Dust Component Research Articles

Short- and medium-chain chlorinated paraffins in urban road dust of Shanghai, China: concentrations, source apportionment and human exposure assessment.

Chlorinated paraffins (CPs) are ubiquitous anthropogenic contaminants that have been found in various environmental media. The objective of this study was to determine concentrations, spatial distribution, possible sources and potential health risk of SCCPs and MCCPs in urban road dust collected from Shanghai, China. The concentrations ranged from 9.74 to 11,400ngg-1 for ΣSCCPs, 44.1 to 49,900ngg-1 for ΣMCCPs and 53.9 to 61,400ngg-1 for total CPs, respectively. MCCPs were the dominant component in all road dust, averagely accounting for 82.8% of total CPs. The concentrations of CPs in dust collected from traffic and commercial areas were significantly higher than those from campus, industrial, park and residential areas (p < 0.01), which could be attributed to tire wear in heavy traffic. All dust samples were divided into two groups by hierarchical cluster analysis for both SCCPs and MCCPs, and the most abundant homologue groups in most samples were C10Cl7-10 and C13Cl7-9 for SCCPs, and C14Cl7-9 and C15Cl8-9 for MCCPs. Correlation analysis showed that all carbon homologues in road dusts were highly correlated each other, suggesting SCCPs and MCCPs in dust maybe came from similar sources. Three sources for CPs in dust samples were apportioned by the PMF model; their relative contributions to the total CPs burden in dust were 25.6% for factor 1 (commercial CP mixture), 13.7% for factor 2 (long-distance transport) and 60.7% for factor 3 (commercial CP mixture). The median estimated daily intakes of total CPs via road dust were 1.78 × 10-5 for children and 3.0 × 10-6mgkg-1day-1 for adults, respectively. Quantitative risk assessment using non-cancer hazard index and total margin of exposure of total CPs indicated that total CPs at the present level in road dust pose no significant risk for both children and adults in Shanghai.

Numerical modeling of open pit aeration under major blasts according to the dust factor

Research objective is to estimate the effect of major blast location, dust and gas cloud initial height, the wind current velocity at the upper pit slope on the time of pit aeration and on the level of atmospheric pollution of the upper pit slope downwind according to the dust factor. Methods of research. Aerodynamics and fine dust transport in 2D geometry was modeled in the COMSOL program. The aerodynamic characteristics were calculated using the incompressible fluid approximation with the standard (k–ε) turbulence model. The process of fine dust spreading is modeled by numerically calculating the convective-diffusion equation for pollutants transfer, considering the settling rate. Numerical experiments were performed under a fixed initial concentration of fine dust and varying velocity of the oncoming wind current for three locations of major blasts and six values of the dust and gas cloud initial height (from 70 to 420 m with a step of 70 m). Results and analysis. Significant qualitative (but not quantitative) similarity was noted in the calculated spatial-temporal parameters for fine dust and the gas component. It is shown that for the recirculation aeration scheme, the longest duration of pit cleaning from dust is observed during major blasts displaced to the weather pit slope. A wave-like removal is predicted of dust pollutants with different heights of peaks and time to reach the peak value. Differences are demonstrated in the processes of pit aeration during major blasts in terms of fine dust and gas component, which do not contradict the physics of the process. Conclusions and scope. A functional dependence has been obtained, which makes it possible to predict the time of reaching the first peak of dust pollution at the upper pit slope downstream as a function of two variables, namely, the initial height of the dust and gas cloud rise and the oncoming wind current velocity.

Effect of Negative Ion Generation on Complex Plasma Structure Properties.

We propose a low-density discharge plasma model that takes into account the impact of oxygen admixture in typical conditions of complex (dusty) plasmas. Numerical simulations based on this model show that the concentration of negative ions turns out to be very high, and they play an important role in the overall kinetics in this particular range of plasma conditions. The ambipolar diffusion electric field drags these negative ions into the center of the plasma. The density of negative ions is high enough to push the negatively charged dust component out of the center, both by weakening the radial electric field and by increasing the thermophoretic force. This phenomenon was observed in the published experiment and qualitatively supports the proposed model. Additionally, the proposed model allows an alternative explanation of the experiment.

