The stellar content of low redshift BL Lac host galaxies from multicolour imaging

: Hyvönen T, Kotilainen JK, Falomo R, Pursimo T

: The Nuclear Region, Host Galaxy and Environment of Active Galaxies

: 2008

Revista mexicana de astronomía y astrofísica : serie de conferencias

: NUCLEAR REGION, HOST GALAXY AND ENVIRONMENT OF ACTIVE GALAXIES

: REV MEX AST ASTR

: Revista Mexicana de Astronomia y Astrofisica Serie de Conferencias

: 32

: 161

: 163

: 2

: 978-970-32-5297-8

: 1405-2059

: https://www.astroscu.unam.mx/rmaa/RMxAC..32/PDF/RMxAC..32_thyvonen.pdf

We present UBV-band imaging of 18 low redshift (z <= 0.3) BL Lac objects. These data are used to investigate the blue-red-near-infrared colours and colour gradients of the host galaxies. The distributions of the integrated blue/near-infrared colour and colour gradient of the BL Lac hosts are much wider than those for inactive ellipticals, and most BL Lac objects have bluer hosts and/or steeper colour gradients than those in inactive 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 supported by stellar population modelling, indicating a presence of young/intermediate age populations in the majority of the sample.

BL Lacertae objects : general, galaxies : active, galaxies : interactions, galaxies : nuclei, galaxies : photometry