Looks like Joachim died without direct heirs in 1675. Wondered why his brother Johannes Henrichsen Irgens' ( died 1659) male heirs didn't inherit the barony on Joachim's death. I see he died bankrupt but I was wondering how that would affect the passing on of a noble title.
Later his widow, Cornelia Irgens von Westervick, managed to buy back some parts of the estate, among other the Troms Estate. After her death in 1708 her brother Baron Jacob de Petersen inherited some of this land. However the title seems to have become extinct.
http://en.wikipedia.org/wiki/Joachim_Irgens_von_Westervick
http://snl.no/.nbl_biografi/Joachim_Irgens/utdypning
http://en.wikipedia.org/wiki/Irgens_Estate
Found a further reference in Fredrikke Waaler's excellent treatise on the Rynning family which mentions that "Joachim Irgens nobilit von Westervick" -" Hans linje utdode 1698 med hans son H. Bieckers , Irgens von Westerwich". So looks like he had a son. His wifes maiden name was Bicker - she was from Dutch minor nobilty.
Sorry don't have Danish/Norwegian keyboard.