Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 150
Human-Machine Interface; Confusion
Conflict NMAC
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory
Airspace Structure; Human Factors; Procedure
It was a very busy day coming into DAL. We were being vectored from the northeast for a Visual Approach. We had Company traffic in sight and were told to follow them and cleared for the Visual Approach. We ensured clearance from them and began maneuvering for the runway with a more direct path to ZZZZZ.  It was about that time I noticed a TCAS target ahead. I cannot remember if we had already been switched to Tower or not at that point; but ATC told us about the traffic ahead. I responded; 'looking for traffic.' Shortly after that we heard ATC tell Aircraft Y [the traffic ] to turn east immediately. We were given no more instruction and weren't sure which way would be best for avoidance. I told the Captain that we may get an RA here and he prepared. We then got a climb RA. The Captain responded immediately and we avoided the conflict.We were able to regain approach stability and land uneventfully. We have no idea why a small aircraft was in Class B airspace between us and our line to the airport while we were cleared for a Visual Approach; or why we were given no instruction by ATC other than a traffic notification. By the time the traffic was noticed by us as a threat; the rate of closure was so fast we only had a few seconds to process what we may needed to do. We never got Aircraft Y in sight; but I noticed on the TCAS indication that he was 300 feet below us at what looked like our position on the 2.5 NM display.I am not sure what needs to happen to prevent this from happening again because I'm not sure why this happened. I'm hoping this report brings some attention to this event so we can find out why something like this happened. I know they were busy but I feel this incident should have been prevented by either keeping us in their control until we were clear of Aircraft Y or keeping them out of Class B at such a busy time.
Air Carrier First Officer on a Visual Approach in DAL airspace reported a NMAC and TCAS/RA alert for a VFR small aircraft.