News - Highlights

You will find here some highlights about my research and links towards press releases.

  • 2017: Clues emerge in mystery of flickering quasars: Our negative measurement of the linear polarization of a "changing-look" quasar has caught the attention of Nature. Our work, together with recent results from Sheng et al., supports the idea that those systems are effectively getting short of fueling material (gas and dust), but not being obscured by a dust cloud obscuring their central engine.
  • 2017: Cosmic lenses support finding on faster than expected expansion of the Universe: With colleagues from the H0LICOW collaboration, we have measured the expansion rate of the Universe (the Hubble Constant H0) using the "time-delay distance technique". This consists, on one hand, in measuring the time-delay between multiple images of a lensed quasar, and on the other hand, in accurately modeling the gravitational potential of the lensing galaxy. By combining those two ingredients for three gravitationaly lensed quasars, we have been able to infer H0 with a relative uncertainty of about 3.8 %. Our result suggest that the Universe expands slightly faster than expectation using some other cosmic probes.
  • 2014: Spooky Alignment of Quasars Across Billions of Light-years: We found that the rotation axes of the central supermassive black holes in a sample of quasars are parallel to each other over distances of billions of light-years. We also found that the rotation axes of these quasars tend to be aligned with the vast structures in the cosmic web in which they reside. The associated paper can be found following this link
  • 2012: | Quasars Acting as Gravitational Lenses: We have found several examples of galaxies containing quasars, which act as gravitational lenses, amplifying and distorting images of galaxies aligned behind them. The associated paper can be found following this link
  • 2010: | Unusual Cosmic lens: We report the discovery of the first quasar lensing a more distant galaxy. The associated paper can be found following this link
  • 2008: | Astronomers Dissect a Supermassive Black Hole with Natural Magnifying Glasses: Combining a double natural "magnifying glass" with the power of ESO's Very Large Telescope, astronomers have scrutinised the inner parts of the disc around a supermassive black hole 10 billion light-years away. They were able to study the disc with a level of detail a thousand times better than that of the best telescopes in the world, providing the first observational confirmation of the prevalent theoretical models of such discs.
  • 2007: | It Is No Mirage!: We unveiled a third quasar image in the vicinity of a system which was previously believed to be a lensed quasar. The quasar pair was in fact a close trio of supermassive black holes. The associated paper can be found following this link
  • 2003: Nearest cosmic mirage: During my PhD thesis, I discovered RXS J1131-1231, still the closest gravitationally lensed quasar discovered so far, a jewel in the sky, and still one of my favourite systems ! The associated paper can be found following this link