The 20-year-old from Killygordan was found shortly before 1.40am on Wednesday morning, near a car park on Spear Street.
He has been formally identified as Dylan Crawford.
He was taken to Manchester Royal Infirmary where he was later confirmed dead.
A Home Office post mortem took place yesterday which was inconclusive and an investigation is underway to establish the cause of death.
Officers investigating the death have now arrested two men on suspicion of theft and supplying prohibited drugs.
Police are also appealing for anyone who was in the area at the time to get in touch.
Detective Inspector Rebecca Boyce of GMP’s City of Manchester team said: “We are still working to determine the exact circumstances surrounding Dylan’s death.
“This has been a fast moving investigation and we have now made two arrests, however our investigation continues and we need witnesses to come forward.
“We are also looking for anyone who was around the Spear Street, Back Piccadilly Street and Oldham Street area between 11.30pm on Tuesday and 12.30am on Wednesday to come forward.
“Even at this time of night the area would be fairly busy so it is possible that somebody may have seen something. No piece of information is too small.”
The Manchester Evening News says his family said: “Our Dylan was a loving, kind and a very trustworthy individual. He saw the good in everyone and that was his downfall.
“He loved to travel and would give the world to anyone. He was the heart of our family and words can’t describe how devastated we are.
“Our home will never be the same without him. We love you son, brother, cousin and friend. May you rest in peace, darling.”