Dust Distribution Research Articles

Seasonal variation of airborne fungal diversity and community structure in Urmia Lake, Iran.

A study conducted around Urmia Lake, Iran, investigated the impact of dust storms on fungal concentrations in the air. Researchers collected samples over a year, analyzing fungal variations during dusty and normal days. The average fungal concentration was found to be 436.2 CFU/m3, with Cladosporium cladosporioides, Penicillium chrysogenum, and Cladosporium iridis being the most prevalent species. Notably, fungal concentrations during dust days averaged 967.65 CFU/m3, which is 3.6 times higher than on normal days (267.10 CFU/m3). A total of 61 species were detected on normal days, compared to 45 on dusty days, with Aspergillus and Cladosporium spp. dominating both conditions. The study also linked environmental factors like temperature, humidity, and wind speed to fungal concentrations. Additionally, the distribution of dust was analyzed using the HYSPLIT model and MODIS satellite imagery, highlighting the health risks associated with high fungal concentrations and changing mycobiota due to dust disturbances.

Little Red Dots: Rapidly Growing Black Holes Reddened by Extended Dusty Flows

Abstract The James Webb Space Telescope (JWST) observations have revolutionized extragalactic research, particularly with the discovery of little red dots (LRDs), which have been discovered as a population of dust-reddened broad-line active galactic nuclei (AGNs). Their unique V-shaped spectral feature, characterized by a red optical continuum and a UV excess in the rest frame, challenges us to discern the relative contributions of the galaxy and AGN. We study a spectral energy distribution (SED) model for LRDs from rest-frame UV to infrared bands. We hypothesize that the incident radiation from an AGN, characterized by a typical SED, is embedded in an extended dusty medium with an extinction law similar to those seen in dense regions such as Orion Nebula or certain AGN environments. The UV−optical spectrum is described by dust-attenuated AGN emission, featuring a red optical continuum at λ > 4000 Å and a flat UV spectral shape established through a gray extinction curve at λ < 3000 Å, due to the absence of small-size grains. There is no need for additional stellar emission or AGN scattered light. In the infrared, the SED is shaped by an extended dust and gas distribution (γ < 1; ρ ∝ r −γ ) with characteristic gas densities of ≃10–103 cm−3, which allows relatively cool dust temperatures to dominate the radiation. As a result, these dust structures shift the emission energy peak from near-infrared to mid-infrared bands in the rest frame; for sources at z ~ 4–7, the corresponding wavelengths shift from the JWST/MIRI to Herschel range. This model, unlike the typical AGN hot torus models, can produce an infrared SED flattening that is consistent with LRD observations through JWST MIRI. Such a density structure can arise from the coexistence of inflows and outflows during the early assembly of galactic nuclei. This might be the reason why LRDs emerge preferentially in the high-redshift Universe younger than 1 billion years.

UNCOVER: The Rest-ultraviolet to Near-infrared Multiwavelength Structures and Dust Distributions of Submillimeter-detected Galaxies in A2744

UNCOVER: The Rest-ultraviolet to Near-infrared Multiwavelength Structures and Dust Distributions of Submillimeter-detected Galaxies in A2744

ALMA observations of super-early galaxies: Attenuation-free model predictions

The abundance and blue color of the super-early (redshift z>10) luminous galaxies discovered by the James Webb Space Telescope (JWST) can be explained if radiation-driven outflows have ejected their dust on kiloparsec-scales. To test this hypothesis, we predict the Atacama Large Millimeter Array (ALMA) detectability of this extended dust component. Based on the observed properties of the galaxy, its observed continuum flux at 88 μm, F_88, depends on the dust-to-stellar mass ratio, ξ_d, and on the extent of the dust distribution, r_d. When this is applied to the most distant known galaxy, GS-z14-0 at z=14.32, the fiducial model (ξ_d = 1/529) predicts F_ fid = 14.9, μJy and a dust extent r_d=1.4 kpc. If the galaxy is very dust rich (ξ_d =1/40) max = 40.1, μJy. These values are lower fid = 9.5, μJy) if the dust is predominantly made of large grains such as those that form in supernova ejecta. Forthcoming ALMA observations might come very close to constraining the fiducial predictions of the outflow-based attenuation-free model. Other super-early galaxies are predicted to be fainter at 88 μm, mostly because their star formation rate is lower than that of GS-z14-0, with fiducial fluxes in the range $2-5.2 μ$Jy.

