Simultaneous Planck, Swift, and Fermi observations of X-ray and gamma-ray selected blazars
Abstract
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by Fermi-LAT, whereas ~40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma-ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-mm spectral slope of blazars is quite flat up to ~70GHz, above which it steepens to <\alpha>~-0.65. BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (\nupS) in the SED of FSRQs is the same in all the blazar samples with <\nupS>=10^13.1 Hz, while the mean inverse-Compton peak frequency, <\nupIC>, ranges from 10^21 to 10^22 Hz. The distributions of \nupS and of \nupIC of BL Lacs are much broader and are shifted to higher energies than those of FSRQs and strongly depend on the selection method. The Compton dominance of blazars ranges from ~0.2 to ~100, with only FSRQs reaching values >3. Its distribution is broad and depends strongly on the selection method, with gamma-ray selected blazars peaking at ~7 or more, and radio-selected blazars at values ~1, thus implying that the assumption that the blazar power is dominated by high-energy emission is a selection effect. Simple SSC models cannot explain the SEDs of most of the gamma-ray detected blazars in all samples. The SED of the blazars that were not detected by Fermi-LAT may instead be consistent with SSC emission. Our data challenge the correlation between bolometric luminosity and \nupS predicted by the blazar sequence.
Keywords
Cite
@article{arxiv.1108.1114,
title = {Simultaneous Planck, Swift, and Fermi observations of X-ray and gamma-ray selected blazars},
author = {P. Giommi and G. Polenta and A. Lahteenmaki and D. J. Thompson and M. Capalbi and S. Cutini and D. Gasparrini and J. Gonzalez-Nuevo and J. Leon-Tavares and M. Lopez-Caniego and M. N. Mazziotta and C. Monte and M. Perri and S. Raino and G. Tosti and A. Tramacere and F. Verrecchia and H. D. Aller and M. F. Aller and E. Angelakis and D. Bastieri and A. Berdyugin and A. Bonaldi and L. Bonavera and C. Burigana and D. N. Burrows and S. Buson and E. Cavazzuti and G. Chincarini and S. Colafrancesco and L. Costamante and F. Cuttaia and F. D'Ammando and G. de Zotti and M. Frailis and L. Fuhrmann and S. Galeotta and F. Gargano and N. Gehrels and N. Giglietto and F. Giordano and M. Giroletti and E. Keihanen and O. King and T. P. Krichbaum and A. Lasenby and N. Lavonen and C. R. Lawrence and C. Leto and E. Lindfors and N. Mandolesi and M. Massardi and W. Max-Moerbeck and P. F. Michelson and M. Mingaliev and P. Natoli and I. Nestoras and E. Nieppola and K. Nilsson and B. Partridge and V. Pavlidou and T. J. Pearson and P. Procopio and J. P. Rachen and A. Readhead and R. Reeves and A. Reimer and R. Reinthal and S. Ricciardi and J. Richards and D. Riquelme and J. Saarinen and A. Sajina and M. Sandri and P. Savolainen and A. Sievers and A. Sillanpaa and Y. Sotnikova and M. Stevenson and G. Tagliaferri and L. Takalo and J. Tammi and D. Tavagnacco and L. Terenzi and L. Toffolatti and M. Tornikoski and C. Trigilio and M. Turunen and G. Umana and H. Ungerechts and F. Villa and J. Wu and A. Zacchei and J. A. Zensus and X. Zhou},
journal= {arXiv preprint arXiv:1108.1114},
year = {2012}
}
Comments
Version accepted by A&A. Joint Planck, Swift, and Fermi collaborations paper