Velocity Differences Δv Research Articles

Double-peaked Narrow Emission-line Galaxies in SDSS-IV MaNGA

Narrow emission lines in a galaxy’s spectrum that show double peaks indicate the presence of distinct gas components with different velocities, and its physical origin remains uncertain. This study uses galaxies from the final MaNGA data release to detect double-peaked narrow emission-line spaxels (DPSs) by examining the double Gaussian profiles of the Hα-[N ii] doublets across all MaNGA spaxels. A total of 5420 DPSs associated with 304 double-peaked narrow emission-line galaxies (DPGs) are identified, with each DPG containing a minimum of five DPSs and being free from overlap with other galaxies. We find that DPSs can be categorized into three groups according to their central distance r/R e and the velocity difference Δv between their two components: the inner low-Δv, inner high-Δv, and outer DPSs. By incorporating the physical characteristics of the DPGs into their DPSs, we demonstrate for the first time the existence of statistical correlations between barred DPGs and inner low-Δv DPSs, AGN-hosting DPGs, and inner high-Δv DPSs, as well as tidal DPGs and outer DPSs.

Birds of a Feather: Resolving Stellar Mass Assembly with JWST/NIRCam in a Pair of Kindred z ∼ 2 Dusty Star-forming Galaxies Lensed by the PLCK G165.7+67.0 Cluster

We present a new parametric lens model for the G165.7+67.0 galaxy cluster, which was discovered with Planck through its bright submillimeter flux, originating from a pair of extraordinary dusty star-forming galaxies (DSFGs) at z ≈ 2.2. Using JWST and interferometric mm/radio observations, we characterize the intrinsic physical properties of the DSFGs, which are separated by only ∼1″ (8 kpc) and a velocity difference ΔV ≲ 600 km s−1 in the source plane, and thus are likely undergoing a major merger. Boasting intrinsic star formation rates SFRIR = 320 ± 70 and 400 ± 80 M ⊙ yr−1, stellar masses of log[M⋆/M⊙]=10.2±0.1 and 10.3 ± 0.1, and dust attenuations of A V = 1.5 ± 0.3 and 1.2 ± 0.3, they are remarkably similar objects. We perform spatially resolved pixel-by-pixel spectral energy distribution (SED) fitting using rest-frame near-UV to near-IR imaging from JWST/NIRCam for both galaxies, resolving some stellar structures down to 100 pc scales. Based on their resolved specific star formation rates (SFRs) and UVJ colors, both DSFGs are experiencing significant galaxy-scale star formation events. If they are indeed interacting gravitationally, this strong starburst could be the hallmark of gas that has been disrupted by an initial close passage. In contrast, the host galaxy of SN H0pe has a much lower SFR than the DSFGs, and we present evidence for the onset of inside-out quenching and large column densities of dust even in regions of low specific SFR. Based on the intrinsic SFRs of the DSFGs inferred from UV through far-infrared SED modeling, this pair of objects alone is predicted to yield an observable 1.1 ± 0.2 core-collapse supernovae per year, making this cluster field ripe for continued monitoring.

Hidden Companions to Intermediate-mass Stars. XVI. Unveiling a 41,300 au Companion to the Very Eccentric Binary Zeta Boötis

Zeta Boötis is a nearby 2.2 M ⊙ + 2.2 M ⊙ 125 yr period visual binary distinguished by its very high eccentricity e ≈ 0.98. Here we report that HIP 71759 is a very wide 1.65 M ⊙ companion to ζ Boo at a projected separation ρ=13.′3↔41,300au , an association that has been missed in previous wide binary searches. We estimate a projected velocity difference Δv 2D = 0.86 ± 0.20 km s−1 compared to the Newtonian 2D escape velocity v esc,2D = 0.5 km s−1. We propose that the triple system is gravitationally bound and that it was once much more compact, with the outer companion exciting high amplitude Kozai–Lidov eccentricity oscillations in ζ Boo as it also migrated outwards by removing energy from the inner binary. The Galactic tidal field eventually shut off the triple interaction, freezing the e ≈ 0.98 eccentricity of ζ Boo.