I Zw 1 and H0557-385: The dusty tori of two high Eddington AGNs observed in the MATISSE LM-Bands

Abstract The torus in Active Galactic Nuclei (AGN) is a complex dynamical structure of gas and dust. It is thought to be composed of an equatorial dusty disk and a polar dusty wind launched by radiation pressure. However, this picture is based on studies of moderately accreting AGN. Models suggest that the disk/wind structure will change with specific accretion rate. Here we examine the wind launching region in two high accretion rate objects, I Zw 1 (super-Eddington) and H0557-385 (high-Eddington), using high spatial resolution interferometric observations in the K-band from VLTI/GRAVITY and LM-bands VLTI/MATISSE. We recover wavelength-dependent sizes of the dust emission using a Gaussian and power law fit to the visibilities. Both objects are partially resolved and have radial sizes in the KLM-bands between 0.3 – 1.5 mas, with no signs of elongation. Combining our measurements with VLTI/MIDI N-band data gives a full multi-wavelength picture of the dust structure. We find that in H0557-385, the dust sizes between 3.5 − 8 μm are independent of the wavelength, roughly constant at 3 − 10 sublimation radii. We argue that this indicates a direct view of the wind launching region and, together with an absence of polar elongation, this implies that any wind would be launched in a preferentially equatorial direction or blown out by strong radiation pressure. The size-wavelength relation for both objects shows a preferentially disky equatorial dust distribution. We conclude that there is strong evidence that the Eddington ratio shapes the inner dust structure, most notably the wind-launching region and wind direction.

A Study on Dust Storm Pollution and Source Identification in Northwestern China.

In April 2023, a major dust storm event in Lanzhou attracted widespread attention. This study provides a comprehensive analysis of the causes, progression, and dust sources of this event using multiple data sources and methods. Backward trajectory analysis using the HYSPLIT model was employed to trace the origins of the dust, while FY-2H satellite data provided high-resolution dust distribution patterns. Additionally, the MAIAC AOD product was used to analyze Aerosol Optical Depth, and concentration-weighted trajectory (CWT) analysis was used to identify key dust source regions. The study found that PM10 played a dominant role in the storm, and the AOD values during the storm in Lanzhou were significantly higher than the annual average, highlighting the severe impact on regional air quality. Key meteorological conditions influencing the storm's occurrence were analyzed, including the formation and eastward movement of a high-potential ridge, convection driven by diurnal temperature variations, and surface temperature increases coupled with decreased relative humidity, which together promoted the generation and development of dust. Backward trajectory and dust distribution analyses revealed that the dust primarily originated from Central Asia, western Mongolia, Xinjiang, and Gansu. From the 19th to the 21st, the dust distribution showed similarities between day and night, with a noticeable increase in dust concentration from night to day due to strong vertical atmospheric mixing. To mitigate the impacts of future dust storms, this study highlights both short-term and long-term strategies, including enhanced monitoring systems, public health advisories, and vegetation restoration in key source regions. Strengthening regional and international cooperation for transboundary dust management is also emphasized as critical for sustainable mitigation efforts. These findings are significant for understanding and predicting the causes, characteristics, and environmental impacts of dust storms in Lanzhou and the Northwestern region.

Intermediate mass T Tauri disk masses and a comparison to their Herbig disk descendants

