Vignali, C.C.VignaliSEVERGNINI, PaolaPaolaSEVERGNINIPiconcelli, E.E.PiconcelliLANZUISI, GiorgioGiorgioLANZUISIGILLI, RobertoRobertoGILLIMIGNOLI, MarcoMarcoMIGNOLICOMASTRI, AndreaAndreaCOMASTRIBallo, L.L.BalloIwasawa, K.K.IwasawaLA PAROLA, VALENTINAVALENTINALA PAROLA2020-10-062020-10-0620180004-6361http://hdl.handle.net/20.500.12386/27638Context. The search for heavily obscured active galactic nuclei has been revitalized in the last five years by NuSTAR, which has provided a good census and spectral characterization of a population of such objects, mostly at low redshift, thanks to its enhanced sensitivity above 10 keV compared to previous X-ray facilities, and its hard X-ray imaging capabilities. Aims: We aim at demonstrating how NGC 2785, a local (z = 0.009) star-forming galaxy, is responsible, in virtue of its heavily obscured active nucleus, for significant contamination in the non-imaging BeppoSAX/PDS data of the relatively nearby (≈17') quasar IRAS 09104+4109 (z = 0.44), which was originally mis-classified as Compton thick. <BR /> Methods: We analyzed ≈71 ks NuSTAR data of NGC 2785 using the MYTorus model and provided a physical description of the X-ray properties of the source for the first time. <BR /> Results: We found that NGC 2785 hosts a heavily obscured (N<SUB>H</SUB> ≈ 3 × 10<SUP>24</SUP> cm<SUP>-2</SUP>) nucleus. The intrinsic X-ray luminosity of the source, once corrected for the measured obscuration (L<SUB>2</SUB><SUB>-10keV</SUB> ≈ 10<SUP>42</SUP> erg s<SUP>-1</SUP>), is consistent within a factor of a few with predictions based on the source mid-infrared flux using widely adopted correlations from the literature. <BR /> Conclusions: Based on NuSTAR data and previous indications from the Neil Gehrels Swift Observatory (BAT instrument), we confirm that NGC 2785, because of its hard X-ray emission and spectral shape, was responsible for at least one third of the 20-100 keV emission observed using the PDS instrument onboard BeppoSAX, originally completely associated with IRAS 09104+4109. Such emission led to the erroneous classification of this source as a Compton-thick quasar, while it is now recognized as Compton thin.STAMPAenArticle10.1051/0004-6361/2018338052-s2.0-85056091788000448956700001https://www.aanda.org/articles/aa/abs/2018/11/aa33805-18/aa33805-18.html2018A&A...619A..16VFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems