THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS

By M. Ajello, R. Romani, D. Gasparrini, M. Shaw, J. Bolmer, G. Cotter, J. Finke, J. Greiner, S. E. Healey, O. King and 7 more. 2013

202 citations recorded by the source corpus.

Fermi has provided the largest sample of γ-ray-selected blazars to date. In this work we use a uniformly selected set of 211 BL Lacertae (BL Lac) objects detected by Fermi during its first year of operation. We obtained redshift constraints for 206 out of the 211 BL Lac objects in our sample, making it the largest and most complete sample of BL Lac objects available in the literature. We use this sample to determine the luminosity function of BL Lac objects and its evolution with cosmic time. We find that for most BL Lac classes the evolution is positive, with a space density peaking at modest redshift (z ≈ 1.2). Low-luminosity, high-synchrotron–peaked (HSP) BL Lac objects are an exception, showing strong negative evolution, with number density increasing for z ≲ 0.5. Since this rise corresponds to a drop-off in the density of flat-spectrum radio quasars (FSRQs), a possible interpretation is that these HSPs represent an accretion-starved end state of an earlier merger-driven gas-rich phase. We additionally find that the known BL Lac correlation between luminosity and photon spectral index persists after correction for the substantial observational selection effects with implications for the so-called “blazar sequence.” Finally, by estimating the beaming corrections to the luminosity function, we find that BL Lac objects have an average Lorentz factor of , and that most are seen within 10° of the jet axis.

Subfields: Atmospheric Science, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/316de4832b331999ae38cad839e98564424fe93d

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Citations in the corpus

Open Questions in Cosmic-Ray Research at Ultrahigh Energies (2019, methodology): “For blazars, the quoted values are based on the gamma-ray luminosity as estimated by Ajello et al. (2014), at z = 0.”
Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background (2015, methodology): “In a companion Fermi LAT paper [96], the contribution of blazars in the full energy range has been reevaluated using an updated luminosity function and spectral energy distribution model, taking advantage of recent follow-up observations [77].”