CONFRONTING MODELS OF STAR FORMATION QUENCHING IN GALAXY CLUSTERS WITH ARCHIVAL SPITZER DATA LARGE SCALE STRUCTURES IN THE UNIVERSE FORM HIERARCHICALLY: SMALL STRUCTURES MERGE TO FORM LARGER ONES. OVER THE SAME EPOCH WHERE THESE STRUCTURES EXPERIENCE SIGNIFICANT GROWTH THE FRACTION OF STAR FORMING GALAXIES WITHIN THEM DECREASES AND AT A FASTER RATE THAN FOR FIELD GALAXIES. IT IS NOW WIDELY ACCEPTED THAT THERE MUST BE PHYSICAL PROCESSES AT WORK IN THESE DENSE ENVIRONMENTS TO ACTIVELY QUENCH STAR FORMATION. HOWEVER DESPITE NO SHORTAGE OF CANDIDATE MECHANISMS SOPHISTICATED COSMOLOGICAL SIMULATIONS STILL CANNOT REPRODUCE THE STAR FORMATION RATE DISTRIBUTIONS WITHIN DENSE ENVIRONMENTS SUCH AS GALAXY CLUSTERS. INSUFFICIENT OBSERVATIONAL CONSTRAINTS ARE A PRIMARY OBSTACLE TO FURTHER PROGRESS. IN PARTICULAR THE INTERPRETATION OF OBSERVATIONS OF NEARBY CLUSTERS RELIES ON UNTESTED ASSUMPTIONS ABOUT THE PROPERTIES OF GALAXIES BEFORE THEY ENTERED THE DENSE CLUSTER ENVIRONMENT AT HIGHER REDSHIFTS. CLEARLY DIRECT CONSTRAINTS ON THESE PROPERTIES ARE REQUIRED. OUR GROUP HAS ASSEMBLED TWO DATA SETS DESIGNED TO ADDRESS THESE CONCERNS. THE FIRST FOCUSES ON AN INTERMEDIATE WIDE-FIELD CLUSTER SAMPLE AND THE SECOND FOCUSES ON A WELL-MATCHED LOW-REDSHIFT CLUSTER SAMPLE. WE WILL USE THESE SAMPLES ALONG WITH SOPHISTICATED MODELS OF HIERARCHICAL GALAXY FORMATION TO MEET THE FOLLOWING OBJECTIVES: 1. DIRECTLY MEASURE THE SFR DISTRIBUTION OF THE PROGENITORS OF PRESENT-DAY CLUSTER GALAXIES. WE WILL USE GROUND-BASED SPECTROSCOPY TO IDENTIFY CLUSTER MEMBERS WITHIN FOUR VIRIAL RADII OF EIGHT INTERMEDIATE-REDSHIFT CLUSTERS. WE WILL COUPLE THIS WITH ARCHIVAL SPITZER/MIPS DATA TO MEASURE THE SFRS OF GALAXIES OUT TO THE CLUSTER OUTSKIRTS. 2. MEASURE THE SFR DISTRIBUTION OF THE PRESENT-DAY CLUSTER GALAXIES USING SPITZER AND WISE. ROBUST N-BODY SIMULATIONS TELL US STATISTICALLY WHICH GALAXIES AT INTERMEDIATE REDSHIFTS WILL HAVE ENTERED THE CLUSTER VIRIAL RADIUS BY THE CURRENT EPOCH. BY COMBINING OUR WIDE-FIELD COVERAGE AT HIGH REDSHIFT WITH OUR LOCAL CLUSTER SAMPLE WE WILL DETERMINE THE EVOLUTION IN CLUSTER GALAXY SFRS OVER 6 BILLION YEARS MAKING MINIMAL ASSUMPTIONS ABOUT THE INFALLING GALAXY POPULATION. 3. PROVIDE A RIGOROUS TEST OF THE QUENCHING PROCESSES EMBEDDED IN THE THEORETICAL MODELS. WE WILL CREATE OBSERVED REALIZATIONS OF THE THEORETICAL MODELS BY SUBJECTING THEM TO OUR OBSERVATIONAL SELECTION. THIS WILL ENABLE A FAIR COMPARISON BETWEEN THE MODELS AND THE DATA WHICH WILL PROVIDE A VALUABLE TEST OF CURRENT THEORETICAL IMPLEMENTATIONS OF QUENCHING PROCESSES. WE WILL ALSO MODIFY THE QUENCHING PRESCRIPTIONS IN THE MODELS TO DETERMINE THE PARAMETERS REQUIRED TO REPRODUCE THE OBSERVATIONS. THE PROPOSED RESEARCH IS NOVEL FOR SEVERAL REASONS. 1) WE HAVE WIDE-FIELD SPITZER/MIPS DATA THAT ALLOWS US TO ROBUSTLY MEASURE SFRS IN OUR DISTANT CLUSTER GALAXIES. WISE DATA ON LOCAL CLUSTERS WILL PROVIDE US WITH ANALOGOUS MEASUREMENTS IN THE NEARBY UNIVERSE. 2) OUR SIGNIFICANT INVESTMENT IN ANCILLARY SPECTROSCOPY ALLOWS US TO IDENTIFY INFALLING GALAXIES THAT WILL EVENTUALLY JOIN THE CENTRAL REGIONS OF THE CLUSTER Z=0. 3) OUR INTERMEDIATE REDSHIFT CLUSTER SAMPLE WAS CHOSEN TO HAVE CHARACTERISTICS EXPECTED FOR THE PROGENITORS OF A LARGE FRACTION OF THE KNOWN CLUSTERS AT Z=0. 4) WE WILL TAKE ADVANTAGE OF OUR OWN COSMOLOGICAL SIMULATIONS OF STRUCTURE GROWTH TO INTERPRET OUR DATA. 5) WE HAVE OPTICAL PHOTOMETRY OVER THE FULL INFALL REGION ALLOWING US TO CONTROL FOR STELLAR MASSES AND TO DISTINGUISH PASSIVE FROM DUSTY STAR-FORMING GALAXIES. WE WILL LEARN WHICH IF ANY OF THE QUENCHING PRESCRIPTIONS CURRENTLY EMPLOYED IN SEMI-ANALYTIC MODELS CORRECTLY REPRODUCES THE OBSERVED CHARACTERISTICS OF THE GALAXIES THAT WILL BECOME CLUSTER GALAXIES AT Z=0. WE WILL PINPOINT THE CLUSTER-CENTRIC RADII OVER WHICH QUENCHING TAKES PLACE BETWEEN. WE WILL DETERMINE THE TIMESCALE (AS A FUNCTION OF STELLAR MASS) OVER WHICH IT MUST TAKE PLACE. THIS PROGRAM WILL CEMENT THE LEGACY OF SPIT