tokens: stars (FRMS) has been already discussed by several authors (e.g. Decressin et al. 2007 ). This FRMS self-enrichment scenario has no problem associate with later SNe that can severely suppress secondary star formation. However, it is not clear in this FRMS scenario how SG star formation can be completed well before SN explosion can brow away the cold gas of the molecular cloud (MC). We here do not discuss how to avoid this potentially serious problem, because it is beyond the scope of this paper to investigate the FRMS scenario in detail. 4.3 Metallicity spreads in GCs Although Lee et al. ( 2009 ) investigated the colour magnitude diagrams ( V versus b − y or hk ) of the Galactic GCs and found evidence of Ca abundance spreads in the 7 GCs, Carretta et al. ( 2010 ) showed that Ca abundance spreads among FG and SG stars in 17 Galactic GCs are less than 0.02–0.03 dex. The most massive Galactic GC ω Cen and 8 GCs (e.g. M22) have been observed to show [Fe/H] spreads among GC stars so far (e.g. Freeman Rodgers 1975 ; Marino et al. 2015 ). The apparent lack of internal [Fe/H] spreads among GC stars in most GCs implies that self-enrichment by SNe did not proceed efficiently at GC formation for some physical reasons. Since these GCs show anticorrelations between light elements, which could be due to self-enrichment by AGB stars, the physical mechanisms that suppress self-enrichment by SNe in GC formation need to be understood clearly. Nakasato, Mori Nomoto ( 2000 ) investigated SFHs of proto-GC clouds with the masses of 10 6 M ⊙ , sizes of 150–300 pc, and initial temperature of 10 4 K using their original SPH simulations with feedback effects chemical enrichment by SNe. They found that although star formation in shell-like gaseous structures formed through compression of gas through SNe feedback effects is possible, self-enrichment is not seen to occur in all of their models. This study have demonstrated that although new star formation from gas contaminated by SNe is possible, the mass fraction of such stars is quite small. Furthermore, most of such stars can be formed mostly in the shocked gas that are distant from the main GC-forming regions, and therefore they cannot be finally within the central regions of GCs. As a result of this, the mass fraction of such (SG) stars with [Fe/H] by more than 0.05 dex larger than (FG) stars formed from original cold gas of GC-forming GCs is quite small within the central 10pc of GCs. This implies that the apparent lack of [Fe/H] spreads in typical GCs is due largely to SN feedback effects in GC-forming MCs. Baumgardt, Kroupa Parmentier ( 2008 ) show that the stellar masses of GCs required for self-enrichment by SNe is more than 10 7 M ⊙ , which means that original GC-hosting MC should be very massive (∼10 8 M ⊙ ) for a reasonable SFE (∼0.1). Therefore, typical GCs are unlikely to have [Fe/H] spreads. The most massive Galactic GC ω Cen has been suggested to originate from a nucleated dwarf galaxy (e.g. Freeman 1993
ner_tags: O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O B-Wavelength O B-Wavelength O B-Wavelength O B-Wavelength O O O B-CelestialObject O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O B-CelestialObject O O O O O O O O O B-CelestialObject O B-CelestialObject I-CelestialObject O O O O B-CelestialObject O O O O O O O O O O O O O B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Model I-Model O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O B-CelestialObject I-CelestialObject O O O O O O O O O O O B-Citation I-Citation