Investigating the effect of food trays porosity on the drying process

Improving the dynamics of airflow behavior in the drying system is essential for improving its efficiency. In this study, the impact of the porosity of the plum-filled drying trays on the airflow behavior inside the chamber is investigated. Three configurations of constant porosity (30%, 50%, 70%), and 4 additional configurations of porosity varying linearly along trays 1 and 2 as a function of the x-axis are evaluated. To model the trays as a porous medium, the Power-low mathematical model was used, with the built-in parameters C0 and C1 were given experimentally. Both were formed as a subroutine in C++ and integrated into the CFD code, as was done for the integration of unsteady weather parameters. The CFD method used for visualizing and analyzing the airflow behavior in the drying chamber has been previously validated with the experimental result. The obtained results indicate that the average temperature of the drying trays reaches a maximum of 316,91 k at tray 1 for a porosity of 50% and an inlet velocity of 0.1 m/s. For the case of non-uniform trays porosity, it was found that for low air inlet velocity of 0.1 m/s, the velocity difference ΔV is generally low in cases (b) and (d), where it is equal respectively to 0.02 m/s and 0.01 m/s for tray 1, and 0.01 in both cases for tray 2. While for high air inlet velocity of 1 m/s the difference ΔV in both trays reaches 0.17 m/s.

Electrical-tomographic imaging of physiological-induced conductive response in calf muscle compartments during voltage intensity change of electrical muscle stimulation (vic-EMS)

Objectives. The electrical-tomographic imaging has been achieved for exploring differential tendency of physiological-induced conductive response in calf muscle compartments during voltage intensity change of electrical muscle stimulation (vic-EMS). Approach. In the experiments, the differential tendency of conductivity distribution images σ during vic-EMS were clearly imaged as three responsive muscle compartments, which are called M 1 compartment composed of gastrocnemius muscle, M 2 compartment composed of tibialis anterior, extensor digitorum longus, and peroneus longus muscles, and M 3 compartment composed of soleus muscle. Main results. The differential tendency of spatial-mean conductivity 〈σ〉 M1 is the same as the differential tendency of venous blood flow velocity v bl and blood lactate concentration C bl during vic-EMS by the increased tendency of spatial-mean conductivity difference Δ〈σ〉 M1, venous blood flow velocity difference Δv bl and blood lactate concentration difference ΔC bl . The 〈σ〉 M1 is increased with the increase of voltage intensity from 〈σ pre 〉 M1 = 0.142 [-] to 〈σ l14 〉 M1 = 0.442 [-] (pre: pre-training, l14: voltage level during vic-EMS l = 14) by Δ〈σ l14-pre 〉 M1 = 204.2% (n = 16, p < 0.01). Correspondingly, the v bl and C bl are increased with the increase of voltage intensity by Δv bl l14-pre = 1480.5% (n = 16, p < 0.01) and ΔC bl l14-pre = 230.1% (n = 16, p < 0.01) respectively. Significance: The reason for the differential tendency of increase in <σ> M1 suggests an increase in muscle extracellular volumes during vic-EMS due to the co-effect of venous blood flow velocity and blood lactate metabolism. Based on the conductivity second-order difference images and spatial-mean conductivity second-order difference optimum voltage intensity φ OVI is discussed among sixteen volunteer subjects, which increased with a thicker subcutaneous fat layer.

4D flow imaging with 2D-selective excitation.

