Super-critical accretion in nearby galaxies

Roberto Soria

Sala Seminari Villa Magliola



I present a selection of recent results on the broad subject of super-critical accretion and feedback in non-nuclear sources, without any attempt to cover the whole topic.

  1. First, I illustrate examples of ionized nebulae around ultraluminous X-ray sources, and how such nebulae constrain the mechanical power of the disk outflows.
  2. Second, I discuss our search for super-critical accretion in X-ray binaries with Wolf-Rayet donor stars, which are a crucial step along the path towards binary compact objects and mergers.
  3. Third, I show that not all super-critical sources appear ultraluminous along our line of sight, because, in some cases, their X-ray emitting regions are obscured by optically thick material.
  4. Fourth, I touch on the opposite situation, that is how to spot (rare) off-nuclear X-ray sources that are extremely luminous but not in the super-critical regime, because they are powered by intermediate-mass black holes.
Multi-color optical image around the ULX "X-1"

Multi-color optical image around the ULX “X-1” (indicated by the arrow) in the dwarf galaxy Holmberg II, is located in the direction of the constellation Ursa Major, at a distance of 11 million light-years. The image size corresponds to 1,100 × 900 light-years at the galaxy. The red color represents spectral line emission from hydrogen atoms. Credit: Special Astrophysical Observatory/Hubble Space Telescope

Referente locale: Roberto Soria
Responsabile seminari OATo: Paolo Giacobbe– Mario Damasso