Asymmetric X-ray emission and powerful cluster-scale radio halo indicate that A2319 is a merging cluster of galaxies .
This paper presents our multicolor photometry for A2319 with 15 optical intermediate filters in the Beijing-Arizona-Taiwan-Connecticut ( BATC ) system .
There are 142 galaxies with known spectroscopic redshifts within the viewing field of 58 ^ { \prime } \times 58 ^ { \prime } centered on this rich cluster , including 128 member galaxies ( called sample I ) .A large velocity dispersion in the rest frame , 1622 ^ { +91 } _ { -70 } km s ^ { -1 } , suggests a merger dynamics in A2319 .
The contour map of projected density and localized velocity structure confirm the so-called A2319B substructure , at \sim 10 ^ { \prime } NW to the main concentration A2319A .
The spectral energy distributions ( SEDs ) of more than 30,000 sources are obtained in our BATC photometry down to V \sim 20 mag .
A u -band ( \sim 3551Å ) image with better seeing and spatial resolution , obtained with the Bok 2.3m telescope at Kitt Peak , is taken to make star-galaxy separation and distinguish the overlapping contamination in the BATC aperture photometry .
With color-color diagrams and photometric redshift technique , 233 galaxies brighter than h _ { BATC } = 19.0 are newly selected as member candidates after an exclusion of false candidates with contaminated BATC SEDs by eyeballing checking the u -band Bok image .
The early-type galaxies are found to follow a tight color-magnitude correlation .
Based on sample I and the enlarged sample of member galaxies ( called sample II ) , subcluster A2319B is confirmed .
The star formation properties of cluster galaxies are derived with the evolutionary synthesis model , PEGASE , assuming a Salpeter IMF and an exponentially decreasing star formation rate ( SFR ) .
A strong environmental effect on star formation histories is found in the manner that galaxies in the sparse regions have various star formation histories , while galaxies in the dense regions are found to have shorter SFR time scales , older stellar ages , and higher ISM metallicities .
For the merging cluster A2319 , local surface density is a better environmental indicator rather than the clustercentric distance .
Compared with the well-relaxed cluster A2589 , a higher fraction of star-forming galaxies is found in A2319 , indicating that the galaxy-scale turbulence stimulated by the subcluster merger might have played a role in triggering the star formation activity .