Flight Crew Air Transport Pilot (ATP)
Workload
ATC Issue All Types; Conflict Airborne Conflict
Flight Crew FLC complied w / Automation / Advisory
Aircraft; Human Factors; Procedure
Cleared to descend via the arrival.  Approaching an intersection we noticed traffic displayed to our north on our TCAS.  We were descending out of 17;000 feet.  As I queried ATC about the traffic; we received an RA to climb for the traffic.  ATC did not notify us of the traffic.  These arrivals are so heads down for pilots flying the MD-82 that we did not acquire the traffic visually.  I advised ATC of the TCAS RA and that we were climbing as directed by TCAS.  After we were clear of the conflicting aircraft we returned to the assigned altitude restrictions via the arrival.  I informed ATC we were returning to our clearance of 'descending via' This traffic conflict could have been avoided with ATC intervention to maintain our altitude due to traffic.  I'm not knowledgeable of ATC radar systems and maybe this traffic just 'popped up on radar' with no time to manage the conflict.  I will say; the TCAS system functioned great.  I would suggest; based on the last few weeks of flying these arrivals on the MD-82; that anytime the TCAS is not operational the crew should not accept any arrival with a 'descend via' clearance.
MD-82 Captain reported receiving a Resolution Advisory (RA) on a 'descend via' clearance; citing workload in the old technology transports as interfering with their traffic scan.