4D flow MRI permits to quantify non-invasively time-dependent velocity vector fields, but it demands long acquisition times. 2D-selective excitation allows to accelerate the acquisition by reducing the FOV in both phase encoding directions. In this study, we investigate 2D-selective excitation with reduced FOV imaging for fast 4D flow imaging while obtaining correct velocity quantification. Two different 2D-selective excitation pulses were designed using spiral k-space trajectories. Further, their isophase time point was analyzed using simulations that considered both stationary and moving spins. On this basis, the 2D-selective RF pulses were implemented into a 4D flow sequence. A flow phantom study and seven 4D flow in vivo measurements were performed to assess the accuracy of velocity quantification by comparing the proposed technique to non-selective and conventional 1D slab-selective excitation. The isophase time point for spiral 2D-selective RF pulses was found to be located at the end of excitation for both stationary and moving spins. Based on that, 2D-selective excitation with reduced FOV allowed us to successfully quantify velocities both in a flow phantom and in vivo. In a flow phantom, the velocity difference between the smaller reduced FOV and the reference scan was similar to the inter-scan variability of . In vivo, the differences in flow (P = 0.995) and flow volume (P = 0.469) between the larger reduced FOV and the reference scan were non-significant. By reducing the FOV by two-thirds, acquisition time was halved. A reduced field-of-excitation allows to limit the FOV and therefore shorten 4D flow acquisition times while preserving successful velocity quantification.

Kinetic equilibrium for an asymmetric tangential layer

Finding kinetic (Vlasov) equilibria for tangential current layers is a long standing problem, especially in the context of reconnection studies, when the magnetic field reverses. Its solution is of pivotal interest for both theoretical and technical reasons when such layers must be used for initializing kinetic simulations. The famous Harris equilibrium is known to be limited to symmetric layers surrounded by vacuum, with constant ion and electron flow velocities, and with current variation purely dependent on density variation. It is clearly not suited for the “magnetopause-like” layers, which separate two plasmas of different densities and temperatures, and for which the localization of the current density j=nδv is due to the localization of the electron-to-ion velocity difference δv and not of the density n. We present here a practical method for constructing a Vlasov stationary solution in the asymmetric case, extending the standard theoretical methods based on the particle motion invariants. We show that, in the case investigated of a coplanar reversal of the magnetic field without electrostatic field, the distribution function must necessarily be a multi-valued function of the invariants to get asymmetric profiles for the plasma parameters together with a symmetric current profile. We show also how the concept of “accessibility” makes these multi-valued functions possible, due to the particle excursion inside the layer being limited by the Larmor radius. In the presented method, the current profile across the layer is chosen as an input, while the ion density and temperature profiles in between the two asymptotic imposed values are a result of the calculation. It is shown that, assuming the distribution is continuous along the layer normal, these profiles have always a more complex profile than the profile of the current density and extends on a larger thickness. The different components of the pressure tensor are also outputs of the calculation and some conclusions concerning the symmetries of this tensor are pointed out.

The Velocity Field of Baryonic Gas in the Universe

The dynamic evolution of the baryonic intergalactic medium (IGM) caused by the underlying dark matter gravity is governed by the Navier-Stokes equations in which many cooling and heating processes are involved. However, it has long been recognized that the growth mode dynamics of cosmic matter clustering can be sketched by a random force driven Burgers equation if cooling and heating are ignored. Just how well the dynamics of the IGM can be described as a Burgers fluid has not been fully investigated, probably because cooling and heating are essential for a detailed understanding of the IGM. Using IGM samples produced by a cosmological hydrodynamic simulation in which heating and cooling processes are properly accounted for, we show that the IGM velocity field in the nonlinear regime shows the features of a Burgers fluid, that is, when the Reynolds number is high, the velocity field consists of an ensemble of shocks. Consequently, (1) the IGM velocity v is generally smaller than that of dark matter; (2) for the smoothed field, the IGM velocity shows tight correlation with dark matter given by v ≃ svdm, with s < 1, such that the lower the redshift, the smaller the s; (3) the velocity probability density functions (pdf's) are asymmetric between acceleration and deceleration events; (4) the pdf of velocity difference Δv = v(x + r) - v(x) satisfies the scaling relation for a Burgers fluid, i.e., P(Δv) = (1/ry)F(Δv/ry). We find the scaling function and parameters for the IGM that are applicable to the entire scale range of the samples (0.26-8 h-1 Mpc). These properties show that the similarity mapping between the IGM and dark matter is violated on scales much larger than the Jeans length of the IGM.

