scholarly journals Effects of rotational disruption on the evolution of grain size distribution in galaxies

2020 ◽  
Vol 494 (1) ◽  
pp. 1058-1070 ◽  
Author(s):  
Hiroyuki Hirashita ◽  
Thiem Hoang
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Size Distribution ◽  
Galaxy Evolution ◽  
Grain Size Distribution ◽  
Extinction Curve ◽  
Short Time Scale ◽  
Dust Grains ◽  
Grain Production ◽  
Dust Temperature

ABSTRACT Interstellar dust grains can be spun up by radiative torques, and the resulting centrifugal force may be strong enough to disrupt large dust grains. We examine the effect of this rotational disruption on the evolution of grain size distribution in galaxies. To this goal, we modify our previous model by assuming that rotational disruption is the major small-grain production mechanism. We find that rotational disruption can have a large influence on the evolution of grain size distribution in the following two aspects especially for composites and grain mantles (with tensile strength ∼107   erg cm −3). First, because of the short time-scale of rotational disruption, the small-grain production occurs even in the early phase of galaxy evolution. Therefore, even though stars produce large grains, the abundance of small grains can be large enough to steepen the extinction curve. Secondly, rotational disruption is important in determining the maximum grain radius, which regulates the steepness of the extinction curve. For compact grains with tensile strength ≳109   erg cm −3, the size evolution is significantly affected by rotational disruption only if the radiation field is as strong as (or the dust temperature is as high as) expected for starburst galaxies. For compact grains, rotational disruption predicts that the maximum grain radius becomes less than 0.2 $\rm{\mu m}$ for galaxies with a dust temperature ≳50 K.

Effect of Different Processing on Properties of Silica Sand

2010 ◽  
Vol 139-141 ◽  
pp. 528-531
Author(s):  
Qing Zhou Sun ◽  
Rong Fu Xu ◽  
Zhong Kui Zhao ◽  
Pu Qing Zhang ◽  
Wei Liu
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Downward Trend ◽  
Silica Sand ◽  
Test Results ◽  
Molding Sand ◽  
Physical Chemical ◽  
Chemical Attributes

This paper will cover some processing routes along with grading and physical/chemical attributes of silica sand. The silica sand in this experiment was divided into four lots, and each of them was processed by the methods of calcining, scrubbing, mulling or rubbing respectively. The test results show that the sand grains which processed by different processing methods are irregular, the acid demand value of sand is lower than that of the base sand, and the grain size distribution of sand is similar to that of the base sand. However, the SiO2 content of processed sand is increased, the impurities content has a downward trend. Compared with the base sand, it can be found that the tensile strength value of molding sand prepared using the processed sands is higher and the bench life is almost no change.

scholarly journals Evolution of grain size distribution in galactic discs

2020 ◽  
Vol 636 ◽  
pp. A18 ◽  
Author(s):  
M. Relaño ◽  
U. Lisenfeld ◽  
K.-C. Hou ◽  
I. De Looze ◽  
J. M. Vílchez ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Radial Distribution ◽  
Molecular Gas ◽  
Evolutionary Stage ◽  
Dust Grains ◽  
Cosmological Simulations ◽  
Dust Grain ◽  
Dust Evolution

