stellar feedback only. Simulations with active galactic nucleus (AGN) thermal and AGN jet feedback, however, exhibit progressively more Lyman- |$\alpha$| transmission at fixed matter overdensity. Compared with the seven protoclusters observed in the COSMOS field, only two display the excess absorption expected from protoclusters. The others exhibit deviations: four show some increased transparency suggested by AGN X-ray thermal feedback models while the highly transparent COSTCO-I protocluster appears to reflect intense jet feedback. Discrepancies with the stellar-feedback-only model suggests processes at play beyond gravitational heating and/or stellar feedback as the cause of the protocluster transparencies. Some form of AGN feedback is likely at play in the observed protoclusters, and possibly long-ranged AGN jets in the case of COSTCO-I. While more detailed and resolved simulations are required to move forward, our findings open new avenues for probing AGN feedback at Cosmic Noon. [ABSTRACT FROM AUTHOR]

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

We present determinations of the gas-phase and stellar metallicities of a sample of 65 star-forming galaxies at |$z \simeq 3.5$| using rest-frame far-ultraviolet (FUV) spectroscopy from the VANDELS survey in combination with follow-up rest-frame optical spectroscopy from VLT /KMOS and Keck/MOSFIRE. We infer gas-phase oxygen abundances (⁠|$Z_{\mathrm{g}}$|⁠ ; tracing O/H) via strong optical nebular lines and stellar iron abundances (⁠|$Z_{\star }$|⁠ ; tracing Fe/H) from full spectral fitting to the FUV continuum. Our sample spans the stellar mass range |$8.5 \lt \mathrm{log}(M_{\star }/\mathrm{M}_{\odot }) \lt 10.5$| and shows clear evidence for both a stellar and gas-phase mass-metallicity relation (MZR). We find that our O and Fe abundance estimates both exhibit a similar mass-dependence, such that |$\mathrm{Fe/H}\propto M_{\star }^{0.30\pm 0.11}$| and |$\mathrm{O/H}\propto M_{\star }^{0.32\pm 0.09}$|⁠. At fixed |$M_{\star }$| we find that, relative to their solar values, O abundances are systematically larger than Fe abundances (i.e. α-enhancement). We estimate an average enhancement of |$\mathrm{(O/Fe)} = 2.65 \pm 0.16 \times \mathrm{(O/Fe)_\odot }$| which appears to be independent of |$M_{\star }$|⁠. We employ analytic chemical evolution models to place a constraint on the strength of galactic-level outflows via the mass-outflow factor (⁠|$\eta$|⁠). We show that outflow efficiencies that scale as |$\eta \propto M_{\star }^{-0.32}$| can simultaneously explain the functional form of of the stellar and gas-phase MZR, as well as the degree of α-enhancement at fixed Fe/H. Our results add further evidence to support a picture in which α-enhanced abundance ratios are ubiquitous in high-redshift star-forming galaxies, as expected for young systems whose interstellar medium is primarily enriched by core-collapse supernovae. [ABSTRACT FROM AUTHOR]

In recent years, cosmological hydrodynamical simulations have proven their utility as key interpretative tools in the study of galaxy formation and evolution. In this work, we present a comparative analysis of the baryon cycle in three publicly available, leading cosmological simulation suites: EAGLE, IllustrisTNG, and SIMBA. While these simulations broadly agree in terms of their predictions for the stellar mass content and star formation rates of galaxies at |$z\approx 0$|⁠ , they achieve this result for markedly different reasons. In EAGLE and SIMBA, we demonstrate that at low halo masses (⁠|$M_{\rm 200c}\lesssim 10^{11.5}\, \mathrm{M}_{\odot }$|⁠), stellar feedback (SF)-driven outflows can reach far beyond the scale of the halo, extending up to |$2\!-\!3\times R_{\rm 200c}$|⁠. In contrast, in TNG, SF-driven outflows, while stronger at the scale of the interstellar medium, recycle within the circumgalactic medium (within |$R_{\rm 200c}$|⁠). We find that active galactic nucleus (AGN)-driven outflows in SIMBA are notably potent, reaching several times |$R_{\rm 200c}$| even at halo masses up to |$M_{\rm 200c}\approx 10^{13.5}\, \mathrm{M}_{\odot }$|⁠. In both TNG and EAGLE, AGN feedback can eject gas beyond |$R_{\rm 200c}$| at this mass scale, but seldom beyond |$2\!-\!3\times R_{\rm 200c}$|⁠. We find that the scale of feedback-driven outflows can be directly linked with the prevention of cosmological inflow, as well as the total baryon fraction of haloes within |$R_{\rm 200c}$|⁠. This work lays the foundation to develop targeted observational tests that can discriminate between feedback scenarios, and inform subgrid feedback models in the next generation of simulations. [ABSTRACT FROM AUTHOR]

