تقرير
First VLBI detection of Fornax A
| العنوان: | First VLBI detection of Fornax A |
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| المؤلفون: | Paraschos, G. F., Wielgus, M., Benke, P., Mpisketzis, V., Rösch, F., Dasyra, K., Ros, E., Kadler, M., Ojha, R., Edwards, P. G., Hyland, L., Quick, J. F. H., Weston, S. |
| المصدر: | A&A 687, L6 (2024) |
| سنة النشر: | 2024 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena |
| الوصف: | Radio galaxies harbouring jetted active galactic nuclei are a frequent target of very-long-baseline interferometry (VLBI) because they play an essential role in exploring how jets form and propagate. Hence, only few have not been detected with VLBI yet; Fornax A is one of the most famous examples. Here we present the first detection of the compact core region of Fornax A with VLBI. At 8.4 GHz the faint core is consistent with an unresolved point source. We constrained its flux density to be $S_0 = 47.5-62.3\,\textrm{mJy}$ and its diameter to be $D^\textrm{min}_0 \leq 70\,\mu\textrm{as}$. The high values of the measured brightness temperature ($T_\textrm{B} \gtrsim 10^{11}\,\textrm{K}$) imply that the observed radiation is of non-thermal origin, likely associated with the synchrotron emission from the active galactic nucleus. We also investigated the possibility of a second radio source being present within the field of view. Adding a second Gaussian component to the geometrical model-fit does not significantly improve the quality of the fit and we, therefore, conclude that our detection corresponds to the compact core of Fornax A. Analysis of the non-trivial closure phases provides evidence for the detection of more extended flux density, on the angular scale of $\sim4000\,\mu\textrm{as}$. Finally, the fractional circular polarisation of the core is consistent with zero, with a conservative upper limit being $m_\textrm{circ} \leq 4\%$. Comment: 4 pages, 2 figures, accepted for publication in A&A |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1051/0004-6361/202450590 |
| URL الوصول: | http://arxiv.org/abs/2406.02660 |
| رقم الأكسشن: | edsarx.2406.02660 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1051/0004-6361/202450590 |
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