Studies of the Second Byurakan Survey Galaxies. I. Mergers, Interacting Systems, and Close Pairs

This paper reports on a study of the morphological characteristics of several samples of galaxies drawn from the 1401 objects which comprise the Second Byurakan Survey (SBS). These samples have been chosen to provide information for studies of the relation between galaxy interactions and galaxy star formation activity. Our samples include 110 SBS galaxies in 107 mergers, 58 SBS galaxies in 47 interacting systems, and 49 SBS galaxies in 30 close pairs (projected separations ΔD ≤ 50 kpc and radial velocity differences ΔV ≤ 600 km s -1). Data are also presented for eight SBS galaxies forming four wider pairs (ΔD ≤ 100 kpc and ΔV ≤ 700 km s -1), and 15 SBS galaxies forming five triplets (ΔD ≤ 100 kpc and ΔV ≤ 900 km s -1). Four, and possibly another three SBS galaxies, may be satellites of larger galaxies. Finally, six other SBS objects are possibly H II regions in their host galaxies.

Velocity fluctuations in a turbulent soap film: The third moment in two dimensions

Quasi-two-dimensional decaying turbulence is studied in a flowing soap film by measuring the moments of the probability density function P(δv(r)) for the longitudinal velocity differences δv(r) on a scale r. As in three-dimensional (3-D) turbulence, P becomes non-Gaussian with decreasing r. The third moment S3(r)≡〈(δv(r))3〉 is small and negative at small scales, but becomes positive at larger scales. The exact calculation of S3(r) for 2-D homogeneous isotropic turbulence relates this change in sign to the development of the velocity correlation function as the turbulence decays.

Measurement of the velocity difference by photon correlation spectroscopy: an improved scheme

Homodyne photon correlation spectroscopy is used to measure the velocity difference delta v (l) over varying distance l. Different length scales are probed when the magnification factor M and the width S of a slit in the collecting optics are varied. The measured intensity autocorrelation function is found to be of scaling form for different values of M, provided S is kept at a value below the critical width S (c). A new convenient collecting optics is devised to expand the variable range of l up to 2 decades, over which delta v (l) can be accurately measured. The new scheme is useful for the study of turbulent and other self-similar flows.

Helium abundance and dynamics in different types of solar wind streams: The Prognoz 7 observations

On the basis of the Prognoz 7 selective plasma measurements of α particles and protons the correlations of helium parameters (relative abundance nα/np, velocity difference ΔV = |Vα| − |Vp|, and temperature ratio Tα/Tp) with bulk parameters in different types of solar wind streams are studied. Helium abundance increases with increasing wind velocity in quasi‐stationary streams from 1.7 ± 2.6% in the heliospheric current sheet (HCS) up to 4.7 ± 6.6% in the coronal streamers (CS) and 6.6 ± 8.0% in the coronal holes (CH). The maximum value of nα/np of 10.5 ± 10.1% is observed in coronal mass ejections (CME) and an intermediate value between HCS and CS 3.4 ± 4.2% in the shocked plasma. Helium abundance increases with increasing mass flux and density in streams from CHs and decreases in streams from CSs. Velocity difference ΔV increases with increasing velocity in HCS and streams from CSs and CHs, but it is usually small or negative in CMEs and in shocked plasma. The temperature ratio Tα/Tp increases with increasing velocity in the HCS and in streams from CSs, and it is approximately constant in streams from CHs, CMEs, and shocked plasma. No evidence has been obtained that the processes of α particle acceleration differ from each other in streams from CSs and CHs, but they differ from the one in the HCS. In contrast to processes of acceleration, the processes of α particle heating in streams from CHs and CSs are suggested to differ from each other, but they may be the same in streams from CSs and HCS. The value of α particle and proton heating in streams from CHs increases with increasing absolute value of velocity difference of α particles and protons.

Are there binary galaxies in clusters?

