Finite-resolution Deconvolution of Multiwavelength Imaging of 20,000 Galaxies in the COSMOS Field: The Evolution of Clumpy Galaxies over Cosmic Time

Compact star-forming clumps observed in distant galaxies are often suggested to play a crucial role in galaxy assembly. In this paper, we use a novel approach of applying finite-resolution deconvolution on ground-based images of the COSMOS field to resolve 20,185 star-forming galaxies (SFGs) at 0.5 < z < 2 to an angular resolution of 0.″3 and study their clump fractions. A comparison between the deconvolved images and HST images across four different filters shows good agreement and validates image deconvolution. We model spectral energy distributions using the deconvolved 14-band images to provide resolved surface brightness and stellar-mass density maps for these galaxies. We find that the fraction of clumpy galaxies decreases with increasing stellar masses and with increasing redshift: from ∼30% at z ∼ 0.7 to ∼50% at z ∼ 1.7. Using abundance matching, we also trace the progenitors for galaxies at z ∼ 0.7 and measure the fractional mass contribution of clumps toward their total mass budget. Clumps are observed to have a higher fractional mass contribution toward galaxies at higher redshift: increasing from ∼1% at z ∼ 0.7 to ∼5% at z ∼ 1.7. Finally, the majority of clumpy SFGs have higher specific star formation rates (sSFR) compared to the average SFGs at fixed stellar mass. We discuss the implication of this result for in situ clump formation due to disk instability.

Dufour Effect on Transient MHD Double Convection Flow of Fractionalized Second-Grade Fluid with Caputo–Fabrizio Derivative

This article presents the problem, in which we study the unsteady double convection flow of a magnetohydrodynamics (MHD) differential-type fluid flow in the presence of heat source, Newtonian heating, and Dufour effect over an infinite vertical plate with fractional mass diffusion and thermal transports. The constitutive equations for the mass flux and thermal flux are modeled for noninteger-order derivative Caputo–Fabrizio (CF) with nonsingular kernel, respectively. The Laplace transform and Laplace inversion numerical algorithms are used to derive the analytical and semianalytical solutions for the dimensionless concentration, temperature, and velocity fields. Expressions for the skin friction and rates of heat and mass transfer from the plate to fluid with noninteger and integer orders, respectively, are also determined. Furthermore, the influence of flow parameters and fractional parameters α and β on the concentration, temperature, and velocity fields are tabularly and graphically underlined and discussed. Furthermore, a comparison between second-grade and viscous fluids for noninteger and integer is also depicted. It is observed that integer-order fluids have greater velocities than noninteger-order fluids. This shows how the fractional parameters affect the fluid flow.

The nature of the Schönberg–Chandrasekhar limit

ABSTRACT We present a comprehensive description of the Schönberg–Chandrasekhar (S–C) transition, which is an acceleration of the stellar evolution from the nuclear to the thermal time scales occurring when the fractional mass of the helium core reaches a critical value, i.e. about 0.1. It occurs in the 1.4–7 $\, {\rm M}_{\odot }$ mass range due to impossibility of maintaining the thermal equilibrium after the nuclear energy sources in the core disappear. We present the distributions of the hydrogen abundance, the energy generation rate and the temperature for stars crossing that limit. We confirm that a sharp S–C limit is present for strictly isothermal cores, but it is much smoother for real stars. The way the boundary of the core is defined is important for the picture of this transition. With a strict definition of the core as the region where the helium abundance is close to null, it occurs in an extended range of the fractional core mass of roughly 0.03–0.11. The cause of that is a gradual core contraction causing a correspondingly gradual loss of the core isothermality with the increasing core mass. On the other hand, when using definitions allowing for some H abundance in the core, the S–C transition is found to be sharper, at the fractional core mass of between about 0.07 and 0.11. Still, it is more a smooth transition than a sharp limit. We have also searched for specific signatures of that transition, and found that it is associated with the stellar radius first decreasing and then increasing again. We have considered whether the S–C limit can be used as a diagnostic constraining the evolutionary status of accreting X-ray binaries, but found such uses unfounded.

