Small Amount Of Dust Research Articles

Micro-extraction method for the analysis of flame retardants in dust collected from air filters from HVAC systems

Dust is a sink for many semi-volatile compounds including flame retardants of the organophosphate ester (OPE) and brominated flame-retardant (BFR) classes. Given the large amount of time that we spend indoors, our exposure to these compounds via dust is of significant interest. Here, we present a novel microextraction approach to determine quantitative levels of selected OPEs and BFRs sampled from residential air filters from HVAC systems using a small volume of solvent. Dust samples (25 mg) is extracted with 1 mL of hexane/acetone (50/50, v/v). Upon solvent extraction of these HVAC dust samples, the analytes (TCPP, TDCPP, TPHP, T24DtBPP, TBBPA, and TriBBPA) were quantified via gas chromatography-mass spectrometry (GC/MS) or liquid chromatography-mass spectrometry (LC/MS). The methods for extracting these compounds from HVAC dust samples are detailed here with extensive method validation data to demonstrate accuracy and precision of these methods.•Dust is a sink for many semi-volatile compounds, including novel or emerging indoor pollutants like the organophosphate ester flame retardant T24DtBPP.•Here, a small amount of dust (25 mg) is extracted with a small volume of solvent (1 mL hexane and acetone) prior to analysis via chromatographic separation and mass spectrometric detection.

Chapter 3: The Origins and Evolution of Planetary Systems.

The materials that form the diverse chemicals and structures on Earth-from mountains to oceans and biological organisms-all originated in a universe dominated by hydrogen and helium. Over billions of years, the composition and structure of the galaxies and stars evolved, and the elements of life, CHONPS, were formed through nucleosynthesis in stellar cores. Climactic events such as supernovae and stellar collisions produced heavier elements and spread them throughout the cosmos, often to be incorporated into new, more metal-rich stars. Stars typically form in molecular clouds containing small amounts of dust through the collapse of a high-density core. The surrounding nebular material is then pulled into a protoplanetary disk, from which planets, moons, asteroids, and comets eventually accrete. During the accretion of planetary systems, turbulent mixing can expose matter to a variety of different thermal and radiative environments. Chemical and physical changes in planetary system materials occur before and throughout the process of accretion, though many factors such as distance from the star, impact history, and level of heating experienced combine to ultimately determine the final geophysical characteristics. In Earth's planetary system, called the Solar System, after the orbits of the planets had settled into their current configuration, large impacts became rare, and the composition of and relative positions of objects became largely fixed. Further evolution of the respective chemical and physical environments of the planets-geosphere, hydrosphere, and atmosphere-then became dependent on their local geochemistry, their atmospheric interactions with solar radiation, and smaller asteroid impacts. On Earth, the presence of land, air, and water, along with an abundance of important geophysical and geochemical phenomena, led to a habitable planet where conditions were right for life to thrive.

ALMA Observation of a z ≳ 10 Galaxy Candidate Discovered with JWST

We report the observation by the Atacama Large Millimeter/submillimeter Array (ALMA) of a z ≳ 10 galaxy candidate (GHZ1) discovered from the GLASS–JWST Early Release Science Program. Our ALMA program aims to detect the [O iii] emission line at the rest-frame frequency 3393.0062 GHz (88.36 μm) and far-IR continuum emission with the spectral window setup seamlessly covering a 26.125 GHz frequency range (10.10 < z < 11.14). A total of 7 hr of on-source integration was employed, using four frequency settings to cover the full range (1.7 hr per setting), with 0.″7 angular resolution. No line or continuum is clearly detected, with 5σ upper limits on the line emission of 0.93 mJy beam−1 at 25 km s−1 channel−1 and on the continuum emission of 30 μJy beam−1. We report marginal spectral (at 225 km s−1 resolution) and continuum features (4.1σ and 2.6σ peak signal-to-noise ratio, respectively), within 0.″17 from the JWST position of GHZ1. This spectral feature implies z = 10.38 and needs to be verified with further observations. Assuming that the best estimate of photometric redshift () is correct, the model of the galaxy’s broadband spectral energy distribution for the 3σ upper limit of the continuum flux from GHZ1 suggests that GHZ1 has a small amount of dust (M d ≲ 104 M ⊙) at a high temperature (T d ≳ 90 K). The 5σ upper limit on the [O iii]88μm line luminosity and the inferred star formation rate of GHZ1 are consistent with the properties of low-metallicity dwarf galaxies. We also report serendipitous clear detections of six continuum sources at the locations of the JWST galaxy counterparts in the field.

