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Saturn's moon Enceladus is erupting a plume of gas and ice grains from its south pole. Linked directly to the moon's subsurface global ocean, plume material travels through cracks in the icy crust and is ejected into space. The subsurface ocean is believed to be in contact with the rocky core, with ongoing hydrothermal activity present. The Cassini spacecraft's Ion and Neutral Mass Spectrometer (INMS) detected volatile, gas phase, organic species in the plume and the Cosmic Dust Analyser (CDA) discovered high-mass, complex organic material in a small fraction of ice grains. Here, we present a broader compositional analysis of CDA mass spectra from organic-bearing ice grains. Through analogue experiments, we find spectral characteristics attributable to low-mass organic compounds in the Enceladean ice grains: nitrogen-bearing, oxygen-bearing, and aromatic. By comparison with INMS results, we identify low-mass amines [particularly (di)methylamine and/or ethylamine] and carbonyls (with acetic acid and/or acetaldehyde most suitable) as the best candidates for the N- and O-bearing compounds, respectively. Inferred organic concentrations in individual ice particles vary but may reach tens of mmol levels. The low-mass nitrogen- and oxygen-bearing compounds are dissolved in the ocean, evaporating efficiently at its surface and entering the ice grains via vapour adsorption. The potentially partially water soluble, low-mass aromatic compounds may alternatively enter ice grains via aerosolization. These amines, carbonyls, and aromatic compounds could be ideal precursors for mineral-catalysed Friedel–Crafts hydrothermal synthesis of biologically relevant organic compounds in the warm depths of Enceladus' ocean. [ABSTRACT FROM AUTHOR]

Detection of areas of increased density of cosmic dust in near-Earth space is important from both theoretical and practical points of view. To continue our explication of the phenomenon of appearance-disappearance of the Kodylewski dust clouds, we consider dynamics of charged dust particles in the small vicinity of Lagrange libration point. The masses of particles are comparable to the masses of protons and electrons. These particles induce a self-consistent electric as well as a self-consistent gravitational fields. As a result, we obtain an existence of periodically changing stable configuration of an ensemble of the charged particles. It should be taken into account when planning space missions. [ABSTRACT FROM AUTHOR]

"You realise that the Earth is nothing but accumulated cosmic dust having formed a rock that is encompassed by a flimsy, fragile atmosphere. To grasp this, I needed the view out of the window." German ESA Astronaut Alexander Gerst's perspective on Earth was changed sustainably by the view from the International Space Station (ISS) onto our home planet. It is possible to give pupils a very similar perspective within the means of public education due to the availability of Earth Observation data from the ISS. However, the data can be put to more educational use than providing a taste of the overview effect. Applying common remote sensing methods and modern teaching concepts to EO (Earth Observation) data from the National Aeronautics and Space Administration (NASA) High Definition Earth Viewing experiment, teaching modules for several STEM (Science, Technology, Engineering, and Mathematics) subjects could be implemented successfully. Building on this success, more ISS EO sensors are being implemented in teaching materials and new media techniques are explored. The more recent addition to the material pool are smartphone apps using Augmented Reality (AR) with which the pupils can experiment on their own. These apps are developed in a partial What You See Is What You Get (WYSIWYG) application development system called Unity with the Vuforia extension, the latter allowing the use of printed images as reference markers for AR. Complex theoretical topics can be visualised in 3-dimensional (3D) animations or turned into inexpensive, easy digital experiments. The app "The Earth-Moon System" applies this with experiments on the effects of changes in the distance between Earth and Moon and a 3D animation on the barycentre between two celestial bodies. Development of such apps is feasible for researchers to visualise their data even with no prior app development knowledge. • AR apps for smartphones are suitable for digital education in STEM subjects. • An AR app was created to teach about gravitational effects and Kepler laws. • Digital experiments include a tide simulation, Moon position, distortion, and shadow. • The app balances limited smartphone computing resources and scientific accuracy. • Preliminary tests show interest and understanding in previously indifferent pupils. [ABSTRACT FROM AUTHOR]

The JAXA/ISAS spacecraft DESTINY+ will be launched to the active asteroid (3200) Phaethon in 2022. Among the proposed core payload is the DESTINY+ Dust Analyzer (DDA) which is an upgrade of the Cosmic Dust Analyzer flown on the Cassini spacecraft to Saturn (Srama et al., 2011). We use two up-to-date computer models, the ESA Interplanetary Meteoroid Engineering Model (IMEM, Dikarev et al., 2005a, c), and the interstellar dust module of the Interplanetary Meteoroid environment for EXploration model (IMEX;Sterken et al. 2013; Strub et al., 2019) to study the detection conditions and fluences of interplanetary and interstellar dust with DDA. Our results show that a statistically significant number of interplanetary and interstellar dust particles will be detectable with DDA during the 4-years interplanetary cruise of DESTINY+. The particle impact direction and speed can be used to descriminate between interstellar and interplanetary particles and likely also to distinguish between cometary and asteroidal particles. [ABSTRACT FROM AUTHOR]

