Constraining the star formation rate in the solar neighbourhood with star clusters

Abstract

This paper investigates the star formation rate (SFR) in the solar neighbourhood. First, we build the local age distribution function (ADF) with an updated sample of 442 star clusters located at less than 1 kpc from the Sun. Next, we define the SFR, compute the individual mass evolution of a population of artificial clusters covering the broad range of parameters observed in actual clusters, and assume 100M as the low-mass limit for effective cluster observation. This leads to a simulated ADF, which is compared to the low-noise solar neighbourhood ADF. The best match corresponds to a non-constant SFR presenting two conspicuous excesses for ages ≤9Myr and between 220–600 Myr (the local starburst). The average SFR is SFR ≈ (2500 ± 500)M Myr−1, corresponding to the average surface SFR SFR ≈ (790 ± 160)M Myr−1 kpc−2. These values are consistent with the SFR inferred from embedded clusters (ECs), but much lower ( 16 per cent) than that implied by field stars. Both the local starburst and the recent star formation period require SFR ∼ 2 × SFR to be described. The simulations show that 91.2 ± 2.7 per cent of the clusters created in the solar neighbourhood do not survive the first 10 Myr, which is consistent with the rate of EC dissolution.