Metal Outflow Research Articles

Modelling the mass-metallicity relation of star-forming galaxies from z ∼ 3.5 to z ∼ 0

We study the origin and cosmic evolution of the mass-metallicity relation (MZR) in star-forming galaxies based on a full, numerical chemical evolution model. The model was designed to match the local MZRs for both gas and stars simultaneously. This is achieved by invoking a time-dependent metal enrichment process which assumes either a time-dependent metal outflow with larger metal loading factors in galactic winds at early times, or a time-dependent Initial Mass Function (IMF) with steeper slopes at early times. We compare the predictions from this model with data sets covering redshifts 0<z<3.5. The data suggests a two-phase evolution with a transition point around z ~ 1.5. Before that epoch the MZRgas has been evolving parallel with no evolution in the slope. After z ~ 1.5 the MZRgas started flattening until today. We show that the predictions of both the variable metal outflow and the variable IMF model match these observations very well. Our model also reproduces the evolution of the main sequence, hence the correlation between galaxy mass and star formation rate. We also compare the predicted redshift evolution of the MZRstar with data from the literature. As the latter mostly contains data of massive, quenched early-type galaxies, stellar metallicities at high redshifts tend to be higher in the data than predicted by our model. Data of stellar metallicities of lower-mass (< 10^11 solar mass), star-forming galaxies at high redshift is required to test our model.

Metal-enriched galactic outflows shape the mass–metallicity relationship

The gas-phase metallicity of low-mass galaxies increases with increasing stellar mass ($M_\ast$) and is nearly constant for high-mass galaxies. Theory suggests that this tight mass-metallicity relationship is shaped by galactic outflows removing metal-enriched gas from galaxies. Here, we observationally model the outflow metallicities of the warm outflowing phase from a sample of seven local star-forming galaxies with stellar masses between 10$^{7}$-10$^{11}$ M$_\odot$. We estimate the outflow metallicities using four weak rest-frame ultraviolet absorption lines, the observed stellar continua, and photoionization models. The outflow metallicity is flat with $M_\ast$, with a median metallicity of $1.0\pm0.6$ Z$_\odot$. The observed outflows are metal-enriched: low and high-mass galaxies have outflow metallicities 10-50 and 2.6 times larger than their ISM metallicities, respectively. The observed outflows are mainly composed of entrained ISM gas with at most 22% of the metals directly coming from recent supernovae enrichment. The metal outflow rate shallowly increases with $M_\ast$, as $M_\ast^{0.2 \pm 0.1}$, because the mass outflow rate shallow increases with $M_\ast$. Finally, we normalize the metal outflow rate by the rate at which star formation retains metals to calculate the metal-loading factor. The metal-loading factor inversely scales with $M_\ast$. The normalization and scaling of the metal-loading factor agree with analytic expressions that reproduce observed mass-metallicity relations. Galactic outflows fundamentally shape the observed mass-metallicity relationship.

Fluid Flow Characteristics and Weld Formation Quality in Gas Tungsten Arc Welding of a Thick-Sheet Aluminum Alloy Structure by Varying Welding Position

This study aims to reveal the cause of different weld formation quality for varying welding position in the GTAW (Gas Tungsten Arc Welding) of a thick-sheet aluminum alloy structure. The fluid flow characteristics of weld pools are investigated by CFD (Computational Fluid Dynamic) modeling and high-speed imaging for the climbing and flat welding positions, which correspond to the start and finish ends of the welds of the structure, respectively. Results show that the directions of gravity relative to weld pools may notably affect the fluid flows in weld pools for different welding positions. For flat welding, gravity will accelerate the fluid flow in the direction of sheet thickness only and in turn result in a high velocity downwards, which implies a good penetrating capability. Welds of good formation with smooth surface and consistent width can be produced under flat welding position. In contrast, for climbing welding, gravity will act on the molten metal in both the direction of sheet thickness and the lateral direction of the weld pool. As a result, the velocity in sheet-thickness direction is decreased, which implies a decreased penetrating capability. Meanwhile, the velocity backwards is increased in the top portion of the weld pool, which makes the molten metal apt to flow out of the weld pool. Both the decreased penetrating capability and the accelerated molten metal outflow would render the climbing welding process unstable, and result in welds of poor formation with uneven weld surface and inconsistent weld width. Based on the study, possible methods are proposed that could be used to improve the weld formation quality when welding thick-sheet aluminum alloys structures using various welding positions.