Heterogeneous Formation of Organonitrates (ON) and Nitroxy-Organosulfates (NOS) from Adsorbed α-Pinene-Derived Organosulfates (OS) on Mineral Surfaces.

Organonitrates (ON) and nitroxy-organosulfates (NOS) are important components of secondary organic aerosols (SOAs). Gas-phase reactions of α-pinene (C10H16), a primary precursor for several ON compounds, are fairly well understood although formation pathways for NOS largely remain unknown. NOS formation may occur via reactions of ON and organic peroxides with sulfates as well as through radical-initiated photochemical processes. Despite the fact that organosulfates (OS) represent a significant portion of the organic aerosol mass, ON and NOS formation from OS is less understood, especially through nighttime heterogeneous and multiphase chemistry pathways. In the current study, surface reactions of adsorbed α-pinene-derived OS with nitrogen oxides on hematite and kaolinite surfaces, common components of mineral dust, have been investigated. α-Pinene reacts with sulfated mineral surfaces, forming a range of OS compounds on the surface. These OS compounds when adsorbed on mineral surfaces can further react with HNO3 and NO2, producing several ON and NOS compounds as well as several oxidation products. Overall, this study reveals the complexity of reactions of prevalent organic compounds leading to the formation of OS, ON, and NOS via heterogeneous and multiphase reaction pathways on mineral surfaces. It is also shown that this chemistry is mineralogy-specific.

Quantum mechanical modeling of interstellar molecules on cosmic dusts: H2O, NH3, and CO2.

Since the first detection of CH molecule in interstellar medium (ISM), more than 270 molecules have been identified in various astronomical sources in ISM. These molecules include big complex ones, such as fullerene (C60) and polycyclic aromatic hydrocarbons (PAHs), which are the main components of carbonaceous dust. Dust surface chemistry plays an important role in explaining the formation of interstellar molecules. However, many of the dust surface chemical parameters, such as the adsorption energies, are still of uncertainty. Here we present a study of the adsorption of water (H2O), ammonia (NH3), and carbon dioxide (CO2) on graphene-like substrate within the framework of density functional theory (DFT). We used Gaussian 16 software and adopted the corrected generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functions. We determined the optimal accretion position of the studied molecules on the graphene-like surface and calculated the adsorption energies. Furthermore, according to the density of states and molecular orbitals of the adsorbed states, we analyzed the charge transfer between the molecules and the graphene-like surface. These results can provide more accurate parameters for calculating the chemical reaction rates on the dust surface, thus contributing to the understanding of dust-surface reactions in ISM.

The effective equation of state in Rastall gravity

In this paper, we study a homogeneous and isotropic flat Friedmann–Robertson–Walker (FRW) universe in Rastall gravity, in which there exist the components of radiation and dust. That is to say, the density of fluid [Formula: see text] satisfies the barotropic equation of state [Formula: see text], where [Formula: see text] and [Formula: see text], and the equation of state [Formula: see text]. We derive the modified Friedmann equations, and the effective equation of state [Formula: see text] in this universe model. For the dust-dominated case, the effective equation of state [Formula: see text] is described by [Formula: see text], where [Formula: see text] is the Rastall parameter. As [Formula: see text], we have [Formula: see text] which means an accelerated expansion of the universe occurs. Along with the conditions for the convergent modified Friedmann equations and the positive density of dust, the Rastall parameter [Formula: see text] should be in the range of [Formula: see text]. In other words, the various [Formula: see text] for [Formula: see text] correspond to those of quintessence with the general barotropic equation of state [Formula: see text]. For the general case, the Rastall universe full of radiation and dust, the expression of [Formula: see text] is complicated involving the Rastall parameter, the density of radiation and the density of dust. As the ratio of the densities of dust and radiation is smaller than [Formula: see text], [Formula: see text] is less than [Formula: see text]. Moreover, to keep the density of dust positive, the Rastall parameter should be restricted in [Formula: see text] too. By the numerical calculation, we find that [Formula: see text] from [Formula: see text] decreases as [Formula: see text] increases. And [Formula: see text] for different [Formula: see text] ultimately tend to [Formula: see text], the value of which are in the range of [Formula: see text]. Obviously, the expansion of the cosmology filled with radiation and dust or only dust in Rastall gravity [Formula: see text] accelerates without any “exotic” energy whose equation of state [Formula: see text].