We investigate a sample of 73 rich clusters containing in total 7754 galaxies and find, after a thorough assessment of the projection effects, that 6 per cent of the galaxies are part of a ‘binary’ system. Apparent ‘binaries’ are defined as nearest-neighbour pairs for which the velocity difference ΔV of the galaxies does not exceed 300 km s−1 and the maximum separation AR is less than 0.1 h−1 Mpc. This results in 1514 pairs. Monte Carlo simulations show that 1047 of these must be accidental, leaving 467 binaries. These binaries cannot be identified individually, but their properties can be studied statistically. The binaries found in this way are dynamically ‘soft’, i.e. ΔV is less than the global σV of the cluster. Despite this, they only seem to avoid the inner 0.4 h−1 Mpc of clusters, suggesting that outside a radius of 0.4 h−1 Mpc the velocity dispersion must locally be lower than the global value of σV that we measure in projection, or that many of the found pairs are unbound. There is a significant correlation between the presence of binaries and the detection of substructure with the Dressier & Shectman test. Binaries in binary-rich clusters seem to be directly associated with the low-σV subclusters for which the DS-test is sensitive. The fraction of binaries in the 19 binary-rich clusters is nearly as high (≈ 12 per cent) as in the population of fore- and background galaxies (‘interlopers’) that is normally removed from the cluster surveys (≈14.5 per cent). In the remaining 54 clusters the binary fraction is considerably lower (≈3 per cent). Depending on the assumed form of the orbits of the galaxies in a binary, the average mass of the binaries lies in the range of 2–5 × 10 11h−1 M⊙, while the average M/L-ratio lies in the range of 20–40 h M⊙/L⊙ for circular orbits to about 45–100 h M⊙/L⊙ for eccentric orbits, which is consistent with the results for field binaries. Monte Carlo models of the binaries suggest that the orbits are likely to have low eccentricities. Both the masses and the M/L-ratios of binaries are larger inside 1.2 h−1 Mpc than outside, which argues against the tidal stripping of galaxy haloes in the central regions of clusters. We have compared our Monte Carlo methods with recent N-body models of clusters which incorporate galaxy formation in a crude way. These models reproduce the main statistical properties of the binaries. When applied to the models, our statistical method detects about 75 per cent of the bound pairs of galaxies that satisfy our selection criteria for binaries. In comparison with the binaries in the data, the masses of bound pairs in these models are systematically larger by a factor of 6. This prevents more detailed comparisons between the data and the models.

Velocity probability density functions in developed turbulence: A finite Reynolds theory

The probability density function of velocity differences δv i=v i( x+ r)−v i( x) in turbulent flows has a stricking evolution when r goes from large scales to small dissipative ones developing wide non gaussian wings. A formalism has been developed, generalizing the multifractal formalism, which well describes this evolution for finite Reynolds numbers. The extrapolation to infinite Reynolds number presents unexpected features.

Observations of a Rain-Formed Mixed Layer

The structure and dynamics of a rain-formed mixed layer (ML) are studied using hourly STD and profiling current meter casts. Because the fluid beneath the rain-formed ML was vertically homogeneous, the ML buoyancy g′ and horizontal velocity difference δV were easily observable as the ML depth h increased by entrainment from 7 to 18 m in a period of 8 h. The overall Richardson number of the mixed layer g′(h + d/2)/δV2 ≈ 0.7 during that period, where d is the thickness of the transition layer at the base of the ML. The entrainment rate was consistent with that of a laboratory surface half-jet (Ellison and Turner, 1959). The transition layer thickness was an appreciable fraction of the ML thickness, roughly d ≈ h/3. The density profile through the transition layer was linear and symmetric, and the overall Richardson number of the transition layer g′d/δV2 ≈ 1/4.

The galactic distribution of OH/IR stars

Through systematic surveys (Johansson et al., Caswell and Haynes, Bowers, Baud, Caswell et al.) some 200 OH masers have been detected that are presumably associated with long period variables of very late spectral type (&gt;M5). Tentatively these stars will be called “OH/IR stars”. They are characterized by their strong emission in the 1612 MHz line which shows a double peak due to the expansion of the shell surrounding these stars. The velocity difference ΔV between the peaks is generally between 10 and 50 km s−1.