Development of calculation schemes for the combined extrusion to predict the shape formation of axisymmetric parts with a flange

We have developed calculation schemes for the process of combined radial-reverse extrusion of parts with a flange. Based on the energy method, we have derived formulae for calculating the reduced pressure of deformation and a phased increase in the dimensions of a semi-finished product. Relevance of the research is based on ensuring the simplification of estimation of the application of a given deformation process to obtain parts with a required configuration. In addition, we have proved the efficiency of determining the limit of using the derived calculation scheme for ratios 2h 1 R 2 /(R 2 2 –R 1 2 )<1. We analyzed a product range manufactured at the enterprises of machine-building and instrument-making, which includes a significant number of hollow parts with flanges and branches of various shapes. It was substantiated that the use of combined extrusion schemes in the manufacture of parts of the type «a cup with a flange», when compared to employing simple deformation techniques, improves technological possibilities of the process. That is achieved through the reduction in energy costs, as well as in the number of technological transitions, and through making the shape of the parts obtained more complex. We confirmed the lack of proper studies into technologies for the implementation of combined extrusion schemes and the absence of appropriate technological recommendations. We determined the power mode of extrusion that corresponds to reality and estimated a possibility to control the outflow of metal at deformation. A study was conducted into the process of cold combined extrusion of hollow parts with a flange; the calculation schemes of the process were proposed. We modeled the process of combined extrusion based on the experimental-analytical method and established patterns in the shape formation of parts with a flange due to the geometrical and technological parameters. Data were acquired on the phased form change in a semi-finished product in the process of deformation. It was confirmed that the proposed models simplify the development of technological recommendations to determine the power mode of extrusion and to control the outflow of metal during deformation process.

SDSS-IV MaNGA: modelling the metallicity gradients of gas and stars – radially dependent metal outflow versus IMF

In our previous work, we found that only two scenarios are capable of reproducing the observed integrated mass-metallicity relations for the gas and stellar components of local star-forming galaxies simultaneously. One scenario invokes a time-dependent metal outflow loading factor with stronger outflows at early times. The other scenario uses a time-dependent IMF slope with a steeper IMF at early times. In this work, we extend our study to investigate the radial profile of gas and stellar metallicity in local star-forming galaxies using spatially resolved spectroscopic data from the SDSS-IV MaNGA survey. We find that most galaxies show negative gradients in both gas and stellar metallicity with steeper gradients in stellar metallicity. The stellar metallicity gradient tend to be mass dependent with steeper gradients in more massive galaxies while no clear mass dependence is found for the gas metallicity gradient. Then we compare the observations with the predictions from a chemical evolution model of the radial profiles of gas and stellar metallicities. We confirm that the two scenarios proposed in our previous work are also required to explain the metallicity gradients. Based on these two scenarios we successfully reproduce the radial profiles of gas metallicity, stellar metallicity, stellar mass surface density, and star formation rate (SFR) surface density simultaneously. The origin of the negative gradient in stellar metallicity turns out to be driven by either radially dependent metal outflow or IMF slope. In contrast, the radial dependence of the gas metallicity is less constrained because of the degeneracy in model parameters.