The results of laboratory mass-spectrometer studies of the laser-induced dissociation of molecules of simple aromatic hydrocarbons adsorbed on a quartz substrate under the conditions of deep vacuum and low temperatures are adapted to the physical and chemical conditions in regions of active star formation in molecular clouds. The main properties of the photolysis of physically adsorbed molecules compared to the photodissociation of isolated molecules in the gas phase are identified. The relevance of molecular photolytic desorption to the real conditions in the interstellar medium is analyzed, in particular, to the conditions in photodissociation regions. It is shown that the photodissociation of adsorbed benzene occurs along other channels and with appreciably lower efficiency than does the corresponding process in the gas phase. The photodissociation of aromatic hydrocarbons adsorbed on the surfaces of interstellar grains cannot make a large contribution to the abundance of hydrocarbons with small numbers of atoms observed in the interstellar medium. [ABSTRACT FROM AUTHOR]

In this paper we present the results of numerical modeling of the Chelyabinsk dust train during the first 3 min after the meteoroid entry which are in qualitative agreement with observations. Then we analyze the possibility of plume formation after impacts of small cosmic bodies and make some calculations for the Tunguska event which, unfortunately, cannot be compared directly with observations. We also estimate long-lasting disturbances in the upper atmosphere caused by the plume formation. [ABSTRACT FROM AUTHOR]

NASA's strategy in exploring Mars has been to follow the water, because water is essential for life, and it has been found that there are many locations where there was once liquid water on the surface. Now perhaps, to narrow down the search for life on a barren basalt‐dominated surface, there needs to be a refocusing to a strategy of "follow the nutrients." Here we model the entry of metallic micrometeoroids through the Martian atmosphere, and investigate variations in micrometeorite abundance at an analogue site on the Nullarbor Plain in Australia, to determine where the common limiting nutrients available in these (e.g., P, S, Fe) become concentrated on the surface of Mars. We find that dense micrometeorites are abundant in a range of desert environments, becoming concentrated by aeolian processes into specific sites that would be easily investigated by a robotic rover. Our modeling suggests that micrometeorites are currently far more abundant on the surface of Mars than on Earth, and given the far greater abundance of water and warmer conditions on Earth and thus much more active weather system, this was likely true throughout the history of Mars. Because micrometeorites contain a variety of redox sensitive minerals including FeNi alloys, sulfide and phosphide minerals, and organic compounds, the sites where these become concentrated are far more nutrient rich, and thus more compatible with chemolithotrophic life than most of the Martian surface. Plain Language Summary: NASA's exploration program has allowed the scientific community to demonstrate clearly that Mars had a watery past, so the search for life needs to move on to identifying the places where water and nutrients coincided. We have investigated the relative abundance of micrometeorites on Mars compared to the Earth because these contain key nutrients that the earliest life forms on Earth used, and because their contained minerals can be used to investigate past atmospheric chemistry. We suggest that micrometeorites should be far more abundant on the Martian surface than on Earth's, and that wind‐driven modification of sediments is expected to concentrate micrometeorites, and their contained nutrients, in gravel beds and cracks in exposed bedrock. Key Points: Micrometeorites are predicted to be far more abundant on Mars than on EarthMicrometeorites are concentrated in the residue of aeolian sediment removal, such as at bedrock cracks and gravel accumulationsMicrometeorite accumulation sites are enriched in key nutrients for primitive microbes: reduced phosphorus, sulfur, and iron [ABSTRACT FROM AUTHOR]

Peat cores sampled from different climatic zones are studied. The petromagnetic and microprobe methods are used to find peat layers enriched with cosmic dust. It is established that the behavior of saturation isothermal remanent magnetization (SIRM) of peat deposits from the zones where the aeolian transfer of terrigenous particles is negligible can be used for studying the dynamics of the fall of cosmic matter on the Earth's surface. The cosmic dust flux can be conditionally divided into the background and burst components. Here, the background flux of cosmic dust varies cyclically. The characteristic times of these cycles are about 100 years. The cyclicity in the background flux of cosmic material most clearly manifested itself in the interval of 1200 to 500 years ago. The most significant burst in the influx of cosmic material (by an order of magnitude above the background) is revealed in the layer that was formed about 5000 years ago. The microprobe studies established that the mineralogical content of cosmic dust differs between the background and burst fluxes. [ABSTRACT FROM AUTHOR]

Aims. Within the framework of the DustPedia project we investigate the properties of cosmic dust and its interaction with stellar radiation (originating from different stellar populations) for 814 galaxies in the nearby Universe, all observed by the Herschel Space Observatory. Methods. We take advantage of the widely used fitting code CIGALE, properly adapted to include the state-of-the-art dust model THEMIS. For comparison purposes, an estimation of the dust properties is provided by approximating the emission at far-infrared and sub-millimeter wavelengths with a modified blackbody. Using the DustPedia photometry we determine the physical properties of the galaxies, such as the dust and stellar mass, the star-formation rate, the bolometric luminosity, the unattenuated and the absorbed by dust stellar light, for both the old (> 200 Myr) and young (≤200 Myr) stellar populations. Results. We show how the mass of stars, dust, and atomic gas, as well as the star-formation rate and the dust temperature vary between galaxies of different morphologies and provide recipes to estimate these parameters given their Hubble stage (T). We find a mild correlation between the mass fraction of the small a-C(:H) grains with the specific star-formation rate. On average, young stars are very efficient in heating the dust, with absorption fractions reaching as high as ∼77% of the total unattenuated luminosity of this population. On the other hand, the maximum absorption fraction of old stars is ∼24%. Dust heating in early-type galaxies is mainly due to old stars, up to a level of ∼90%. Young stars progressively contribute more for "typical" spiral galaxies and they become the dominant source of dust heating for Sm-type and irregular galaxies, with ∼60% of their luminosity contributing to that purpose. Finally, we find a strong correlation of the dust heating fraction by young stars with morphology and the specific star-formation rate. [ABSTRACT FROM AUTHOR]

