Relativistic Jets in the Radio Reference Frame Image Database. I. Apparent Speeds from the First 5 Years of Data

Piner, B. G.; Mahmud, M.; Fey, A. L.; Gospodinova, K.

doi:10.1086/514812

Cited by 72 publications

(93 citation statements)

References 33 publications

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“…Among the radio-loud blazars, there are 15 gamma-ray sources, this emission being an important component of the relaticistic jet (Mukherjee et al 1997;Abdo et al 2009). Superluminal motions are detected in 11 radio blazars (Piner et al 2006(Piner et al , 2007Fan et al 2009) and, of those, eight are indeed also known gamma-ray emitters. Our 42 observed sources are presented in Table 1 as well as information on the three northern BL Lacs.…”

Section: Target Selectionmentioning

confidence: 99%

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Bergeron

Boissé

Ménard

2010

A&A

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In order to investigate the origin of the excess of strong Mg ii systems towards GRB afterglows as compared to QSO sightlines, we have measured the incidence of Mg ii absorbers towards a third class of objects: the blazars. This class includes the BL Lac object population for which a tentative excess of Mg ii systems had already been reported. We observed with FORS1 at the ESO-VLT 42 blazars with an emission redshift 0.8 < z em < 1.9, to which we added the three high z northern objects belonging to the 1 Jy BL Lac sample. We detect 32 Mg ii absorbers in the redshift range 0.35-1.45, leading to an excess in the incidence of Mg ii absorbers compared to that measured towards QSOs by a factor ∼2, detected at 3σ. The amplitude of the effect is similar to that found along GRB sightlines. Our analysis provides a new piece of evidence that the observed incidence of Mg ii absorbers might depend on the type of background source. In front of blazars, the excess is apparent for both "strong" (w r (2796) > 1.0 Å) and weaker (0.3 < w r (2796) < 1.0 Å) Mg ii systems. The dependence on velocity separation with respect to the background blazars indicates, at the ∼1.5σ level, a potential excess for β ≡ v/c ∼ 0.1. We show that biases involving dust extinction or gravitational amplification are not likely to notably affect the incidence of Mg ii systems towards blazars. Finally we discuss the physical conditions required for these absorbers to be gas entrained by the powerful blazar jets. More realistic numerical modelling of jet-ambient gas interaction is required to reach any firm conclusions as well as repeat observations at high spectral resolution of strong Mg ii absorbers towards blazars in both high and low states.

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Section: Target Selectionmentioning

confidence: 99%

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Bergeron

Boissé

Ménard

2010

A&A

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“…Within the Radio Reference Frame Image Database, the source was observed five times at 8 GHz between 1994 and 1998 (Piner et al 2007). The authors report apparent velocities from (−7 ± 14) c up to (24 ± 29) c. Higher quality images have been obtained within the 15 GHz VLBI observations within the VLBA 2 cm-Survey (e.g., Kellermann et al 1998;Zensus et al 2002) and its successor, the MOJAVE 1 program (Lister et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

Catching the radio flare in CTA 102

Fromm¹,

Ros²,

Perucho³

et al. 2013

A&A

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Context. Very Long Baseline Interferometry (VLBI) observations can resolve the radio structure of active galactic nuclei (AGN) and provide estimates of the structural and kinematic characteristics on parsec-scales in their jets. The changes in the kinematics of the observed jet features can be used to study the physical conditions in the innermost regions of these sources. We performed multifrequency multiepoch Very Long Baseline Array (VLBA) observations of the blazar CTA 102 during its 2006 radio flare, the strongest ever reported for this source. These observations provide an excellent opportunity to investigate the evolution of the physical properties of blazars, especially during these flaring events Aims. We want to study the kinematic changes in the source during the strong radio outburst in April 2006 and test the assumption of a shock-shock interaction. This assumption is based on the analysis and modeling of the single-dish observations of CTA 102 (Paper I). Methods. In this paper we study the kinematics of CTA 102 at several frequencies using VLBI observations. From the modeled jet features we derived estimates for the evolution of the physical parameters, such as the particle density and the magnetic field. Furthermore, we combined our observations during the 2006 flare with long-term VLBA monitoring of the source at 15 GHz and 43 GHz. Results. We cross-identified seven features throughout our entire multifrequency observations and find evidence of two possible recollimation shocks around 0.1 mas (deprojected 18 pc at a viewing angle ϑ = 2.6 • ) and 6.0 mas (deprojected 1 kpc) from the core. The 43 GHz observations reveal a feature ejected at epoch t ej = 2005.9 ± 0.2, which could be connected to the 2006 April radio flare. Furthermore, this feature might be associated with the traveling component involved in the possible shock-shock interaction, which gives rise to the observed double peak structure in the single-dish light curves reported in Paper I.

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“…Abdo et al (2010) show a light curve with two flaring events, occurring around February and June 2009 respectively. Previous VLBI observations have found the source to be strongly core dominated on the milli-arcsecond scale (Ojha et al 2010(Ojha et al , 2004Piner et al 2007). On the kilo-parsec scale, ATCA imaging shows some extended structure (Marshall et al 2005;Burgess & Hunstead 2006) extending over 4 arcsec.…”

Section: Resultsmentioning

confidence: 95%

High resolution rapid response observations of compact radio sources with the Ceduna Hobart Interferometer (CHI)

Blanchard

Lovell

Ojha

et al. 2012

A&A

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Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including active galactic nuclei. A key tool of such studies is the ability to observe an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific observational procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer that can rapidly observe a flaring object. This is the only facility that is dedicated to rapid high resolution radio observations of an object south of −30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at γ-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer, the Ceduna Hobart Interferometer (CHI), was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our observing strategy within half an hour of a triggering event. These observations can be calibrated with amplitude errors better than 15%. Lower limits to the brightness temperatures of the sources can also be calculated using CHI.

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Relativistic Jets in the Radio Reference Frame Image Database. I. Apparent Speeds from the First 5 Years of Data

Cited by 72 publications

References 33 publications

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Incidence of Mg ii absorbers towards blazars and the GRB/QSO puzzle

Catching the radio flare in CTA 102

High resolution rapid response observations of compact radio sources with the Ceduna Hobart Interferometer (CHI)

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