Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Procedure
While descending into ZZZ for the visual to Runway X on a clear day; we were given a descent to 3;000 ft. As we were approaching 4;500 ft.; we were given a traffic alert by ATC that there was an aircraft 500 ft. below us and that we could level off in needed. I was Pilot Flying and immediately disconnected the auto pilot and reduce our descent rate. At that point; we were approximately 500 ft. from the aircraft. We then got the TCAS RA to monitor vertical speed and the VSI showed us to maintain altitude. I did this; and we acquired the aircraft visually. No further issues happened after we passed the aircraft and I would estimate that we were never less than 400 ft. from the aircraft.Aircraft appeared to be in the class B airspace or was not talking to the approach control facility.
Captain reported a TA and RA caused him to disconnect the autopilot and take evasive action to avoid a NMAC.