118161430
Population study for gamma-ray pulsars; II Millisecond pulsars
The population of $\gamma$-ray emitting millisecond pulsars (MSPs) is studied by using Monte-Carlo techniques. We simulate the Galactic distributions of the MSPs, and apply the outer gap model for the $\gamma$-ray emission from each simulated MSP. We take into account the dependence of the observed $\gamma$-ray flux on the viewing angle and inclination angle, which is the angle between the rotation axis and the magnetic axis, respectively. Using the sensitivity of the six-month long observation of the $Fermi$ telescope and radio sensitivities of existing pulsar surveys, 9-13 radio-selected and 22-35 $\gamma$-ray-selected pulsars are detected within our simulation. The statistical properties of the simulated population are consistent with the $Fermi$ observations. Scaling the observed sensitivity $\propto \sqrt{T}$, where $T$ is the length of observation time, the present model predicts that over the 5-year mission $Fermi$ would detect 15-22 radio-selected $\gamma$-ray MSPs, and 95-152 $\gamma$-ray-selected MSPs. Our simulation also predicts that about 100 (or 200-300) $\gamma$-ray MSPs with a flux larger $F\ge 10^{-11}~\mathrm{erg/cm^2 s}$ (or $5\times 10^{-12}~\mathrm{erg/cm^2 s}$) irradiate the Earth. With the present sensitivities of the radio surveys, most of them are categorized as $\gamma$-ray-selected pulsars, indicating that most of the $\gamma$-ray MSPs have been missed by the present $Fermi$ observations. We argue that the Galactic $Fermi$ unidentified sources located at high latitudes should be dominated by MSPs, whereas the sources in the galactic plane are dominated by radio-quiet canonical pulsars.
119299391
Outer gap accelerator closed by magnetic pair-creation process
We discuss outer gap closure mechanism in the trans-field direction with the magnetic pair-creation process near the stellar surface. The gap closure by the magnetic pair-creation is possible if some fraction of the pairs are produced with an outgoing momentum. By assuming that multiple magnetic field will affect the local field near the stellar surface, we show a specific magnetic field geometry near the stellar surface resulting in the outflow of the pairs. Together with the fact that the electric field is weak below null charge surface, the characteristic curvature photon energy emitted by incoming particles, which were accelerated in the outer gap, decreases drastically to ∼ 100MeV near the stellar surface. We estimate the height measured from the last-open field line, above which 100 MeV photons is converted into pairs by the magnetic pair-creation. We also show the resultant multiplicity due to the magnetic pair-creation process could acquire Me± ∼ 10− 10. In this model the fractional outer gap size is proportional to P. The predicted gamma-ray luminosity (Lγ) and the characteristic curvature photon energy (Ec) emitted from the outer gap are proportional to B P and BP respectively. This model also predicts that Lγ and Ec are related to the spin down power (Lsd) or the spin down age of pulsars (τ) as Lγ ∝ L 5/8 sd or Lγ ∝ τ , and Ec ∝ L 1/4 sd or Ec ∝ τ −1/2 respectively. Subject headings: pulsars: general– radiation mechanisms:non-thermal– -gamma rays:theory–magnetic field
118889930
POPULATION STUDY FOR γ-RAY PULSARS WITH THE OUTER GAP MODEL
Inspired by the increase of the population of {gamma}-ray emitting pulsars by the Fermi telescope, we perform a population study for {gamma}-ray emitting canonical pulsars. We use a Monte Carlo technique to simulate the Galactic population of neutron stars and the radio pulsars. For each simulated neutron star, we consider the {gamma}-ray emission from the outer gap accelerator in the magnetosphere. In our outer gap model, we apply the gap closure mechanism proposed by Takata et al., in which both photon-photon pair-creation and magnetic pair-creation processes are considered. Simulating the sensitivities of previous major radio surveys, our simulation predicts that there are {approx}18-23 radio-loud and {approx}26-34 {gamma}-ray-selected {gamma}-ray pulsars, which can be detected with a {gamma}-ray flux F{sub {gamma}} {>=} 10{sup -10} erg cm{sup -2} s{sup -1}. Applying the sensitivity of the six month observation of the Fermi telescope, 40-61 radio-selected and 36-75 {gamma}-ray selected pulsars are detected within our simulation. We show that the distributions of various pulsar parameters for the simulated {gamma}-ray pulsars can be consistent with the observed distribution of the {gamma}-ray pulsars detected by the Fermi telescope. We also predict that {approx}64 radio-loud and {approx}340 {gamma}-ray-selected pulsars irradiate the Earth with a flux F{sub {gamma}} {>=}more » 10{sup -11} erg cm{sup -2} s{sup -1}, and most of those {gamma}-ray pulsars are distributed with a distance greater than 1 kpc and a flux F{sub {gamma}} {approx} 10{sup -11} erg cm{sup -2} s{sup -1}. The ratio between the radio-selected and {gamma}-ray-selected pulsars depends on the sensitivity of the radio surveys. We also discuss the Galactic distribution of the unidentified Fermi sources and the canonical {gamma}-ray pulsars.« less
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.
