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J/A+A/604/A111      22GHz image of 3C 273                         (Bruni+, 2017)

Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron. II. Observations of 3C 273 at minimum activity. Bruni G., Gomez J.L., Casadio C., Lobanov A., Kovalev Y.Y., Sokolovsky K.V., Lisakov M.M., Bach U., Marscher A., Jorstad S., Anderson J.M., Krichbaum T.P., Savolainen T., Vega-Garcia L., Fuentes A., Zensus J.A., Alberdi A., Lee S.-S., Lu R.-S., Perez-Torres M., Ros E. <Astron. Astrophys. 604, A111 (2017)> =2017A&A...604A.111B (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Magnetic fields ; Radio sources Keywords: galaxies: active - galaxies: jets - galaxies: magnetic fields Abstract: RadioAstron is a 10m orbiting radio telescope mounted on the Spektr-R satellite, launched in 2011, performing Space Very Long Baseline Interferometry (SVLBI) observations supported by a global ground array of radio telescopes. With an apogee of ∼350000km, it is offering for the first time the possibility to perform as-resolution imaging in the cm-band. The RadioAstron Active Galactic Nuclei (AGN) polarization Key Science Project (KSP) aims at exploiting the unprecedented angular resolution provided by RadioAstron to study jet launching/collimation and magnetic-field configuration in AGN jets. The targets of our KSP are some of the most powerful blazars in the sky. We present observations at 22GHz of 3C 273, performed in 2014, designed to reach a maximum baseline of approximately nine Earth diameters. Reaching an angular resolution of 0.3mas, we study a particularly low-activity state of the source, and estimate the nuclear region brightness temperature, comparing with the extreme one detected one year before during the RadioAstron early science period.We also make use of the VLBA-BU-BLAZAR survey data, at 43GHz, to study the kinematics of the jet in a ∼1.5-year time window. We find that the nuclear brightness temperature is two orders of magnitude lower than the exceptionally high value detected in 2013 with RadioAstron at the same frequency (1.4x1013K, source-frame), and even one order of magnitude lower than the equipartition value. The kinematics analysis at 43 GHz shows that a new component was ejected ∼2 months after the 2013 epoch, visible also in our 22GHz map presented here. Consequently this was located upstream of the core during the brightness temperature peak. Fermi-LAT observations for the period 2010-2014 do not show any gamma-ray flare in conjunction with the passage of the new component by the core at 43GHz. These observations confirm that the previously detected extreme brightness temperature in 3C 273, exceeding the inverse Compton limit, is a short-lived phenomenon caused by a temporary departure from equipartition. Thus, the availability of interferometric baselines capable of providing as angular resolution does not systematically imply measured brightness temperatures over the known physical limits for astrophysical sources. Description: A global ground array of 22 antennas was used to perform observations, including VLBA (Sc, Hn, Nl, Fd, La, Kp, Pt, Ov, Br, Mk), EVN (Hh, Mc, Nt, Tr, Jb, Ef, Ys), Long Baseline Array (-LBA- At, Mp, Ho, Cd), and two Kvazar antennas (Sv, Zc), plus Kalyazin (managed by ASC, Russia), and Green Bank (NRAO, USA). The observations took place on January 18-19, 2014, for a total of 16.8 hours, and at three different frequencies: 15GHz, 22GHz, and 43GHz. RA was involved only for the 22GHz part, while for the other bands only the VLBA was used. Both the Green Bank and Pushchino tracking station took part in the experiment. A RA-compatible total bandwidth of 32MHz, split into two 16-MHz IFs, was used. RA was scheduled to observe three consecutive 9.5 minute scans every 1.25 hours, to allow for antenna cooling. Objects: ----------------------------------------------------------- RA (2000) DE Designation(s) ----------------------------------------------------------- 12 29 06.70 +02 03 08.7 3C 273 = 1RXS J122906.5+020311 ----------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 94 1 Information on FITS image 3C273RA22GHz.fits 2880 1641 RadioAstron FITS image
See also: J/A+A/576/A122 : 3C 273 high energy spectrum (Esposito+, 2015) J/A+A/601/A35 : High-fidelity VLA imaging of 3C273 (Perley+, 2017) J/ApJS/213/26 : Optical light curves of PHL1811 and 3C273 (Fan+, 2014) J/ApJS/229/21 : VRI monitoring of the QSO 3C 273 in 2005-2016 (Xiong+, 2017) J/MNRAS/392/1181 : BV(RI)c photometry of 3C 273 (Dai+, 2009) Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 23 I4 --- Nx Number of pixels along X-axis 25- 28 I4 --- Ny Number of pixels along Y-axis 30- 39 A10 "date" Obs.dat Observation date 41- 47 F7.4 GHz Freq Observed frequency 49- 52 I4 Kibyte size Size of FITS file 54- 72 A19 --- FileName Name of FITS file 74- 94 A21 --- Title Title of the FITS file
Acknowledgements: Gabriele Bruni, bruni(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 24-Jul-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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