Structure formation in the effective field theory of holographic dark energy

We investigate the structure formation in the effective field theory (EFT) of the holographic dark energy. The equation of motion for the energy contrast δ m of the cold dark matter is the same as the one in the general relativity up to the leading order in the small scale limit, provided the equation of state is quintessence-like. Our EFT breaks down while the equation of state becomes phantom-like. By imposing additional constraints by hand at the Hamiltonian level the unstable scalar graviton can be eliminated solving the instability problem without changing the background evolution. In this case depending on the form of the constraint the effective gravitational constant can be modified and the dust component can obtain a non-vanishing sound speed.

Unveiling the warm and dense ISM in z &gt; 6 quasar host galaxies via water vapor emission

Water vapor (H2O) is one of the brightest molecular emitters after carbon monoxide (CO) in galaxies with high infrared (IR) luminosity, allowing us to investigate the warm and dense phase of the interstellar medium (ISM) where star formation occurs. However, due to the complexity of its radiative spectrum, H2O is not frequently exploited as an ISM tracer in distant galaxies. Therefore, H2O studies of the warm and dense gas at high-z remain largely unexplored. In this work, we present observations conducted with the Northern Extended Millimeter Array (NOEMA) toward three z &gt; 6 IR-bright quasars J2310+1855, J1148+5251, and J0439+1634 targeted in their multiple para- and ortho-H2O transitions (312 − 303, 111 − 000, 220 − 211, and 422 − 413), as well as their far-IR (FIR) dust continuum. By combining our data with previous measurements from the literature, we estimated the dust masses and temperatures, continuum optical depths, IR luminosities, and star formation rates (SFR) from the FIR continuum. We modeled the H2O lines using the MOLPOP-CEP radiative transfer code, finding that water vapor lines in our quasar host galaxies are primarily excited in the warm, dense (with a gas kinetic temperature and density of Tkin = 50 K, nH2 ∼ 104.5 − 105 cm−3) molecular medium with a water vapor column density of NH2O ∼ 2 × 1017 − 3 × 1018 cm−3. High-J H2O lines are mainly radiatively pumped by the intense optically-thin far-IR radiation field associated with a warm dust component at temperatures of Tdust ∼ 80 − 190 K that account for &lt; 5 − 10% of the total dust mass. In the case of J2310+1855, our analysis points to a relatively high value of the continuum optical depth at 100 μm (τ100 ∼ 1). Our results are in agreement with expectations based on the H2O spectral line energy distribution of local and high-z ultra-luminous IR galaxies and active galactic nuclei (AGN). The analysis of the Boltzmann diagrams highlights the interplay between collisions and IR pumping in populating the high H2O energy levels and it allows us to directly compare the excitation conditions in the targeted quasar host galaxies. In addition, the observations enable us to sample the high-luminosity part of the H2O–total-IR (TIR) luminosity relations (LH2O − LTIR). Overall, our results point to supralinear trends that suggest H2O–TIR relations are likely driven by IR pumping, rather than the mere co-spatiality between the FIR continuum- and line-emitting regions. The observed LH2O/LTIR ratios in our z &gt; 6 quasars do not show any strong deviations with respect to those measured in star-forming galaxies and AGN at lower redshifts. This supports the notion that H2O can be likely used to trace the star formation activity buried deep within the dense molecular clouds.

