Dust in Hot Plasma of Nearby Dusty Elliptical Galaxies Observed with the Spitzer Space Telescope

We report on mid- and far-IR Spitzer observations of 7 nearby dusty elliptical galaxies by using the Multiband Imaging Photometer (MIPS) and Infrared Spectrograph (IRS). Our sample galaxies are known to contain an excessive amount of interstellar dust against sputtering destruction in hot plasma filling the interstellar space of elliptical galaxies. In order to study the origin and the properties of the excess dust in the hot plasma, we selected galaxies with a wide range of X-ray luminosities but similar optical luminos ities for our Spitzer Guest Observers (GO1) program. The 7 galaxies are detected at the MIPS 24 um, 70 um, and 160 um bands; the far- to mid-IR flux ratios of relatively X-ray-bright elliptical galaxies are lower than those of X-ray-faint galaxies. From the IRS spectra, polycyclic aromatic hydrocarbon (PAH) emission features are detected significantly from 5 of the 7 galaxies; t he emission intensities are weaker as the X-ray luminosity of the galaxy is larger. We have found a correlation between the far- to mid-IR flux ratio and the equivalent width of the PAH emission feature. We have obtained apparent spatial correspondence between mid-IR and X-ray distributions in the outer regions for the three X-ray-brightest galaxies in our sample. Possible interpretations for our observational results are discussed.Comment: 25 pages, 7 figures, accepted for publication in Publications of the Astronomical Society of Japa

Investigating the hard X-ray emission from the hottest Abell cluster A2163 with Suzaku

We present the results from Suzaku observations of the hottest Abell galaxy cluster A2163 at $z=0.2$. To study the physics of gas heating in cluster mergers, we investigated hard X-ray emission from the merging cluster A2163, which hosts the brightest synchrotron radio halo. We analyzed hard X-ray spectra accumulated from two-pointed Suzaku observations. Non-thermal hard X-ray emission should result from the inverse Compton (IC) scattering of relativistic electrons by the CMB photons. To measure this emission, the dominant thermal emission in the hard X-ray band must be modeled in detail. To this end, we analyzed the combined broad-band X-ray data of A2163 collected by Suzaku and XMM-Newton, assuming single- and multi-temperature models for thermal emission and the power-law model for non-thermal emission. From the Suzaku data, we detected significant hard X-ray emission from A2163 in the 12-60 keV band at the $28\sigma$ level (or at the $5.5\sigma$ level if a systematic error is considered). The Suzaku HXD spectrum alone is consistent with the single-T thermal model of gas temperature $kT=14$ keV. From the XMM data, we constructed a multi-T model including a very hot ($kT=18$ keV) component in the NE region. Incorporating the multi-T and the power-law models into a two-component model with a radio-band photon index, the 12-60 keV energy flux of non-thermal emission is constrained within $5.3 \pm 0.9 (\pm 3.8)\times 10^{-12}~{\rm erg\, s^{-1} cm^{-2}}$. The 90% upper limit of detected IC emission is marginal ($< 1.2\times 10^{-11}~{\rm erg\, s^{-1} cm^{-2}}$ in the 12-60 keV). The estimated magnetic field in A2163 is $B > 0.098~{\rm \mu G}$. While the present results represent a three-fold increase in the accuracy of the broad band spectral model of A2163, more sensitive hard X-ray observations are needed to decisively test for the presence of hard X-ray emission due to IC emission.Comment: 7 pages, 7 figures, A&A accepted. Minor correctio

Supernova Explosions in the Early Universe: Evolution of Radiative Remnants and the Halo Destruction Efficiency

We study the evolution of supernova (SN) remnants of the first stars, taking proper account of the radiative feedback of the progenitor stars on the surroundings. We carry out a series of one-dimensional hydrodynamic simulations with radiative cooling, starting from initial configurations that are drawn from the results of our earlier radiation hydrodynamic simulations of the first HII regions. In low-mass (< 10^6 M_sun) halos, the stellar radiation significantly reduces the ambient gas density prior to the SN explosion. The blastwave quickly propagates over the halo's virial radius, leading to complete evacuation of the gas even with the input energy of 10^50 erg. We find that a large fraction of the remnant's thermal energy is lost in 0.1-10 Myr by line cooling, whereas, for larger explosion energies, the remnant expands even more rapidly with decreasing interior density, and cools predominantly via inverse Compton process. In higher mass halos, the gas density near the explosion site remains high and the SN shock is heavily confined; the thermal energy of the remnant is quickly radiated away by free-free emission, even if the total input energy exceeds the binding energy of halos by two orders of magnitude. We show that the efficiency of halo destruction is determined not only by the explosion energy but also by the gas density profile, and thus controlled by radiative feedback prior to the explosion. Several implications of our results for the formation of first quasars and second-generation stars in the universe are also discussed.Comment: 13 pages, 11 embedded figures. Accepted for publication in Ap