Investigation of aerosol optical properties and pollutant transmission mechanisms in Qinhuangdao, North China – A case study during a pollution event

In this study, the aerosol optical properties, vertical distributions, and pollutant transmission characteristics were analyzed using multi-source data during a pollution event that occurred in March 2019 in Qinhuangdao (QHD), China. During this event, the air pollutant (PM, SO2, NO2, and CO) concentrations increased by 100 μgm−3, 10 μgm−3, 40 μgm−3, and 0.7 mgm−3, respectively. The key meteorological factors were investigated and are closely related to the variations in the concentration of the pollutant. The aerosol optical depth at 500 (AOD500) measured using the Cimel Sunphotometer reached 1.6 on polluted days. Also, the water vapor content increased from 0.55 to 1.25 cm. The result of scatter plots between AOD and the Ångström exponent (AE) indicates that the primary pollutants were fine particles and small amounts of dust, showing the characteristics of mixed pollution. Furthermore, the results of the wind field and backward trajectory indicate that the pollutants with high concentrations originated from the central and northern parts of China, including Henan, Hebei, and Shandong provinces. It is revealed from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) that the pollutants were mainly mixed aerosols in the source area, and this is consistent with the results obtained from the ground-based Sunphotometer. The study could provide a reference for understanding the pollution characteristics and pollutants transmission mechanism in Northeast China.

Impact of local pressure enhancements on dust concentration in turbulent protoplanetary discs

The standard core accretion model for planetesimal formation in protoplanetary discs (PPDs) is subject to a number of challenges. One is related to the vertical settling of dust to the disc mid-plane against turbulent stirring. This is particularly relevant in the presence of the vertical shear instability (VSI), a purely hydrodynamic instability applicable to the outer parts of PPDs, which drives moderate turbulence characterized by large-scale vertical motions. We investigate the evolution of dust and gas in the vicinity of local pressure enhancements (pressure bumps) in a PPD with turbulence sustained by the VSI. Our goal is to determine the morphology of dust concentrations and if dust can concentrate sufficiently to reach conditions that can trigger the streaming instability (SI). We performed a suite of global 2D axisymmetric and 3D simulations of dust and gas for a range of values for Σd∕Σg (ratio of dust-to-gas surface mass densities or metallicity), particle Stokes numbers, τ, and pressure bump amplitude, A. Dust feedback onto the gas is included. For the first time, we use global 3D simulations to demonstrate the collection of dust in long-lived vortices induced by the VSI. These vortices, which undergo a slow radial inward drift, are the dusty analogs of large long-lived vortices found in previous dust-free simulations of the VSI. Without a pressure bump and for solar metallicity Z ≈ 0.01 and Stokes numbers τ ~ 10−2, we find that such vortices can reach dust-to-gas density ratios slightly below unity in the discs’ mid-plane, while for Z ≳ 0.05, long-lived vortices are largely absent. In the presence of a pressure bump, for Z ≈ 0.01 and τ ~ 10−2, a dusty vortex forms that reaches dust-to-gas ratios of a few times unity, such that the SI is expected to develop, before it eventually shears out into a turbulent dust ring. At intermediate metallicities, Z ~ 0.03, this occurs for τ ~ 5 × 10−3, but with a weaker and more short-lived vortex, while for larger τ, only a turbulent dust ring forms. For Z ≳ 0.03, we find that the dust ring becomes increasingly axisymmetric for increasing τ and dust-to-gas ratios reach order unity for τ ≳ 5 × 10−3. Furthermore, the vertical mass flow profile of the disc is strongly affected by dust for Z ≳ 0.03, such that gas is transported inward near the mid-plane and outward at larger heights, which is the reversed situation compared to simulations with zero or small amounts of dust. We find viscous α-values to drop moderately as ~10−3–10−4 for metallicities increasing as Z = 0–0.05. Our results suggest that the VSI can play an active role in the formation of planetesimals through the formation of vortices for plausible values of metallicity and particle size. Also, it may provide a natural explanation for the presence or absence of asymmetries of observed dust rings in PPDs, depending on the background metallicity.

