Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-11-21
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
4 pages, 2 figures, accepted in Astronomy & Astrophysics (main journal)
Scientific paper
The nearby spiral galaxy M81 harbors in its core a Low-Luminosity AGN (LLAGN), and appears closely related to the more distant and powerful AGNs seen in quasars and radio galaxies. The intrinsic size of this object is unknown due to scattering, and it has shown a core-jet morphology with weak extended emission rotating with wavelength. The proximity of M\,81 (D=3.63 Mpc) allows a detailed investigation of its nucleus to be made. The nucleus is four orders of magnitude more luminous than the Galactic centre, and is therefore considered a link between SgrA* and the more powerful nuclei of radio galaxies and quasars. Our main goal was to determine the size of M81* at a shorter wavelength thus directly testing whether the frequency-size dependent law Theta propto nu^(-0.8) was still valid for wavelengths shorter than 1cm. In addition, we also aimed to confirm the rotation of the source as a function of frequency. We observed the continuum 7mm radio emission of M81* using the Very Long Baseline Array on Sep 13, 2002, using nearby calibrators to apply their interferometric observables to the target source, to increase the chances of detection. The source was detected on all baselines and hybrid mapping was possible. We present the first 7mm VLBI image of the core of M81*, which represents the highest resolution image ever of this source. Modeling the interferometric visibilities with two Gaussian functions sets constraints on the angular size of its core down to 38 microarcseconds, corresponding to a maximum (projected) linear size of 138AU, and shows extended emission towards the NE with a position angle of ~50deg. A fit of one Gaussian elliptical function yields a position angle of 28+/-8 degrees for its elongated, compact structure. Combining the 7mm size with earlier measurements at other frequencies we determine a frequency-size dependence of Theta propto nu^(-0.88+/-0.04).
Perez-Torres Miguel Angel
Ros Eduardo
No associations
LandOfFree
VLBI imaging of M81* at 43GHz does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with VLBI imaging of M81* at 43GHz, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and VLBI imaging of M81* at 43GHz will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-376920