Context. Herbig disks are prime sites for the formation of massive exoplanets and looking into the precursors of these disks can offer clues for determining planet formation timescales. The precursors of Herbig stars, called intermediate-mass T Tauri (IMTT) stars, have spectral types later than F, but stellar masses between 1.5 and 5 M⊙. These stars will eventually become Herbig stars of spectral types A and B. Aims. The aim of this work is to obtain the dust and gas masses and radii of all IMTT disks with ALMA archival data. The obtained disk masses are then compared to Herbig disks and T Tauri disks and the obtained disks sizes to those of Herbig disks. Methods. ALMA Band 6 and 7 archival data were obtained for 34 IMTT disks with continuum observations, 32 of which have at least 12CO, 13CO, or C18O observations, but with most of them at quite shallow integrations. The disk integrated flux together with a stellar luminosity-scaled disk temperature were used to obtain a total disk dust mass by assuming optically thin emission. Using thermochemical Dust And LInes (DALI) models drawn from previous works, we also obtained gas masses of 10 out of 35 of the IMTT disks based on the CO isotopologues. From the disk masses and sizes, we obtained the cumulative distributions. Results. The IMTT disks in this study have the same dust mass and radius distributions as Herbig disks. The dust mass of the IMTT disks is higher compared to that of the T Tauri disks, as also found for the Herbig disks. No differences in dust mass were found for group I versus group II disks, in contrast to Herbig disks. The disks for which a gas mass could be determined display a similarly high-mass as to the Herbig disks. Comparing the disk dust and gas mass distributions to the mass distribution of exoplanets shows that there also is not enough dust mass in disks around intermediate-mass stars to form massive exoplanets. On the other hand, there is more than enough gas to form the atmospheres of exoplanets. Conclusions. We conclude that the sampled IMTT disk population is almost indistinguishable compared to Herbig disks, as their disk masses are the same, even though the former objects are younger. Based on this study, we conclude that planet formation is already well underway in these objects and, thus, planet formation is expected to start early on in the lifetime of Herbig disks. Combined with our findings on group I and group II disks, we conclude that most disks around intermediate-mass pre-main sequence stars converge quickly to small disks, unless they are prevented from doing so by a nearby massive exoplanet.

Study on the dust production characteristics of coal cutting at different drilling speeds of cutting head

Study on the dust production characteristics of coal cutting at different drilling speeds of cutting head

A computationally efficient semi-analytical model for the dust environment of comets and asteroids

Aims. We present a model for the distribution of dust ejected by asteroids and comets. Our model incorporates the effects of solar gravity and radiation pressure. In specific cases it can also account for additional forces and the re-impacts of ejected dust onto the source body. Methods. The number density of dust at a given point in space was computed as the sum of contributions from a set of point sources placed along a given trajectory, ejecting dust in a temporal sequence that approximates the motion of the source body. The dust ejection from each source was modeled using continuous distributions of the dynamical parameters the dust grains have at ejection. We developed three methods to solve for the dust number density from a single point source that differ in complexity and applicability. Results. We applied the model to investigate the dust environment of the near-Earth asteroid Phaethon, and estimated the number of dust grains that will be observed by the dust detector on the flyby of the forthcoming DESTINY+ mission by JAXA. Additionally, as an illustrative example, we reconstructed an image of comet C/1996 B2 (Hyakutake) to demonstrate the details of working with the model. The implementation of our model, verified with a comparison to independent software, is freely available as a Fortran-95 package, DUDI-heliocentric.

A Compilation of Optical Starlight Polarization Catalogs

Polarimetry of stars at optical and near-infrared wavelengths is an invaluable tool for tracing interstellar dust and magnetic fields. Recent studies have demonstrated the power of combining stellar polarimetry with distances from the Gaia mission, in order to gain accurate, 3D information on the properties of the interstellar magnetic field and the dust distribution. However, access to optical polarization data is limited, as observations are conducted by different investigators, with different instruments, and are made available in many separate publications. To enable a more widespread accessibility of optical polarimetry for studies of the interstellar medium, we compile a new catalog of stellar polarization measurements. The data are gathered from 81 separate publications spanning two decades since the previous, widely used agglomeration of catalogs by C. Heiles. The compilation contains a total of 55,742 measurements of stellar polarization. We combine this database with stellar distances based on the Gaia Early Data Release 3, thereby providing polarization and distance data for 42,482 unique stars. We provide two separate data products: an extended catalog (containing all polarization measurements) and a unique source catalog (containing a subset of sources excluding duplicate measurements). We propose the use of a common tabular format for the publication of stellar polarization catalogs to facilitate accessibility and increase discoverability in the future.

