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Photometric redshift accuracy in <i>AKARI</i> deep surveys
Negrello, M.,Serjeant, S.,Pearson, C.,Takagi, T.,Efstathiou, A.,Goto, T.,Burgarella, D.,Jeong, W.-S.,Im, M.,Lee, H. M.,Matsuhara, H.,Oyabu, S.,Wada, T.,White, G. Blackwell Publishing Ltd 2009 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.394 No.1
<P>ABSTRACT</P><P>We investigate the photometric redshift accuracy achievable with the <I>AKARI</I> infrared data in deep multiband surveys, such as in the North Ecliptic Pole field. We demonstrate that the passage of redshifted polycyclic aromatic hydrocarbons (PAH) and silicate features into the mid-infrared wavelength window covered by <I>AKARI</I> is a valuable means to recover the redshifts of starburst galaxies. To this end, we have collected a sample of ∼60 galaxies drawn from the Great Observatories Origins Deep Survey-North Field with spectroscopic redshift 0.5 ≲<I>z</I><SUB>spec</SUB>≲ 1.5 and photometry from 3.6 to 24 μm, provided by the <I>Spitzer</I>, <I>Infrared Space Observatory</I> and <I>AKARI</I> satellites. The infrared spectra are fitted using synthetic galaxy spectral energy distributions which account for starburst and active nuclei emission. For ∼90 per cent of the sources in our sample, the redshift is recovered with an accuracy |<I>z</I><SUB>phot</SUB>−<I>z</I><SUB>spec</SUB>|/(1 +<I>z</I><SUB>spec</SUB>) ≲ 10 per cent. A similar analysis performed on a set of simulated spectra shows that the <I>AKARI</I> infrared data alone can provide photometric redshifts accurate to |<I>z</I><SUB>phot</SUB>−<I>z</I><SUB>spec</SUB>|/(1 +<I>z</I><SUB>spec</SUB>) ∼ 10 per cent (1σ) at <I>z</I>≲ 2. At higher redshifts, the PAH features are shifted outside the wavelength range covered by <I>AKARI</I> and the photo-<I>z</I> estimates rely on the less prominent 1.6 μm stellar bump; the accuracy achievable in this case on (1 +<I>z</I>) is ∼10–15 per cent, provided that the active galactic nuclei contribution to the infrared emission is subdominant. Our technique is no more prone to redshift aliasing than optical-ultraviolet photo-<I>z</I>, and it may be possible to reduce this aliasing further with the addition of submillimetre and/or radio data.</P>
Enhanced FDCH Rendezvous Algorithm against Jamming Attack in Cognitive Radio Networks
Enguerrand Negrello(네그렐로),Yongchul Kim(김용철) 육군사관학교 화랑대연구소 2019 한국군사학논집 Vol.75 No.1
Cognitive radio is considered to be an adequate response to the scarcity of the radio spectrum by allowing the secondary user (SUs) to access the unused licensed spectrum. These radios analyze the available surrounding frequencies and determine which ones are best able to ensure quality transmission and reception without causing the legal primary users(PUs). The rendezvous process is considered as a necessary step for enabling SUs to communicate with each other in the cognitive radio networks (CRN). Many researchers focus only on the raw performance of rendezvous algorithms without ever considering the possibility of a jamming attack. Indeed, the problem of jamming within a network of cognitive radios is a subject still little discussed. Therefore, in this paper, we show that jamming attacks can significantly reduce the rendezvous performances even in the state of the art rendezvous algorithm. Then we propose a new rendezvous algorithm that can significantly enhance robustness under jamming attacks.
Hopwood, R.,Serjeant, S.,Negrello, M.,Pearson, C.,Egami, E.,Im, M.,Kneib, J.-P.,Ko, J.,Lee, H. M.,Lee, M. G.,Matsuhara, H.,Nakagawa, T.,Smail, I.,Takagi, T. IOP Publishing 2010 ASTROPHYSICAL JOURNAL LETTERS - Vol.716 No.1
<P>We present extragalactic number counts and a lower limit estimate for the cosmic infrared background (CIRB) at 15 mu m from AKARI ultra deep mapping of the gravitational lensing cluster Abell 2218. These data are the deepest taken by any facility at this wavelength and uniquely sample the normal galaxy population. We have de-blended our sources, to resolve photometric confusion, and de-lensed our photometry to probe beyond AKARI's blank-field sensitivity. We estimate a de-blended 5 sigma sensitivity of 28.7 mu Jy. The resulting 15 mu m galaxy number counts are a factor of 3 fainter than previous results, extending to a depth of similar to 0.01 mJy and providing a stronger lower limit constraint on the CIRB at 15 mu m of 1.9 +/- 0.5 nW m(-2) sr(-1).</P>