REVERSAL OF FORTUNE: CONFIRMATION OF AN INCREASING STAR FORMATION-DENSITY RELATION IN A CLUSTER AT z=1.62

We measure the rest-frame colors (dust-corrected), infrared luminosities, star formation rates, and stellar masses of 92 galaxies in a Spitzer-selected cluster at z = 1.62. By fitting spectral energy distributions (SEDs) to 10-band photometry (0.4 mu m < lambda(obs) < 8 mu m) and measuring 24 mu m fluxes for the 12 spectroscopically confirmed and 80 photometrically selected members, we discover an exceptionally high level of star formation in the cluster core of similar to 1700 M(circle dot) yr(-1) Mpc(-2). The cluster galaxies define a strong blue sequence in (U-V) color and span a range in color. We identify 17 members with L(IR) > 10(11) L(circle dot), and these IR luminous members follow the same trend of increasing star formation with stellar mass that is observed in the field at z similar to 2. Using rates derived from both the 24 mu m imaging and SED fitting, we find that the relative fraction of star-forming members triples from the lowest to highest galaxy density regions; e.g., the IR luminous fraction increases from similar to 8% at Sigma similar to 10 gal Mpc(-2) to similar to 25% at Sigma greater than or similar to 100 gal Mpc(-2). The observed increase is a reversal of the well-documented trend at z < 1 and signals that we have reached the epoch when massive cluster galaxies are still forming a substantial fraction of their stars.