Dust extinction map of the Galactic plane based on the VVV survey data

ABSTRACT Dust extinction is one of the most reliable tracers of the gas distribution in the Milky Way. The near-infrared (NIR) Vista Variables in the Vía Láctea (VVV) survey enables extinction mapping based on stellar photometry over a large area in the Galactic plane. We devise a novel extinction mapping approach, XPNICER, by bringing together VVV photometric catalogues, stellar parameter data from StarHorse catalogues, and previously published X percentile and PNICER extinction mapping techniques. We apply the approach to the VVV survey area, resulting in an extinction map that covers the Galactic disc between 295° ≲ l ≲ 350° and −2° ≲ b ≲ 2°, and the Galactic bulge between −10° ≲ b ≲ 5°. The map has 30 arcsec spatial resolution and it traces extinctions typically up to AV ∼ 10–20 mag and maximally up to AV ∼ 30 mag. We compare our map to previous dust-based maps, concluding that it provides a high-fidelity extinction-based map, especially in its ability to recover both the diffuse dust component of the Galaxy and moderately extincted giant molecular cloud regions. The map is especially useful as independent, extinction-based data on the Galactic dust distribution and applicable for a wide range of studies from individual molecular clouds to the studies of the Galactic stellar populations.

Discovering Ca ii absorption lines with a neural network

ABSTRACT Quasar absorption line analysis is critical for studying gas and dust components and their physical and chemical properties as well as the evolution and formation of galaxies in the early universe. Calcium II (Ca ii) absorbers, which are one of the dustiest absorbers and are located at lower redshifts than most other absorbers, are especially valuable when studying physical processes and conditions in recent galaxies. However, the number of known quasar Ca ii absorbers is relatively low due to the difficulty of detecting them with traditional methods. In this work, we developed an accurate and quick approach to search for Ca ii absorption lines using deep learning. In our deep learning model, a convolutional neural network, tuned using simulated data, is used for the classification task. The simulated training data are generated by inserting artificial Ca ii absorption lines into original quasar spectra from the Sloan Digital Sky Survey (SDSS), while an existing Ca ii catalogue is adopted as the test set. The resulting model achieves an accuracy of 96 per cent on the real data in the test set. Our solution runs thousands of times faster than traditional methods, taking a fraction of a second to analyse thousands of quasars, while traditional methods may take days to weeks. The trained neural network is applied to quasar spectra from SDSS’s DR7 and DR12 and discovered 399 new quasar Ca ii absorbers. In addition, we confirmed 409 known quasar Ca ii absorbers identified previously by other research groups through traditional methods.

Toward a population synthesis of disks and planets

Context. Millimeter astronomy provides valuable information on the birthplaces of planetary systems. In order to compare theoretical models with observations, the dust component has to be carefully calculated. Aims. Here, we aim to study the effects of dust entrainment in photoevaporative winds, and the ejection and drag of dust due to the effects caused by radiation from the central star. Methods. We improved and extended the existing implementation of a two-population dust and pebble description in the global Bern/Heidelberg planet formation and evolution model. Modern prescriptions for photoevaporative winds were used and we accounted for settling and advection of dust when calculating entrainment rates. In order to prepare for future population studies with varying conditions, we explored a wide range of disk, photoevaporation, and dust parameters. Results. If dust can grow to pebble sizes, that is, if they are resistant to fragmentation or turbulence is weak, drift dominates and the entrained mass is small but larger than under the assumption of no vertical advection of grains with the gas flow. For the case of fragile dust shattering at velocities of 1m s−1 – as indicated in laboratory experiments –, an order of magnitude more dust is entrained, which becomes the main dust removal process. Radiation pressure effects disperse massive, dusty disks on timescales of a few hundred Myr. Conclusions. These results highlight the importance of dust entrainment in winds as a solid-mass removal process. Furthermore, this model extension lays the foundations for future statistical studies of the formation of planets in their birth environment.

