Spectroscopy of broad-line blazars from 1LAC
Astrophysical Journal 748:1 (2012)
Abstract:
We report on optical spectroscopy of 165 flat spectrum radio quasars (FSRQs) in the Fermi 1LAC sample, which have helped allow a nearly complete study of this population. Fermi FSRQs show significant evidence for non-thermal emission even in the optical; the degree depends on the γ-ray hardness. They also have smaller virial estimates of hole mass than the optical quasar sample. This appears to be largely due to a preferred (axial) view of the γ-ray FSRQ and non-isotropic (H/R ∼ 0.4) distribution of broad-line velocities. Even after correction for this bias, the Fermi FSRQs show higher mean Eddington ratios than the optical population. A comparison of optical spectral properties with Owens Valley Radio Observatory radio flare activity shows no strong correlation. © 2012 The American Astronomical Society. All rights reserved.Synchrotron and inverse-Compton emission from blazar jets - I. A uniform conical jet model
Monthly Notices of the Royal Astronomical Society 423:1 (2012) 756-765
Abstract:
In the first of a series of papers investigating emission from blazar jets from radio to high-energy γ-rays, we revisit the class of models where the jet has a uniform conical ballistic structure. We argue that by using simple developments of these models, in the context of new multifrequency data extending to γ-ray energies, valuable insights may be obtained into the properties that fully realistic models must ultimately have. In this paper we consider the synchrotron and synchrotron-self-Compton emission from the jet, modelling the recent simultaneous multiwavelength observations of BL Lac. This is the first time these components have been fitted simultaneously for a blazar using a conical jet model. In the model we evolve the electron population dynamically along the jet taking into account the synchrotron and inverse-Compton losses. The inverse-Compton emission is calculated using the Klein-Nishina cross-section and a relativistic transformation into the jet frame, and we explicitly show the seed photon population. We integrate synchrotron opacity along the line of sight through the jet plasma, taking into account the emission and opacity of each section of the jet. In agreement with previous studies of radio emission, we find that a conical jet model which conserves magnetic energy produces the characteristic blazar flat radio spectrum; however, we do not require any fine-tuning of the model to achieve this. Of particular note, in our model fit to BL Lac - which at ∼1037W is a relatively low jet-power source - we find no requirement for significant re-acceleration within the jet to explain the observed spectrum. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.Synchrotron and inverse-Compton emission from blazar jets - I. A uniform conical jet model
Monthly Notices of the Royal Astronomical Society (2012)
Blazars in the Fermi era: The ovro 40 m telescope monitoring program
Astrophysical Journal, Supplement Series 194:2 (2011)
Abstract:
The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern (δ > -20°) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrate that, with high significance (6σ), gamma-ray-loud blazars detected by the LAT during its first 11 months of operation vary with almost a factor of two greater amplitude than do the gamma-ray-quiet blazars in our sample. We also find a significant (3σ) difference between variability amplitude in BL Lacertae objects and flat-spectrum radio quasars (FSRQs), with the former exhibiting larger variability amplitudes. Finally, low-redshift (z < 1) FSRQs are found to vary more strongly than high-redshift FSRQs, with 3σ significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent. © 2011. The American Astronomical Society. All rights reserved..Characteristics of Gamma-ray loud blazars in the VLBA Imaging and Polarimetry Survey
Astrophysical Journal Letters 726:1 (2011)