122021518
Lattice and beam dynamics for the pulse mode of the laser-electron storage ring for a Compton x-ray source
119194670
Metal enrichment via ram pressure stripping in the IGM of the compact galaxy group RGH 80
By creating and analyzing two dimensional gas temperature and abundance maps of the RGH 80 compact galaxy group with high-quality Chandra data, we detect a high-abundance (≃0.7 Z ⊙ ) arc, where the metal abundance is significantly higher than the surrounding regions by ≃0.3 Z ⊙ . This structure shows tight spatial correlations with the member galaxy PGC 046529, as well as with the arm-like feature identified on the X-ray image in the previous work of Randall et al. (2009). Since no apparent signature of AGN activity is found to be associated with PGC 046529 in multi-band observations, and the gas temperature, metallicity, and mass of the high-abundance arc resemble those of the ISM of typical early-type galaxies, we conclude that this high-abundance structure is the remnant of the ISM of PGC 046529, which was stripped out of the galaxy by ram pressure stripping due to the motion of PGC 046529 in RGH 80. This novel case shows that ram pressure stripping can work as efficiently in the metal enrichment process in galaxy groups as it can in galaxy clusters.
12882522
THE CLUSTERING OF SDSS GALAXY GROUPS: MASS AND COLOR DEPENDENCE
We use a large sample of galaxy groups selected from the SDSS data release 4 with an adaptive halo-based group finder to probe how the clustering strength of groups depends on their masses and colors. In particular, we determine the relative biases of groups of different masses, as well as that of groups with the same mass but with different colors. In agreement with previous studies, we find that more massive groups are more strongly clustered, and the inferred mass dependence of the halo bias is in good agreement with predictions for the ΛCDM concordance cosmology. Regarding the color dependence, we find that groups with red centrals are more strongly clustered than groups of the same mass but with blue centrals. Similar results are obtained when the color of a group is defined to be the total color of its member galaxies. The color dependence is more prominent in less massive groups and becomes insignificant in groups with masses 1014 h−1 M☉. These results are consistent with those obtained by Yang et al. from an analysis of the 2dFGRS, but inconsistent with those obtained by Berlind et al., who also used an SDSS group catalog. We construct a mock galaxy redshift survey from the large Millennium N-body simulation. Applying our group finder to this mock survey, and analyzing the mock data in exactly the same way as the true data, we are able to accurately recover the intrinsic mass and color dependencies of the halo bias in the model. Interestingly, the semianalytical model reveals the same color dependence of the halo bias as we find in our group catalog. We discuss these results in light of the assembly bias of dark matter halos and the star formation histories of galaxies.
12346298
THE NATURE OF RED DWARF GALAXIES
Using dark matter halos traced by galaxy groups selected from the Sloan Digital Sky Survey Data Release 4, we find that about 1/4 of the faint galaxies ({sup 0.1} M{sub r} - 5log h> - 17.05, hereafter dwarfs) that are the central galaxies in their own halo are not blue and star forming, as expected in standard models of galaxy formation, but are red. In contrast, this fraction is about 1/2 for dwarf satellite galaxies. Many red dwarf galaxies are physically associated with more massive halos. In total, about {approx}45% of red dwarf galaxies reside in massive halos as satellites, while another {approx}25% have a spatial distribution that is much more concentrated toward their nearest massive halos than other dwarf galaxies. We use mock catalogs to show that the reddest population of nonsatellite dwarf galaxies is distributed within about three times the virial radii of their nearest massive halos. We suggest that this population of dwarf galaxies is hosted by low-mass halos that have passed through their massive neighbors, and that the same environmental effects that cause satellite galaxies to become red are also responsible for the red colors of this population of galaxies. We do not find any significantmore » radial dependence of the population of dwarf galaxies with the highest concentrations, suggesting that the mechanisms operating on these galaxies affect color more than structure. However, over 30% of dwarf galaxies are red and isolated and their origin remains unknown.« less
15367156
A High-Abundance Arc in the Compact Group of Galaxies HCG 62: An AGN- or Merger-Induced Metal Outflow?
