Abstrakti
Context. RadioAstron is a 10 m 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 350 000 km, it is
offering for the first time the possibility to perform μas-resolution
imaging in the cm-band. Aims: 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.
Methods: We present observations at 22 GHz of 3C 273, performed
in 2014, designed to reach a maximum baseline of approximately nine
Earth diameters. Reaching an angular resolution of 0.3 mas, 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 43 GHz, to study the
kinematics of the jet in a 1.5-yr time window. Results: 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 (1.4 × 1013 K, 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 22 GHz 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 γ-ray flare in conjunction with the
passage of the new component by the core at 43 GHz. Conclusions:
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 μas angular resolution does not systematically
imply measured brightness temperatures over the known physical limits
for astrophysical sources.
The reduced image (FITS file) is only available at the CDS via anonymous
ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A111
Alkuperäiskieli | Englanti |
---|---|
Artikkeli | A111 |
Sivumäärä | 9 |
Julkaisu | Astronomy & Astrophysics |
Vuosikerta | 604 |
DOI - pysyväislinkit | |
Tila | Julkaistu - 2017 |
OKM-julkaisutyyppi | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä |
Sormenjälki
Sukella tutkimusaiheisiin 'Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron: II. Observations of 3C 273 at minimum activity'. Ne muodostavat yhdessä ainutlaatuisen sormenjäljen.Laitteet
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Metsähovin radiotutkimusasema
Tammi, J. (Manager)
Sähkötekniikan korkeakouluLaitteistot/tilat: Facility