scholarly journals SDSS-IV MaNGA: stellar population correlates with stellar root-mean-square velocity Vrms gradients or total-density-profile slopes at fixed effective velocity dispersion σe

2020 ◽  
Vol 495 (4) ◽  
pp. 4820-4827
Author(s):  
Shengdong Lu ◽  
Michele Cappellari ◽  
Shude Mao ◽  
Junqiang Ge ◽  
Ran Li
Keyword(s):  
Root Mean Square ◽  
Total Mass ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Total Density ◽  
Mean Square ◽  
Root Mean Square Velocity ◽  
Effective Velocity ◽  
Hydrodynamical Simulations

ABSTRACT Galaxy properties are known to correlate most tightly with the galaxy effective stellar velocity dispersion σe. Here, we look for additional trends at fixed σe using 1339 galaxies (M* ≳ 6 × 109 M⊙) with different morphologies in the MaNGA (DR14) sample with integral-field spectroscopy data. We focus on the gradients (γrms ≡ σ(Re/4)/σe) of the stellar root-mean-square velocity ($V_{\rm rms} \equiv \sqrt{V^2 + \sigma ^2}$), which we show traces the total mass density gradient γtot derived from dynamical models and, more weakly, the bulge fraction. We confirm that γrms increases with σe, age, and metallicity. We additionally find that these correlations still exist at fixed σe, where galaxies with larger γrms are found to be older and more metal-rich. It means that mass density gradients contain information of the stellar population which is not fully accounted for by σe. This result puts an extra constraint on our understanding of galaxy quenching. We compare our results with galaxies in the IllustrisTNG hydrodynamical simulations and find that, at fixed σe, similar trends exist with age, the bulge fraction, and the total mass density slope but, unlike observations, no correlation with metallicity can be detected in the simulations.

scholarly journals Effect of scanning speed on texture-elicited vibrations

2020 ◽  
Vol 17 (167) ◽  
pp. 20190892
Author(s):  
Charles M. Greenspon ◽  
Kristine R. McLellan ◽  
Justin D. Lieber ◽  
Sliman J. Bensmaia
Keyword(s):  
Root Mean Square ◽  
Laser Doppler Vibrometer ◽  
Scanning Speed ◽  
Mean Square ◽  
Root Mean Square Velocity ◽  
Dependent Change ◽  
Fine Surface ◽  
Neuronal Representation ◽  
Human Participants ◽  
Exploratory Movements

To sense the texture of a surface, we run our fingers across it, which leads to the elicitation of skin vibrations that depend both on the surface and on exploratory parameters, particularly scanning speed. The transduction and processing of these vibrations mediate the ability to discern fine surface features. The objective of the present study is to characterize the effect of changes in scanning speed on texture-elicited vibrations to better understand how the exploratory movements shape the neuronal representation of texture. To this end, we scanned a variety of textures across the fingertip of human participants at a variety of speeds (10–160 mm s −1 ) while measuring the resulting vibrations using a laser Doppler vibrometer. First, we found that the intensity of the vibrations—as indexed by root-mean-square velocity—increases with speed but that the skin displacement remains constant. Second, we found that the frequency composition of the vibrations shifts systematically to higher frequencies with increases in scanning speed. Finally, we show that the speed-dependent shift in frequency composition accounts for the speed-dependent change in intensity.

scholarly journals IMF radial gradients in most massive early-type galaxies

2019 ◽  
Vol 489 (3) ◽  
pp. 4090-4110 ◽  
Author(s):  
F La Barbera ◽  
A Vazdekis ◽  
I Ferreras ◽  
A Pasquali ◽  
C Allende Prieto ◽  
...  
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Initial Mass Function ◽  
Early Type ◽  
Low Mass Stars ◽  
Surface Mass ◽  
Low Mass ◽  
Surface Mass Density ◽  
The Imf

ABSTRACT Using new long-slit spectroscopy obtained with X-Shooter at ESO-VLT, we study, for the first time, radial gradients of optical and near-infrared initial mass function (IMF)-sensitive features in a representative sample of galaxies at the very high mass end of the galaxy population. The sample consists of seven early-type galaxies (ETGs) at z ∼ 0.05, with central velocity dispersion in the range 300 ≲ σ ≲ 350 km s−1. Using state-of-the-art stellar population synthesis models, we fit a number of spectral indices, from different chemical species (including TiO and Na indices), to constrain the IMF slope (i.e. the fraction of low-mass stars), as a function of galactocentric distance, over a radial range out to ∼4 kpc. ETGs in our sample show a significant correlation of IMF slope and surface mass density. The bottom-heavy population (i.e. an excess of low-mass stars in the IMF) is confined to central galaxy regions with surface mass density above $\rm \sim 10^{10}\, M_\odot \, kpc^{-2}$, or, alternatively, within a characteristic radius of ∼2 kpc. Radial distance, in physical units, and surface mass density are the best correlators to IMF variations, with respect to other dynamical (e.g. velocity dispersion) and stellar population (e.g. metallicity) properties. Our results for the most massive galaxies suggest that there is no single parameter that fully explains variations in the stellar IMF, but IMF radial profiles at z ∼ 0 rather result from the complex formation and mass accretion history of galaxy inner and outer regions.