Mass concentration estimates of long-range-transported Canadian biomass burning aerosols from a multi-wavelength Raman polarization lidar and a ceilometer in Finland

Abstract. A quantitative comparison study for Raman lidar and ceilometer observations, and for model simulations of mass concentration estimates of smoke particles is presented. Layers of biomass burning aerosol particles were observed in the lower troposphere, at 2 to 5 km height on 4 to 6 June 2019, over Kuopio, Finland. These long-range-transported smoke particles originated from a Canadian wildfire event. The most pronounced smoke plume detected on 5 June was intensively investigated. Optical properties were retrieved from the multi-wavelength Raman polarization lidar PollyXT. Particle linear depolarization ratios (PDRs) of this plume were measured to be 0.08±0.02 at 355 nm and 0.05±0.01 at 532 nm, suggesting the presence of partly coated soot particles or particles that have mixed with a small amount of dust or other non-spherical aerosol type. The layer-mean PDR at 355 nm (532 nm) decreased during the day from ∼0.11 (0.06) in the morning to ∼0.05 (0.04) in the evening; this decrease with time could be linked to the particle aging and related changes in the smoke particle shape properties. Lidar ratios were derived as 47±5 sr at 355 nm and 71±5 sr at 532 nm. A complete ceilometer data processing for a Vaisala CL51 ceilometer is presented from a sensor-provided attenuated backscatter coefficient to particle mass concentration (including the water vapor correction for high latitude for the first time). Aerosol backscatter coefficients (BSCs) were measured at four wavelengths (355, 532, 1064 nm from PollyXT and 910 nm from CL51). Two methods, based on a combined lidar and sun-photometer approach, are applied for mass concentration estimations from both PollyXT and the ceilometer CL51 observations. In the first method, no. 1, we used converted BSCs at 532 nm (from measured BSCs) by corresponding measured backscatter-related Ångström exponents, whereas in the second method, no. 2, we used measured BSCs at each wavelength independently. A difference of ∼12 % or ∼36 % was found between PollyXT and CL51 estimated mass concentrations using method no. 1 or no. 2, showing the potential of mass concentration estimates from a ceilometer. Ceilometer estimations have an uncertainty of ∼50 % in the mass retrieval, but the potential of the data lies in the great spatial coverage of these instruments. The mass retrievals were compared with the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) meteorological and aerosol reanalysis. The inclusion of dust (as indicated by MERRA-2 data) in the retrieved mass concentration is negligible considering the uncertainties, which also shows that ceilometer observations for mass retrievals can be used even without exact knowledge of the composition of the smoke-dominated aerosol plume in the troposphere.

Evidence of Exposed Dusty Water Ice within Martian Gullies

AbstractMidlatitude slopes on Mars are mantled by deposits proposed to contain H2O ice and dust, overlaid by a desiccated lag. However, direct evidence of their volatile content is lacking. Here we present novel evidence of light‐toned materials within midlatitude gully alcoves eroded into these mantles. The appearance and Lambert albedo of these materials suggests that they are either dust or H2O ice. We interpret them to be H2O ice because it is unlikely for a short‐term, localized dust deposit to form only within the mantle walls. The temperatures are generally too warm (&gt;∼240 K) for the ice to be a frost in equilibrium. Therefore, this ice is likely similar to the dusty ice documented within midlatitude scarps, but with more dust, and exposed in smaller patches by slumping. It has been proposed that CO2 frosts remove the overlying lag, causing the exposed H2O ice to sublimate, liberate dust within the ice for transport, and erode gullies in the mantle. But we observe gullies eroded in wall rock that continue into the mantle, implying that the same process erodes both substrates. H2O ice melt can explain gullies eroded in the wall rock and the mantle. Numerical models show that relatively dense H2O snow on Mars melts only when it contains small amounts of dust. The observed exposure of dusty ice provides a mechanism for it to melt under some conditions and form some gullies. Access to liquid water within this ice could provide potential abodes for any extant life.

