Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-09-18
Astronomy and Astrophysics
Astrophysics
16 pages, 10 figures
Scientific paper
We present B-band imaging of 18 low redshift (z<0.3) BL Lac objects for which their host galaxies were previously resolved in the R-band and the near-infrared H-band. For a subset of the objects, also U- and V-band imaging is presented. These data are used to investigate the blue-red-near-infrared colours and the colour gradients of the host galaxies of BL Lacs in comparison with other elliptical galaxies with and without nuclear activity. In all cases galaxies are well represented by an elliptical model, with average absolute magnitude M_B=-21.6+-0.7 and average scale length R_e=7.6+-3.2 kpc. The best-fit B-band Kormendy relation is in reasonable agreement with that obtained for normal ellipticals and radio galaxies. This structural and dynamical similarity indicates that all massive elliptical galaxies can experience nuclear activity without significant perturbation of their global structure. The distributions of the integrated blue/near-infrared colour (with average B-H=3.5+-0.5) and colour gradient (with average Delta(B-R)/Delta(log r)=-0.14+-0.75) of the BL Lac hosts are much wider than those for normal ellipticals, and most BL Lac objects have bluer hosts and/or steeper colour gradients than those in normal ellipticals. The blue colours are likely caused by a young stellar population component, and indicates a link between star formation caused by an interaction/merging event and the onset of the nuclear activity. This result is corroborated by stellar population modelling, indicating a presence of young/intermediate age populations in the majority of the sample, in agreement with low redshift quasar hosts. The lack of strong signs of interaction may require a significant time delay between the event with associated star formation episodes and the start of the nuclear activity.
Falomo Renato
Hyvonen Tomi
Kotilainen Jari K.
Orndahl Eva
Pursimo Tapio
No associations
LandOfFree
The stellar content of low redshift BL Lac host galaxies from multicolour imaging does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The stellar content of low redshift BL Lac host galaxies from multicolour imaging, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The stellar content of low redshift BL Lac host galaxies from multicolour imaging will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-456644