arXiv subjects

Makoto Hattori

Publications and source records attributed to Makoto Hattori.

39 records · Page 3Linked to original sources

arXiv1999

Detection of Iron Emission Line from the Galaxy Cluster Including the Distant Radio Galaxy 3C220.1

We detected an emission line feature at 4 keV in the X-ray spectrum of a sky region including the distant radio galaxy 3C220.1(z=0.62) obtained with ASCA. The line energy is 6.1 - 7.0 keV (90% confidence) in the rest frame of 3C220.1. Within the present statistics, the observed spectra are consistent with two different models; a non-thermal model consisting of a power-law continuum plus a 6.4 keV iron emission line, and a Raymond-Smith thin-thermal emission model of kT ~6 keV with a metal abundance of ~0.5 solar. However, the large (~500 eV) equivalent width of the line indicates that a significant fraction of the X-ray emission is likel y to arise from the hot intracluster gas which associates the galaxy cluster including 3C220.1. The spectral parameters of the thermal emission is consistent with the luminosity-temperature relation of nearby clusters and the mass estimates from the giant luminous arc.

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arXiv1997

ICM masses in nearby and distant clusters of galaxies

We compile X-ray data of clusters of galaxies at a wide range of redshift $z=0.0\sim1.0$ and compare X-ray luminosities, gas masses, iron abundances and iron masses of nearby clusters and those of distant clusters as a function of plasma temperature. All the date presented in this paper have been obtained only with \ASCA and/or \ROSAT. No evidence for a change in the \KT -\LX\ relationship or \KT - iron abundance at $z<0.6$ is found. No significant change in \KT -\LX relationship at $z>0.6$ is seen, either. However, the gas masses of very distant clusters at $z\sim0.8-1.0$ and some clusters around $z\sim0.6$ are significantly lower than those of nearby clusters, which indicates a hint of evolution. The iron masses of the two very distant clusters at $z\sim0.8-1.0$ are significantly different from each other, which suggests that the epoch of the metal injection into ICM is different from cluster to cluster.

astro-ph↗

arXiv1996

Effect of kick velocity on the gamma-ray burster distribution

The effect of kick velocity to newly born pulsars on the distribution of $γ$-ray bursters is examined in the context of a disk origin model and a halo model of $γ$-ray bursters. The conversion formula from a 2-dimensional velocity distribution function to a 3-dimensional distribution function is derived and applied to reproduce the distribution function of the kick velocity of radio pulsars. Monte Carlo simulations of the kicked neutron stars show that the disk neutron star model of $γ$-ray bursters still needs unnatural assumptions if the velocity distribution of the $γ$-ray bursters is the same as that of neutron stars---only neutron stars with very high kick velocities can become $γ$-ray bursters and there are silent majorities. On the other hand, the core radius of $γ$-ray bursters is not found to be extended by the kick velocity if the core-halo structure similar to the Galactic dark matter distribution is based on the initial distribution of the halo neutron stars. Thus the introduction of a kick velocity to neutron stars do not improve the statistics of neither the disk model nor the halo model. Two possibilities to save Galactic models are suggested: (1) The $γ-$ray bursters are old neutron stars which were accelerated to velocities faster than $750~{\rm km\; s^{-1}}$ by jet propulsion and passed the death line for pulsars due to spin down from the rotational energy loss by jet ejection. (2) The initial distribution of neutron stars is fairly uniform and the extent of the halo is large enough for the halo model to be consistent with the observations. It implies that the initial star formation burst of the Galaxy occurred fairly uniformly in the extended halo region.

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