Massive deposition of Sahelian dust on the Canary Island Lanzarote during North Atlantic Heinrich Events

Abstract New IRSL ages of eolianites close to Muñique (Lanzarote) demonstrate the influence of millennial scale climatic variability on the sedimentary dynamics on the Canary Islands during the last glacial cycle. The repetitive succession of interstadial and stadial climatic conditions formed multiple sequences of eolian deposits, each in general comprising three depositional types. DepoType 1 and DepoType 2 consist mainly of marine biogenic carbonate detritus with small amounts of dust from the Sahara representing interstadial conditions. DepoType 2 compared to DepoType 1 is characterized by larger amounts of land snails and calcified brood cells. A DepoType 3 rich in dust from African subtropical/tropical Latisols terminates a sequence. IRSL dating on DepoType 3 type deposits clearly shows that these were deposited during Heinrich Events under stadial conditions. The stadial cooling of the North Atlantic Ocean caused a southern shift of climate zones that culminated during Heinrich Events when the arctic climate reaches its most southerly extent. As a consequence, atmospheric changes led to massive dust supply from the then-dry Sahel. The increase in dust and precipitation from the dry DepoTypes 1 to the more humid DepoTypes 3 originates from a modified atmospheric dynamic during a millennial cycle.

Antisoiling Performance of Lotus Leaf and Other Leaves after Prolonged Outdoor Exposure.

Recently, the antisoiling performances of superhydrophobic (SH) surfaces have received much attention due to their potential applications in self-cleaning photovoltaic glass and other surfaces without the need to be rinsed with water. In this work, we systematically compared the antisoiling performances of lotus leaf and other plant leaves by first drying them in the shade and then placing them outdoors in a slight breeze for 1-2 months. The results show that after being dried in the shade, the lotus leaf and the canna leaf retain their SH properties, comparable with their fresh states. The firmiana leaf is still hydrophilic. However, when the leaves are exposed to rain, no rain drops adhere to the surface of the lotus leaf but many droplets adhere to the canna leaf. Furthermore, after being incubated outdoors in the absence of rain for 1 month, the lotus leaf retained its SH properties, the canna leaf was no longer SH, and the firmiana leaf became more hydrophilic. SEM imaging with EDS and elemental mapping all confirmed that after outdoor exposure for 1-2 months, only a small amount of dust was found on the lotus leaf but a significant amount of dust was present on the canna leaf, with even more on the firmiana leaf. These results confirm that the lotus leaf has excellent antisoiling performance. The low interactions between the lotus leaf surface and the dust particles are most likely responsible for this unique property. On the contrary, the canna leaf, and especially the firmiana leaf, do not possess this property because neither their surface microstructures nor their surface free energies are favorable to reduce interactions between the leaf surface and dust particles. This study will be helpful in designing and preparing a surface with antisoiling performance.

Non-linear evolution of the resonant drag instability in magnetized gas

Abstract We investigate, for the first time, the non-linear evolution of the magnetized ‘resonant drag instabilities’ (RDIs). We explore magnetohydrodynamic simulations of gas mixed with (uniform) dust grains subject to Lorentz and drag forces, using the gizmo code. The magnetized RDIs exhibit fundamentally different behaviour than purely acoustic RDIs. The dust organizes into coherent structures and the system exhibits strong dust–gas separation. In the linear and early non-linear regime, the growth rates agree with linear theory and the dust self-organizes into 2D planes or ‘sheets.’ Eventually the gas develops fully non-linear, saturated Alfvénic, and compressible fast-mode turbulence, which fills the underdense regions with a small amount of dust, and drives a dynamo that saturates at equipartition of kinetic and magnetic energy. The dust density fluctuations exhibit significant non-Gaussianity, and the power spectrum is strongly weighted towards the largest (box scale) modes. The saturation level can be understood via quasi-linear theory, as the forcing and energy input via the instabilities become comparable to saturated tension forces and dissipation in turbulence. The magnetized simulation presented here is just one case; it is likely that the magnetic RDIs can take many forms in different parts of parameter space.

Lower explosion limit/minimum explosible concentration testing for hybrid mixtures in the Godbert-Greenwald furnace

Experimental investigations of the lower explosion limits (LEL) of three-component hybrid mixtures of six combustible dusts, three gases, and four solvents were performed in the modified Godbert-Greenwald furnace. The test protocol was in accordance with European standard EN 50281-2-1 which is originally used to determine the minimum ignition temperature of dusts. Modification was done on the equipment to test for the explosion limits for dusts, gases, solvents, and hybrid mixtures. In order to prove the validity of our experimental procedure, the LEL for pure gases were initially tested and the results were compared with values found in literature obtained from the standard procedure which show very good agreement. The experimental results demonstrated a significant decrease of the explosion limits of gas, solvent, or dust and an increase in the likelihood of explosion when a small amount of dust was mixed with gas or solvent and vice versa. For example, the minimum explosible concentration (MEC) of high density polyethylene (HDPE) of 174 g/m3 decreased to 130 g/m3 upon addition of methane the concentration of which itself was below the LEL. The MEC of HDPE further decreased to 65 g/m3 when a nonexplosible concentration of hexane was added. © 2016 American Institute of Chemical Engineers Process Saf Prog 36: 81–94, 2017