Modeling of fine dust distribution in atmospheric air within residential buildings

Modeling of fine dust distribution in atmospheric air within residential buildings

Uncovering the truth about M101, NGC 3938, and their significant others through radiative transfer

ABSTRACT Solving the inverse problem in spiral galaxies, that allows the derivation of the spatial distribution of dust, gas, and stars, together with their associated physical properties, directly from panchromatic imaging observations, is one of the main goals of this work. To this end, we used radiative transfer models to decode the spatial and spectral distributions of the nearby face-on galaxies M101 and NGC 3938. In both cases, we provide excellent fits to the surface-brightness distributions derived from GALEX, SDSS, 2MASS, Spitzer, and Herschel imaging observations. Together with previous results from M33, NGC 628, M51, and the Milky Way, we obtain a small statistical sample of modelled nearby galaxies that we analyse in this work. We find that in all cases Milky Way-type dust with Draine-like optical properties provide consistent and successful solutions. We do not find any ‘submm excess’, and no need for modified dust-grain properties. Intrinsic fundamental quantities like star-formation rates (SFR), specific SFR (sSFR), dust opacities, and attenuations are derived as a function of position in the galaxy and overall trends are discussed. In the SFR surface density versus stellar mass surface density space, we find a structurally resolved relation (SRR) for the morphological components of our galaxies, that is steeper than the main sequence (MS). Exception to this is for NGC 628, where the SRR is parallel to the MS.

Imaging of the Vega Debris System Using JWST/MIRI

We present images of the Vega planetary debris disk obtained at 15.5, 23, and 25.5 μm with the Mid-Infrared Instrument on JWST. The debris system is remarkably symmetric, smooth, and centered accurately on the star. There is a broad Kuiper-belt-analog ring at ∼80–170 au that coincides with the planetesimal belt detected with the Atacama Large Millimeter/submillimeter Array at 1.34 mm. The interior of the broad belt is filled with warm debris that shines most efficiently at mid-infrared, along with a shallow flux dip/gap at 60 au from the star. These qualitative characteristics argue against any Saturn-mass planets orbiting the star outside of about 10 au, assuming the unseen planet would be embedded in the very broad planetesimal disk from a few to hundreds of astronomical units. We find that the distribution of dust detected interior to the broad outer belt is consistent with grains being dragged inward by the Poynting–Robertson effect. Under the drag-dominated disk assumption, tighter constraints can be derived for planets in specific locations; for example, any planet shepherding the inner edge of the outer belt is likely to be less than six Earth masses. The disk surface brightness profile along with the available infrared photometry suggest a disk inner edge near ∼3−5 au, disconnected from the sub-astronomical-unit region that gives rise to the hot near-infrared excess. The gap between the hot, sub-astronomical-unit zone and the inner edge of the warm debris might be shepherded by a modest-mass, Neptune-size planet.

Analysis of the Generation and Spatiotemporal Distributions of Dust During Tunnel Construction

The dust generated during tunnel construction poses serious health risks to workers, as it not only causes respiratory obstruction but also leads to pneumoconiosis and respiratory failure after prolonged exposure. However, most existing studies focus on specific construction stages or particular particle sizes and often assume an ideal airflow, neglecting the complex flow fields, vortex effects, and dust composition variations at different stages in tunnel and mine construction. This study systematically analyzes the spatiotemporal distribution characteristics of dust at various stages of tunnel construction and proposes targeted prevention and control strategies. On the basis of measured data from three construction stages—the working face, initial support, and secondary lining stages—and SPSS 27 statistical analysis, a dynamic analysis was conducted on the concentration and distribution patterns of total suspended particulates (TSPs) and particulate matter of different sizes (PM10, PM4, PM2.5, and PM1). The results show that coarse particles dominate during the working face stage, whereas fine particles gradually accumulate during the initial support and secondary lining stages. Finally, this work establishes a dust concentration–excavation time/tunnel depth equation and proposes targeted dust control measures. These findings offer important practical value for enhancing construction safety and air quality.

