http://www.castlegarden.orglists:
Catherine Monaghan / Wife / age: 30 / arrived: 22 May 1861 / origin: England / ship: Edinburgh
Ann Monaghan / Child, Youngster / age: 5 / arrived: 22 May 1861 / origin: England / ship: Edinburgh
Catherine's husband is not listed, so no doubt he arrived earlier. There's this Thomas from England:
Thomas Monaghan / Laborer / age: 24 / arrived: 30 Mar 1857 / origin: England / ship: Albion
But four years is a long time to fetch one's family, so maybe it's not him.
There is an Edward, however:
Edward Monaghan / Laborer / age: 22 / arrived: 1 May 1861 / origin: Ireland / ship: Escort
But he came from Ireland - then again "origin" is a vague term.
Have you found Thomas on the 1860 US Census or Catherine and Ann on the 1861 UK Census? Since the 1861 census was taken on 07/08 April 1861, Catherine and Ann may be on it.