2,362 research outputs found
Searching for MgII absorbers in and around galaxy clusters
To study environmental effects on the circumgalactic medium (CGM), we use the
samples of redMaPPer galaxy clusters, background quasars and cluster galaxies
from the SDSS. With ~82 000 quasar spectra, we detect 197 MgII absorbers in and
around the clusters. The detection rate per quasar is 2.70.7 times higher
inside the clusters than outside the clusters, indicating that MgII absorbers
are relatively abundant in clusters. However, when considering the galaxy
number density, the absorber-to-galaxy ratio is rather low inside the clusters.
If we assume that MgII absorbers are mainly contributed by the CGM of massive
star-forming galaxies, a typical halo size of cluster galaxies is smaller than
that of field galaxies by 3010 per cent. This finding supports that galaxy
haloes can be truncated by interaction with the host cluster.Comment: 11 pages, 12 figures. To appear in MNRA
Understanding the Formation and Evolution of Dark Galaxies in a Simulated Universe
We study the formation and evolution of dark galaxies using the IllustrisTNG
cosmological hydrodynamical simulation. We first identify dark galaxies with
stellar-to-total mass ratios, , smaller than ,
which differ from luminous galaxies with .
We then select the galaxies with dark matter halo mass of for mass completeness, and compare their physical
properties with those of luminous galaxies. We find that at the present epoch
(), dark galaxies are predominantly located in void regions without
star-forming gas. We also find that dark galaxies tend to have larger sizes and
higher spin parameters than luminous galaxies. In the early universe, dark and
luminous galaxies show small differences in the distributions of spin and local
environment estimates, and the difference between the two samples becomes more
significant as they evolve. Our results suggest that dark galaxies tend to be
initially formed in less dense regions, and could not form stars because of
heating from cosmic reionization and of few interactions and mergers with other
systems containing stars unlike luminous galaxies. This study based on
numerical simulations can provide important hints for validating dark galaxy
candidates in observations and for constraining galaxy formation models.Comment: 15 pages, 10 figures, accepted for publication in Ap
Peccei-Quinn Inflation at the Pole and Axion Kinetic Misalignment
We propose a minimal extension of the Standard Model with the Peccei-Quinn
(PQ) scalar field and explain the relic density of the QCD axion through the
kinetic misalignment with a relatively small axion decay constant. To this
purpose, we consider a slow-roll inflation from the radial component of the PQ
field with the PQ conserving potential near the pole of its kinetic term and
investigate the post-inflationary dynamics of the PQ field for reheating. The
angular mode of the PQ field, identified with the QCD axion, receives a nonzero
velocity during inflation due to the PQ violating potential, evolving with an
approximately conserved Noether PQ charge. We determine the reheating
temperature from the perturbative decays and scattering processes of the
inflaton and obtain dark radiation from the axions produced from the inflaton
scattering at a testable level in the future Cosmic Microwave Background
experiments. We show the correlation between the reheating temperature, the
initial velocity of the axion and the axion decay constant, realizing the axion
kinetic misalignment for the correct relic density.Comment: 25 pagesm 3 figure
Increasing the Durability of Piezoelectric Impact-based Micro Wind Generator in Real Application
AbstractThe purpose of this study is to increase the durability of piezoelectric impact-based micro wind generator (PIMWG) in real application. Using new PIMWG design, numerical simulation, and experimental comparison analysis, we improved the durability of PIMWGs in real application. The experimental results show that the optimized PIMWG generated 2.4 mW (RMS value), and it did not crack within 40h. In this study, we improved the durability of PIMWGs for real application
Possible link between Arctic Sea ice and January PM10 concentrations in South Korea
In this study, we investigated the possible teleconnection between PM10 concentrations in South Korea and Arctic Sea ice concentrations at inter-annual time scales using observed PM10 data from South Korea, NCEP R2 data, and NOAA Sea Ice Concentration (SIC) data from 2001 to 2018. From the empirical orthogonal function (EOF) analysis, we found that the first mode (TC1) was a large-scale mode for PM10 in South Korea and explained about 27.4% of the total variability. Interestingly, the TC1 is more dominantly influenced by the horizontal ventilation effect than the vertical atmospheric stability effect. The pollution potential index (PPI), which is defined by the weighted average of the two ventilation effects, is highly correlated with the TC1 of PM10 at a correlation coefficient of 0.75, indicating that the PPI is a good measure for PM10 in South Korea at inter-annual time scales. Regression maps show that the decrease of SIC over the Barents Sea is significantly correlated with weakening of high pressure over the Ural mountain range region, the anomalous high pressure at 500 hPa over the Korean peninsula, and the weakening of the Siberian High and Aleutian low. Moreover, these patterns are similar to the correlation pattern with the PPI, suggesting that the variability of SIC over the Barents Sea may play an important role in modulating the variability of PM10 in South Korea through teleconnection from the Barents Sea to the Korean peninsula via Eurasia
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