Abstract Silicate minerals such as "Mg-Fe-Si-O" compounds, are found in asteroids, planets, and cosmic dust grains in the interstellar medium. As the silicate dust grains traverse regions of space, they are irradiated by energetic ions, such as alpha particles, which can modify the crystalline phase of the mineral dust. Silicate dust grain analogues were synthesized using multiple low energy (<60 keV) ion (Fe−, Mg−, O−) implantations into a silicon wafer. The low energy ion beam as-implanted samples were cut into several smaller sections. Some of these low-energy as-implanted samples were further irradiated with a 600 keV helium ion beam at varying current densities (ions/unit area/unit time) and subsequent furnace annealed at 1000 °C temperature in Ar gas environment. The crystalline phases of the post annealed samples were monitored and reported as a function of current densities using x-ray diffraction (XRD). The XRD results showed an increase in the crystalline phases of olivine by the high-energy helium ion irradiation processing with a beam of current density of 500 nA/cm2. This work is relevant for space weathering processes as well as solid material evolution in astrophysical environments, especially asymptotic giant branch stars with an oxygen rich outflow. [ABSTRACT FROM AUTHOR]

We search for far-infrared counterparts of known supernova remnants (SNRs) in the Galactic plane (10° < | l | < 60°) at 70–500 μm using the Herschel Infrared Galactic Plane Survey (Hi-GAL). Of 71 sources studied, we find that 29 (41   per cent) SNRs have a clear FIR detection of dust emission associated with the SNR. Dust from 8 of these is in the central region, and 4 indicate pulsar wind nebulae (PWNe) heated ejecta dust. A further 23 have dust emission in the outer shell structures which is potentially related to swept-up material. Many Galactic SNe have dust signatures but we are biased towards detecting ejecta dust in young remnants and those with a heating source (shock or PWN). We estimate the dust temperature and mass contained within three PWNe, G11.2–0.3, G21.5–0.9, and G29.7–0.3, using modified blackbody fits. To more rigorously analyse the dust properties at various temperatures and dust emissivity index β, we use point process mapping (PPMAP). We find significant quantities of cool dust (at 20–40 K) with dust masses of M d  =  0.34 ± 0.14 M⊙, M d  =  0.29 ± 0.08 M⊙, and M d  =  0.51 ± 0.13 M⊙ for G11.2–0.3, G21.5–0.9, and G29.7–0.3, respectively. We derive the dust emissivity index for the PWN ejecta dust in G21.5–0.3 to be |$\beta \, =\, 1.4 \pm 0.5$| compared to dust in the surrounding medium where |$\beta \, =\, 1.8 \pm 0.1$|⁠. [ABSTRACT FROM AUTHOR]

We present resolution-enhanced images of warm dust at multiple temperatures and opacity index values in the star-forming bubble/H  ii region, RCW 120. The image set, representing a four-dimensional hypercube of differential column density, was obtained using our Bayesian procedure, ppmap. The cool peripheral material (∼16–22 K) exhibits ragged clumpy structure as noted previously by others. However, at higher temperatures (≲26 K) the geometry changes dramatically, showing a bubble boundary which is accurately circular in projection, except for the previously reported opening in the north. Comparison with Spitzer 8 |$\mu$| m data suggests that the ∼26–30 K dust seen by Herschel resides in the photodissociation region (PDR) surrounding the H  ii region. Its projected radial profile is consistent with that of a spherical shell, thus arguing against previous suggestions of cylindrical or planar geometry. The inferred geometry is, in fact, consistent with previous interpretations of the H  ii region as a classical Strömgren sphere, except for the fact that the ionizing star (CD −38 |${^{\circ}_{.}}$| 11636; O8V) is displaced by more than half a radius from its geometric centre. None of the previously published models has satisfactorily accounted for that displacement. It could, however, be explained by proper motion of the O star at ∼2–4 km s−1 since its formation, possibly due to a cloud–cloud collision. We suggest that the current spherical bubble constitutes the fossilized remnant of the initial expansion of the H  ii region following the formation of the star, which now continues to flee its formation site. [ABSTRACT FROM AUTHOR]

The gas-driven dust activity of comets is still an unresolved question in cometary science. In the past, it was believed that comets are dirty snowballs and that the dust is ejected when the ice retreats. However, thanks to the various space missions to comets, it has become evident that comets have a much higher dust-to-ice ratio than previously thought and that most of the dust mass is ejected in large particles. Here, we report on new comet-simulation experiments dedicated to the study of the ejection of dust aggregates caused by the sublimation of solid water ice. We find that dust ejection exactly occurs when the pressure of the water vapour above the ice surface exceeds the tensile strength plus the gravitational load of the covering dust layer. Furthermore, we observed the ejection of clusters of dust aggregates, whose sizes increase with increasing thickness of the ice-covering dust-aggregate layer. In addition, the trajectories of the ejected aggregates suggest that most of the aggregates obtained a non-vanishing initial velocity from the ejection event. [ABSTRACT FROM AUTHOR]

