PRINCIPE, GIACOMOGIACOMOPRINCIPEMIGLIORI, GiuliaGiuliaMIGLIORIJohnson, T. J.T. J.JohnsonD'AMMANDO, FilippoFilippoD'AMMANDOGIROLETTI, MarcelloMarcelloGIROLETTIORIENTI, MonicaMonicaORIENTISTANGHELLINI, CarloCarloSTANGHELLINITaylor, G. B.G. B.TaylorTORRESI, ELEONORAELEONORATORRESICheung, C. C.C. C.Cheung2025-02-172025-02-1720200004-6361http://hdl.handle.net/20.500.12386/36009Context. According to radiative models, radio galaxies may produce γ-ray emission from the first stages of their evolution. However, very few such galaxies have been detected by the Fermi Large Area Telescope (LAT) so far. <BR /> Aims: NGC 3894 is a nearby (z = 0.0108) object that belongs to the class of compact symmetric objects (CSOs, i.e., the most compact and youngest radio galaxies), which is associated with a γ-ray counterpart in the Fourth Fermi-LAT source catalog. Here we present a study of the source in the γ-ray and radio bands aimed at investigating its high-energy emission and assess its young nature. <BR /> Methods: We analyzed 10.8 years of Fermi-LAT data between 100 MeV and 300 GeV and determined the spectral and variability characteristics of the source. Multi-epoch very long baseline array (VLBA) observations between 5 and 15 GHz over a period of 35years were used to study the radio morphology of NGC 3894 and its evolution. <BR /> Results: NGC 3894 is detected in γ-rays with a significance >9σ over the full period, and no significant variability has been observed in the γ-ray flux on a yearly time-scale. The spectrum is modeled with a flat power law (Γ = 2.0 ± 0.1) and a flux on the order of 2.2 × 10<SUP>-9</SUP> ph cm<SUP>-2</SUP> s<SUP>-1</SUP>. For the first time, the VLBA data allow us to constrain with high precision the apparent velocity of the jet and counter-jet side to be β<SUB>app, NW</SUB> = 0.132 ± 0.004 and β<SUB>app, SE</SUB> = 0.065 ± 0.003, respectively. <BR /> Conclusions: Fermi-LAT and VLBA results favor the youth scenario for the inner structure of this object, with an estimated dynamical age of 59 ± 5 years. The estimated range of viewing angle (10° < θ < 21°) does not exclude a possible jet-like origin of the γ-ray emission.STAMPAenArticle10.1051/0004-6361/2019370492-s2.0-85082883588http://arxiv.org/abs/2003.01476v1https://www.aanda.org/articles/aa/full_html/2020/03/aa37049-19/aa37049-19.html2020A&A...635A.185PFIS/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