Models to estimate the minimum ignition temperature of dusts and hybrid mixtures

The minimum ignition temperatures (MIT) of hybrid mixtures have been investigated by performing several series of tests in a modified Godbert–Greenwald furnace. Five dusts as well as three perfect gases and three real were used in different combinations as test samples. Further, seven mathematical models for prediction of the MIT of dust/air mixtures were presented of which three were chosen for deeper study and comparison with the experimental results based on the availability of the input quantities needed and their applicability. Additionally, two alternative models were proposed to calculate the MIT of hybrid mixtures and were validated against the experimental results. A significant decrease of the minimum ignition temperature of either the gas or the vapor as well as an increase in the explosion likelihood could be observed when a small amount of dust which was either below its minimum explosible concentration or not ignitable itself at that particular temperature was mixed with the gas. The various models developed by Cassel, Krishma and Mitsui to predict the MIT of dust were in good agreement with the experimental results as well as the two models proposed to predict the MIT of hybrid mixtures were also in agreement with the experimental value.

Experimental investigation on the minimum ignition temperature of hybrid mixtures of dusts and gases or solvents

Investigations on the minimum ignition temperatures (MIT) of hybrid mixtures of dusts with gases or solvents were performed in the modified Godbert–Greenwald (GG) furnace. Five combustible dusts and six flammable gases (three ideal and three real) were used. The test protocol was according to EN 50281-2-1 for dust–air mixtures whereas in the case of gases, solvents and hybrid mixtures this standard was used with slight modification. The experimental results demonstrated a significant decrease of the MIT of gas, solvent or dust and an increase in the likelihood of explosion when a small amount of dust, which was either below the minimum explosion concentration or not ignitable by itself, was mixed with gas and vice versa. For example, the MIT of toluene decreased from 540°C to 455°C when small amount of lycopodium was added. It was also confirmed that a hybrid mixture explosion is possible even when both dust and vapour or gas concentrations are respectively lower than their minimum explosion concentration (MEC) and lower explosion limit (LEL). Another example is CN4, the MEC of which of 304g/m3 decreased to 37g/m3 when propane was added, even though the concentrations of the gas was below its LEL.

The VIMOS Ultra-Deep Survey (VUDS): fast increase in the fraction of strong Lyman-αemitters fromz= 2 toz= 6

Aims. The aim of this work is to constrain the evolution of the fraction of Lya emitters among UV selected star forming galaxies at 2<z<6, and to measure the stellar escape fraction of Lya photons over the same redshift range. Methods. We exploit the ultradeep spectroscopic observations collected by the VIMOS Ultra Deep Survey (VUDS) to build an unique, complete and unbiased sample of 4000 spectroscopically confirmed star forming galaxies at 2<z<6. Our galaxy sample UV luminosities brighter than M* at 2<z<6, and luminosities down to one magnitude fainter than M* at 2<z<3.5. Results. We find that 80% of the star forming galaxies in our sample have EW0(Lya)<10A, and correspondingly fesc(Lya)<1%. By comparing these results with literature, we conclude that the bulk of the Lya luminosity at 2<z<6 comes from galaxies that are fainter in the UV than those we sample in this work. The strong Lya emitters constitute, at each redshift, the tail of the distribution of the galaxies with extreme EW0(Lya) and fesc(Lya) . This tail of large EW0 and fesc(Lya) becomes more important as the redshift increases, and causes the fraction of Lya with EW0> 25A to increase from 5% at z=2 to 30% at z=6, with the increase being relatively stronger beyond z=4. We observe no difference, for the narrow range of UV luminosities explored in this work, between the fraction of strong Lya emitters among galaxies fainter or brighter than M*, although the fraction for the FUV faint galaxies evolves faster, at 2<z<3.5, than for the bright ones. We do observe an anticorrelation between E(B-V) and fesc(Lya): generally galaxies with high fesc(Lya) have also small amounts of dust (and viceversa). However, when the dust content is low (E(B-V)<0.05) we observe a very broad range of fesc(Lya), ranging from 10^-3 to 1. This implies that the dust alone is not the only regulator of the amount of escaping Lya photons.

