Properties of active galaxies at the extreme of Eigenvector 1

¹ Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
² Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
e-mail: bcz@camk.edu.pl
³ Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
⁴ School of Physics and Technology, Wuhan University, Wuhan 430072, PR China
⁵ Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, PR China

Received: 13 January 2017
Accepted: 3 January 2018

Abstract

Context. Eigenvector 1 (EV1) is the formal parameter which allows the introduction of some order in the properties of the unobscured type 1 active galaxies.

Aims. We aim to understand the nature of this parameter by analyzing the most extreme examples of quasars with the highest possible values of the corresponding eigenvalues R_Fe.

Methods. We selected the appropriate sources from the Sloan Digital Sky Survey (SDSS) and performed detailed modeling, including various templates for the Fe II pseudo-continuum and the starlight contribution to the spectrum.

Results. Out of 27 sources with R_Fe larger than 1.3 and with the measurement errors smaller than 20% selected from the SDSS quasar catalog, only six sources were confirmed to have a high value of R_Fe, defined as being above 1.3. All other sources have an R_Fe of approximately 1. Three of the high R_Fe objects have a very narrow Hβ line, below 2100 km s⁻¹ but three sources have broad lines, above 4500 km s⁻¹, that do not seem to form a uniform group, differing considerably in black hole mass and Eddington ratio; they simply have a very similar EW([OIII]5007) line. Therefore, the interpretation of the EV1 remains an open issue.