The mass–metallicity relations for gas and stars in star-forming galaxies: strong outflow versus variable IMF

We investigate the mass-metallicity relations for the gaseous (MZRgas) and stellar components (MZRstar) of local star-forming galaxies based on a representative sample from SDSS DR12. The mass-weighted average stellar metallicities are systematically lower than the gas metallicities. This difference in metallicity increases toward galaxies with lower masses and reaches 0.4-0.8 dex at 10^9 Msun (depending on the gas metallicity calibration). As a result, the MZRstar is much steeper than the MZRgas. The much lower metallicities in stars compared to the gas in low mass galaxies implies dramatic metallicity evolution with suppressed metal enrichment at early times. The aim of this paper is to explain the observed large difference in gas and stellar metallicity and to infer the origin of the mass-metallicity relations. To this end we develop a galactic chemical evolution model accounting for star formation, gas inflow and outflow. By combining the observed mass-metallicity relation for both gas and stellar components to constrain the models, we find that only two scenarios are able to reproduce the observations. Either strong metal outflow or a steep IMF slope at early epochs of galaxy evolution is needed. Based on these two scenarios, for the first time we successfully reproduce the observed MZRgas and MZRstar simultaneously, together with other independent observational constraints in the local universe. Our model also naturally reproduces the flattening of the MZRgas at the high mass end leaving the MZRstar intact, as seen in observational data.

Do salt and low temperature impair metal treatment in stormwater bioretention cells with or without a submerged zone?

Although seasonal temperature changes and (road) salt in winter and/or coastal stormwater runoff might interfere with the metal treatment performance of stormwater bioretention cells, no previous study has evaluated the effect of these factors and their interactions under controlled conditions. In this 18week long study 24 well established pilot-scale bioretention columns were employed to evaluate the individual and combined effect(s) of low/high temperature, salt and presence of a submerged zone with an embedded carbon source on metal removal using a three factor, two-level full factorial experimental design. In most instances, the three factors significantly influenced the metal outflow concentrations and thus the treatment performance; the effect of temperature depended on the metal in question, salt had an overall negative effect and the submerged zone with carbon source had an overall positive effect. Despite these statistically significant effects, the discharge water quality was generally markedly improved. However, leaching of dissolved Cu and Pb did occur, mainly from bioretention cells dosed with salt-containing stormwater. The highest concentrations of metals were captured in the top layer of the filter material and were not significantly affected by the three factors studied. Overall, the results confirmed that bioretention provides a functioning stormwater treatment option in areas experiencing winter conditions (road salt, low temperatures) or coastal regions (salt-laden stormwater). However, validation of these results in the field is recommended, especially focusing on dissolved metal removal, which may be critically affected under certain conditions.

METAL DIFFUSION IN SMOOTHED PARTICLE HYDRODYNAMICS SIMULATIONS OF DWARF GALAXIES

ABSTRACT We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]–[Fe/H] distribution in the gas and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.

철도 노반 재료의 중금속 흡착특성과 안전성에 관한 연구

Domestic railway industry has grown in numbers, scale of railway ndustrial and operation because was focused on an environmentally sustainable transportation. However, it is not enough to treat and prevent heavy metals which occur as the railway operation increases. The heavy metals occurred when the operating railway and it will be flow into water system with rainfall effluent during rainfall. will flow out along with the rainfall effluent when rainfall comes. In case of a railway bridge, In particular, heavy metals were flow into the water system without any treatment from railway bridges where located nearby rivers and lakes. So, rainfall effluent from railway facilities was occurred pollution of water system. For the prevent of heavy metal runoff during rainfall, the adsorptivity of material in railway roadbed is important.In this study, adsorptivity of gravel which is main gravel and blast-furnace slag were conducted adsorption test and deducted Freundlich`s and Langmuir`s isothermal adsorption equations. Safety as railway subbase course material was evaluated using modeling. As a result, absorption amount of slag, Cd and Cu, was shown higher than gravel and Pb along with Zn showed higher absorption amount of gravel. However, absorption amount of slag was shown higher than gravel used as railway subbase course material as time passes by. Absorption features had more suitable determination coefficient of heavy metals in warm absorption type such as Langnmuir compared to warm absorption type like Freundlich. To add, they showed less transformation by about 10% compared to gravel in safety evaluation through modeling. This is a railway subbase course material that prevents water outflow of heavy metal thus we can know slag is needed to be used.

