evn:evn_science
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evn:evn_science [2018/09/12 09:12] – antonis | evn:evn_science [2018/09/12 09:19] – [Gravitationally-lensed radio arcs observed with global VLBI] antonis | ||
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=====Gravitationally-lensed radio arcs observed with global VLBI===== | =====Gravitationally-lensed radio arcs observed with global VLBI===== | ||
- | [[https:// | + | |
The Strong lensing at High Angular ResoluTon Program (SHARP) led by McKean (ASTRON) has | The Strong lensing at High Angular ResoluTon Program (SHARP) led by McKean (ASTRON) has | ||
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show extended arcs on VLBI-scales. The global VLBI L-band deep imaging detects all of the extended | show extended arcs on VLBI-scales. The global VLBI L-band deep imaging detects all of the extended | ||
arcs at high significance, | arcs at high significance, | ||
- | source in unprecedented detail (see Figure). Because of the complexity of this system, the imaging was | + | source in unprecedented detail (see Figure |
performed using multi-scale cleaning within the wsclean algorithm (Offringa et al. 2014). The total | performed using multi-scale cleaning within the wsclean algorithm (Offringa et al. 2014). The total | ||
flux density of the target is 350 mJy and the off-source rms is 41 μJy/beam. Never before have such | flux density of the target is 350 mJy and the off-source rms is 41 μJy/beam. Never before have such | ||
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MG J0751+2716. | MG J0751+2716. | ||
- | {{: | + | {{: |
**Figure 1.**Global VLBI imaging of MG J0751+2716 at 1.65 GHz (Spingola et al. (2018)). The off-source | **Figure 1.**Global VLBI imaging of MG J0751+2716 at 1.65 GHz (Spingola et al. (2018)). The off-source | ||
rms is 41 μJy/beam and the peak surface brightness is 2.9 mJy/beam. The restored beam is 5.5x1.8 | rms is 41 μJy/beam and the peak surface brightness is 2.9 mJy/beam. The restored beam is 5.5x1.8 | ||
mas, and is shown within the white box in the bottom-hand corner. | mas, and is shown within the white box in the bottom-hand corner. | ||
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+ | Spingola et al. (2018) analysed these observations and identified lensed emission corresponding to the same source component, providing a very large number of constraints on the mass model that also sampled a large radial and tangential extent. When performing the mass modelling of this system, they found a discrepancy between the observed and predicted positions of the lensed images, with an average position rms of the order of 3 mas, which is much larger that the measurement errors (40 μas on average). A possible explanation for the offset between the observed and model-predicted positions is the presence of some additional mass structure (e.g. Metcalf & Madau 2001). However, since the lensing galaxy lies in a small group of galaxies, it is not clear whether this extra mass is in the form of sub-haloes within the lens or along the line of sight, or from a more complex halo for the galaxy group. Furthermore, | ||
===== The Repeating Fast Radio Burst FRB 121102 as seen on milliarcsecond angular scales ===== | ===== The Repeating Fast Radio Burst FRB 121102 as seen on milliarcsecond angular scales ===== |
evn/evn_science.txt · Last modified: 2021/05/03 07:30 by kazi