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The Crab nebula originated from a core-collapse supernova (SN) explosion observed in 1054 A.D. When viewed as a supernova remnant (SNR), it has an anomalously low observed ejecta mass and kinetic energy for an Fe-core collapse SN. Intensive searches were made for a massive shell that solves this discrepancy, but none has been detected. An alternative idea is that the SN1054 is an electron-capture (EC) explosion with a lower explosion energy by an order of magnitude than Fe-core collapse SNe. In the X-rays, imaging searches were performed for the plasma emission from the shell in the Crab outskirts to set a stringent upper limit to the X-ray emitting mass. However, the extreme brightness of the source hampers access to its vicinity. We thus employed spectroscopic technique using the X-ray micro-calorimeter onboard the Hitomi satellite. By exploiting its superb energy resolution, we set an upper limit for emission or absorption features from yet undetected thermal plasma in the 2-12 keV range. We also re-evaluated the existing Chandra and XMM-Newton data. By assembling these results, a new upper limit was obtained for the X-ray plasma mass of

The origin of the narrow Fe-K�� fluorescence line at 6.4 keV from active galactic nuclei has long been under debate; some of the possible sites are the outer accretion disk, the broad line region, a molecular torus, or interstellar/intracluster media. In February-March 2016, we performed the first X-ray microcalorimeter spectroscopy with the Soft X-ray Spectrometer (SXS) onboard the Hitomi satellite of the Fanaroff-Riley type I radio galaxy NGC 1275 at the center of the Perseus cluster of galaxies. With the high energy resolution of ~5 eV at 6 keV achieved by Hitomi/SXS, we detected the Fe-K�� line with ~5.4 �� significance. The velocity width is constrained to be 500-1600 km s$^{-1}$ (FWHM for Gaussian models) at 90% confidence. The SXS also constrains the continuum level from the NGC 1275 nucleus up to ~20 keV, giving an equivalent width ~20 eV of the 6.4 keV line. Because the velocity width is narrower than that of broad H�� line of ~2750 km s$^{-1}$, we can exclude a large contribution to the line flux from the accretion disk and the broad line region. Furthermore, we performed pixel map analyses on the Hitomi/SXS data and image analyses on the Chandra archival data, and revealed that the Fe-K�� line comes from a region within ~1.6 kpc from the NGC 1275 core, where an active galactic nucleus emission dominates, rather than that from intracluster media. Therefore, we suggest that the source of the Fe-K�� line from NGC 1275 is likely a low-covering fraction molecular torus or a rotating molecular disk which probably extends from a pc to hundreds pc scale in the active galactic nucleus system., 20 pages, 8 figures, 6 tables, accepted for publication in PASJ

We constrain gas and dark matter (DM) parameters of galaxy groups and clusters, by comparing X-ray scaling relations to theoretical expectations, obtained assuming that the gas is in hydrostatic equilibrium with the DM and follows a polytropic relation. We vary four parameters: the gas polytropic index Gamma, its temperature at large radii T_xi, the DM logarithmic slope at large radii zeta and its concentration c_vir. When comparing the model to the observed mass-temperature (M-T) relation of local clusters, our results are independent of both T_xi and c_vir. We thus obtain constraints on Gamma, by fixing the DM profile, and on zeta, by fixing the gas profile. For an NFW DM profile, we find that 6/5, Comment: 20 pages, 18 figures, 2 tables. Accepted for publication in MNRAS, with minor changes. Accepted version plus two typos corrected. Abstract abridged for astro-ph submission