Galaxy ecosystems: gas contents, inflows and outflows

We use a set of observational data for galaxy cold gas mass fraction and gas phase metallicity to constrain the content, inflow and outflow of gas in central galaxies hosted by halos with masses between $10^{11} M_{\odot}$ to $10^{12} M_{\odot}$. The gas contents in high redshift galaxies are obtained by combining the empirical star formation histories of Lu et al. (2014) and star formation models that relate star formation rate with the cold gas mass in galaxies. We find that the total baryon mass in low-mass galaxies is always much less than the universal baryon mass fraction since $z = 2$, regardless of star formation model adopted. The data for the evolution of the gas phase metallicity require net metal outflow at $z\lesssim 2$, and the metal loading factor is constrained to be about $0.01$, or about $60\%$ of the metal yield. Based on the assumption that galactic outflow is more enriched in metal than both the interstellar medium and the material ejected at earlier epochs, we are able to put stringent constraints on the upper limits for both the net accretion rate and the net mass outflow rate. The upper limits strongly suggest that the evolution of the gas phase metallicity and gas mass fraction for low-mass galaxies at $z < 2$ is not compatible with strong outflow. We speculate that the low star formation efficiency of low-mass galaxies is owing to some preventative processes that prevent gas from accreting into galaxies in the first place.

A Scottish vision of Korea and East Asia before the ‘Great Divergence - John Campbell and Early Modern European Comparative Historical Discourse -

This article explores the intellectual significance of the early modern British interest in global and comparative historical discourse. It highlights the prominent concern with the relations between East Asia and Europe as central to the dynamic patterns of world order. Early modern British intellectual life was shaped profoundly by the insights of the Scottish Enlightenment about East Asia’s importance in global history. We can see this clearly in the writings of one of the most wide-ranging but now largely neglected eighteenth-century Scottish authors: John Campbell (1708-1775). A leading contributor to the Universal History project (London, 1747-1766), Campbell wrote extensively on European settlements in the East Indies. For Campbell, the key benefit of disseminating knowledge of East Asia was the encouragement of commercial relationships that would elevate the wealth and power of Britain. His work illustrates the self-conscious realization of Europe’s peripheral status in regard to East Asian power and economy. Crucially, Campbell highlighted the central global historical dynamic of the enormous outflow of precious metals to Asia in the early modern era. His arguments contribute new details and insights to the perspective of Chinese economic historians such as Kenneth Pomeranz and Robert B. Marks who contend that the hegemony of a Western-dominated world system was both a historically contingent and very recent phenomenon.

Empirical constraints for the magnitude and composition of galactic winds

Galactic winds are a key physical mechanism for understanding galaxy formation and evolution, yet empirical and theoretical constraints for the character of winds are limited and discrepant. Recent empirical models find that local star-forming galaxies have a deficit of oxygen that scales with galaxy stellar mass. The oxygen deficit provides unique empirical constraints on the magnitude of mass loss, composition of outflowing material and metal reaccretion onto galaxies. We formulate the oxygen deficit constraints so they may be easily implemented into theoretical models of galaxy evolution. We parameterize an effective metal loading factor which combines the uncertainties of metal outflows and metal reaccretion into a single function of galaxy virial velocity. We determine the effective metal loading factor by forward-fitting the oxygen deficit. The effective metal loading factor we derive has important implications for the implementation of mass loss in models of galaxy evolution.

