dc.contributor.author | Wojaczyński, Rafał | |
dc.contributor.author | Niedźwiecki, Andrzej | |
dc.date.accessioned | 2017-10-13T09:10:29Z | |
dc.date.available | 2017-10-13T09:10:29Z | |
dc.date.issued | 2017 | |
dc.identifier.issn | 1538-4357 | |
dc.identifier.uri | http://hdl.handle.net/11089/22934 | |
dc.description.abstract | We report hints for the correlation between the X-ray and gamma-ray emission in the nearby galaxy NGC 4945, which harbors both an active galactic nucleus and a nuclear starburst region. We have divided the Fermi/LAT observations of NGC 4945 into two datasets, comprising events detected during the low (L) and high (H) level of X-ray emission from the active nucleus of this galaxy, determined using the Swift/BAT light curve. Both datasets contain an equal amount of 3.8 years of LAT data and NGC 4945 is detected with a similar statistical significance of ∼ 15 sigma in L and 14sigma in H. However, the slope of the gamma-ray spectrum hardens with the increase of the X-ray flux, with the photon index = 2.47 ± 0.07 in L and 2.11 ± 0.08 in H. The change is confirmed by a systematic variation of the spectral energy
distribution as well as a substantial reversal of the -ray signal in significance maps for low and high -ray energies.The X/gamma-ray correlation indicates that the gamma-ray production is dominated by the active nucleus rather than by cosmic rays interacting with the interstellar medium. We discuss possible locations of the gamma-ray source. We also compare NGC 4945 with other starburst galaxies detected by LAT and we note similarities between those with active nuclei,e.g. unlikely high efficiencies of gamma-ray production in starburst scenario, which argues for a significant contribution of their active nuclei to the gamma-ray emission. | pl_PL |
dc.description.sponsorship | ETIUDA doctoral grant
DEC-2016/20/T/ST9/00386,OPUS grant DEC-2016/21/B/ST9/02388 | pl_PL |
dc.language.iso | en | pl_PL |
dc.publisher | IOP Publishing for the American Astronomical Society | pl_PL |
dc.relation.ispartof | Astrophysical Journal;AAS04978R1 | |
dc.relation.ispartofseries | Astrophysical Journal; | |
dc.rights | Uznanie autorstwa-Użycie niekomercyjne-Bez utworów zależnych 3.0 Polska | * |
dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/3.0/pl/ | * |
dc.subject | individual (NGC 4945) | pl_PL |
dc.subject | gamma rays: galaxies | pl_PL |
dc.subject | galaxies: Seyfert | pl_PL |
dc.subject | radiation mechanisms: non-thermal | pl_PL |
dc.title | The X/gamma-ray correlation in NGC 4945 and the nature of its gamma-ray source | pl_PL |
dc.type | Preprint | pl_PL |
dc.contributor.authorAffiliation | Uniwersytet Łódzki | pl_PL |
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dc.contributor.authorEmail | rafal.wojaczynski@wp.pl | pl_PL |