Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 445, Issue 1, Pages 428-436Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu1749
Keywords
galaxies: active; BL Lacertae objects: general; quasars: general; gamma rays: galaxies; radio continuum: galaxies
Categories
Funding
- NASA [NNX08AW31G, NNX11A043G]
- NSF [AST-0808050, AST-1109911]
- Jenny and Antti Wihuri foundation
- Academy of Finland [267324]
- NASA in the United States
- DOE in the United States
- CEA/Irfu in France
- IN2P3/CNRS in France
- ASI in Italy
- INFN in Italy
- MEXT in Japan
- KEK in Japan
- JAXA in Japan
- K. A. Wallenberg Foundation in Sweden
- Swedish Research Council in Sweden
- National Space Board in Sweden
- Academy of Finland (AKA) [267324, 267324] Funding Source: Academy of Finland (AKA)
- Science and Technology Facilities Council [ST/L000768/1] Funding Source: researchfish
- STFC [ST/L000768/1] Funding Source: UKRI
Ask authors/readers for more resources
In order to determine the location of the gamma-ray emission site in blazars, we investigate the time-domain relationship between their radio and gamma-ray emission. Light curves for the brightest detected blazars from the first 3 yr of the mission of the Fermi Gamma-ray Space Telescope are cross-correlated with 4 yr of 15 GHz observations from the Owens Valley Radio Observatory 40 m monitoring programme. The large sample and long light-curve duration enable us to carry out a statistically robust analysis of the significance of the cross-correlations, which is investigated using Monte Carlo simulations including the uneven sampling and noise properties of the light curves. Modelling the light curves as red noise processes with power-law power spectral densities, we find that only one of 41 sources with high-quality data in both bands shows correlations with significance larger than 3 sigma (AO 0235+164), with only two more larger than even 2.25 sigma (PKS 1502+106 and B2 2308+34). Additionally, we find correlated variability in Mrk 421 when including a strong flare that occurred in 2012 July-September. These results demonstrate very clearly the difficulty of measuring statistically robust multiwavelength correlations and the care needed when comparing light curves even when many years of data are used. This should be a caution. In all four sources, the radio variations lag the gamma-ray variations, suggesting that the gamma-ray emission originates upstream of the radio emission. Continuous simultaneous monitoring over a longer time period is required to obtain high significance levels in cross-correlations between gamma-ray and radio variability in most blazars.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available