Context. Dust is formed out of stellar material and it is constantly affected by different mechanisms occurring in the interstellar medium. Depending on their size, the behaviour of dust grains vary under these mechanisms and, therefore, the dust grain size distribution evolves as part of the dust evolution itself. Following how the grain size distribution evolves is a difficult computing task that has only recently become the subject of consideration. Smoothed particle hydrodynamic (SPH) simulations of a single galaxy, together with cosmological simulations, are producing the first predictions of the evolution of dust grain size distribution. Aims. We compare, for the first time, the evolution of the dust grain size distribution as predicted by SPH simulations and results from observations. We are able to validate not only the predictions of the evolution of the small-to-large grain mass ratio (DS/DL) within a galaxy, but we also provide observational constraints for recent cosmological simulations that include the grain size distribution in the dust evolution framework. Methods. We selected a sample of three spiral galaxies with different masses: M 101, NGC 628, and M 33. We fitted the dust spectral energy distribution across the disc of each object and derived the abundance of the different grain types included in the dust model. We analysed how the radial distribution of the relative abundance of the different grain size populations changes over the whole disc within each galaxy. The DS/DL ratio as a function of the galactocentric distance and metallicity is directly compared to what has been predicted by the SPH simulations. Results. We find a good agreement between the observed radial distribution of DS/DL and what was obtained from the SPH simulations of a single galaxy. The comparison agrees with the expected evolutionary stage of each galaxy. We show that the central parts of NGC 628 at a high metallicity and with a high molecular gas fraction are mainly affected not only by accretion, but also by the coagulation of dust grains. The centre of M 33, having a lower metallicity and lower molecular gas fraction, presents an increase in the DS/DL ratio, demonstrating that shattering is very effective for creating a large fraction of small grains. Finally, the observational results provided by our galaxies confirm the general relations predicted by the cosmological simulations based on the two-grain size approximation. However, we also present evidence that the simulations could be overestimating the amount of large grains in high massive galaxies.

scholarly journals Expected dust grain-size distributions in galaxies detected by ALMA at z > 7

2019 ◽  
Vol 490 (1) ◽  
pp. 540-549 ◽  
Author(s):  
Hsin-Min Liu ◽  
Hiroyuki Hirashita
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Galaxy Evolution ◽  
Grain Size Distribution ◽  
High Redshift ◽  
Size Distributions ◽  
Total Dust ◽  
Dust Sources ◽  
Grain Size Distributions ◽  
Different Grain Size

ABSTRACT The dust properties in high-redshift galaxies provide clues to the origin of dust in the Universe. Although dust has been detected in galaxies at redshift z > 7, it is difficult to constrain the dominant dust sources only from the total dust amount. Thus, we calculate the evolution of grain-size distribution, expecting that different dust sources predict different grain-size distributions. Using the star formation time-scale and the total Baryonic mass constrained by the data in the literature, we calculate the evolution of grain-size distribution. To explain the total dust masses in ALMA-detected z > 7 galaxies, the following two solutions are possible: (i) high dust condensation efficiency in stellar ejecta and (ii) efficient accretion (dust growth by accreting the gas-phase metals in the interstellar medium). We find that these two scenarios predict significantly different grain-size distributions: in (i), the dust is dominated by large grains ($a\gtrsim 0.1\,{\mu m}$, where a is the grain radius), while in (ii), the small-grain ($a\lesssim 0.01\,{\mu m}$) abundance is significantly enhanced by accretion. Accordingly, extinction curves are expected to be much steeper in (ii) than in (i). Thus, we conclude that extinction curves provide a viable way to distinguish the dominant dust sources in the early phase of galaxy evolution.

scholarly journals Evolution of the grain size distribution in Milky Way-like galaxies in post-processed IllustrisTNG simulations

2020 ◽  
Vol 501 (1) ◽  
pp. 1336-1351
Author(s):  
Yu-Hsiu Huang ◽  
Hiroyuki Hirashita ◽  
Yun-Hsin Hsu ◽  
Yen-Ting Lin ◽  
Dylan Nelson ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Milky Way ◽  
Extinction Curve ◽  
Size Distributions ◽  
Grain Size Distributions ◽  
Nearby Galaxies ◽  
Hydrodynamical Simulations ◽  
Dust Evolution

