The centres of galaxies are powerful laboratories to test the current $Lambda$CDM model for structure formation and evolution. While these sub-galactic scales can be directly investigated in the local Universe, it is observationally extremely difficult to access them at high redshift. The combination of strong gravitational lensing and VLBI observations allows us to access these scales to study both the baryonic and the dark matter distribution at the largest distances. For example, it becomes possible to unveil complex mass density distribution of lensing galaxies, faint cold molecular gas reservoirs, offset and binary AGN candidates at $z>1$. Currently, these detailed studies are limited by the small number of known radio-loud lensed sources. Wide-field VLBI observations may provide a viable way to search for many more radio-loud systems and test strategies in preparation for the future surveys with the next generation of interferometers.
{"title":"Using strong gravitational lensing to zoom in on high-redshift galaxies","authors":"C. Spingola","doi":"10.22323/1.399.0022","DOIUrl":"https://doi.org/10.22323/1.399.0022","url":null,"abstract":"The centres of galaxies are powerful laboratories to test the current $Lambda$CDM model for structure formation and evolution. While these sub-galactic scales can be directly investigated in the local Universe, it is observationally extremely difficult to access them at high redshift. The combination of strong gravitational lensing and VLBI observations allows us to access these scales to study both the baryonic and the dark matter distribution at the largest distances. For example, it becomes possible to unveil complex mass density distribution of lensing galaxies, faint cold molecular gas reservoirs, offset and binary AGN candidates at $z>1$. Currently, these detailed studies are limited by the small number of known radio-loud lensed sources. Wide-field VLBI observations may provide a viable way to search for many more radio-loud systems and test strategies in preparation for the future surveys with the next generation of interferometers.","PeriodicalId":136428,"journal":{"name":"Proceedings of European VLBI Network Mini-Symposium and Users' Meeting 2021 — PoS(EVN2021)","volume":"152 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115170195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Paraschos, Jae-Young Kim, T. Krichbaum, Junghwan Oh, J. Hodgson, M. Gurwell, J. Zensus
Jets which are powered by an AGN are a crucial element in the study of their central black holes (BH) and their immediate surroundings. The formation of such jets is the subject of intense research, mainly based on the dichotomy presented by the two main jet launching scenarios $-$ the one from Blandford&Payne (1982), and the one from Blandford&Znajek (1977). In this work we study the prominent and nearby radio galaxy 3C 84 (NGC 1275) with 15, 43, and 86 GHz quasi-simultaneous VLBI observations. From these we determine the jet apex to be located $83pm7,mu$as ($0.028-0.11$pc) upstream of the 86 GHz VLBI core, applying a two dimensional cross-correlation analysis. A byproduct of this analysis are spectral index maps, in which we identify a robust spectral index gradient in the north-south direction, for the first time at such high resolution, for the 43-86 GHz pair. The magnetic field strength at distances from the VLBI core comparable to measurements from the literature ($sim10$ Schwarzschild radii) for other prominent AGN, like NGC 1052 and M 87, is computed to be $70-600$G. Implications for the magnetic field topology are also discussed.
{"title":"Pinpoint the jet apex in 3C 84","authors":"G. Paraschos, Jae-Young Kim, T. Krichbaum, Junghwan Oh, J. Hodgson, M. Gurwell, J. Zensus","doi":"10.22323/1.399.0043","DOIUrl":"https://doi.org/10.22323/1.399.0043","url":null,"abstract":"Jets which are powered by an AGN are a crucial element in the study of their central black holes (BH) and their immediate surroundings. The formation of such jets is the subject of intense research, mainly based on the dichotomy presented by the two main jet launching scenarios $-$ the one from Blandford&Payne (1982), and the one from Blandford&Znajek (1977). In this work we study the prominent and nearby radio galaxy 3C 84 (NGC 1275) with 15, 43, and 86 GHz quasi-simultaneous VLBI observations. From these we determine the jet apex to be located $83pm7,mu$as ($0.028-0.11$pc) upstream of the 86 GHz VLBI core, applying a two dimensional cross-correlation analysis. A byproduct of this analysis are spectral index maps, in which we identify a robust spectral index gradient in the north-south direction, for the first time at such high resolution, for the 43-86 GHz pair. The magnetic field strength at distances from the VLBI core comparable to measurements from the literature ($sim10$ Schwarzschild radii) for other prominent AGN, like NGC 1052 and M 87, is computed to be $70-600$G. Implications for the magnetic field topology are also discussed.","PeriodicalId":136428,"journal":{"name":"Proceedings of European VLBI Network Mini-Symposium and Users' Meeting 2021 — PoS(EVN2021)","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122322421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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