Seismic Imaging of Small Faults in Coal Seams by Prestack Time Migration

2014 ◽  
Vol 556-562 ◽  
pp. 592-596
Author(s):  
Su Zhen Shi ◽  
Juan Li ◽  
Yi Chen Zhao ◽  
Li Biao Yang ◽  
Yao Tang ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Seismic Data ◽  
Mean Square ◽  
Root Mean Square Velocity ◽  
Coal Seams ◽  
Time Migration ◽  
Geological Conditions ◽  
Small Fault ◽  
Prestack Time Migration ◽  
And Migration

In order to improve imaging precision of small structures and small fault blocks of coal seams, the prestack time migration method is used for imaging. Preserved amplitude processing (PAP) is applied to prestack gather firstly after geological data and original seismic data of the exploration area are fully understood. Initial root mean square velocity field is established through the method of picking up root mean square velocity on CRP gather. Then, a precise root mean square velocity model is created after continuous iteration and modification. Meanwhile, appropriate algorithm and migration parameters are selected during the migration process. Finally, the imaging of small fault blocks and small faults in the prestack time migration section is clear and migration is highly coinciding with the case disclosed by boreholes. It’s proved that prestack time migration is especially suitable for processing 3D seismic data of small faults and small fault blocks in coal seams with complicated geological conditions.

scholarly journals Vibration Criteria Assessment due to Piling Works

2021 ◽  
Vol 13 (3) ◽  
Author(s):  
Tuan Norhayati Tuan Chik ◽  
◽  
Cheng Sok Rou ◽  
Ahmad Fahmy Kamarudin ◽  
Seyed Jamalaldin Seyed Hakim ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Vibration Amplitude ◽  
Laser Doppler Vibrometer ◽  
Field Testing ◽  
Mean Square ◽  
Construction Site ◽  
Root Mean Square Velocity ◽  
Construction Sites ◽  
External Sources ◽  
Klang Valley

In the recent years, the level and nature of the ground vibrations has been more concerned in worldwide. Vibration affected on surrounding building is often associated with the vibration from the ground that is mainly caused by internal and external sources. One of the external sources is construction activities. Identify the effects of vibration caused by piling works in construction sites was the purpose of this paper. It is also aiming to determine the vibration criteria due to piling works in Klang Valley construction site. In addition, the objective of this study is to compare the level of vibration with Department of Environment (DOE) guideline between both Kajang MRT and Klang Valley MRT construction sites. The data used for this study is obtained from past researchers and field testing is performed by using Polytec Laser Doppler Vibrometer and Rion VM-55. The data has been analyzed by using ModalV of MATLAB software. Based on the results, it can be concluded that the vibration amplitude for three distance includes 5m, 10m and 20m are located above the ISO level which stated that the area within the distances not suitable for placement of sensitive equipment. The highest value of root mean square velocity is occurred in the distance of 5m and the reading is 80000 µm/s. According to Department of Environment (DOE) guidelines, the vibration at distance of 1m and 3m at Kajang MRT will cause major damage to surrounding buildings while minor damage was produced by the vibration at 5m, 10m and 20m distance from bored piling point which located around the area of Klang Valley MRT.

scholarly journals SDSS-IV MaNGA: the inner density slopes of nearby galaxies

2019 ◽  
Vol 490 (2) ◽  
pp. 2124-2138 ◽  
Author(s):  
Ran Li ◽  
Hongyu Li ◽  
Shi Shao ◽  
Shengdong Lu ◽  
Kai Zhu ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
Velocity Dispersion ◽  
Large Fraction ◽  
Mean Value ◽  
Dynamical Analysis ◽  
Total Density ◽  
Anisotropic Models ◽  
Wide Range ◽  
Nearby Galaxies ◽  
Hydrodynamical Simulations

ABSTRACT We derive the mass-weighted total density slopes within the effective (half-light) radius, γ′, for more than 2000 nearby galaxies from the SDSS-IV (Sloan Digital Sky Survey IV) MaNGA survey using Jeans-anisotropic-models applied to integral field unit observations. Our galaxies span a wide range of the stellar mass (109 M⊙ < M* < 1012 M⊙) and the velocity dispersion (30 km s−1 < σv < 300 km s−1). We find that for galaxies with velocity dispersion σv > 100 km s−1, the density slope has a mean value 〈γ′〉 = 2.24 and a dispersion σγ = 0.22, almost independent of velocity dispersion, consistent with previous lensing and stellar dynamical analysis. We also quantitatively confirm with high accuracy a turnover in the γ′–σv relation is present at σ ∼ 100 km s−1, below which the density slope decreases rapidly with σv, consistent with the results reported by previous analysis of ${\rm ATLAS^{\rm 3D}}$ survey. Our analysis shows that a large fraction of dwarf galaxies (below M* = 1010 M⊙) have total density slopes shallower than 1, which implies that they may reside in cold dark matter haloes with shallow density slopes. We compare our results with that of galaxies in hydrodynamical simulations of EAGLE, Illustris, and IllustrisTNG projects, and find all simulations predict shallower density slopes for massive galaxies with high σv. Finally, we explore the dependence of γ′ on the positions of galaxies in haloes, namely centrals versus satellites, and find that for the same velocity dispersion, the amplitude of γ′ is higher for satellite galaxies by about 0.1.

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