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IERS Message No. 395                                   February 05, 2020
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Workshop on the Celestial Reference Frame and Active Galactic Nuclei


Dear colleagues,

Quasars and AGNs, which play a fundamental role in the evolution of
their host galaxies, are also used to build fundamental celestial
reference systems (i.e., the ICRF) because of their extreme distances
and therefore negligible proper motions. With the advent of the Gaia
astrometric mission, however, visual-wavelength astrometry has entered
the micro-arcsecond domain, in which significant positional offsets have
been found with the radio positions of quasars. These offsets are likely
physical in nature, owing to processes of direct interest to the AGN
community more broadly, such as radio jet production, outflows,
dual/binary AGNs, lensing, circumnuclear star formation, etc.

This conference will bring together AGN and CRF researchers to discuss
these issues. The chosen venue is the Institut d'astrophysique de Paris,
next to Observatoire de Paris, both institutions with a long and rich
history of astrophysical research across a broad range of fields,
including those pertaining to navigation, the celestial reference frame
(CRF), quasar research and galaxy evolution. The date of this
conference, 15-19 June 2020, is optimal as it lies between Gaia DR2, the
3rd realization of the ICRF, and Gaia DR3. During this period, the
international reference frame community will be developing a road map
for the next realization of the ICRF, including integration of high
accuracy, visible AGN data from Gaia with the radio VLBI data that
currently composes the ICRF3.


The workshop website is at the following URL:

https://syrte.obspm.fr/astro/agnworkshop2020/


Best regards,

Bryan Dorland (USNO) and Jean Souchay (Observatoire de Paris)


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