evn:evn_science
Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
evn:evn_science [2018/09/12 08:45] – antonis | evn:evn_science [2018/09/12 09:19] – [Gravitationally-lensed radio arcs observed with global VLBI] antonis | ||
---|---|---|---|
Line 34: | Line 34: | ||
\\ | \\ | ||
+ | |||
+ | =====Gravitationally-lensed radio arcs observed with global VLBI===== | ||
+ | |||
+ | |||
+ | |||
+ | The Strong lensing at High Angular ResoluTon Program (SHARP) led by McKean (ASTRON) has | ||
+ | obtained a deep global VLBI observaTon of the gravitaTonal lens MG J0751+2716 at 1.65 GHz | ||
+ | (project GM070; PI: McKean). The 18.5 hours observation used 24 antennas from the EVN and | ||
+ | the VLBA, including the large apertures (> 50 m) of the Lovell, Effelsberg, Robledo and Green Bank | ||
+ | telescopes. Data were recorded at 512 Mbps and correlated at JIVE to produce 8 spectral | ||
+ | windows (IFs) with 8 MHz bandwidth and 32 channels each, through both circular polarisaTons. | ||
+ | MG J0751+2716 is one of the few quadruply imaged radio-loud gravitationally lensed quasars that | ||
+ | show extended arcs on VLBI-scales. The global VLBI L-band deep imaging detects all of the extended | ||
+ | arcs at high significance, | ||
+ | source in unprecedented detail (see Figure from [[https:// | ||
+ | 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 | ||
+ | extended (200-600 mas) gravitaTonal arcs been detected at an angular resoluTon of a few mas. The | ||
+ | excellent uv-coverage and surface brightness sensiTvity provided by the global VLBI array have been | ||
+ | fundamental for a precise study of the structure of the extended arcs on mas-scales from | ||
+ | MG J0751+2716. | ||
+ | |||
+ | {{: | ||
+ | |||
+ | **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 | ||
+ | mas, and is shown within the white box in the bottom-hand corner. | ||
+ | |||
+ | |||
+ | 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 ===== | ||
[[http:// | [[http:// |
evn/evn_science.txt · Last modified: 2021/05/03 07:30 by kazi