Abstract The Beagle family is a C-type subgroup of the Themis family, in the outer main belt. Previous works suggested that it could be younger than 20 Myr and a possible source for the dust in the i ≃ 1.4 ∘ α zodiacal dust band. Here we took advantage of a much larger database for Beagle family members to revisit previous age estimates of this group. Standard dating techniques based on the family V-shape or on Monte Carlo methods of Yarkovsky and YORP mobility suggest that i) there might be a dichotomy for the inner and outer part of the Beagle family, which may be either two separate families or the product of an anisotropic ejection velocity field and that ii) the age of the possibly younger outer part of the Beagle family should be 35 − 35 + 65 Myr. The past convergence of Beagle longitude of the node is compatible with a family age of ≃ 14 Myr, when (1678) Glarona is used as a reference orbit. Without further information on Beagle members spin states, however, only very lower limits on the family age can be currently obtained when the Yarkovksy force is accounted for. Highlights • The Beagle family is a sub-family of the larger Themis asteroid group. • It is a possible source for the dust in the i ∼ 1.4° α zodiacal dust band. • Here we obtained improved age estimates of this group. • There might be a dichotomy for the inner and outer part of the Beagle family. • The past convergence of Beagle longitude of the node suggests an age of ∼14 Myr. [ABSTRACT FROM AUTHOR]

Abstract In this paper we show that Sun-viewing images obtained by the Mars Science Laboratory (MSL) Navigation Cameras (Navcam) can be used for retrieving the dust optical depth and constrain the aerosol physical properties at Gale Crater by evaluating the sky brightness as a function of the scattering angle. We have used 65 Sun-pointing images covering a period of almost three Martian years, from MSL mission sol 21 to sol 1646 (MY 31 to 33). Radiometric calibration and geometric reduction were performed on MSL Navcam raw image data records to provide the observed sky radiance as a function of the scattering angle for the near-Sun region (scattering angle from 4° to 30°). These curves were fitted with a multiple scattering radiative transfer model for a plane-parallel Martian atmosphere model using the discrete ordinates method. Modelled sky brightness curves were generated as a function of two parameters: the aerosol particle size distribution effective radius and the dust column optical depth at the surface. A retrieval scheme was implemented for deriving the parameters that generated the best fitting curve under a least-square error criterion. The obtained results present a good agreement with previous work, showing the seasonal dependence of both dust column optical depth and the effective particle radius. [ABSTRACT FROM AUTHOR]

Highlights • We directly observe the formation of striated features in a comet's dust tail for the first time at C/2006 P1 McNaught. • We show how the temporal mapping technique - plotting dust tails in terms of radiation pressure effects against time - aligns features between multiple observations from Earth and spacecraft. • The striated tail features are shown to remain at the same locations in temporal maps over time, demonstrating the accuracy of the technique. • The mapping technique highlights a period of morphological change during 2007 January 13–14, which we argue from a comparison with solar wind simulations is from changing Lorentz force effects on dust grains as they cross the heliospheric current sheet. Abstract Striated features, or striae , form in cometary dust tails due to an as-yet unconstrained process or processes. For the first time we directly display the formation of striae, at C/2006 P1 McNaught, using data from the SOHO LASCO C3 coronagraph. The nature of this formation suggests both fragmentation and shadowing effects are important in the formation process. Using the SOHO data with STEREO-A and B data from the HI-1 and HI-2 instruments, we display the evolution of these striae for two weeks, with a temporal resolution of two hours or better. This includes a period of morphological change on 2007 January 13–14 that we attribute to Lorentz forces caused by the comet's dust tail crossing the heliospheric current sheet. The nature of this interaction also implies a mixing of different sized dust along the striae, implying that fragmentation must be continuous or cascading. To enable this analysis, we have developed a new technique – temporal mapping – that displays cometary dust tails directly in the radiation beta (ratio of radiation pressure to gravity) and dust ejection time phase space. This allows for the combination of various data sets and the removal of transient motion and scaling effects. [ABSTRACT FROM AUTHOR]

Highlights • Photometric observations of comet 29P/Schwassmann-Wachmann1 with the broad-band B, V, R, I filters are reported. • Comet showed activity and three radial features. • The gaseous-emission contribution appears to be vanishingly small, 2.5%. • Dust production Afr and its growth with the wavelength are computed. • Color slope of dust was modeled using agglomerated debris particles. • Analysis of the color slope suggests dust particles consisting of Fe-Mg silicates. Abstract We report photometric observations of comet 29P/Schwassmann-Wachmann 1 made on August 12, 2016 with the broad-band B, V, R and I filters and the SOAR 4.1-meter telescope (Chile). We find the comet active at that time. Enhanced images obtained in all filters reveal three radial features in the 29P/Schwassmann-Wachmann 1 coma, regardless of the image-processing algorithm. Using a high-resolution spectrum of comet 29P/Schwassmann-Wachmann 1 reported by Ivanova et al. (2018) on the same date, we estimate the relative contribution of the gaseous emission and the continuum to the total response measured with our broadband B and V filters. The gaseous-emission contribution appears to be very small, 2.5%. We compute the dust production Af ρ in 29P/Schwassmann-Wachmann 1 for the four filters and find its growth with the wavelength, from 3,393 ± 93 cm in the B filter to 8,561 ± 236 cm in the I filter. We model the color slope of dust in Comet 29P/Schwassmann-Wachmann 1 using agglomerated debris particles. Simultaneous analysis of the color slope in the B–R and R–I pairs suggests a single dominant chemical species of 29P/Schwassmann-Wachmann 1 dust particles consisting of Fe–Mg silicates and obeying a power-law size distribution with index n ≈ 2.55. This conclusion is consistent with the previous thermal-emission study of 29P/Schwassmann-Wachmann 1. [ABSTRACT FROM AUTHOR]

