Connection between the Age Distributions of Star Clusters and Field Stars: A First Application to the Small Magellanic Cloud

We present the age distributions for star clusters and individual stars inthe Small Magellanic Cloud (SMC) based on data from the Magellanic CloudsPhotometric Survey by Zaritsky and collaborators. The age distribution of theSMC clusters shows a steep decline, dN_{cluster}/dt \propto t^{-0.85\pm0.15},over the period 10^7 < t <10^9 yr. This decline is essentially identical tothat observed previously for more massive clusters in the merging Antennaegalaxies, and also for lower-mass embedded clusters in the solar neighborhood.The SMC cluster age distribution therefore provides additional evidence for therapid disruption of star clusters (``infant mortality''). These disruptedclusters deliver their stars to the general field population, implying that thefield star age distribution, dN_{fld star}/dt, should have an inverse relationto dN_{cluster}/dt if most stars form initially in clusters. We make specificpredictions for dN_{fldstar}/dt based on our cluster disruption models, andcompare them with current data available for stars in the SMC. While these datado not extend to sufficiently young ages for a definitive test, they areconsistent with a scenario wherein most SMC stars formed in clusters. Futureanalyses of dN_{fldstar}/dt that extend down to ages of approximately fewmillion years are needed to verify the age relationship between stars residingin clusters and in the field.Comment: 4 pages, 2 figures; Astrophysical Journal Letters, in pres