The HRX-BL Lac sample - evolution of BL Lac objects
Feb, 2003
24 pages
Published in:
- Astron.Astrophys. 401 (2003) 927-938
e-Print:
- astro-ph/0302242 [astro-ph]
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Abstract: (arXiv)
The unification of X-ray and radio selected BL Lacs has been an outstanding problem in the blazar research in the past years. Recent investigations have shown that the gap between the two classes can be filled with intermediate objects and that apparently all differences can be explained by mutual shifts of the peak frequencies of the synchrotron and inverse Compton component of the emission. We study the consequences of this scheme using a new sample of X-ray selected BL Lac objects comprising 104 objects with z<0.9 and a mean redshift z=0.34. 77 BL Lacs, of which the redshift could be determined for 64 (83%) objects, form a complete sample. The new data could not confirm our earlier result, drawn from a subsample, that the negative evolution vanishes below a synchrotron peak frequency log (peak-frequency) = 16.5. The complete sample shows negative evolution at the 2 sigma level (References(30)
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