Probing narrow-line Seyfert 1 galaxies in the southern hemisphere^⋆

¹ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
e-mail: sina.chen@phd.unipd.it
² Center for Astrophysics, Guangzhou University, 510006 Guangzhou, PR China
³ Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Padova, 35131 Padova, Italy
⁴ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy
⁵ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova, Italy

Received: 21 January 2018
Accepted: 17 April 2018

Abstract

We present a new accurate catalog of narrow-line Seyfert 1 galaxies (NLS1s) in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release, which is currently the most extensive spectroscopic survey available in the southern sky whose database has not yet been systematically explored. We classified 167 sources as NLS1s based on their optical spectral properties. We derived flux-calibrated spectra for the first time that the 6dFGS does not provide. By analyzing these spectra, we obtained strong correlations between the monochromatic luminosity at 5100 Å and the luminosities of Hβ and [O III]λ5007 lines. The central black hole mass and the Eddington ratio have average values of 8.6 × 10⁶M_⊙ and 0.96 L_Edd respectively, which are typical values for NLS1s. In the sample, 23 (13.8%) NLS1s were detected at radio frequencies, and 12 (7.0%) of them are radio-loud. Our results confirmed that radio-loud sources tend to have higher redshift, a more massive black hole, and higher radio and optical luminosities than radio-quiet sources.