A Danbury man has been arrested for allegedly sexually and physically assaulting a woman.  Police say 41-year old Daniel Hernandez-Castellanos was arrested last week on charges including sexual assault, threatening and assault.  A woman filed a complaint that said the man, who was known to her, showed up unannounced an assaulted her last month.  According to the warrant, Hernandez-Castellanos allegedly threatened her if she told anyone about the abuse.  He was arraigned and was held on $200,000 bond for a court appearance on Monday.