ABSTRACT We model dust evolution in Milky Way-like galaxies by post-processing the IllustrisTNG cosmological hydrodynamical simulations in order to predict dust-to-gas ratios and grain size distributions. We treat grain-size-dependent dust growth and destruction processes using a 64-bin discrete grain size evolution model without spatially resolving each galaxy. Our model broadly reproduces the observed dust–metallicity scaling relation in nearby galaxies. The grain size distribution is dominated by large grains at z ≳ 3 and the small-grain abundance rapidly increases by shattering and accretion (dust growth) at z ≲ 2. The grain size distribution approaches the so-called MRN distribution at z ∼ 1, but a suppression of large-grain abundances occurs at z < 1. Based on the computed grain size distributions and grain compositions, we also calculate the evolution of the extinction curve for each Milky Way analogue. Extinction curves are initially flat at z > 2, and become consistent with the Milky Way extinction curve at z ≲ 1 at $1/\lambda \lt 6~\rm{\mu m}^{-1}$. However, typical extinction curves predicted by our model have a steeper slope at short wavelengths than is observed in the Milky Way. This is due to the low-redshift decline of gas-phase metallicity and the dense gas fraction in our TNG Milky Way analogues that suppresses the formation of large grains through coagulation.

scholarly journals Spectral energy distributions of dust and PAHs based on the evolution of grain size distribution in galaxies

2020 ◽  
Vol 499 (2) ◽  
pp. 3046-3060
Author(s):  
Hiroyuki Hirashita ◽  
Weining Deng ◽  
Maria S Murga
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Galaxy Evolution ◽  
Grain Size Distribution ◽  
Theoretical Calculations ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Intermediate Stage ◽  
Spectral Energy ◽  
Spatially Resolved

ABSTRACT Based on a one-zone evolution model of grain size distribution in a galaxy, we calculate the evolution of infrared spectral energy distribution (SED), considering silicate, carbonaceous dust, and polycyclic aromatic hydrocarbons (PAHs). The dense gas fraction (ηdense) of the interstellar medium (ISM), the star formation time-scale (τSF), and the interstellar radiation field intensity normalized to the Milky Way value (U) are the main parameters. We find that the SED shape generally has weak mid-infrared (MIR) emission in the early phase of galaxy evolution because the dust abundance is dominated by large grains. At an intermediate stage (t ∼ 1 Gyr for τSF = 5 Gyr), the MIR emission grows rapidly because the abundance of small grains increases drastically by the accretion of gas-phase metals. We also compare our results with observational data of nearby and high-redshift (z ∼ 2) galaxies taken by Spitzer. We broadly reproduce the flux ratios in various bands as a function of metallicity. We find that small ηdense (i.e. the ISM dominated by the diffuse phase) is favoured to reproduce the 8 $\rm{\mu m}$ intensity dominated by PAHs for both the nearby and the z ∼ 2 samples. A long τSF raises the 8 $\rm{\mu m}$ emission to a level consistent with the nearby low-metallicity galaxies. The broad match between the theoretical calculations and the observations supports our understanding of the grain size distribution, but the importance of the diffuse ISM for the PAH emission implies the necessity of spatially resolved treatment for the ISM.

Reclamation of Green Sand Containing Hot-Box Resin Sand and its Application

2010 ◽  
Vol 97-101 ◽  
pp. 1037-1040 ◽  
Author(s):  
Qing Zhou Sun ◽  
Rong Fu Xu ◽  
Zhong Kui Zhao ◽  
Pu Qing Zhang
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Shape Factor ◽  
Clay Content ◽  
Casting Process ◽  
Green Sand ◽  
Molding Sand

The green sand containing hot-box resin sand was reclaimed by the process of calcination followed by mechanical reclamation. The reclaimed sands were reused in the hot-box process. The grain size distribution, the shape factor, the clay content and the acid demand value were determined. The results show that the acid demand value of the reclaimed sand is higher than that of the base sand. Compared with the base sand, the grain size of the reclaimed sand is almost no difference. It can also be observed that the tensile strength of the molding sand is influenced by the acid demand value and clay content, but the reclaimed sand can still meet the casting process needs. In addition, the reclaimed green sand is satisfactory for hot-box process.

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