Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0809.0006

Galaxy Clusters in the Swift/BAT era: Hard X-rays in the ICM

M. Ajello·P. Rebusco·N. Cappelluti·O. Reimer·H. Boehringer·J. Greiner·N. Gehrels·J. Tueller·A. Moretti
View original source ↗Read source document ↗Export metadata ↓

Abstract

We report about the detection of 10 clusters of galaxies in the ongoing Swift/BAT all-sky survey. This sample, which comprises mostly merging clusters, was serendipitously detected in the 15--55 keV band. We use the BAT sample to investigate the presence of excess hard X-rays above the thermal emission. The BAT clusters do not show significant (e.g. >2 $σ$) non-thermal hard X-ray emission. The only exception is represented by Perseus whose high-energy emission is likely due to NGC 1275. Using XMM-Newton, Swift/XRT, Chandra and BAT data, we are able to produce upper limits on the Inverse Compton (IC) emission mechanism which are in disagreement with most of the previously claimed hard X-ray excesses. The coupling of the X-ray upper limits on the IC mechanism to radio data shows that in some clusters the magnetic field might be larger than 0.5 $μ$G. We also derive the first logN-logS and luminosity function distribution of galaxy clusters above 15 keV.

Explore related subjects

astro-ph

Keep this discovery

BibTeXRIS

M. Ajello, P. Rebusco, N. Cappelluti, O. Reimer, H. Boehringer, J. Greiner, N. Gehrels, J. Tueller, A. Moretti. 2008-08-30. Galaxy Clusters in the Swift/BAT era: Hard X-rays in the ICM. https://doi.org/10.1088/0004-637x/690/1/367

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2010

Extremely Red Objects in a hierarchical universe

We analyse whether hierarchical formation models based on Lambda cold dark matter cosmology can produce enough massive red galaxies to match observations. For this purpose, we compare with observations the predictions from two published models for the abundance and redshift distribution of Extremely Red Objects (EROs), which are red, massive galaxies observed at z >= 1. One of the models invokes a "superwind" to regulate star formation in massive haloes and the other suppresses cooling through "radio-mode" AGN feedback. The first one underestimates the number counts of EROs by an order of magnitude, whereas the radio-mode AGN feedback model gives excellent agreement with the number counts of EROs and redshift distribution of K-selected galaxies. This study highlights the need to consider AGN feedback in order to understand the formation and evolution of massive galaxies at z >= 1.

astro-ph↗
arXiv2010

Simulations and Analytic Calculations of Bubble Growth During Hydrogen Reionization

We present results from a large volume simulation of Hydrogen reionization. We combine 3d radiative transfer calculations and an N-body simulation, describing structure formation in the intergalactic medium, to detail the growth of HII regions around high redshift galaxies. Our simulation tracks 1024^3 dark matter particles, in a box of co-moving side length 65.6 Mpc/h. This large volume allows us to accurately characterize the size distribution of HII regions throughout most of the reionization process. At the same time, our simulation resolves many of the small galaxies likely responsible for reionization. It confirms a picture anticipated by analytic models: HII regions grow collectively around highly-clustered sources, and have a well-defined characteristic size, which evolves from a sub-Mpc scale at the beginning of reionization to R > 10 Mpc towards the end. We present a detailed statistical description of our results, and compare them with a numerical scheme based on the analytic model by Furlanetto, Zaldarriaga, and Hernquist. We find that the analytic calculation reproduces the size distribution of HII regions and the 21 cm power spectrum of the radiative transfer simulation remarkably well. The ionization field from the simulation, however, has more small scale structure than the analytic calculation, owing to Poisson scatter in the simulated abundance of galaxies on small scales. We propose and validate a simple scheme to incorporate this scatter into our calculations. Our results suggest that analytic calculations are sufficiently accurate to aid in predicting and interpreting the results of future 21 cm surveys. In particular, our fast numerical scheme is useful for forecasting constraints from future 21 cm surveys, and in constructing mock surveys to test data analysis procedures.

astro-ph↗