We present an analytic formulation for the equilibrium gas density profile of early-type galaxies that explicitly includes the contribution of stars in the gravitational potential. We build a realistic model for an isolated elliptical galaxy and explore the equilibrium gas configurations as a function of multiple parameters. For an assumed central gas temperature k_B*T_0=0.6 keV, we find that neglecting the gravitational effects of stars, which can contribute substantially in the innermost regions, leads to an underestimate of the enclosed baryonic gas mass by up to ~65% at the effective radius, and by up to ~15% at the NFW scale radius, depending on the stellar baryon fraction. This formula is therefore important for estimating the baryon fraction in an unbiased fashion. These new hydrostatic equilibrium solutions, derived for the isothermal and polytropic cases, can also be used to generate more realistic initial conditions for simulations of elliptical galaxies. Moreover, the new formulation is relevant when interpreting X-ray data. We compare our composite isothermal model to the standard beta-model used to fit X-ray observations of early-type galaxies, to determine the value of the NFW scale radius r_s. Assuming a 10% stellar baryon fraction, we find that the exclusion of stars from the gravitational potential leads to (i) an underestimate of r_s by ~80%, and to (ii) an overestimate of the enclosed dark matter at r_s by a factor of ~2, compared to the equivalent beta-model fit results when stars are not taken into account. For higher stellar mass fractions, a beta-model is unable to accurately reproduce our solution, indicating that when the observed surface brightness profile of an isolated elliptical galaxy is found to be well fitted by a beta-model, the stellar mass fraction cannot be much greater than ~10%., 10 pages, 3 figures, 1 table. Version accepted for publication in MNRAS. Added references, corrected typos, added legends to figures

We present the discovery of a high redshift, X-ray selected AGN by the Calan-Yale Deep Extragalactic Research (CYDER) survey: CXOCY J033716.7-050153, located at $z=4.61$, the second high redshift AGN discovered by this survey. Here, we present its optical, near-IR and X-ray properties and compare it with other optical and X-ray selected high redshift AGN. The optical luminosity of this object is significantly lower than most optically selected high redshift quasars. It also has a lower rest frame UV to X-ray emission ratio than most known quasars at this redshift. This mild deviation can be explained either by dust obscuring the UV radiation of a normal radio quiet AGN emitting at 10% of its Eddington luminosity or because this is intrinsically a low luminosity radio loud AGN, with a super-massive Black Hole of $\sim 10^8M_\sun$ emitting at 1% of its Eddington luminosity. Deep radio observations can discriminate between these two hypotheses., ApJ accepted, 16 pages, 5 figures

If the high-energy emission from TeV blazars is produced by the Synchrotron Self-Compton (SSC) mechanism, then simultaneous X-ray and Gamma-ray observations of these objects are a powerful probe of the electron (and/or positron) populations responsible for this emission. Understanding the emitting particle distributions and their evolution in turn allow us to probe physical conditions in the inner blazar jet and test, for example, various acceleration scenarios. By constraining the SSC emission model parameters, such observations also allow us to predict the intrinsic (unabsorbed) Gamma-ray spectra of these sources, a major uncertainty in current attempts to use the observed Gamma-ray spectra to constrain the intensity of the extragalactic background at optical/infrared wavelengths. As a next step in testing the SSC model and as a demonstration of the potential power of coordinated X-ray and Gamma-ray observations, we attempt to model in detail the X-ray and Gamma-ray light curves of the TeV Blazar Mrk 501 during its April-May 1997 outburst using a time dependent SSC emission model. Extensive, quasi-simultaneous X-ray and gamma-ray coverage exists for this period. We discuss and explore quantitatively several of the flare scenarios presented in the literature. We show that simple two-component models (with a soft, steady X-ray component plus a variable SSC component) involving substantial pre-acceleration of electrons to Lorentz factors on the order of 1E+5 describe the data train surprisingly well. All considered models imply an emission region that is strongly out of equipartition and low radiative efficiencies (ratio between kinetic jet luminosity and comoving radiative luminosity) of 1 per-mill and less., 16 pages, Refereed Manuscript. Minor changes to previous version

Paramount among the processes that ended the cosmic `dark ages' must have been the formation of the first generation of stars (the so-called Population III). We summarize recent progress in constraining its nature, and we discuss the basic physical reasons for why the first stars might have been quite massive, possibly even very massive with M > 100 M_sun., 7 pages, 4 figures, talk contributed to the conference:"Lighthouses of the Universe: The Most Luminous Celestial Objects and Their Use for Cosmology", Garching, August 2001

著者人数: 14名, Accepted: 2013-07-05, 資料番号: SA1004536000