Global characterization of the early-season dust storm of Mars year 36

Global characterization of the early-season dust storm of Mars year 36

Investigating the extinction and magnetic field geometry in the Bok globule CB26

ABSTRACT This study investigates the extinction properties, dust distribution, and magnetic field characteristics of the CB26 cloud. Extinction mapping, derived from near-infrared photometry, reveals a good correlation with the dust distribution, as traced by Herschel1SPIRE 500 $\mu\mathrm{ m}$ data, indicating a close link between dust and extinction. The derived column density estimates align with previous Herschel studies. Our optical polarization observations of CB26 reveal a well-aligned magnetic field in the cloud’s low-density envelope, closely following the Galactic plane. In contrast, our reanalysis of archival submillimetre polarization data of CB26 suggests a distinct magnetic field orientation within the cloud core. The offset angle between the core and Galactic magnetic fields is approximately 90$^\circ$, suggesting a decoupling of the core’s magnetic field from the large-scale Galactic field. A relationship is found between polarization rate and distance for 24 field stars in CB26, suggesting that most of the polarization is contributed by dust within 600 pc along the line of sight.

Spatiotemporal evolution of dust over Tarim Basin under continuous clear-sky

Spatiotemporal evolution of dust over Tarim Basin under continuous clear-sky

Implications of scattering for CMB foreground emission modelling

Context. The extreme precision and accuracy of forthcoming observations of the cosmic microwave background (CMB) temperature and polarisation anisotropies, aiming to detect the tiny signatures of primordial gravitational waves or of light relic particles beyond the standard three light neutrinos, requires commensurate precision in the modelling of foreground Galactic emission that contaminates CMB observations. Aims. We evaluate the impact of second-order effects in Galactic foreground emission due to Thomson scattering off interstellar free electrons and to Rayleigh scattering off interstellar dust particles. Methods. We used existing sky survey data and models of the distribution of free electrons and dust within the Milky Way to estimate the amplitude and power spectra of the emission originating from radiation scattered either by free electrons or by dust grains at CMB frequencies. Results. Both processes generate corrections to the total emission that are small compared to direct emission and are small enough not to pose problems for current-generation observations. Conclusions. However, B modes generated by Thomson scattering of incoming radiation off interstellar free electrons at CMB frequencies are within an order of magnitude compared to the sensitivity of the most advanced forthcoming CMB telescopes, and might require more precise evaluation in the future.

DUST DISTRIBUTION PATTERN AND OPTIMIZATION OF TUNNEL VENTILATION SYSTEM

This paper focuses on examining the effectiveness of a long-pressure and short-pumping ventilation system in a highway tunnel construction project in China. Utilizing computational fluid dynamics theory and ventilation system design principles, the study involves numerical simulations through finite element method to analyze dust distribution within the tunnel. The research investigates the effect of the distance of the duct from the working face and pumping ratio on dust concentration. The results indicate that optimal ventilation and dust removal occur when Lpressure set at 20m, Lpumping set at 3m, and pumping ratio is 0.7, resulting in an average dust concentration of 250mg/m3. These findings offer valuable insights for designing effective ventilation systems in tunnel construction projects, thereby enhancing dust control measures to ensure a safer working environment.

Evaluation of 10‐m Wind Speed From ISD Meteorological Stations and the MERRA‐2 Reanalysis: Impacts on Dust Emission in the Arabian Peninsula

AbstractMineral dust is one of the most important aerosols when studying the radiative balance and climate of the planet. There are different dust emission schemes utilized by the atmospheric modeling communities, many of which disagree on basic output quantities such as mass of dust emitted and distribution of mass among size bins. In this work, we examined mineral dust emission from a leading model scheme, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), as utilized in the Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2) Reanalysis and compared it to dust emissions calculated using wind measurements from ground based weather stations located in the Arabian Peninsula that are included in the National Oceanic and Atmospheric Administration’s (NOAA) integrated surface database (ISD). An intercomparison of 10‐m wind speed is shown for the Arabian Peninsula region, differences of the observed and modeled wind field are quantified, and impacts of differences on dust emissions are calculated. This analysis shows 10‐m winds in the ISD were generally lower than MERRA‐2 winds, which propagated to dust emissions errors. Our estimate of one of the most significant mass impacts in dust emission is 0.178 Tg/year/grid box with a percent change of over 200% to the recalculated dust emissions from MERRA‐2. These differences in wind speed propagated to a difference in dust mass emitted by the use of a static source function which aids in scaling the mass emitted by the availability of dust in each grid. Additionally, the magnitude of these differences varies seasonally.