The central density of R136 in 30 Doradus

TL;DR

This paper refines estimates of the central density of the R136 star cluster, revealing extremely high densities that influence its dynamical evolution and core collapse status, using reanalyzed observational data and assumptions about the cluster's core size.

Contribution

It provides new lower limits on R136's central density by combining previous density profiles with updated core size assumptions, highlighting the cluster's extreme density conditions.

Findings

Central density >~ 1.5x10^4 Msun/pc^3 under conservative assumptions

Central density > 10^7 Msun/pc^3 with smaller core size estimate

Implication of high density on cluster evolution and reddening mechanisms

Abstract

The central density rho_0 of a stellar cluster is an important physical parameter for determining its evolutionary and dynamical state. How much mass segregation there is, or whether the cluster has undergone core collapse both depends on rho_0. We reanalyze the results of a previous paper that gives the mass density profile of R136 and combine them with both a conservative upper limit for the core parameter and a more uncertain recent measurement. We thus place a lower limit on rho_0 under reasonable and defensible assumptions about the IMF, finding rho_0 >~ 1.5x10^4 Msun/pc^3 for the conservative assumption a < 0.4 pc for the cluster core parameter. If we use the lower, but more uncertain value a = 0.025 pc, the central density estimate becomes greater than 10^7 Msun/pc^3. A mechanism based on the destruction of a large number of circumstellar disks is posited to explain the hitherto unexplained increase in reddening presented in that same work.