Near- and mid-IR morphology of the water maser emitting planetary nebula K 3-35

The shaping process of planetary nebulae (PNe) takes place during the short transition from the asymptotic giant branch (AGB) phase to the white dwarf stage. The young PN K 3-35 represents a unique case where a small-sized water maser ring has been linked to the launch of collimated outflows that shape the nebula. The contrasting optical and radio continuum morphologies of K 3-35 indicate that they disclose different structural components that are apparently unconnected. To bridge the gap between optical and radio continuum observations, we present here new broadband and narrowband near- and mid-IR images of K 3-35. These images, and their comparison with optical and radio continuum images, are revealing. The radio continuum and mid-IR images are dominated by a compact source at the core of K 3-35 whose emission gives evidence of very dense ionized material embedded within a dust cocoon. The emission from the core, obscured at optical wavelengths, is faintly detected in the Ks band. We suggest that the dust may shield the water molecules at the inner ring from the central star ionizing radiation. The precessing collimated outflows, very prominent in radio continuum, are also detected in mid-IR, very particularly in the [S iv] image. The mid-IR emission from these outflows consist mostly of ionized material, although the broadband filter at 11.85 μm seems to imply that a small amount of dust may be carried out by the outflow. The interactions of these outflows with the nebular shell result in shocks that excite the emission of H2 as well as low-excitation lines from ionized species, such as [N ii] at the tips of the outflows.

Development and testing of a laser-based decontamination system

Decontamination of radioactive concrete surfaces may be necessary during operation or decommissioning of nuclear power plants. Usually only the upper layers of the concrete structure are contaminated and are removed using labor-intensive mechanical milling processes. Production of a large amount of dust, which can lead to secondary contamination, is inherent to these processes. Improvements in high-energy laser technology have now made it possible for laser radiation to be used in decontamination technologies for the removal of concrete layers. A decontamination unit comprising a diode laser with a beam power of 10kW in continuous wave (CW) mode in combination with an autonomous manipulator was developed for use in nuclear plants. The laser beam melts the concrete surface to a depth of approximately 5mm. Compressed air jets then detach the molten layer from the concrete surface and convey it to a suction system, with which it is transported to a collection container. Most of the radionuclides are trapped in the solidifying melt particles, which form an extremely stable effluent well suited to long-term storage. A relatively small amount of dust is generated in the process. Because there is no backlash during energy transfer, the laser device carrier can be designed to be lightweight and flexible. A specially developed manipulator that can move freely along walls and ceilings by means of suction plates is used for the carrier unit. This results in short setup times for preparing for use of the device and minimal personnel exposure to the radiation. Experiments were conducted on a concrete wall to demonstrate the functionality of the overall system in realistic conditions. An optimal ablation rate of 2.16m²/h at an ablation depth of 1–5mm was achieved. Today’s commercially available diode lasers with powers higher than 50kW enable ablation rates of >10m²/h to be achieved and hence make these laser-based systems competitive alternatives to mechanical systems.

880 μm IMAGING OF A TRANSITIONAL DISK IN UPPER SCORPIUS: HOLDOVER FROM THE ERA OF GIANT PLANET FORMATION?

We present 880 micron images of the transition disk around the star [PZ99] J160421.7-213028, a solar-mass star in the nearby Upper Scorpius association. With a resolution down to 0.34 arcsec, we resolve the inner hole in this disk, and via model fitting to the visibilities and spectral energy distribution we determine both the structure of the outer region and the presence of sparse dust within the cavity. The disk contains about 0.1 Jupiter masses of mm-emitting grains, with an inner disk edge of about 70 AU. The inner cavity contains a small amount of dust with a depleted surface density in a region extending from about 20-70 AU. Taking into account prior observations indicating little to no stellar accretion, the lack of a binary companion, and the presence of dust near 0.1 AU, we determine that the most likely mechanism for the formation of this inner hole is the presence of one or more giant planets.