Low-temperature optical constants of amorphous silicate dust analogues

Context. Cosmic dust models are key ingredients in advancing our understanding of astronomical environments as diverse as interstellar clouds in galaxies, circumstellar envelopes around evolved and young stars, and protoplanetary disks. Such models consist of several dust populations, each with different compositions and size distributions. They may also consider different grain shapes, although most models assume spherical grains. All include a component of silicate dust. The absorption and emission properties of these dust components are calculated from the optical constants of each dust material which have various experimental, phenomenological, and theoretical origins depending on the model. Aims. We aim to provide the community with new sets of optical constants for amorphous silicate dust analogues at low temperatures. The analogues consist of four Mg-rich silicate samples of stoichiometry ranging from enstatite to olivine, and of eight samples of Mg- and Fe-rich silicates with a pyroxene stoichiometry and differing magnesium and iron content. Methods. We calculated the optical constants from transmission measurements using the Kramers-Kronig relations, assuming that the grains are small compared to the wavelength and prolate in shape with axis ratios of 1.5 and 2 for the Mg- and Fe-rich samples, respectively. Results. New optical constants for silicate dust analogues of various compositions were calculated over the wavelength range from 5 to 800 µm or 1000 µm, depending on the sample, and at temperatures of 10, 30, 100, 200, and 300 K. We determined the uncertainties on the derived optical constants based on the assumptions used to calculate them. To facilitate the use of these data in cosmic dust models, we provide optical constants extrapolated outside the measured spectral range into the ultraviolet(UV)/visual(VIS)/near-infrared(NIR) and millimetre and centimetre wavelength ranges, as well as formulae that can be used to interpolate the optical constants at any temperature in the range 10–300 K.

The Chocolate Chip Cookie Model: Dust Geometry of Milky Way–like Disk Galaxies

We present a new two-component dust geometry model, the Chocolate Chip Cookie model, where the clumpy nebular regions are embedded in a diffuse stellar/interstellar medium disk, like chocolate chips in a cookie. By approximating the binomial distribution of the clumpy nebular regions with a continuous Gaussian distribution and omitting the dust scattering effect, our model solves the dust attenuation process for both the emission lines and stellar continua via analytical approaches. Our Chocolate Chip Cookie model successfully fits the inclination dependence of both the effective dust reddening of the stellar components derived from stellar population synthesis and that of the emission lines characterized by the Balmer decrement for a large sample of Milky Way–like (MW-like) disk galaxies selected from the main galaxy sample of the Sloan Digital Sky Survey. Our model shows that the clumpy nebular disk is about 0.55 times thinner and 1.6 times larger than the stellar disk for MW-like galaxies, whereas each clumpy region has a typical optical depth of τ cl,V ∼ 0.5 in the V band. After considering the aperture effect, our model prediction on the inclination dependence of dust attenuation is also consistent with observations. Not only that, in our model, the dust attenuation curve of the stellar population naturally depends on the inclination, and its median case is consistent with the classical Calzetti law. As the modeling constraints are from the optical wavelengths, our model is unaffected by the optically thick dust component, which however could bias the model’s prediction of the infrared emissions.

Dust reverberation mapping and light-curve modelling of Zw229-015

ABSTRACT Multiwavelength variability studies of active galactic nuclei can be used to probe their inner regions that are not directly resolvable. Dust reverberation mapping (DRM) estimates the size of the dust emitting region by measuring the delays between the infrared (IR) response to variability in the optical light curves. We measure DRM lags of Zw229-015 between optical ground-based and Kepler light curves and concurrent IR Spitzer 3.6 and 4.5 µm light curves from 2010 to 2015, finding an overall mean rest-frame lag of 18.3 ± 4.5 d. Each combination of optical and IR light curve returns lags that are consistent with each other within 1σ, which implies that the different wavelengths are dominated by the same hot dust emission. The lags measured for Zw229-015 are found to be consistently smaller than predictions using the lag–luminosity relationship. Also, the overall IR response to the optical emission actually depends on the geometry and structure of the dust emitting region as well, so we use Markov chain Monte Carlo modelling to simulate the dust distribution to further estimate these structural and geometrical properties. We find that a large increase in flux between the 2011–2012 observation seasons, which is more dramatic in the IR light curve, is not well simulated by a single dust component. When excluding this increase in flux, the modelling consistently suggests that the dust is distributed in an extended flat disc, and finds a mean inclination angle of 49$^{+3}_{-13}$ deg.

