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Blue colours of BL Lac host galaxies

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 نشر من قبل Jari Kotilainen
 تاريخ النشر 2004
  مجال البحث فيزياء
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 تأليف J.K. Kotilainen




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Near-infrared and optical imaging of BL Lac host galaxies is used to investigate their colour properties. We find that the R-H colour and colour gradient distributions of the BL Lac hosts are much wider than those for normal ellipticals, and many objects have very blue hosts and/or steep colour gradients. The blue colours are most likely caused by recent star formation. The lack of obvious signs of interaction may, however, require a significant time delay between the interaction event with associated star formation episodes and the onset of the nuclear activity.



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