Journal Article

Study of a homogeneous QSO sample: relations between the QSO and its host galaxy*

Y. Letawe, G. Letawe and P. Magain

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 4, pages 2088-2104
Published in print April 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI:
Study of a homogeneous QSO sample: relations between the QSO and its host galaxy*

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We analyse a sample of 69 quasi-stellar objects (QSOs) which have been randomly selected in a complete sample of 104 QSOs (R≤ 18, 0.142 < z < 0.198, δ < 10°). 60 have been observed with the NTT/SUSI2 at La Silla, through two filters in the optical band (WB 655 and V 812), and the remaining nine are taken from archive data bases. The filter V 812 contains the redshifted Hβ and forbidden [O iii] emission lines, while WB 655 covers a spectral region devoid of emission lines, thus measuring the QSO and stellar continua. The contributions of the QSO and the host are separated thanks to the MCS deconvolution algorithm, allowing a morphological classification of the host, and the computation of several parameters such as the host and nucleus absolute V magnitude, distance between the luminosity centre of the host and the QSO and colour of the host and nucleus. We define a new asymmetry coefficient, independent of any galaxy models and well suited for QSO host studies. The main results from this study are (i) 25 per cent of the total number of QSO hosts are spirals, 51 per cent are ellipticals and 60 per cent show signs of interaction, (ii) highly asymmetric systems tend to have a higher gas ionization level and (iii) elliptical hosts contain a substantial amount of ionized gas and some show off-nuclear activity. These results agree with hierarchical models merger driven evolution.

Keywords: galaxies: active; galaxies: fundamental parameters; galaxies: interactions; quasars: general

Journal Article.  12309 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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