Measurement report: The 10-year trend of PM2.5 major components and source tracers from 2008 to 2017 in an urban site of Hong Kong, China

Abstract. Fine particulate matter (PM2.5) remains a major air pollutant of significant public health concern in urban areas. Long-term monitoring data of PM2.5 chemical composition and source-specific tracers provide essential information for the identification of major sources as well as evaluation and planning of control measures. In this study, we present and analyze a 10-year dataset of PM2.5 major components and source-specific tracers (e.g., levoglucosan, hopanes, K+, Ni, V, Al, and Si) collected over the period of 2008–2017 in an urban site in Hong Kong, China. The time series of pollutants were analyzed by the seasonal and trend decomposition using the locally estimated scatter plot smoothing (LOESS) method and general least squares with the autoregressive moving average method. Bulk PM2.5 and all its major components displayed a significant decline of varying degrees over the decade. PM2.5 was reduced by 40 % at −1.5 µgm-3yr-1. PM2.5 components that are predominantly influenced by local vehicular emissions showed the steepest decline, with nitrate decreasing by −66 %, elemental carbon by −60 %, and hopanes by −75 %, confirming effective control of local vehicular emissions. For components that are significantly impacted by regional transport and secondary formation, they had a notably lower percentage reduction, with sulfate declining by −40 % and organic carbon by −23 %, reflecting complexity in their region-wide contributing sources and formation chemistry. Levoglucosan and K+, two tracers for biomass burning, differed in their reduction extent, with K+ at −60 % and levoglucosan at −47 %, indicating they likely track different biomass burning types. Dust components in PM2.5 also decreased, by −37 % for Al and −46 % for Si. The year of 2011 was an anomaly in the overall trend in having higher concentrations of PM2.5 and components than its adjacent years, and the long time series analysis attributed the anomaly to unusually lower rainfall associated with strong La Niña events. This 10-year trend analysis based on measurements exemplifies the utility of chemical composition data in support of an evidence-based approach for control policy formulation.

Determination of Dust Emission Fractions as an Optimizing Tool for Monitoring and Managing the Quality of Atmospheric Air

Comprehensive studies of dust emissions were performed and the dust components profile of the main sources was determined using industrial example. Based on the results of dispersion calculations and a study of the quality of atmospheric air in the adjacent territory, the share contribution of the enterprise to the total air pollution was identified and priority (marker) substances for production were identified. Conclusions were drawn about the reliability of using the dust emission profile as a tool for assessing the actual impact of the enterprise in terms of monitoring, standardization and quotas.

Spatial disconnection between stellar and dust emissions: The test of the Antennae Galaxies (Arp 244)

Context. The detection of dust-rich high-redshift galaxies with the Atacama Large Millimeter Array (ALMA), the cold dust emission of which is spatially disconnected from the ultraviolet emission, bears a challenge for modelling their spectral energy distributions (SEDs) with codes based on an energy budget between the stellar and dust components. Aims. We want to test the validity of energy balance modelling on a nearby resolved galaxy with vastly different ultraviolet and infrared spatial distributions and to decipher the kinds of information that can be reliably retrieved from the analysis of the full SED. Methods. We used 15 broadband images of the Antennae Galaxies ranging from far-ultraviolet to far-infrared and divided Arp 244 into 58 square ∼1 kpc2 regions. We fit the data with CIGALE to determine the star formation rate, stellar mass, and dust attenuation of each region. We compared these quantities to those obtained for Arp 244 as a whole. Results. The SEDs of the 58 regions and Arp 244 are well fitted. The estimates of the star formation rate and stellar mass for the whole galaxy are found to be consistent – within one sigma – with the same parameters summed over the 58 regions. We present the spatial distribution of these physical parameters as well as the shape of the attenuation curve across the Antennae Galaxies. We find that the Overlap Region exhibits a high star formation rate, attenuation, and a shallow attenuation curve. We observe a flattening of the attenuation curves with increasing attenuation and dust surface density in agreement with the predictions of hydrodynamical simulations coupled with radiative transfer modelling.