使用済み自動車に着目した日本からの資源流出

In order to examine the risk to resource security in Japan, this paper quantifies the outflow of base metals (iron, aluminum, copper, lead, and zinc) through export of end-of-life vehicles (ELVs) from Japan from 1988 to 2005 using the Trade Statistics of Japan and vehicles composition data. Estimates were also made for engine-related rare metals (manganese, nickel, chromium, and molybdenum), under statistical restrictions. This analysis shows that 24% of iron, 38% of aluminum, 13% of copper, 53% of lead, 11% of zinc, and 38% of rare metals in ELVs in Japan were not recycled and flowed out of the country, mostly in the form of used vehicle and parts. The destinations of these metals were mainly developing countries with rudimentary recycling technology. These results strongly indicate that many metal resources that could be utilized domestically from automobiles in Japan were instead scattered and lost overseas. [doi:10.2320/matertrans.MAW200712]

Scaling Relations of Dwarf Galaxies without Supernova‐driven Winds

Nearby dwarf galaxies exhibit tight correlations between their global stellar and dynamical properties, such as circular velocity, mass-to-light ratio, stellar mass, surface brightness, and metallicity. Such correlations have often been attributed to gas or metal-rich outflows driven by supernova energy feedback to the interstellar medium. We use high-resolution cosmological simulations of high-redshift galaxies with and without energy feedback, as well as analytic modeling, to investigate whether the observed correlations can arise without supernova-driven outflows. We find that the simulated dwarf galaxies exhibit correlations similar to those observed as early as z~10, regardless of whether supernova feedback is included. We also show that the correlations can be well reproduced by our analytic model that accounts for realistic gas inflow but assumes no outflows, and star formation rate obeying the Kennicutt-Schmidt law with a critical density threshold. We argue that correlations in simulated galaxies arise due to the increasingly inefficient conversion of gas into stars in low-mass dwarf galaxies rather than supernova-driven outflows. We also show that the decrease of the observed effective yield in low-mass objects, often used as an indicator of gas and metal outflows, can be reasonably reproduced in our simulations without outflows. We show that this trend can arise if a significant fraction of metals in small galaxies is spread to the outer regions of the halo outside the stellar extent via mixing. In this case the effective yield can be significantly underestimated if only metals within the stellar radius are taken into account. Measurements of gas metallicity in the outskirts of gaseous disks of dwarfs would thus provide a key test of such explanation.

A High‐Abundance Arc in the Compact Group of Galaxies HCG 62: An AGN‐ or Merger‐Induced Metal Outflow?

We present a Chandra study of the metal distribution in the X-ray bright compact group of galaxies HCG 62. We find that the diffuse X-ray emission is peaked at the core of the central galaxy NGC 4778 and is dominated by the contribution of the hot gas. The diffuse emission is roughly symmetric within ≃0.25', which is straddled by double-sided X-ray cavities aligned in the northeast-southwest direction. By mapping the emission hardness ratio distributions and by performing a two-dimensional spectral analysis, we identify a remarkable high-abundance arc region at about 2' (33.6 h kpc) from the X-ray peak that spans over a vast region from south to northwest, a part of which roughly coincides with the outer edge of the southwest X-ray cavity. The measured average abundance in this arc is higher than that in its neighboring regions by a factor of about 2, and the abundance ratios therein are nicely consistent with the dominance of the SN Ia yields. We estimate that the mass of iron contained in the arc is >3 × 106 h M☉, which accounts for >3% of the iron synthesized in the galaxy. The high-abundance arc could have been formed by AGN activity. However, it is also possible that the arc was formed in a recent merger, as implied by the recent optical kinematic study by Spavone and colleagues, which suggests that mergers may be as important as AGN activity in metal redistributions in early-type galaxies and their associated groups or clusters.

Measurement of flatness of hot-rolled strips under coiler tension using IP-4 optoelectronic sensors

We describe a domestically-manufactured flatness sensor capable of measuring nonuniformities in metal outflow from the gap between rollers-a quantity directly required for adjustment of flatness in rolled strips.

