The blazar content in the Swift-BAT hard X-ray sky
Abstract
Aims: We present the results from a study of the blazar content in the 15-150 keV map of the entire sky obtained analysing 39 months of data collected by the BAT telescope aboard the Swift satellite.
Methods: We performed a cross-correlation of the significance map, obtained with a dedicated highly efficient algorithm for data processing and image reconstruction of the BAT survey data, with the blazar population of the Roma-BZCAT. After corrections for source confusion and spurious detections, we found significance excesses higher than two standard deviations for 304 sources, and the corresponding fraction of expected spurious associations is ~20%. We selected hard X-ray blazars according to their significance level and carried out a statistical analysis to characterise their emission properties.
Results: A sample of 121 blazars detected at a significance level σ > 3 is discussed in greater detail. The fraction of blazars with uncertain classification in this sample is considerable (~23%), more than twice the percentage obtained considering all the blazars classified in the Roma-BZCAT (~9%). We attribute the X-ray flux of the majority of selected BL Lac objects to the synchrotron emission.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- September 2010
- DOI:
- 10.1051/0004-6361/201014331
- Bibcode:
- 2010A&A...520A..47M
- Keywords:
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- galaxies: active;
- BL Lacertae objects: general;
- radiation mechanisms: non-thermal