Аннотация
Massive stars are typically in star clusters and live short lives, so the
supernovae (SNe) they produce are clustered in space and time. Since the amount
of momentum that SNe can deliver to the interstellar medium depends on how
their outflowing remnants make the transition from adiabatic to radiative, this
clustering may alter the momentum budget per SN, an effect we systematically
explore over a large parameter space. We perform a parameter study of 1D
hydrodynamic simulations, varying the number of SNe, and the background gas
metallicity and density. For a few SNe, we find that the asymptotic momentum
scales superlinearly with the number of SNe. As a result, the asymptotic
momentum per SN can be an order of magnitude greater than that delivered by
isolated SNe, with a maximum efficiency occurring for clusters that produce
~10-100 SNe. Adequately capturing this effect in simulations requires very high
resolution to avoid over-cooling (a typical resolution for our simulations is
0.3 pc). We show that inadequate resolution led a number of previous studies to
underestimate the momentum injection. This strong momentum feedback has
significant implications for galactic and cosmological models, so we use our
numeric results to construct a simple analytic fitting formula for the momentum
of clustered SNe for use in semi-analytic and lower-resolution numeric work.
Integrating our model over a realistic cluster mass function for a star-forming
galaxy, we find that the total SNe momentum budget is ~0.5-1 dex higher than
the conventional value.
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