IAR   05382
INSTITUTO ARGENTINO DE RADIOASTRONOMIA
Unidad Ejecutora - UE
artículos
Título:
Discovery of a deep Seyfert-2 galaxy at z = 0.222 behind NGC300
Autor/es:
RODRIGUEZ, M.J.; GARCÍA, F.; CELLONE, S.; COMBI, J.; GAMEN, R. C.
Revista:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2016 vol. 460 p. 1640 - 1644
ISSN:
0035-8711
Resumen:
We report on the unveiling of the nature of the unidentified X-ray source 3XMM J005450.3?373849 as a Seyfert 2 galaxy located behind the spiral galaxy NGC 300 using Hubble Space Telescope data, new spectroscopic Gemini observations and available XMM-Newton and Chandra data. We showthat the X-ray source is positionally coincident with an extended optical source, composed by a marginally resolved nucleus/bulge, surrounded by an elliptical disc-like feature and two symmetrical outer rings. The optical spectrum is typical of a Seyfert 2 galaxy redshifted to z = 0.222 ± 0.001,which confirms that the source is not physically related to NGC 300. At this redshift the source would be located at 909±4 Mpc (comoving distance in the standard model). The X-ray spectra of the source are well-fitted by an absorbed power-law model. By tying NH between the six availablespectra, we found a variable index Γ running from ∼2 in 2000-2001 years, to 1.4?1.6 in the 2005-2014 period. Alternatively, by tying Γ, we found variable absorption columns of NH ∼ 0.34 × 10−22 cm−2 in 2000-2001 years, and 0.54 − 0.75 × 10−22 cm−2 in the 2005-2014 period. Although we cannotdistinguish between an spectral or absorption origin, from the derived unabsorbed X-ray fluxes, we are able to assure the presence of long-term X-ray variability. Furthermore, the unabsorbed X-ray luminosities of 0.8 − 2×1043 erg s−1 derived in the X-ray band are in agreement with a weaklyobscured Seyfert-2 AGN at z ≈ 0.22