The Relationship of Ultrasonic Velocities to c-axis Fabrics and Relaxation Characteristics of Ice Cores from Byrd Station, Antarctica

Abstract Deep cores from Byrd Station were used to calibrate an ultrasonic technique of evaluating crystal anisotropy in the Antarctic ice sheet. Velocities measured parallel (V p ↓) and perpendicular (V p →) to the vertical axis of the cores yielded data in excellent agreement with the observed c-axis fabric profile and with the in-situ P-wave velocity profile measured parallel to the bore-hole axis by Bentley. Velocity differences ΔV (ΔV = V p ↓ – V p→) in excess of 140 m s−1 for cores from below 1300 m attest to the tight clustering of c-axes of crystals about the vertical, especially in the zone 1 300-1800 m. A small but significant decline in V p ↓ with ageing of the core, as deduced from Bentley’s down-hole data, is attributed to the formation of oriented cracks that occur in the ice cores as they relax from environmental stresses. This investigation of cores from the 2164 m thick ice sheet at Byrd Station establishes the ultrasonic technique as a viable method of monitoring relaxation characteristics of drilled cores and for determining the gross trends of c-axis orientation in ice sheets. The Byrd Station data, in conjunction with Barkov’s investigation of deep cores from Vostok, East Antarctica, also indicate that crystal anisotropy in the Antarctic ice sheet is dominated by a clustering of c-axes about a vertical symmetry axis.

The Relationship of Ultrasonic Velocities to c-axis Fabrics and Relaxation Characteristics of Ice Cores from Byrd Station, Antarctica

AbstractDeep cores from Byrd Station were used to calibrate an ultrasonic technique of evaluating crystal anisotropy in the Antarctic ice sheet. Velocities measured parallel (Vp ↓) and perpendicular (Vp →) to the vertical axis of the cores yielded data in excellent agreement with the observed c-axis fabric profile and with the in-situ P-wave velocity profile measured parallel to the bore-hole axis by Bentley. Velocity differences ΔV (ΔV = Vp ↓ – Vp→) in excess of 140 m s−1 for cores from below 1300 m attest to the tight clustering of c-axes of crystals about the vertical, especially in the zone 1 300-1800 m. A small but significant decline in Vp ↓ with ageing of the core, as deduced from Bentley’s down-hole data, is attributed to the formation of oriented cracks that occur in the ice cores as they relax from environmental stresses. This investigation of cores from the 2164 m thick ice sheet at Byrd Station establishes the ultrasonic technique as a viable method of monitoring relaxation characteristics of drilled cores and for determining the gross trends of c-axis orientation in ice sheets. The Byrd Station data, in conjunction with Barkov’s investigation of deep cores from Vostok, East Antarctica, also indicate that crystal anisotropy in the Antarctic ice sheet is dominated by a clustering of c-axes about a vertical symmetry axis.

Elastic Surface Wave Guidance by (Δv/v) Effect Guidance Structures

The possibility of utilizing guided surface acoustic waves in signal processing devices has generated interest in basic investigations of guidance mechanisms and structures for surface acoustic waves. Surface wave propagation, investigated in detail thus far in guidance structures, has unfortunately proven sufficiently dispersive to rule out many practical device applications. Reported here are theoretical investigations of the basic physical phenomena of a (Δv/v) guidance structure which is substantially nondispersive. Acoustic guidance in the (Δv/v) structure is assumed to be due principally to the velocity reduction Δv of a thin conducting strip on a piezoelectric substrate. With this assumption, major features of (Δv/v) guidance can be predicted theoretically from an isotropic nonpiezoelectric model which incorporates the velocity difference Δv. Numerical results are presented for quartz and lithium niobate. In addition, a generalized description for guided waves is developed which is approximately independent of the (Δv/v) velocity ratio. Thus, with the use of scaling factors, the normalized data are applicable to materials with a range of (Δv/v) ratios. Simply put, our principal conclusion is that for many common piezoelectrics, strong guidance and low dispersion are theoretically predicted. Basic experimental investigations thus appear warranted.