Unresolved gas and dust observations show a surprising diversity in the amount of interstellar matter in early-type galaxies. Using Atacama Large Millimetre/submillimeter Array (ALMA) observations we resolve the ISM in z  ∼ 0.05 early-type galaxies. From a large sample of early-type galaxies detected in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), we selected five of the dustiest cases, with dust masses M d ∼several × 107 M⊙, with the aim of mapping their submillimetre continuum and 12CO(2–1) line emission distributions. These observations reveal molecular gas discs. There is a lack of associated, extended continuum emission in these ALMA observations, most likely because it is resolved out or surface brightness limited, if the dust distribution is as extended as the CO gas. However, two galaxies have central continuum ALMA detections. An additional, slightly offset, continuum source is revealed in one case, which may have contributed to confusion in the Herschel fluxes. Serendipitous continuum detections further away in the ALMA field are found in another case. Large and massive rotating molecular gas discs are mapped in three of our targets, reaching a few ×109 M⊙. One of these shows evidence of kinematic deviations from a pure rotating disc. The fields of our two remaining targets contain only smaller, weak CO sources, slightly offset from the optical galaxy centres. These may be companion galaxies seen in ALMA observations or background objects. These heterogeneous findings in a small sample of dusty early-type galaxies reveal the need for more such high spatial resolution studies to understand statistically how dust and gas are related in early-type galaxies. [ABSTRACT FROM AUTHOR]

A long-term sublimation model to explain how Phaethon could provide the Geminid stream is proposed. We find that it would take ∼6 Myr or more for Phaethon to lose all of its internal ice (if ever there was) in its present orbit. Thus, if the asteroid moved from the region of a 5:2 or 8:3 mean motion resonance with Jupiter to its present orbit less than 1 Myr ago, it may have retained much of its primordial ice. The dust mantle on the sublimating body should have a thickness of at least 15 m but the mantle could have been less than 1 m thick 1000 yr ago. We find that the total gas production rate could have been as large as |$10^{27}\rm \,s^{-1}$| then, and the gas flow could have been capable of lifting dust particles of up to a few centimetres in size. Therefore, gas production during the past millennium could have been sufficient to blow away enough dust particles to explain the entire Geminid stream. For present-day Phaethon, the gas production is comparatively weak. But strong transient gas release with a rate of |${\sim }4.5\times 10^{19}\rm \,m^{-2}\,s^{-1}$| is expected for its south polar region when Phaethon moves from 0° to 2° mean anomaly near perihelion. Consequently, dust particles with radii of <∼260 μm can be blown away to form a dust tail. In addition, we find that the large surface temperature variation of >600 K near perihelion can generate sufficiently large thermal stress to cause fracture of rocks or boulders and provide an efficient mechanism to produce dust particles on the surface. The time-scale for this process should be several times longer than the seasonal thermal cycle, thereby dominating the cycle of appearance of the dust tail. [ABSTRACT FROM AUTHOR]

We develop a new method, which is based on the optimal redshift weighting scheme, to extract the maximal tomographic information of baryonic acoustic oscillations (BAO) and redshift space distortions (RSD) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 14 quasar (DR14Q) survey. We validate our method using the Extended Zel'dovich mocks, and apply our pipeline to the eBOSS DR14Q sample in the redshift range of 0.8 < |$z$| < 2.2. We report a joint measurement of f σ8 and two-dimensional BAO parameters D A and H at four effective redshifts of |$z$| eff = 0.98, 1.23, 1.52, and 1.94, and provide the full data covariance matrix. Using our measurement combined with BOSS DR12, Main Galaxy Sample (MGS), and 6 degree Field Galaxy Survey (6dFGS) BAO measurements, we find that the existence of dark energy is supported by observations at a 7.4σ significance level. Combining our measurement with BOSS DR12 and Planck observations, we constrain the gravitational growth index to be γ = 0.580 ± 0.082, which is fully consistent with the prediction of general relativity. This paper is part of a set that analyses the eBOSS DR14 quasar sample. [ABSTRACT FROM AUTHOR]

