Serendipitous Discovery of a Projected Pair of QSOs Separated by 4.5 arcsec on the Sky

• Published in: The Astronomical Journal
• Main Authors: Heintz, K. E., Fynbo, J. P. U., Krogager, J. -K., Vestergaard, M., Møller, P., Arabsalmani, M., Geier, S., Noterdaeme, P., Ledoux, C., Saturni, F. G., Venemans, B.
• Other Authors: Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: quasars: general; Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Astrophysics of Galaxies; [SDU]Sciences of the Universe [physics]; Norway; Observatorio; Iceland
• Online Access: https://hal.science/hal-03645128; https://doi.org/10.3847/0004-6256/152/1/13

International audience We present the serendipitous discovery of a projected pair of quasi-stellar objects (QSOs) with an angular separation of Δθ = 4.50 arcsec. The redshifts of the two QSOs are widely different: one, our program target, is a QSO with a spectrum consistent with being a narrow line Seyfert 1 active galactic nucleus at z = 2.05. For this target we detect Lyα, C IV, and C III]. The other QSO, which by chance was included on the spectroscopic slit, is a Type 1 QSO at a redshift of z = 1.68, for which we detect C IV, C III], and Mg II. We compare this system to previously detected projected QSO pairs and find that only about a dozen previously known pairs have smaller angular separation. Based on observations made with the Nordic Optical Telescope, on the island of La Palma jointly operated by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.