Open AccessThree quasars from a survey of strong 25‐ μ m emitters
Author(s) -
Wolstencroft R. D.,
Parker Q. A.,
Lonsdale C. J.,
Scarrott S. M.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03049.x
Subject(s) - quasar , physics , astrophysics , balmer series , torus , active galactic nucleus , asymmetry , emission spectrum , astronomy , galaxy , line of sight , spectral line , geometry , mathematics , quantum mechanics
We have carried out a spectroscopic survey of 750 sources that are strong 25‐μm emitters from the IRAS Faint Source data base. Many of these sources are previously unknown active galactic nuclei including new IRAS quasars, three of which we describe here: F21382−2659, Z06367−6845 and Z05558−5008. They are all radio and X‐ray quiet, and compared to the known IRAS quasars they have similar 25‐μm luminosities, L (25 μm), but lower values of L (25 μm)/ L ( B ). Their F (25 μm)/ F (60 μm) IRAS colours lie in the range 0.33 to 1.08, indicating the presence of relatively warm dust, presumably in a dusty torus surrounding the central source, and with temperatures similar to those of the known IRAS quasars. The quasar with the warmest dust, F21382−2659, exhibits broad (full width at half‐maximum ∼4000 km s −1 ) asymmetric Balmer lines with H γ having an opposite asymmetry to the other broad lines; also H β (only) is double‐peaked. Fe ii is very weak in F21382−2659 but strong in the other two quasars, and the anticorrelation between Fe ii and [O iii ] holds as anticipated. Two of the quasars are unpolarized: although F21382−2659 is optically polarized (2.1 per cent at 4950 Å), we argue that this provides little insight into the orientation of its dust torus relative to the line of sight.