In the past few years, several independent collaborations have presented cosmological constraints from tomographic cosmic shear analyses. These analyses differ in many aspects: the data sets, the shear and photometric redshift estimation algorithms, the theory model assumptions, and the inference pipelines. To assess the robustness of the existing cosmic shear results, we present in this paper a unified analysis of four of the recent cosmic shear surveys: the Deep Lens Survey (DLS), the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS), the Science Verification data from the Dark Energy Survey (DES-SV), and the 450 deg2 release of the Kilo-Degree Survey (KiDS-450). By using a unified pipeline, we show how the cosmological constraints are sensitive to the various details of the pipeline. We identify several analysis choices that can shift the cosmological constraints by a significant fraction of the uncertainties. For our fiducial analysis choice, considering a Gaussian covariance, conservative scale cuts, assuming no baryonic feedback contamination, identical cosmological parameter priors and intrinsic alignment treatments, we find the constraints (mean, 16 per cent and 84 per cent confidence intervals) on the parameter S 8 ≡ σ8(Ωm/0.3)0.5 to be |$S_{8}=0.942_{-0.045}^{+0.046}$| (DLS), |$0.657_{-0.070}^{+0.071}$| (CFHTLenS), |$0.844_{-0.061}^{+0.062}$| (DES-SV), and |$0.755_{-0.049}^{+0.048}$| (KiDS-450). From the goodness-of-fit and the Bayesian evidence ratio, we determine that amongst the four surveys, the two more recent surveys, DES-SV and KiDS-450, have acceptable goodness of fit and are consistent with each other. The combined constraints are |$S_{8}=0.790^{+0.042}_{-0.041}$|⁠, which is in good agreement with the first year of DES cosmic shear results and recent CMB constraints from the Planck satellite. [ABSTRACT FROM AUTHOR]

We investigate the formation of extremely metal-poor (EMP) stars that are observed in the Galactic halo and neighbouring ultra-faint dwarf galaxies. Their low metal abundances ([Fe/H] < −3) indicate that their parent clouds were enriched by a single or several supernovae (SNe) from the first (Pop III) stars. In this study, we perform numerical simulations of the entire formation sequence of an EMP star through the feedback effects of photoionization and metal-enrichment by a Pop III SN. We for the first time employ a metal/dust properties calculated consistently with the progenitor model, and solve all relevant radiative cooling processes and chemical reactions including metal molecular formation and grain growth until the protostar formation. In a minihalo (MH) with mass |$1.77\times 10^{6}\, {\rm M_{\bigodot }}$|⁠, a Pop III star with mass |$13\, {\rm M_{\bigodot }}$| forms at redshift |$z$| = 12.1. After its SN explosion, the shocked gas falls back into the central MH internally enriching itself. The metallicity in the recollapsing region is |$2.6\times 10^{-4}\, {\rm Z_{\bigodot }}$| ([Fe/H] = −3.42). The recollapsing cloud undergoes cooling by HD, CO, and OH molecules and heating along with H2 formation. Eventually by grain growth and dust cooling, knotty filaments appear in the central 100 au region with the help of turbulence driven by the SN, leading to the formation of low-mass EMP stars surviving until the present day. [ABSTRACT FROM AUTHOR]

We review the complex relationship between the dust-to-gas mass ratio usually estimated in the material lost by comets, and the refractory-to-ice mass ratio inside the nucleus, which constrains the origin of comets. Such a relationship is dominated by the mass transfer from the perihelion erosion to fallout over most of the nucleus surface. This makes the refractory-to-ice mass ratio inside the nucleus up to 10 times larger than the dust-to-gas mass ratio in the lost material, because the lost material is missing most of the refractories which were inside the pristine nucleus before the erosion. We review the refractory-to-ice mass ratios available for the comet nuclei visited by space missions, and for the Kuiper Belt Objects with well-defined bulk density, finding the 1-σ lower limit of 3. Therefore, comets and KBOs may have less water than CI-chondrites, as predicted by models of comet formation by the gravitational collapse of cm-sized pebbles driven by streaming instabilities in the protoplanetary disc. [ABSTRACT FROM AUTHOR]

Measuring molecular gas mass is vital for understanding the evolution of galaxies at high redshifts (z  ≳ 1). Most measurements rely on CO as a tracer, but dependencies on metallicity, dynamics, and surface density lead to systematic uncertainties in high- z galaxies, where these physical properties are difficult to observe, and where the physical environments can differ systematically from those at z  = 0. Dust continuum emission provides a potential alternative assuming a known dust/gas ratio, but this must be calibrated on a direct gas tracer at z  ≳ 1. In this paper, we consider the [C  i ] 492-GHz emission line, which has been shown to trace molecular gas closely throughout Galactic clouds and has the advantages of being optically thin in typical conditions (unlike CO), and being observable at accessible frequencies at high redshifts (in contrast to the low-excitation lines of CO). We use the Atacama Large Millimetre/submillimetre Array to measure [C  i ], CO(4–3), and dust emission in a representative sample of star-forming galaxies at z  = 1, and combine these data with multiwavelength spectral energy distributions to study relationships between dust and gas components of galaxies. We uncover a strong [C  i ]–dust correlation, suggesting that both trace similar phases of the gas. By incorporating other samples from the literature, we show that this correlation persists over a wide range of luminosities and redshifts up to z  ∼ 4. Finally, we explore the implications of our results as an independent test of literature calibrations for dust as a tracer of gas mass, and for predicting the C  i abundance. [ABSTRACT FROM AUTHOR]