Outflow of Resources from Japan focusing on End-of-life Vehicles

In order to examine the risk to resource security in Japan, this paper quantifies the outflow of base metals (iron, aluminum, copper, lead, and zinc) through export of end-of-life vehicles (ELVs) from Japan from 1988 to 2005 using the Trade Statistics of Japan and vehicles composition data. Estimates were also made for engine-related rare metals (manganese, nickel, chromium, and molybdenum), under statistical restrictions. This analysis shows that 24% of iron, 38% of aluminum, 13% of copper, 53% of lead, 11% of zinc, and 38% of rare metals in ELVs in Japan were not recycled and flowed out of the country, mostly in the form of used vehicle and parts. The destinations of these metals were mainly developing countries with rudimentary recycling technology. These results strongly indicate that many metal resources that could be utilized domestically from automobiles in Japan were instead scattered and lost overseas. [doi:10.2320/matertrans.MAW200712]

Accumulation of metals by vegetation in a small drainage area exposed to aerotechnogenic pollution

Trends in the accumulation of metals by different plant species have been analyzed in a forest phytocenosis of the southern taiga zone of the Middle Urals, which is polluted by emissions from a copper-smelting plant. The rate of metal accumulation in the course of annual and net phytomass production and metal outflow with surface waters beyond the biogeocenosis boundaries have been estimated.

The star formation history of intermediate-redshift late-type galaxies

We combine the latest observations of disc galaxy photometry and rotation curves at moderate redshift from the FORS Deep Field (FDF) with simple models of chemical enrichment. Our method describes the build-up of the stellar component through infall of gas and allows for gas and metal outflows. In this framework, we keep a minimum number of constraints and we search a large volume of parameter space, looking for the models that best reproduce the photometric observations in the observed redshift range (0.5 < z < 1). We find that star formation efficiency correlates well with v max ,s othat massive discs are more efficient in the formation of stars and have a smaller spread in stellar ages. This trend presents a break at around v max ∼ 140 km s −1 . Galaxies on either side of this threshold have significantly different age distributions. This break has been already suggested by several authors in connection with the contribution from either gravitational instabilities or supernova-driven turbulence to star formation. The gas infall time-scale and gas outflows also present a correlation with galaxy mass, so that massive discs have shorter infall time-scales and smaller outflow fractions. The model presented in this paper suggests that massive discs have formation histories resembling those of early-type galaxies, with highly efficient and short-lived bursts, in contrast with low-mass discs, which have a more extended star formation history. The ages correlate well with galaxy mass or luminosity, and the predicted gas-phase metallicities are consistent with the observations of local and moderate-redshift galaxies. One option to explain the observed shallow slope of the Tully‐Fisher relation at intermediate redshift could be small episodes of star formation in low-mass discs. Ke yw ords: galaxies: evolution ‐ galaxies: formation ‐ galaxies: spiral ‐ galaxies: stellar content.

On the mass-to-light ratio and the initial mass function in disc galaxies

A low mass-to-light (M/L) ratio for the stellar component of spiral galaxies (M/L≲ 1 in the I band) is advocated by various dynamical arguments and by recent cosmological simulations of the formation of these systems. We discuss this possibility by means of chemo-photometric models for galactic discs, adopting different initial mass functions (IMFs). We show that a number of ‘bottom-light’ initial mass functions (namely, with less mass locked in low-mass stars than the standard Salpeter IMF), suggested independently in recent literature, do imply M/L ratios as low as mentioned above, at least for late-type spirals (Sbc/Sc). This conclusion still holds when the bulge contribution to mass and light is included. We also predict the typical stellar M/L ratio, and correspondingly the zero-point of the Tully–Fisher relation, to vary considerably with Hubble type (approximately 0.5–0.7 mag in the red bands, from Sa to Sc type). For some of the bottom-light IMFs considered, the efficiency of metal production tends to exceed what is typically estimated for spiral galaxies. Suitable tuning of the IMF mass limits, post-supernova fallback of metals on to black holes or metal outflows must then be invoked, to reproduce the observed chemical properties of disc galaxies. In the appendix we provide M/L–colour relations to estimate the stellar M/L ratio of a galaxy on the basis of its colours, for several IMFs.