Fr.: bulbe en forme de disque
A → galaxy bulge that is flatter than a → classical bulge. Such bulges might be difficult to see in very inclined galaxies. They may contain sub-structures such as nuclear → bars, → spiral arms, or → rings. They usually show signs of → dust obscuration, younger → stellar populations, or ongoing → star formation. These systems seem to form mostly through disk instabilities (→ disk instability), such as bars, in a relatively slow, continuous and smooth process. Essentially, such instabilities induce a redistribution of → angular momentum along the galaxy, and, as a result, mostly gas but also stars are driven to the disk center. Also called → pseudo-bulge (Kormendy & Kennicutt, 2004, ARA&A 42, 603; Fisher & Drory, 2010, ApJ 716, 942).