Cold neutral gas is a key ingredient for growing the stellar and central black hole mass in galaxies throughout cosmic history. We have used the Atacama Large Millimetre Array to detect a rare example of redshifted 12CO (2–1) absorption in PKS B1740–517, a young (t ∼ 1.6 × 103 yr) and luminous (⁠|$L_{\rm 5\, GHz} \approx 6.6 \times 10^{43}$|  erg s−1) radio galaxy at |$z$|  = 0.44 that is undergoing a tidal interaction with at least one lower mass companion. The coincident H  i 21-cm and molecular absorption have very similar line profiles and reveal a reservoir of cold gas (M gas ∼ 107−108 M⊙), likely distributed in a disc or ring within a few kiloparsecs of the nucleus. A separate H  i component is kinematically distinct and has a very narrow line width (Δ |$v$| FWHM ≲ 5 km s−1), consistent with a single diffuse cloud of cold (T k ∼ 100 K) atomic gas. The 12CO (2–1) absorption is not associated with this component, which suggests that the cloud is either much smaller than 100 pc along our sight line and/or located in low-metallicity gas that was possibly tidally stripped from the companion. We argue that the gas reservoir in PKS B1740–517 may have accreted on to the host galaxy ∼ 50 Myr before the young radio AGN was triggered, but has only recently reached the nucleus. This is consistent with the paradigm that powerful luminous radio galaxies are triggered by minor mergers and interactions with low-mass satellites and represent a brief, possibly recurrent, active phase in the life cycle of massive early-type galaxies. [ABSTRACT FROM AUTHOR]

Remote sensing observations of dust particles ejected from comets provide important hints on the intimate nature of the materials composing these primitive objects. The measurement of dust coma backscattering ratio, BSR, defined as the ratio of the reflectance at phase angle 0° and 30°, helps tuning theoretical models aimed at solving the inverse scattering problem deriving information on the nature of the ejected particles. The Rosetta /OSIRIS camera sampled the coma phase function of comet 67P, with four series acquired at low phase angles from 2015 January to 2016 May. We also added previously published data to our analysis to increase the temporal resolution of our findings. We measured a BSR in the range ∼ [1.7–3.6], broader than the range found in literature from ground-based observations of other comets. We found that during the post-perihelion phase, the BSR is systematically larger than the classical cometary dust values only for nucleocentric distances smaller than ∼100 km. We explain this trend in terms of a cloud of chunks orbiting the nucleus at distances <100 km ejected during perihelion and slowly collapsing on the nucleus over a few months because of the coma gas drag. This also implies that the threshold particle size for the dust phase function to become similar to the nucleus phase function is between 2.5 mm and 0.1 m, taking into account previous Rosetta findings. [ABSTRACT FROM AUTHOR]

Recent discoveries of massive black holes (MBHs) in dwarf galaxies suggest that they may have a more common presence than once thought. Systematic searches are revealing more candidates, but this process could be accelerated by predictions from simulations. We perform a study of several high-resolution, cosmological, zoom-in simulations focusing on dwarf galaxies that host massive black holes at |$z$|  = 0, with the aim of determining when the black holes are most observable. Larger dwarf galaxies are more likely to host MBHs than those of lower mass. About 50 per cent of the MBHs in dwarfs are not centrally located, but rather are wandering within a few kpc of the galaxy centre. The accretion luminosities of MBHs in dwarfs are low throughout cosmic time, rendering them extremely difficult to detect. However, the merger history of these MBHs is optimal for gravitational wave detection by LISA. [ABSTRACT FROM AUTHOR]

Planet migration in protoplanetary discs plays an important role in the longer term evolution of planetary systems, yet we currently have no direct observational test to determine if a planet is migrating in its gaseous disc. We explore the formation and evolution of dust rings – now commonly observed in protoplanetary discs by the Atacama Large Millimeter/submillimeter Array – in the presence of relatively low-mass (12–60 |$\rm M_{\oplus }$|⁠) migrating planets. Through 2D hydrodynamical simulations using gas and dust we find that the importance of perturbations in the pressure profile interior and exterior to the planet varies for different particle sizes. For small sizes, a dust enhancement occurs interior to the planet, whereas it is exterior to it for large particles. The transition between these two behaviours happens when the dust drift velocity is comparable to the planet migration velocity. We predict that an observational signature of a migrating planet consists of a significant outwards shift of an observed mid-plane dust ring as the wavelength is increased. [ABSTRACT FROM AUTHOR]

Large-scale outflows of different gas phases are ubiquitous in the host galaxies of active galactic nuclei (AGNs). Despite their many differences, they share a common property – they all contain dust. The dust is carried with the outflow, heated by the AGN, and emits at infrared wavelengths. This paper shows that the infrared emission of this dust can be used to detect AGN outflows and derive their properties. We use a sample of ∼4000 type II AGNs and compare the infrared properties of systems that show a spectroscopic signature of ionized gas outflows to those of systems that do not. We detect an additional mid-infrared emission component in galaxies with spectroscopically discovered winds, and attribute it to the dust in the outflow. This new component offers novel constraints on the outflow properties, such as its mean location and covering factor. We measure the location of the outflow for ∼1700 systems, with the distribution showing a prominent peak around r ∼ 200 pc, a tail that extends to large distances (∼1 kpc), and no objects with a location smaller than 10 pc. The covering factor of the wind shows a wide distribution, which is centred around 0.1, with 24 per cent (8 per cent) of the winds showing covering factors larger than 0.2 (0.5). The dust emission is not sensitive to various systematics affecting optically selected outflows, and can be used to estimate the mass outflow rate in thousands of galaxies with only 1D spectra. [ABSTRACT FROM AUTHOR]

