Are these rotation flats variable in magnitude? Would one galaxy have a different curve height than another one? What does it depend on? Update: https://en.m.w

Are these rotation flats variable in magnitude? Would one galaxy have a different curve height than another one? What does it depend on? Update: https://en.m.wikipedia.org/wiki/Tully–Fisher_relation https://en.m.wikipedia.org/wiki/Tully–Fisher_relation But the linear regression looks unconvincing