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Paper: Spontaneous and Stimulated Star Formation in Galaxies: Ultraviolet Limits on Star Formation Thresholds and Optical Constraints on Λ-CDM Cosmological Simulations of Galaxy Formation
Volume: 374, From Stars to Galaxies: Building the Pieces to Build Up the Universe
Page: 455
Authors: Madore, B.F.; Boissier, S.; Gil de Paz, A.; Nelson, E.; Petrillo, K.
Abstract: We present recent results from several on-going studies: The first addresses the question of gas-density thresholds for star formation, as probed by the outer disks of normal nearby galaxies. The second concerns the observational evidence for the existence of gravitating non-luminous (GNL) galaxies, as predicted by most recent simulations of galaxy formation in Lambda-CDM cosmologies. We find that (1) If star formation is traced by far-ultraviolet light, then there is no evidence for a threshold to star formation at any gas density so far probed, and (2) there is no evidence for GNL galaxies gravitationally interacting with known optical systems based on the observations (a) that there are no ring galaxies without plausible optically visible intruders, (b) all peculiar galaxies in the Arp Atlas that are bodily distorted have nearby plausibly interacting companions, and (c) there are no convincingly distorted/peculiar galaxies within Karachentsevís sample of more than 1,000 apparently/optically isolated galaxies.
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