The Evolution of Diffuse Radio Sources in Galaxy Clusters

We investigate the evolution and number distribution of radio halos in galaxy clusters. Without re-acceleration or regeneration, the relativistic electrons responsible for the diffuse radio emission will lose their energy via inverse-Compton and synchrotron losses in a rather short time, and radio halos will have lifetimes $\sim$ 0.1 Gyr. Radio halos could last for $\sim$ Gyr if a significant level of re-acceleration is involved. The lifetimes of radio halos would be comparable with the cosmological time if the radio-emitting electrons are mainly the secondary electrons generated by pion decay following proton-proton collisions between cosmic-ray protons and the thermal intra-cluster medium within the galaxy clusters. Adopting both observational and theoretical constraints for the formation of radio halos, we calculate the formation rates and the comoving number density of radio halos in the hierarchical clustering scheme. Comparing with observations, we find that the lifetimes of radio halos are $\sim$ Gyr. Our results indicate that a significant level of re-acceleration is necessary for the observed radio halos and the secondary electrons may not be a dominant origin for radio halos.Comment: 22 pages, 6 figures, ApJ, in press (v2:Corrected typos.

Mass and Redshift Dependence of Dark Halo Structure

Using a combination of N-body simulations with different resolutions, we study in detail how the concentrations of cold dark matter (CDM) halos depend on halo mass at different redshifts. We confirm that halo concentrations at the present time depend strongly on halo mass, but our results also show marked differences from the predictions of some early empirical models. Our main result is that the mass dependence of the concentrations becomes weaker at higher redshifts, and at z >~ 3 halos of mass greater than 10^{11} Msun/h all have a similar median concentration, c ~ 3.5. While the median concentrations of low-mass halos grow significantly with time, those of massive halos change only little with redshifts. These results are quantitatively in good agreement with the empirical model proposed by Zhao et al. which shows that halos in the early fast accretion phase all have similar concentrations.Comment: 11 pages, including 2 figures and 1 table, publicated in ApJL, the first paper stating the zero mass-dependence of concentrations for massive and/or high redshift dark matter halos, which are still in the fast growth phase, quoted by the second version of ; v2: references corrected to be the same as the published versio

Seismic loss assessment of seismically isolated buildings designed by the procedures of ASCE/SEI 7-16

Availability of data and material: The data that support the findings of this study are available from the corresponding author upon reasonable request.Code availability: Some or all data, models, or code generated or used during the study are available in a repository or online in accordance with funder data retention policies (https://github.com/shkma/LossAssessment [last accessed 5.February.2021]).Copyright © The Author(s) 2021. This paper investigates the seismic loss assessment of seismically isolated and non-isolated buildings with steel moment or braced frames, designed by the seismic design standard of ASCE/SEI 7-16. The seismic loss is calculated from the damage to structural and non-structural components, as well as the demolition and the collapse of buildings. This study demonstrates that the expected annual losses for seismically isolated buildings are half or less than half of those calculated for non-isolated buildings. These losses depend on the types of seismic isolation systems and seismic force resisting systems used. Among the cases of isolated buildings studied in this paper, the most cost-effective systems are found to be the buildings designed by minimum strength requirement in ASCE/SEI 7-16 and with isolators which have displacement capacity 1.5 times larger than the minimum required in ASCE/SEI 7-16, in terms of expected annual losses. This study also compares the results obtained from different approaches of selection and scaling of ground motions. The following research finds that when Incremental Dynamic Analysis approach with far-field ground motion set in FEMA P695 is used, the computed expected total annual losses become doubled from the Conditional Spectra approach.The author(s) received no financial support for the research, authorship, and/or publication of this article

Imaging Simulations of the Sunyaev-Zel'dovich Effect for ALMA

We present imaging simulations of the Sunyaev-Zel'dovich effect of galaxy clusters for the Atacama Large Millimeter/submillimeter Array (ALMA) including the Atacama Compact Array (ACA). In its most compact configuration at 90GHz, ALMA will resolve the intracluster medium with an effective angular resolution of 5 arcsec. It will provide a unique probe of shock fronts and relativistic electrons produced during cluster mergers at high redshifts, that are hard to spatially resolve by current and near-future X-ray detectors. Quality of image reconstruction is poor with the 12m array alone but improved significantly by adding ACA; expected sensitivity of the 12m array based on the thermal noise is not valid for the Sunyaev-Zel'dovich effect mapping unless accompanied by an ACA observation of at least equal duration. The observations above 100 GHz will become excessively time-consuming owing to the narrower beam size and the higher system temperature. On the other hand, significant improvement of the observing efficiency is expected once Band 1 is implemented in the future.Comment: 16 pages, 12 figures. Accepted for publication in PASJ. Note added in proof is include