on the Evolution of Spiral Galaxies
Institute of Astrophysics and Space Sciences (IA) | 2020 Aug 26
Previous studies on the formation and evolution of spiral galaxies might have been based on a wrong assumption
Most spiral galaxies are characterized by a disk, where stars, gas and dust spread out in a characteristic pattern of twisted spiral arms, and a bright central area, named the bulge. When studying how galaxies form and evolve, it is crucial to differentiate between these two components. This represents a scientific challenge and previous studies have traditionally assumed that the disk brightness increases exponentially all the way to the galactic centre.
This common assumption is challenged in a new study ... Using a new technique to separate the bulge from the disk applied to 135 spiral galaxies from the CALIFA survey, the researchers found a lesser contribution of stars from the disk to the overall brightness of the galaxy centre. According to the authors, this has wide implications for studies on galaxy formation and evolution. ...
If confirmed, this discovery implies that the relative amount contributed from disk and bulge stars to the galaxy centre is different than previously presented in a substantial number of studies that assumed an exponential increase up to the centre of the disk.
Previous studies on spiral galaxy evolution may be flawed by assuming that the brightness contribution from stars intrinsic to the bulge is less significant than it actually is. For instance, in spiral galaxies in which the disk represents 80 percent of the luminosity in the central area, its overestimation may lead to an erroneous classification of the type of bulge. ...
Indications of the Invalidity of the Exponentiality of the Disk within Bulges
of Spiral Galaxies ~ Iris Breda, Polychronis Papaderos, Jean Michel Gomes