During six nights between January and March 2018 we observed the mesospheric Ni layer by lidar from Kühlungsborn, Germany (54°N, 12°E). For most of the soundings we utilized for the first time a transition from the low‐lying excited Ni(3D) state at 341 nm. For additional soundings we used the ground‐state Ni(3F) transition at 337 nm, giving similar results but a worse signal‐to‐noise ratio. We observed nightly mean Ni peak densities between ∼280 and 450 cm−3 and column abundances between 3.1·108 and 4.9·108 cm−2. Comparing with iron densities we get a Fe/Ni ratio of 38, which is a factor of 2 larger than the ratio in CI chondrites and factor of 32 larger than the Fe/Ni ratio observed by the only previous measurement of mesospheric Ni (Collins et al., 2015, https://doi.org/10.1002/2014GL062716). The underabundance of Ni compared to CI chondrites suggests that Ni is more efficiently sequestered as Ni+ or neutral reservoir species than Fe. Plain Language Summary: In the upper mesosphere between 80‐ and 100‐km altitude, layers of gaseous metals occur whose source is the evaporation of cosmic dust particles, which undergo severe heating when entering the atmosphere. Metals like sodium or iron have been observed for many years by ground‐based laser radar instruments (lidars). Here we report the second‐ever set of observations of nickel (Ni) in the mesosphere. For the first time we used an absorption line in the UV from a slightly excited state of Ni, which provides a much stronger signal‐to‐noise ratio compared to earlier soundings. We observed Ni peak densities between 280 and 450/ccm, which is a factor of 2 lower than expected from Fe measurements and the relative abundances of these elements in cosmic dust. This suggests small differences in chemical reaction rates, converting Ni into Ni‐containing molecules, which are invisible to the lidar, compared to Fe. Observed densities are a factor of 32 lower with respect to Fe than reported in the earlier study in Alaska, and this needs to be further examined. Key Points: First observation of the mesospheric Ni layer from metastable Ni(3D) state revealed peak densities of 280–450 cm−3Compared to Fe and their respective abundance in CI chondrites, Ni is depleted by a factor of about 2Observations hint at faster‐than‐expected conversion of Ni into ions and neutral reservoir molecules [ABSTRACT FROM AUTHOR]

Abstract This study explores the petrology of five giant (>400 μm) hydrated fine-grained micrometeorites from the Transantarctic Mountain (TAM) micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these micrometeorites represent ∼2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of <1.2 in the scheme of Howard et al. (2015)) and reveal a range of alteration styles. Two particles are found to contain pseudomorphic chondrules with thick fine-grained rims, while another micrometeorite contains several aqueously altered CAIs. Their outlines range from well-defined to indistinct, demonstrating that the advanced stages of aqueous alteration progressively remove evidence of coarse-grained components. The remaining two micrometeorites entirely lack coarse-grained components but are similarly altered. Thus, the combined chondrule-to-matrix ratio among these giant micrometeorites is extremely low (6.45 area%), and significantly below the average ratio found in typical CM or CR chondrites (∼20%, Weisberg et al., 2006). Our findings are consistent with previous analyses from smaller Antarctic micrometeorites, which suggest that chondrules (and CAIs) derived from hydrated carbonaceous chondrite parent bodies are underrepresented among the micrometeorite flux, even when considering contributions from coarse-grained micrometeorites. Therefore, to explain the relative paucity of anhydrous material, we propose that the flux of fine-grained micrometeorites is primarily derived from intensely aqueously altered, primitive C-type asteroids, which have lost the majority of their refractory coarse-grained components by replacement with secondary phyllosilicate minerals. [ABSTRACT FROM AUTHOR]

We present ALMA images of the sub-mm continuum polarization and spectral index of the protoplanetary ringed disc HD163296. The polarization fraction at 870 µm is measured to be ∼0.9 per cent in the central core and generally increases with radius along the disc major axis. It peaks in the gaps between the dust rings, and the largest value (∼4 per cent) is found between rings 1 and 2. The polarization vectors are aligned with the disc minor axis in the central core, but become more azimuthal in the gaps, twisting by up to ±9° in the gap between rings 1 and 2. These general characteristics are consistent with a model of self-scattered radiation in the ringed structure, without requiring an additional dust alignment mechanism. The 870/1300 µm dust spectral index exhibits minima in the centre and the inner rings, suggesting these regions have high optical depths. However, further refinement of the dust or the disc model at higher resolution is needed to reproduce simultaneously the observed degree of polarization and the low spectral index. [ABSTRACT FROM AUTHOR]

The JSC curation branch has been an amazing place to work, for too many reasons to adequately detail here, but one of the major reasons is the caliber of people there who care for the labs and samples. Dave McKay was very good friends with Hiroshi Takeda, and Masamichi Miyamoto and Akira Tsuchiyama were postdocs at JSC when I arrived. Two JSC curation scientists left NASA to work at other labs (something that has not happened since), and there was an immediate need in the curation office for someone who knew about cosmic dust. [Extracted from the article]