English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Updating Kormendy & Kennicutt (2004, ARAA, 42, 603), we review internalsecular evolution of galaxy disks. One consequence is the growth ofpseudobulges that often are mistaken for true (merger-built) bulges. Manypseudobulges are recognizable as cold, rapidly rotating, disky structures.Bulges have Sersic function brightness profiles with index n > 2; mostpseudobulges have n <= 2. Recognition of pseudobulges makes the biggest problemwith cold dark matter galaxy formation more acute: How can hierarchicalclustering make so many pure disk galaxies with no evidence for merger-builtbulges? E. g., the giant Scd galaxies M101 and NGC 6946 have rotationvelocities of V ~ 200 km/s but nuclear star clusters with velocity dispersionsof 25 to 40 km/s. Within 8 Mpc of us, 11 of 19 galaxies with V > 150 km/s showno evidence for a classical bulge, while only 7 are ellipticals or haveclassical bulges. It is hard to understand how bulgeless galaxies could form asthe quiescent tail of a distribution of merger histories. Our second theme isenvironmental secular evolution. We confirm that spheroidal galaxies havefundamental plane (FP) correlations that are almost perpendicular to those forbulges and ellipticals. Spheroidals are not dwarf ellipticals. Rather, theirstructural parameters are similar to those of late-type galaxies. We suggestthat spheroidals are defunct late-type galaxies transformed by internalprocesses such as supernova-driven gas ejection and environmental processessuch as secular harassment and ram-pressure stripping. Minus spheroidals, theFP of ellipticals and bulges has small scatter. With respect to these,pseudobulges are larger and less dense.

Secular Evolution in Disk Galaxies: Pseudobulge Growth and the Formation of Spheroidal Galaxies