INTERESTING: changing names as artist.

A lot of people seem to change their name using a stage name.
Upyerkilt told me an example (which I knew already) that a guy named DAVID JONES changed his name in DAVID BOWIE.
Changing a name in an artist name, are this names "officially" recognized by the authorities, meaning that Robert Zimmerman = BOB DYLAN, and resulting in his offspring like JAKOB DYLAN?
Or do they use their names only on stage, and not officially recognized by the authorities?
BUT WHO ELSE DID SO?
1) WHAT ABOUT THESE NAMES are they official changed, or still STAGE NAMES?
- REGINALD DWIGHT became ELTON JOHN.
- DECLAN PATRICK McMANUS became ELVIS COSTELLO
- ROBERT ZIMMERMAN became BOB DYLAN
- RICHARD STARKEY became RINGO STARR
2) WHAT ABOUT THESE NAMES? It's really obvious that these are STAGE NAMES.
- PAUL HEWSON became BONO VOX (= good voice), but now BONO.
- GORDON SUMMER became STING
INCLUDING ACTOR'S NAMES:
- Ramón Gerardo Antonio Estévez became MARTIN SHEEN, and both his suns have different names
- CHARLIE SHEEN adopted his father's stage name SHEEN while his brother kept his father original name ESTEVEZ (Emilio Estevez) which brings me back to OFFICIALLY CHANGED NAMES and STAGE NAMES.
See also KIRK DOUGLAS, his children are all named DOUGLAS too, so did they had to change it legally, or was papa KIRK born as Issur Danielovitch, name change in KIRK DOUGLAS enough?