2021/07/05 by Juno Li, Leo W.H. Fung, Li, Juno +5
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Astronomy and Astrophysical Research #Gamma-ray bursts and supernovae
paper · pdf · doi:10.48550/arxiv.2107.01771
Brightest cluster galaxies (BCGs), particularly those at the centers of cool-core clusters, can exhibit star formation over spatial extents of up to \gtrsim100 kpc at inferred rates of up to \gtrsim100\rm M_\sun yr-1. Is their star formation also extended over time, as might be expected if fuelled by cooling of the surrounding hot intracluster gas -- a residual cooling flow -- as demonstrated hitherto only for the BCG in the Perseus cluster? Here, to infer the formation history of relatively young stars in the BCG of MACS J0329.7-0211, we fit model single-stellar-populations to the spectral energy distributions (spanning near-UV to near-IR) measured along different sightlines towards its young stellar population. Employing a Markov Chain Monte Carlo method, we show that star formation in this BCG has persisted at a relatively constant rate of ∼2\rm M_\sun yr-1 (factors of 10--40 below the rates previously inferred using simpler methods and/or ad hoc assumptions) over the past ∼400 Myr, beyond which any star formation falls below the observational detection threshold. Such persistent star formation from a residual cooling flow can contribute up to ∼10% of the original stellar mass of this BCG if its progenitor was among the most massive red nuggets known at z∼2 having masses of ∼1×1011\rm M_\sun, but only a few percent of its overall growth in stellar mass to ∼8×1011\rm M_\sun at z=0.45. Although constituting only a minor pathway for the stellar growth of this BCG, persistent star formation from a residual cooling flow can nevertheless contribute significantly to the enormous number of globular clusters found around BCGs in the local Universe.