Browsing by Subject "infrared: diffuse background"

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  • Ade, P. A. R.; Juvela, M.; Keihanen, E.; Kurki-Suonio, H.; Poutanen, T.; Suur-Uski, A. -S.; Tuovinen, J.; Valiviita, J.; Planck Collaboration (2014)
  • Abergel, A.; Juvela, M.; Kurki-Suonio, H.; Lähteenmäki, Anne; Suur-Uski, A. -S.; Valiviita, J.; Planck Collaboration (2014)
  • Cappelluti, N.; Arendt, R.; Kashlinsky, A.; Li, Y.; Hasinger, G.; Helgason, K.; Urry, M.; Natarajan, P.; Finoguenov, A. (2017)
    We present new measurements of the large-scale clustering component of the cross-power spectra of the source-subtracted Spitzer-IRAC cosmic infrared background and Chandra-ACIS cosmic X-ray background surface brightness fluctuations Our investigation uses data from the Chandra Deep Field South, Hubble Deep Field North, Extended Groth Strip/AEGIS field, and UDS/SXDF surveys, comprising 1160 Spitzer hours and similar to 12 Ms of Chandra data collected over a total area of 0.3 deg(2). We report the first (> 5 sigma) detection of a cross-power signal on large angular scales > 20" between [0.5-2] keV and the 3.6 and 4.5 mu m bands, at similar to 5 sigma and 6.3 sigma significance, respectively. The correlation with harder X-ray bands is marginally significant. Comparing the new observations with existing models for the contribution of the known unmasked source population at z <7, we find an excess of about an order of magnitude at 5 sigma confidence. We discuss possible interpretations for the origin of this excess in terms of the contribution from accreting early black holes (BHs), including both direct collapse BHs and primordial BHs, as well as from scattering in the interstellar medium and intra-halo light.
  • Cappelluti, Nico; Li, Yanxia; Ricarte, Angelo; Agarwal, Bhaskar; Allevato, Viola; Ananna, Tonima Tasnim; Ajello, Marco; Civano, Francesca; Comastri, Andrea; Elvis, Martin; Finoguenov, Alexis; Gilli, Roberto; Hasinger, Guenther; Marchesi, Stefano; Natarajan, Priyamvada; Pacucci, Fabio; Treister, E.; Urry, C. Megan (2017)
    Using Chandra observations in the 2.15 deg(2) COSMOS-legacy field, we present one of the most accurate measurements of the Cosmic X-ray Background (CXB) spectrum to date in the [0.3-7] keV energy band. The CXB has three distinct components: contributions from two Galactic collisional thermal plasmas at kT similar to 0.27 and 0.07 keV and an extragalactic power law with a photon spectral index Gamma = 1.45 +/- 0.02. The 1 keV normalization of the extragalactic component is 10.91 +/- 0.16 keV cm(-2) s(-1) sr(-1) keV(-1). Removing all X-ray-detected sources, the remaining unresolved CXB is best fit by a power law with normalization 4.18 +/- 0.26 keV cm(-2) s(-1) sr(-1) keV(-1) and photon spectral index Gamma = 1.57 +/- 0.10. Removing faint galaxies down to i(AB) similar to 27-28 leaves a hard spectrum with Gamma similar to 1.25 and a 1 keV normalization of similar to 1.37 keV cm(-2) s(-1) sr(-1) keV(-1). This means that similar to 91% of the observed CXB is resolved into detected X-ray sources and undetected galaxies. Unresolved sources that contribute similar to 8%-9% of the total CXB show marginal evidence of being harder and possibly more obscured than resolved sources. Another similar to 1% of the CXB can be attributed to still undetected star-forming galaxies and absorbed active galactic nuclei. According to these limits, we investigate a scenario where early black holes totally account for non-source CXB fraction and constrain some of their properties. In order to not exceed the remaining CXB and the z similar to 6 accreted mass density, such a population of black holes must grow in Compton-thick envelopes with N-H > 1.6 x 10(25) cm(-2) and form in extremely low-metallicity environments (Z(circle dot)) similar to 10(-3).