Amount Of Dust Emission Research Articles

Relationships between aerosol optical depth and surface-layer extinction in the central part of the Upper Silesia industrial region over the period of 1983–1994

The subject of analysis is the aerosol optical depth (AOD) in the visible part of the solar spectrum ( τ vis ) (wavelength λ = 0.295 – 0.695 μ m ). Calculation of τ vis -values was based on pyrheliometric observation data performed from 1983 to 1994 at IEIA's station (Katowice-Załęże). This paper examines the dependence of τ vis and its relation to surface-layer extinction coefficient σ (Koschmider quotient of 3.912 and visibility V ) on meteorological and anthropological factors during the observation period. Knowledge of the relationship between columnar aerosol turbidity (which can be expressed by τ vis ) and σ allows a more precise and accurate estimation of the aerosol effect on the radiative composition of climate. This work offers some contributions to solving this problem. Therefore, the relations have been described in the form of mathematical/statistical models of AOD (based on “momentary” and mean seasonal values), in which meteorological (and astronomical) parameters as well as the amount of industry dust emission were used as independent variables to improve exactness and credibility in the models.

Sources of Asian dust and role of climate change versus desertification in Asian dust emission

Simulations of Asian dust emissions over the past 43 years are presented based on a size‐dependent soil dust emission and transport model (NARCM) along with supporting data from a network of surface stations. The deserts in Mongolia and in western and northern China (mainly the Taklimakan and Badain Juran, respectively) contribute ∼70% of the total dust emissions; non‐Chinese sources account for ∼40% of this. Several areas, especially the Onqin Daga sandy land, Horqin sandy land, and Mu Us Desert, have increased in dust emissions over the past 20 years, but efforts to reduce desertification in these areas may have little effect on Asian dust emission amount because these are not key sources. The model simulations indicate that meteorology and climate have had a greater influence on the Asian dust emissions and associated Asian dust storm occurrences than desertification.

Estimation of Dust Emission Amount for a Dust Storm Event Occurred in April 1998 in China

The threshold friction velocities for dust rises in inland China are examined using WMO synoptic station data and the soil types in the source region to estimate dust emission amounts for a dust event occurred from 13 to 24 April 1998 in China. The dust-rise reports in the WMO synoptic data are used for the delineation of dust source regions that are found to be composed of the Gobi, Sand and Loess regions according to soil types in inland China. The estimated threshold friction velocities with the use of wind speeds observed in the Gobi, Sand and Loess regions are found to be about 60, 50, and 40 cm s-1, respectively. The estimated dust-rise occurrencegrids by both the grid interpolated observed wind and the MM5 model wind well coincide with the areas of strong wind speeds. However, the dust-rise areas estimated by the model are larger than those estimated by the observed wind, whereas the friction velocities estimated by the model in the dust-rise areas are much smaller than those estimated by the observed wind, which result in less amount of dust emission by the model in all source regions. The 10-day accumulated total dust emission estimated by the observed wind during the dust storm event is found to be 4.64 × 108 ton in the whole source region of 3.29 × 106 km2. Of which 85, 9 and 6% are, respectively, contributed by the Gobi, Sand and Loess regions,suggesting the dominant emission from the Gobi region for this event.The model estimated total dust emission is found to be about 56% of that estimated by the observed wind, indicating some improvement of the model being required.

Thermal Infrared Images of the Remarkable Young Nearby Multiple Star HD 98800

We present thermal infrared images of the unusual multiple stellar system HD 98800, which contains two double-star systems (A and B) separated by ≈08 in the north/south direction. This system may have formed in a recent burst of star formation in a very low mass cloud in the local solar neighborhood. Our images resolve the A and B components. Both A and B emit roughly equal fluxes at 4.71 μm, where radiation is primarily photospheric. The northern component (B) is about 3.7 times brighter than the southern component (A) at 9.78 μm where the radiation is due to thermal emission from dust, showing that 78% of the circumstellar dust in the system resides around component B. The two primary components are nearly identical K5 V pre-main-sequence stars, both with very significant amounts of dust emission. The dust system around the B component may have size, temperature, and possible structure analogous to those of a primitive zodiacal cloud.