119035074
X-Ray Properties of the Point Source Population in the Spiral Galaxy NGC 5055 （M63） with Chandra
Using Chandra ACIS S3 data we studied the X-ray properties of low-and high-mass X-ray binary populations in the nearby spiral galaxy NGC 5055. A total of 43 X-ray point sources were detected within two effective radii, with 31 sources located on the disk and the rest 12 sources in the bulge. The resolved point sources dominate the X-ray emission of the galaxy, accounting for about 80% of the total counts in 0.3–10 keV. From spectral fittings we calculated the 0.3–10.0 keV luminosities of all the detected X-ray point sources and found that they span a wide range from a few times 1037 erg s−1 to over 1039 erg s−1. After compensating for incompleteness at the low luminosity end, we found that the corrected XLF of the bulge population is well fitted with a broken power-law with a break at 1.57+0.21−0.20×1038 erg s−1, while the profile of the disk population's XLF agrees with a single power-law distribution of slope 0.93+0.07−0.06. The disk population is significantly richer at 2×1038 erg s−1 than the bulge population, indicating that the disk may have undergone relatively recent, strong starbursts that significantly increased the HMXB population, although ongoing starbursts are also observed in the nuclear region. Similar XLF profiles of the bulge and disk populations were found in M81. However, in most other spiral galaxies different patterns of spatial variation of the XLF profiles from the bulge to the disk have been observed, indicating that the star formation and evolution history may be more complex than we have expected.
14274089
A Universal Probability Distribution Function for Weak-lensing Amplification
We present an approximate form for the weak-lensing magnification distribution of standard candles, valid for all cosmological models, with arbitrary matter distributions, over all redshifts. Our results are based on a universal probability distribution function (UPDF), P(η), for the reduced convergence, η. For a given cosmological model, the magnification probability distribution, P(μ), at redshift z is related to the UPDF by P(μ) = P(η)/ , where η = 1 + (μ - 1)/(2|κmin|), and κmin (the minimum convergence) can be directly computed from the cosmological parameters (Ωm and ΩΛ). We show that the UPDF can be well approximated by a three-parameter stretched Gaussian distribution, where the values of the three parameters depend only on ξη, the variance of η. In short, all possible weak-lensing probability distributions can be well approximated by a one-parameter family. We establish this family, normalizing to the numerical ray-shooting results for a Λ cold dark matter (CDM) model by Wambsganss et al. (1997). Each alternative cosmological model is then described by a single function ξη(z). We find that this method gives P(μ) in excellent agreement with numerical ray-tracing and three-dimensional shear matrix calculations, and we provide numerical fits for three representative models (SCDM, ΛCDM, and OCDM). Our results provide an easy, accurate, and efficient method to calculate the weak-lensing magnification distribution of standard candles and should be useful in the analysis of future high-redshift supernova data.
118381910
Ultra-Relativistic Magnetic Monopole Search with the ANITA-II Balloon-borne Radio Interferometer
We have conducted a search for extended energy deposition trails left by ultrarelativistic magnetic monopoles interacting in Antarctic ice. The nonobservation of any satisfactory candidates in the 31 days of accumulated ANITA-II (Antarctic Impulsive Transient Antenna) flight data results in an upper limit on the diffuse flux of relativistic monopoles. We obtain a 90% C.L. limit of order 10{sup -19} (cm{sup 2} s sr){sup -1} for values of Lorentz factor, {gamma}, 10{sup 10{<=}{gamma}} at the anticipated energy E{sub tot}=10{sup 16} GeV. This bound is stronger than all previously published experimental limits for this kinematic range.
119228702
Cosmological evolution of the Fanaroff–Riley type II source population
By combining a model for the evolution of the radio luminosity of an individual source with the radio luminosity function, we perform a multidimensional Monte Carlo simulation to investigate the cosmological evolution of the Fanaroff–Riley type II (FR II) radio galaxy population by generating large artificial samples. The properties of FR II sources are required to evolve with redshift in the artificial samples to fit the observations. Either the maximum jet age or the maximum density of the jet environment or both evolve with redshift. We also study the distribution of FR II source properties as a function of redshift. From currently available data we cannot constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately −2. This power-law slope does not change with redshift out to z = 0.6. We also find the distribution of the pressure in the lobes of FR II sources to evolve with redshift up to z ∼ 1.2.