Response of eolian quartz flux and grain size in the Parece Vela Basin sediment to the mid-Pleistocene transition

The most significant climate changes in the Quaternary occurred in the mid-Pleistocene transition (MPT). However, as the main component of eolian dust, it remains unknown how the fluxes and components of quartz responded to the MPT. We recovered a sediment core from the Parece Vela Basin (PVB), which dated back to 2.1 Ma, and quantitatively separated quartz from the sediments in order to track source area and transport mechanism. The grain size compositions, morphological characteristics, oxygen isotope compositions, and crystallinity indices of quartz showed that quartz minerals in the sediments were composed of fine-grained endmembers (EM1) with a mode grain size at 3.2 μm, and coarse-grained endmembers (EM2) with a mode grain size at 9.5 μm. The EM1 quartz mainly came from the Mongolian Gobi and Taklimakan Desert, and the EM2 quartz was predominantly derived from volcanic island arc. By fitting the grain size composition with the Weibull function, we were able to quantitatively separated EM1 and EM2 quartz fractions, and calculated the contents and mass accumulation rates (MARs) of eolian quartz. The mode grain sizes of eolian quartz increased at 1.2 Ma, but fluctuated during the mid-Pleistocene. The MARs of the eolian quartz have increased significantly since the mid-Pleistocene, most likely due to enhanced aridity in the Asia interior. Our study demonstrates that eolian quartz in the northwest Pacific can be used to trace the long-term paleoclimate change in the Asia continent.

Martian Atmospheric Spectral End‐Members Retrieval From ExoMars Thermal Infrared (TIRVIM) Data

AbstractKey knowledge about planetary composition can be recovered from the study of thermal infrared spectral range datasets. This range has a huge diagnostic potential because it contains diagnostic absorptions from a planetary surface and atmosphere. The main goal of this study is to process and interpret the dataset from the Thermal Infrared channel (TIRVIM) which is part of the Atmospheric Chemistry Suite of the ExoMars2016 Trace Gas Orbiter mission to find and characterize dust and water ice clouds in the atmosphere. The method employed here is based on the application of principal component analysis and target transformation techniques to extract the independent variable components present in the analyzed dataset. Spectral shapes of both atmospheric dust and water ice aerosols have been recovered from the analysis of TIRVIM data. The comparison between our results with those previously obtained on Thermal Emission Spectrometer (TES) data and with previous analysis on TIRVIM data, validates the methodology here applied, showing that it allows to correctly recover the atmospheric spectral endmembers present in the TIRVIM data. Moreover, comparison with atmospheric retrievals on PFS, TES and IRIS data, allowed us to assess the temporal stability and homogeneity of dust and water ice components in the Martian atmosphere over a time period of almost 50 years.

Radio Variability and Broad-Band Spectra of Infrared Galaxies with and without OH Megamaser Emission

We study the radio variability of galaxies with and without sources of hydroxyl (OH) megamaser radiation based on the continuum radio measurements conducted in 2019-2022 with the radio telescope RATAN-600 at frequencies of 2.3, 4.7, 8.2, and 11.2 GHz. Presumably, radio continuum emission significantly affects the megamaser radiation brightness, therefore, such a characteristic as the variability of radio emission is important for determining the OHM galaxies parameters. With additional data from the literature, the parameters of radio variability on a time scale up to 30 years were estimated. The median values of the variability index for 48 OHM galaxies are in the range $V_{S}=0.08$-$0.17$, and for 30 galaxies without OH emission they are $V_{S}=0.08$-$0.28$. For some individual galaxies in both samples, flux density variations reach 30-50%. These sources either are commonly associated with AGNs or reveal active star formation. Generally, the variability of luminous infrared galaxies with and without OH megamaser emission is moderate and of the same order of magnitude on long time scales. From estimating the spectral energy distribution parameters in a broad frequency range (from MHz to THz), we determined the spectral index below 50 GHz and the color temperatures of dust components for megamaser and control sample galaxies. At a level of $\rho<0.05$, there are no statistically significant differences in the distribution of these parameters for the two samples, as well there are no statistically significant correlations between the dust color temperatures and the variability index or luminosity in the OH line.