text:   astrometrically-selected quasar candidates using Gaia DR2",10,"['Happy to announce that our new paper: <LINK>  was posted today on ArXiv! \nIn this, we basically ask: can you efficiently identify quasars purely as point-like sources that doesn’t move on the sky? \nTurns out: Yes! \nAs long as its far away from the Galactic plane', 'This has been a rollercoaster of a project, starting with the release of @ESAGaia-DR2 more than 2 years ago, and with several non-succesful observing runs due to clouds, ice, etc. https://t.co/6lmzM4HrAQ', 'When we *finally* got spectra of our targets, we have had several first-year students at @DAWNCopenhagen/@uni_copenhagen help us classify them as either stars ⭐️ or quasars 💥 (some many billion of lightyears away) — and for many of them, this was their first academic paper!', 'Briefly, what we found was: it is possible to efficiently select quasars (~70% of the total number of targets) purely as sources with zero proper motions and parallaxes as measured by @ESAGaia-DR2. https://t.co/AbzczXmkCI', 'This is, however, only feasible to reach at high Galactic latitudes, i.e. far away from the Galactic plane. Moving closer, we would be completely overwhelmed by stars that were apparently non-moving on the sky (at least not in the transverse direction). https://t.co/nN77blhLfA', 'This *complete* sample of quasars allowed us to examine the intrinsic properties of the quasar population, and specifically how large the fraction of “red” quasars is (anyway between 10% and 40% depending on the brightness limit). https://t.co/B9huHsfbo5', 'In this survey we also discovered several very interesting quasars — here is one example that shines right through the disk of a nearby (z~0.02) galaxy! This allowed us to study the dust and metals in this disk, that was imposed on the background quasar spectrum. https://t.co/MY7pw0cXH7', 'Finally, we could also assess how complete other, more commonly used photometric quasar surveys were at similar brightness — turns out, they only manage to find 85-90% of the quasars we do! https://t.co/eEtbUjJTcS', 'This just cements the fact that this survey is the only way to select quasars, or extragalactic point-sources in general, without assumptions of their intrinsic emission (i.e. radio-loud, blue UV colors, etc) — so basically, quasars that don’t look like typical quasars!', '@dr_guangtou No apparently not! As far as I understand, extended sources will not trigger a detection on Gaia’s CCD — however, for bright AGN (and this spectacular case) Gaia will be sensitive enough to disentangle and accurately measure the central (or outlying) point-source.']",20,10,2441