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		| Paper: | The Extreme Nuclear Environments of Sgr A* and Arp 220 |  
		| Volume: | 408, The Starburst−AGN Connection |  
		| Page: | 95 |  
		| Authors: | Scoville, N.Z. |  
		| Abstract: | The dense ISM which is the fuel for both nuclear starbursts is believed to be accreted to the nucleus by stellar bars and galactic interactions. In this contribution, I summarize the observational results for two galactic nuclei at the extreme ends of starburst/AGN activity − our own Galactic nucleus with SgrA* and the ULIRG Arp 220. I discuss theoretical considerations for the properties of the ISM − its density and scale height, whether it is likely to clump into gravitational bound GMCs − and the self-regulation of SB and AGN fueling due to radiation pressure support of the ISM. The latter yields an Eddington-like limit on the activity for both SB and AGN, corresponding to approximately 500 Lʘ /Mʘ for optically thick regions in which the radiation has been degraded to the NIR. |  
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