Massive stars that travel at supersonic speeds can create bow shocks as their stellar winds interact with the surrounding interstellar medium (ISM). These bow shocks – prominent sites for mechanical feedback of individual massive stars – are predominantly observed in the infrared (IR) band. Confirmed high-energy emission from stellar bow shocks has remained elusive and confirmed radio counterparts, while rising in recent years, remain rare. Here, we present an in-depth multiwavelength exploration of the bow shock driven by LS 2355, focusing on its non-thermal properties. Using the most recent Fermi source catalogue, we rule out its previously proposed association with an unidentified γ-ray source. Furthermore, we use deep Australian Square Kilometre Array Pathfinder (ASKAP) observations from the Rapid ASKAP Continuum Survey and the Evolutionary Map of the Universe survey to identify a non-thermal radio counterpart: the third spectrally confirmed non-thermal bow shock counterpart after BD+43°3654 and BD+60°2522. We finally use Wide-field Infrared Survey Explorer (WISE) IR data and Gaia to study the surrounding ISM and update the motion of LS 2355. Specifically, we derive a substantially reduced stellar velocity, |$v_* = 7.0\pm 2.5$| km s−1, compared to previous estimates. The observed non-thermal properties of the bow shock can be explained by an interaction between the wind of LS 2355 and a dense H  ii region, at a magnetic field close to the maximum magnetic field strength allowed by the compressibility of the ISM. Similar to earlier works, we find that the thermal radio emission of the shocked ISM is likely to be substantially suppressed for it to be consistent with the observed radio spectrum. [ABSTRACT FROM AUTHOR]

Three-dimensional dust density maps are crucial for understanding the structure of the interstellar medium of the Milky Way and the processes that shape it. However, constructing these maps requires large data sets and the methods used to analyse them are computationally expensive and difficult to scale up. As a result, it has only recently become possible to map kiloparsec-scale regions of our Galaxy at parsec-scale grid sampling. We present all-sky three-dimensional dust density and extinction maps of the Milky Way out to 2.8 kpc in distance from the Sun using the fast and scalable Gaussian Process algorithm Dustribution. The sampling of the three-dimensional map is l, b, d  = 1° × 1° × 1.7 pc. The input extinction and distance catalogue contains 120 million stars with photometry and astrometry from Gaia DR2, 2MASS and AllWISE. This combines the strengths of optical and infrared data to probe deeper into the dusty regions of the Milky Way. We compare our maps with other published 3D dust maps. All maps quantitatively agree at the 0.001 mag pc−1 scale with many qualitatively similar features, although each map also has its own features. We recover Galactic features previously identified in the literature. Moreover, we also see a large under-density that may correspond to an inter-arm or -spur gap towards the Galactic Centre. [ABSTRACT FROM AUTHOR]

In this work, we present data from the Milky Way Imaging Scroll Painting project for the Maddalena giant molecular cloud (GMC). We decompose the 13CO emission datacube of the observed region into hierarchical substructures using a modified dendrogram algorithm. We investigate the statistical properties of these substructures and examine the role that self-gravity plays on various spatial scales. The statistics of the mass (M), radius (R), velocity dispersion (σ v ), virial parameter (α vir), and sonic Mach number of the substructures are presented. The radius and mass distributions and the σ v –R scaling relationship of the substructures resemble those reported in previous studies that use nonhierarchical algorithms to identify the entities. We find that for the hierarchical substructures α vir decreases as the radius or mass of the substructures increases. The majority of the substructures in the quiescent region of the Maddalena GMC are not gravitationally bound (α vir > 2), while most of the substructures in the star-forming regions are gravitationally bound (α vir < 2). Furthermore, we find that self-gravity plays an important role on scales of 0.8–4 pc in the IRAS 06453 star-forming region, while it is not an important factor on scales below 5 pc in the non-star-forming region. [ABSTRACT FROM AUTHOR]

Amino acids are essential for Earth-like life and are hypothesised to have originated in interstellar space, potentially being transported to Earth via meteorite impacts. Detecting amino acids in interstellar environments and understanding their formation mechanisms through laboratory experiments are crucial for supporting this hypothesis and unravelling the origins of life. In this study, the formation of serine ( $ {\rm NH}_2{\rm CH}({\rm CH}_2{\rm OH}){\rm COOH}) $ NH 2 CH (CH 2 OH) COOH) from α-glycyl ( $ {\rm NH}_2{\rm C}{\cdot }{\rm HCOOH} $ NH 2 C ⋅ HCOOH ) and hydroxymethyl ( $ {\cdot } {\rm CH}_2{\rm OH} $ ⋅ CH 2 OH ) radicals was investigated using quantum chemical computations. It was found that the anticipated recombination reaction, along with analogous formation pathways of other natural amino acids, is accompanied by competing reactions yielding alternative products, potentially diminishing serine formation. Alternative interstellar formation pathways for serine are proposed, which could be experimentally tested by future laboratory studies. [ABSTRACT FROM AUTHOR]

