Recipes for ULX formation: necessary ingredients and garnishments

Abstract

I summarize the main observational features that seem to recur more frequently in the ULX population. I speculate that two of the most important physical requirements for ULX formation are low metal abundance, and clustered star formation triggered by external processes such as molecular cloud collisions. In this scenario, most ULX are formed from recent stellar processes, have BH masses < 100 Msun and do not require merger processes in super star clusters.

4 pages, to appear in the proceedings of "Black Holes: from Stars to Galaxies", IAU Symp. No. 238, V. Karas & G. Matt eds., Cambridge University Press

References in corpus (6)

• The Ultra-Luminous X-ray Source Population from the Chandra Archive of Galaxies
• A Comparison of Intermediate Mass Black Hole Candidate ULXs and Stellar-Mass Black Holes
• On the weakness of disc models in bright ULXs
• Hierarchical Merging, Ultraluminous and Hyperluminous X-ray Sources
• Are Ultra-Luminous X-ray Sources Intermediate Mass Black Holes Accreting from Molecular Clouds?
• Young Crab-like pulsars and luminous X-ray sources in starbursts and optically dull galaxies