G0.253+0.016: a molecular cloud progenitor of an Arches-like cluster

TL;DR

This study characterizes G0.253+0.016 as a massive, dense, and cold molecular cloud with minimal star formation, serving as a prime candidate for understanding the initial conditions of Arches-like massive cluster formation.

Contribution

The paper provides a detailed multi-wavelength analysis of G0.253+0.016, highlighting its unique properties as a potential progenitor of a massive star cluster, and compares it to typical Galactic molecular clumps.

Findings

G0.253+0.016 has a mass of 1.3x10^5 Msun and low temperature (~20K).

It is gravitationally bound and nearly devoid of star formation.

Its properties are extreme and possibly unique in the Galaxy.

Abstract

Young massive clusters (YMCs) with stellar masses of 10^4 - 10^5 Msun and core stellar densities of 10^4 - 10^5 stars per cubic pc are thought to be the `missing link' between open clusters and extreme extragalactic super star clusters and globular clusters. As such, studying the initial conditions of YMCs offers an opportunity to test cluster formation models across the full cluster mass range. G0.253+0.016 is an excellent candidate YMC progenitor. We make use of existing multi-wavelength data including recently available far-IR continuum (Herschel/Hi-GAL) and mm spectral line (HOPS and MALT90) data and present new, deep, multiple-filter, near-IR (VLT/NACO) observations to study G0.253+0.016. These data show G0.253+0.016 is a high mass (1.3x10^5 Msun), low temperature (T_dust~20K), high volume and column density (n ~ 8x10^4 cm^-3; N_{H_2} ~ 4x10^23 cm^-2) molecular clump which is close to virial equilibrium (M_dust ~ M_virial) so is likely to be gravitationally-bound. It is almost devoid of star formation and, thus, has exactly the properties expected for the initial conditions of a clump that may form an Arches-like massive cluster. We compare the properties of G0.253+0.016 to typical Galactic cluster-forming molecular clumps and find it is extreme, and possibly unique in the Galaxy. This uniqueness makes detailed studies of G0.253+0.016 extremely important for testing massive cluster formation models.