UV properties of type Ia supernova and their host galaxies

Type Ia Supernova (SN Ia) are a powerful, albeit not completely understood, tool for cosmology. Gaps in our understanding of their progenitors and detailed physics can lead to systematic errors in the cosmological distances they measure. We use UV data in two context to help further our understanding of SN Ia progenitors and physics. We analyze a set of nearly 700 light curves, and find no signature of the shock heating of a red giant companion, predicted by Kasen (Astrophys. J. 708:1025, 2010), casting doubt as to frequency of this SN Ia channel. We also use UV imaging of high redshift host galaxies of SN Ia to better understand the environments which SN Ia occur. We show that some high-z elliptical galaxies have current star formation, hindering efforts to use them as low-extinction environments. We show cosmological scatter of SN distances at large effective radii in their hosts is significantly reduced, and argue this is due to the smaller amounts of dust affecting the SN Ia. Finally, we find a two component dependence of SN distance measurements as a function of their host galaxy’s FUV-V color. This indicates that both the age and metallicity/mass of the host galaxy maybe important ingredients in measuring SN Ia distances.

A BRIGHT, SPATIALLY EXTENDED LENSED GALAXY ATz= 1.7 BEHIND THE CLUSTER RCS2 032727-132623

We present the discovery of an extremely bright and extended lensed source from the second Red Sequence Cluster Survey (RCS2). RCSGA 032727-132609 is spectroscopically confirmed as a giant arc and counter-image of a background galaxy at $z=1.701$, strongly-lensed by the foreground galaxy cluster RCS2 032727-132623 at $z=0.564$. The giant arc extends over $\sim 38$\,\arcsec and has an integrated $g$-band magnitude of 19.15, making it $\sim 20$ times larger and $\sim 4$ times brighter than the prototypical lensed galaxy MS1512-cB58. This is the brightest distant lensed galaxy in the Universe known to date. Its location in the `redshift desert' provides unique opportunities to connect between the large samples of galaxies known at $z\sim3$ and $z\sim1$. We have collected photometry in 9 bands, ranging from $u$ to $K_s$, which densely sample the rest-frame UV and optical light, including the age-sensitive 4000\AA\ break. A lens model is constructed for the system, and results in a robust total magnification of $2.04 \pm 0.16$ for the counter-image; we estimate an average magnification of $17.2 \pm 1.4$ for the giant arc based on the relative physical scales of the arc and counter-image. Fits of single-component spectral energy distribution (SED) models to the photometry result in a moderately young age, $t = 115 \pm 65$\,Myr, small amounts of dust, $E(B-V) \le 0.035$, and an exponentially declining star formation history with \textit{e}-folding time $\tau = 10-100$\,Myr. After correcting for the lensing magnification, we find a stellar mass of $\log(\mathrm{M}/\mathrm{M}_\odot)=10.0 \pm 0.1$. Allowing for episodic star formation, an underlying old burst could contain up to twice the mass inferred from single-component modeling. This stellar mass estimate is consistent with the average stellar mass of a sample of `BM' galaxies ($1.4 < z < 2.0$) studied by Reddy et al. (2006).

Reflectance spectroscopy of indoor settled dust in Tel Aviv, Israel: comparison between the spring and the summer seasons

Abstract. The influence of mineral and anthropogenic dust components on the VIS-NIR-SWIR spectral reflectance of artificial laboratory dust mixtures was evaluated and used in combination with Partial Least Squares (PLS) regression to construct a model that correlates the dust content with its reflectance. Small amounts of dust (0.018–0.33 mg/cm2) were collected using glass traps placed in different indoor environments in Tel Aviv, Israel during the spring and summer of 2005. The constructed model was applied to reflectance spectroscopy measurements derived from the field dust samples to assess their mineral content. Additionally, field samples were examined using Principal Component Analysis (PCA) to identify the most representative spectral pattern for each season. Across the visible range of spectra two main spectral shapes were observed, convex and concave, though spectra exhibiting hybrid shapes were also seen. Spectra derived from spring season dust samples were characterized mostly by a convex shape, which indicates a high mineral content. In contrast, the spectra generated from summer samples were characterized generally by a concave shape, which indicates a high organic matter content. In addition to this seasonal variation in spectral patterns, spectral differences were observed associated with the dwelling position in the city. Samples collected in the city center showed higher organic content, whereas samples taken from locations at the city margins, near the sea and next to open areas, exhibited higher mineral content. We conclude that mineral components originating in the outdoor environment influence indoor dust loads, even when considering relatively small amounts of indoor settled dust. The sensitive spectral-based method developed here has potentially many applications for environmental researchers and policy makers concerned with dust pollution.