We present a Chandra study of the metal distribution in the X-ray bright compact group of galaxies HCG 62. We find that the diffuse X-ray emission is peaked at the core of the central galaxy NGC 4778 and is dominated by the contribution of the hot gas. The diffuse emission is roughly symmetric within similar or equal to 0.25', which is straddled by double-sided X-ray cavities aligned in the northeast-southwest direction. By mapping the emission hardness ratio distributions and by performing a two-dimensional spectral analysis, we identify a remarkable high-abundance arc region at about 2' (33: 6 h(70)(-1) kpc) from the X-ray peak that spans over a vast region from south to northwest, a part of which roughly coincides with the outer edge of the southwest X-ray cavity. The measured average abundance in this arc is higher than that in its neighboring regions by a factor of about 2, and the abundance ratios therein are nicely consistent with the dominance of the SN Ia yields. We estimate that the mass of iron contained in the arc is > 3 x 10(6) h(70)(-2.5) M-circle dot, which accounts for > 3% of the iron synthesized in the galaxy. The high-abundance arc could have been formed by AGN activity. However, it is also possible that the arc was formed in a recent merger, as implied by the recent optical kinematic study by Spavone and colleagues, which suggests that mergers may be as important as AGN activity in metal redistributions in early-type galaxies and their associated groups or clusters.
12040637
Is the energy generation rate of nuclear reactions in hot accretion flows important
The temperature of hot accretion flows around black holes is sufficiently high for the ignition of nuclear reactions. This is potentially an important nucleosynthesis mechanism in the universe. As the first step in studying this problem, we need to measure physical quantities such as density and temperature of the accretion flow. In usual studies of the hot accretion flow, viscous dissipation is considered to be the only heating mechanism, while the heating caused by nuclear reactions is not considered. In this paper, we investigate whether the energy generation rate of nuclear reaction is important compared to the viscous heating. Our calculation indicates that the former is at most one percent of the latter and thus is not important. The dynamics of accretion flow can be therefore calculated in the usual way, without the need to consider heating due to nuclear reactions.
121568193
Energy determination at BEPC-II
The BEPC-II collider beam energy calibration system is discussed. The system is based on the Compton backscattering method. The expected precision of the electron and positron beam energy e determination is δ e / e ≈ 3 ⋅ 10 − 5 .
54853347
BEAM DYNAMICS IN THE LASER-ELECTRON STORAGE RING FOR A COMPTON X-RAY SOURCE
We present the lattice analysis and simulation study of the beam dynamics in the pulse mode of the laser-electron storage ring. Compton Scattering (CS), Intra-beam Scattering (IBS) with non-Gaussian beam and Synchrotron Radiation (SR) are taken into consideration. Emittance growth, energy spread and phase space of the electron beam, as well as spatial and temporal distribution of the scattered photon are studied in this paper. INTRODUCTION The idea of utilizing a Laser-Electron Storage Ring (LESR) for the purpose of increasing frequency and luminosity of x-ray by means of Compton Scattering was proposed by Huang and Ruth in 1998 [1]. There are two main operation mode proposed for this scheme: the steady mode and the pulse mode. In this paper, we focus on the pulse mode of the LESR, in which electron beams are injected and dumped at the frequency of 50Hz. We will present the lattice design, simulation method and simulation results in this paper.
39000912
Implementation and performance of parallelized elegant
The program elegant is widely used for design and modeling of linacs for free-electron lasers and energy recovery linacs, as well as storage rings and other applications. As part of a multi-year effort, we have parallelized many aspects of the code, including single-particle dynamics, wakefields, and coherent synchrotron radiation. We report on the approach used for gradual parallelization, which proved very beneficial in getting parallel features into the hands of users quickly. We also report details of parallelization of collective effects. Finally, we discuss performance of the parallelized code in various applications.
54056752
Coherent $J/\psi$ photoproduction in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV
Abstract The ALICE Collaboration has made the first measurement at the LHC of J / ψ photoproduction in ultra-peripheral Pb–Pb collisions at s NN = 2.76 TeV . The J / ψ is identified via its dimuon decay in the forward rapidity region with the muon spectrometer for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 55 μb −1 . The cross section for coherent J / ψ production in the rapidity interval − 3.6 y − 2.6 is measured to be d σ J / ψ coh / d y = 1.00 ± 0.18 ( stat ) − 0.26 + 0.24 ( syst ) mb . The result is compared to theoretical models for coherent J / ψ production and found to be in good agreement with those models which include nuclear gluon shadowing.
122172140
Band spectrum for an electron on a Sierpinski gasket in a magnetic field
Abstract We consider a quantum charged particle on a fractal lattice given by a Sierpinski gasket, submitted to a uniform magnetic field, in a tight binding approximation. Its band spectrum is numerically computed and exhibits a fractal structure. The groundstate energy is also compared to the superconductor transition curve measured for a Sierpinski lattice of superconducting material.