6108495
Are GRB 090423 and similar bursts due to superconducting cosmic strings?
Superconducting cosmic strings may be able to power energetic gamma-ray bursts, in particular at high-redshifts ($z>6$). The ultra-relativistic outflows driven by the superconducting cosmic strings, however, seem too narrow to be consistent with the afterglow data of GRB 090423 and GRB 080913.
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.
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.
122021518
Lattice and beam dynamics for the pulse mode of the laser-electron storage ring for a Compton x-ray source
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
16270452
A CHANDRA STUDY OF TEMPERATURE SUBSTRUCTURES IN INTERMEDIATE-REDSHIFT GALAXY CLUSTERS
By analyzing the gas temperature maps created from the Chandra archive data, we reveal the prevailing existence of temperature substructures on ~100 h –1 70 kpc scales in the central regions of nine intermediate-redshift (z ≈ 0.1) galaxy clusters, which resemble those found in the Virgo and Coma Clusters. Each substructure contains a clump of hot plasma whose temperature is about 2-3 keV higher than the environment, corresponding to an excess thermal energy of ~1058-1060 erg per clump. If there were no significant nongravitational heating sources, these substructures would have perished in 108-109 yr due to thermal conduction and turbulent flows, whose velocity is found to range from about 200 to 400 km s–1, we conclude that the substructures cannot be created and sustained by inhomogeneous radiative cooling. We also eliminate the possibilities that the temperature substructures are caused by supernova explosions, or by the nonthermal X-ray emission due to the inverse-Comptonization of the cosmic microwave background photons. By calculating the rising time of active galactic nucleus (AGN)-induced buoyant bubbles, we speculate that the intermittent AGN outbursts (≥1060 erg per burst) may have played a crucial role in the formation of the high-temperature substructures. Our results are supported by the recent study of McNamara and Nulsen, posing a tight observational constraint on future theoretical and numerical studies.
119291530
Quantum Wave Equation of Photon
In this paper, we give the quantum wave equations of single photon when it is in the vacuum and medium. With these wave equations, we can study light interference and diffraction with the approach of quantum theory, and also can study the quantum property of photon when it is in a general crystal and photonic crystal. Otherwise, it can be applied in quantum optics and condensed matter feld.
118575807
Model-Independent Distance Measurements from Gamma-Ray Bursts and Constraints on Dark Energy
Gamma-ray bursts (GRB) are the most energetic events in the Universe and provide a complementary probe of dark energy by allowing the measurement of cosmic expansion history that extends to redshifts greater than 6. Unlike type Ia supernovae (SNe Ia), GRBs must be calibrated for each cosmological model considered, because of the lack of a nearby sample of GRBs for model-independent calibration. For a flat universe with a cosmological constant, we find {omega}{sub m}=0.25{sub -0.11}{sup +0.12} from 69 GRBs alone. We show that the current GRB data can be summarized by a set of model-independent distance measurements, with negligible loss of information. We constrain a dark energy equation of state linear in the cosmic scale factor using these distance measurements from GRBs, together with the ''Union'' compilation of SNe Ia, WMAP five-year observations, and the SDSS (Sloan Digital Sky Survey) baryon acoustic oscillation scale measurement. We find that a cosmological constant is consistent with current data at 68% confidence level for a flat universe. Our results provide a simple and robust method to incorporate GRB data in a joint analysis of cosmological data to constrain dark energy.
119242452
Unified dark fluid with constant adiabatic sound speed and cosmic constraints
As is known above 90% of the energy content in Universe is made of unknown dark component. Usually this dark fluid is separated into two parts: dark matter and dark energy. However, it may be a mixture of these two energy components, or just one exotic unknown fluid. This property is dubbed as dark degeneracy. With this motivation, in this paper, a unified dark fluid having constant adiabatic sound speed $c_s^2=\alpha$, which is in the range $[0,1]$, is studied. At first, via the energy conservation equation, its energy density, $\rho_d/\rho_{d0}=(1-B_s)+B_s a^{-3(1+\alpha)}$ where $B_s$ is related to integration constant from energy conservation equation as another model parameter, is presented. Then by using Markov Chain Monte Carlo method with currently available cosmic observational data sets which include type Ia supernova Union 2, baryon acoustic oscillation and WMAP 7-year data of cosmic background radiation, we show that small values of $\alpha$ are favored in this unified dark fluid model. Furthermore, we show that smaller values of $\alpha<10^{-5}$ are required to match matter (baryon) power spectrum from SDSS DR7.
122028642
The effect of the tensor force on the bubble structure in Ar isotopes
Abstract.The tensor force effect on the proton bubble structure of Ar isotopes is investigated in the framework of the Hartree-Fock-Bogoliubov (HFB) approach with the Skyrme interactions SLy5+T and SLy5+Tw. It is shown that the tensor force effect of the SLy5+Tw interaction favors the bubble structure of 44-56Ar due to the inversion between the proton single-particle states $ 2s_{1/2}$ and $ 1d_{3/2}$ ( $ 2s_{1/2}$ -1d3/2 inversion). However, the SLy5+T interaction cannot lead to any $ 2s_{1/2}$ -1d3/2 inversion of Ar isotopes, consequently, no bubble structure can be found in the isotopes. In addition, taking 46Ar as an example, the competition between the tensor force and pairing interaction on the bubble formation is examined in order to understand the bubble formation mechanism.
118625117
Different Evolutionary Stages in the Massive Star-forming Region W3 Main Complex
Aims. Massive stars form in clusters, and they are often found in different evolutionary stages located close to each other. To understand evolutionary and environmental effects during the formation of high-mass stars, we observed three regions of massive star formation at different evolutionary stages that reside in the same natal molecular cloud. Methods. The three regions S255IR, S255N and S255S were observed at 1.3 mm with the Submillimeter Array (SMA) and followup short spacing information was obtained with the IRAM 30m telescope. Near infrared (NIR) H + K-band spectra and continuum observations were taken for S255IR with VLT-SINFONI to study the different stellar populations in this region. Results. The combination of millimeter (mm) and near infrared data allow us to characterize different stellar populations within the young forming cluster in detail. While we find multiple mm con tinuum sources toward all regions, their outflow, disk and ch emical properties vary considerably. The most evolved source S255IR exhibits a collimated bipolar outflow visible in CO and H 2 emission, the outflows from the youngest region S255S are still small an d rather confined in the regions of the mm continuum peaks. Als o the chemistry toward S255IR is most evolved exhibiting strong emission from complex molecules, while much fewer molecular lines are detected in S255N, and in S255S we detect only CO isotopologues and SO lines. Also, rotational structures are found toward S255N and S255IR. Furthermore, a comparison of the NIR SINFONI and mm data from S255IR clearly reveal two different (proto) stellar populations with an estimated age difference of approximately 1 Myr. Conclusions. A multi-wavelength spectroscopy and mapping study reveals different evolutionary phases of the star formation regions. We propose the triggered outside-in collapse star formation scenario for the bigger picture and the fragmentation scenario for S255IR.