The rovibrational spectrum of the molecular ion H $ _2 $ 2 CCCH $ ^+ $ + was investigated in a 4 K cryogenic ion trap instrument employing the leak-out spectroscopy method. Transitions within the fundamental $ \nu _1 $ ν 1 (C–H stretch) and the combination band $ \nu _3 $ ν 3 + $ \nu _5 $ ν 5 (C–C stretches) were detected, the search aided by high level quantum chemical calculations. The analysis of the rovibrational measurements enabled us to predict the rotational structure of the ground state. Using a rotational-vibrational double-resonance scheme, 14 pure rotational transitions were measured. This, in turn, led to the radio astronomical detection of H $ _2 $ 2 CCCH $ ^+ $ + in the interstellar medium, as recently reported (Silva et al., Astron. Astrophys. 676, L1, 2023). [ABSTRACT FROM AUTHOR]

For a better understanding of the physico-chemistry in the interstellar medium, collisional data are needed. In this work, we provide rate coefficients for the recently detected by Cabezas and collaborators in 2023 sodium cyanoacetylide molecule NaC |$_{3}$| N(⁠|$X^{1}\Sigma ^{+}$|⁠) induced by collisions with He. A new two-dimensional potential energy surface (2D-PES) is derived by adopting the high-level theory of the explicitly correlated coupled cluster with single, double, and perturbative triple excitations (CCSD(T)-F12) in conjunction with the aug-cc-pVTZ basis sets. Our 2D-PES presents two minima: the global one with a well depth of |$-86.58$|  cm |$^{-1}$| and the second well with a |$-47.01$|  cm |$^{-1}$| depth. This was expected by the Natural Bond Orbital analysis showing two electrophilic zones located on Na and N linked Carbon with respective atomic charges : |$+0.96575$| and |$+0.28910$|⁠. This PES was used to calculate inelastic cross-sections within the framework of the close-coupling theory for total energies |$\le 170$|  cm |$^{-1}$| and |$J\le 22$|⁠. Using the Maxwell–Boltzmann distribution of kinetic energies, these cross-sections were integrated to generate the collisional (de)-excitation rate coefficients for temperatures below 30 K. In order to estimate the impact of the computed collisional rates, a non-local thermodynamical equilibrium radiative transfer calculation was performed. The new collisional data can allow accurate NaC |$_{3}$| N abundance determination in the interstellar medium. [ABSTRACT FROM AUTHOR]

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

In the absence of supplementary heat, the radiative cooling of halo gas around massive galaxies (Milky Way mass and above) leads to an excess of cold gas or stars beyond observed levels. Active galactic nucleus jet-induced heating is likely essential, but the specific properties of the jets remain unclear. Our previous work concludes from simulations of a halo with |$10^{14} \,\mathrm{ M}_\odot$| that a successful jet model should have an energy flux comparable to the free-fall energy flux at the cooling radius and should inflate a sufficiently wide cocoon with a long enough cooling time. In this paper, we investigate three jet modes with constant fluxes satisfying the criteria, including high-temperature thermal jets, cosmic ray (CR)-dominant jets, and widely precessing kinetic jets in |$10^{12}-10^{15}\, {\rm M}_{\odot }$| haloes using high-resolution, non-cosmological magnetohydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model, conduction, and viscosity. We find that scaling the jet energy according to the free-fall energy at the cooling radius can successfully suppress the cooling flows and quench galaxies without violating observational constraints. On the contrary, if we scale the energy flux based on the total cooling rate within the cooling radius, strong interstellar medium cooling dominates this scaling, resulting in a jet flux exceeding what is needed. Among the three jet types, the CR-dominant jet is most effective in suppressing cooling flows across all surveyed halo masses due to enhanced CR pressure support. We confirm that the criteria for a successful jet model work across a wider range, encompassing halo masses of |$10^{12}-10^{15} {\rm M_\odot }$|⁠. [ABSTRACT FROM AUTHOR]

Clusters of galaxies are merging during the formation of large-scale structures in the Universe. Based on optical survey data, we identify a large sample of pre-mergers of galaxy clusters and merging subclusters in rich clusters. We find 39 382 partners within a velocity difference of 1500 km s |$^{-1}$| and a projected separation of 5  |$r_{500}$| around 33 126 main clusters, where |$r_{500}$| is the radius of the main cluster. Based on the galaxy distribution inside rich clusters with more than 30 member galaxy candidates, we identify subclusters by modelling the smoothed optical distribution with a two-component profile, and a coupling factor is obtained for merging subclusters in 7845 clusters. In addition, we find 3446 post-collision mergers according to the deviations of brightest cluster galaxies from other member galaxies, most of which have been partially validated by using the Chandra and XMM–Newton X-ray images. Two new bullet-like clusters have been identified by using the optical and X-ray images. The large samples of merging clusters of galaxies presented here are important databases for studying the hierarchical structure formation, cluster evolution, and the physics of intergalactic medium. [ABSTRACT FROM AUTHOR]