Starburst Galaxies. III. Properties of a Radio‐selected Sample

We have analyzed the properties of the 20 most radio-luminous UGC starburst galaxies from Condon, Frayer, & Broderick. Near-infrared images, spectra, and optical rotation curves were presented in Smith et al. In this paper, we use these data and published radio data to assess the stellar populations, dust contents, ionizing conditions, and dynamics of the starbursts. Certain properties of the star formation occurring in these galaxies differ from those observed locally. The infrared excesses (IREs) are lower than and span a narrower range of values than those of Galactic H II regions. The starbursts appear to produce a higher proportion of ionizing photons than most Galactic H II regions. Consequently, the initial mass functions (IMFs) of the starbursts may be more strongly biased toward high-mass star formation. The starbursts may also contain fewer old H II regions than the Milky Way. Furthermore, the starburst IRE is likely to be influenced by the presence of large reservoirs of gas that absorb a larger fraction of the Lyman continuum photons. The OB stellar and far-infrared luminosities imply that the upper mass range of the starburst IMF (M > 10 M?) is characterized by a slope of 2.7 ? 0.2. The starburst IMF thus bears a strong similarity to that observed in Magellanic OB associations. Optical line ratios indicate that a range of excitation conditions are present. We conclude that the near-infrared light from many of the starbursts is dominated by a heavily obscured mixture of emission from evolved red stars and young blue stars with small contributions (? 5%) from thermal gas and hot dust, under the assumptions that a Galactic or SMC extinction law can be applied to these systems and that the true reddening curve follows one of the models currently existing in the literature. In some cases, larger amounts of emission from blue stars or hot dust may be required to explain the observed near-infrared colors. The amount of dust emission exceeds that predicted from comparisons with Galactic H II regions. The near-infrared colors of some of the systems may also be influenced by the presence of a low-luminosity active galactic nucleus (AGN). Emission from blue stars and hot dust, if present, dilutes the observed CO index. The activity in the redder, more luminous systems is strongly peaked. The galaxies hosting the starbursts exhibit a wide range of morphological and star-forming properties. While all of the host galaxies are interacting systems, the nuclear separations of the interacting nuclei range from 1 Mpc. The dynamical behavior ranges from relaxed to strongly perturbed. The off-nuclear regions of the galaxies are sites of active star formation and are characterized by a range of excitation conditions. Spatially extended LINER emission is consistent with shock excitation produced by superwinds or galaxy-galaxy collisions. Violent star formation activity occurs over a larger physical scale in the most active starbursts. Systems containing mergers and widely separated nuclei possess similar colors and luminosities. The burst properties are most likely regulated by the internal structures of the interacting galaxies and not the separations of the interacting galaxies.

The luminous starburst galaxy UGC 8387

We present broad-band J, H, and K images and K-band spectroscopy of the luminous starburst galaxy UGC 8387. The images show a disturbed morphology, tidal tails, and a single elognated nucleus. Near infrared color maps constructed from the images reveal that the nucleus region is highly reddened. Strong emission from the central 3 arcseconds in the 2.166 micrometer Brackett gamma, 2.122 micrometer H2 v = 1-0 S(1), and 2.058 micrometer He I lines is present in the K-band spectrum. From the Brackett gamma and published radio fluxes, we find an optical depth toward the nucleus of tau(sub V) approximately 24. The CO band heads produce strong absorption in the spectral region long-ward of 2.3 micrometers. We measure a 'raw' CO index of 0.17 +/- 0.02 mag, consistent with a population of K2 supergiants of K4 giants. The nuclear colors, however, are not consistent with an obscured population of evolved stars. Instead, the red colors are best explained by an obscured mixture of stellar and warm dust emission. The amount of dust emission predicted by the near-infrared colors exceeds that expected from comparisons to galactic H II regions. After correcting the spectrum of UGC 8387 for dust emission and extinction, we obtain a CO index of greater than or equal to 0.25 mag. This value suggests the stellar component of the 2.2 micrometer light is dominated by young supergiants. The infrared excess, L(sub IR)/L(sub Ly alpha) derived for UGC 8387 is lower than that observed in galactic H II regions and M82. This implies that either the lower or upper mass cutoff of the initial mass function must be higher than those of local star-forming regions and M82. The intense nuclear starburst in this galaxy is presumably the result of merger activity; and we estimate the starburst age to be at least a few times 10(exp 7) yr.

Road dust emission inventory for the metropolitan area of Shanghai City

An inventory of dust emission from paved roads of the metropolitan area of Shanghai City is accomplished on the basis of field experiments and an inventory of traffic and road conditions. The result shows the annual amount of road dust emission contributed to the ambient TSP pollution of Shanghai City is approximately 12,300 tonnes (in 354 km 2).

Large scale distribution of gas, dust and stars deduced from observations from the UV to the IR

We introduce an as yet unpublished set of OAO-II observations of stellar associations in the Large Magellanic Cloud (LMC). Cross-correlation of the photometric characteristics of these fields with the infrared fluxes at these same positions obtained by the IRAS satellite provides information on the local stellar population, the amounts of interstellar extinction and thermal dust emission.

An IRAS search for dust in globular clusters

view Abstract Citations (32) References (80) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An IRAS Search for Dust in Globular Clusters Lynch, David K. ; Rossano, George S. Abstract The IRAS Point-Source Catalog, Small-Scale Structure Catalog, and HCON1 Sky Brightness Images were searched for sources of emission that were spatially coincident with any of 144 globular clusters. The purpose was to measure or place upper limits on the amount of thermal dust emission from the clusters, which would lead to estimates and upper limits to the mass of intraglobular dust. Sputtering by hot gas in the galactic halo can destroy dust grains and thus possibly explain the absence of dust in glogular clusters. Publication: The Astronomical Journal Pub Date: September 1990 DOI: 10.1086/115554 Bibcode: 1990AJ....100..719L Keywords: Cosmic Dust; Globular Clusters; Infrared Astronomy Satellite; Astronomical Catalogs; Sky Brightness; Sky Surveys (Astronomy); Thermal Emission; Astrophysics; CLUSTERS: GLOBULAR full text sources ADS | data products SIMBAD (434)