Fractional Mass-Spring-Damper System Described by Generalized Fractional Order Derivatives

This paper proposes novel analytical solutions of the mass-spring-damper systems described by certain generalized fractional derivatives. The Liouville–Caputo left generalized fractional derivative and the left generalized fractional derivative were used. The behaviors of the analytical solutions of the mass-spring-damper systems described by the left generalized fractional derivative and the Liouville–Caputo left generalized fractional derivative were represented graphically and the effect of the orders of the fractional derivatives analyzed. We finish by analyzing the global asymptotic stability and the converging-input-converging-state of the unforced mass-damper system, the unforced spring-damper, the spring-damper system, and the mass-damper system.

FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45 m telescope (FUGIN). V. Dense gas mass fraction of molecular gas in the Galactic plane

Recent observations of the nearby Galactic molecular clouds indicate that the dense gas in molecular clouds has quasi-universal properties on star formation, and observational studies of extra-galaxies have shown a galactic-scale correlation between the star formation rate (SFR) and the surface density of molecular gas. To reach a comprehensive understanding of both properties, it is important to quantify the fractional mass of dense gas in molecular clouds, fDG. In particular, for the Milky Way (MW) there are no previous studies resolving fDG disk over a scale of several kpc. In this study, fDG was measured over 5 kpc in the first quadrant of the MW, based on the CO J = 1–0 data in l = 10°–50° obtained as part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN) project. The total molecular mass was measured using 12CO, and the dense gas mass was estimated using C18O. The fractional masses, including fDG, in the region within ±30% of the distances to the tangential points of the Galactic rotation (e.g., the Galactic Bar, Far-3 kpc Arm, Norma Arm, Scutum Arm, Sagittarius Arm, and inter-arm regions) were measured. As a result, an averaged fDG of $2.9^{+2.6}_{-2.6}$% was obtained for the entirety of the target region. This low value suggests that dense gas formation is the primary factor in inefficient star formation in galaxies. It was also found that fDG shows large variations depending on the structures in the MW disk. In the Galactic arms, fDG was estimated to be ∼4%–5%, while in the bar and inter-arm regions it was as small as ∼0.1%–0.4%. These results indicate that the formation/destruction processes of the dense gas and their timescales are different for different regions in the MW, leading to differences in Star formation efficiencies.

Properties and structures of Sodium silicate – sand mixtures components

Article is devoted to the questions of structuring regularities detection in sodium silicate – sand mixtures and possibility of forecasting and changing their properties determination. Studies have been performed using quartz sand and sodium silicate solute, and also quartz sand placket with sodium silicate solute. It has been discovered that sand flow ability does not depend on the size of its particles, and the largest value acquires with the content of free water (moisture) less than 0.2% by weight. It has been established that apparent density of rare and placket sand, compacted by vibration, is additive to fractional mass content in it of particles normalized fractions and increases from 1100 to 1900 kg/m3 with average size of its grains decreasing from 0.82 to 0.16 mm and with their fineness modulus increasing from 20 to 60. According to experimental data, analytical relationship between content of sodium silicate in sodium silicate solute and specific density of sodium silicate solute has been elaborated. Estimation of sodium silicate solute drying method influence on residual water content in it has been realized. It has been shown that depending on sodium silicate solute amount in mixture, its physical state up to the time of mixture structuring beginning and method of solidification, the structure of solidified sodium silicate solute in structured sodium silicate – sand mixture may vary from dense-oriented to foam-disoriented, contain or not contain residual water. Obtained data using and recording will allow not only reduce the cost of new sodium silicate – sand mixtures developing, increase prediction of their properties accuracy, but also open a new direction for methods of their implementation in foundry molds and rods production.