Star formation in the massive "starless" infrared dark cloud G0.253$+$0.016

TL;DR

This study reveals early B-type stars within the massive infrared dark cloud G0.253+0.016 using radio observations, challenging the notion that it is completely starless and providing insights into early star formation near the galactic center.

Contribution

First detection of embedded early B-type stars in G0.253+0.016 using JVLA radio continuum observations, indicating initial star formation activity.

Findings

Detection of three compact HII regions indicating early B-type stars.

Identification of non-thermal sources possibly related to the galactic center.

Evidence that the cloud hosts stars earlier than previously thought.

Abstract

G0.253+0.016 is a remarkable massive infrared dark cloud located within $\sim$100 pc of the galactic center. With a high mass of $1.3 \times 10^5 M_\odot$, a compact average radius of $\sim$2.8 pc and a low dust temperature of 23 K, it has been believed to be a yet starless precursor to a massive Arches-like stellar cluster. We present sensitive JVLA 1.3 and 5.6 cm radio continuum observations that reveal the presence on three compact thermal radio sources projected against this cloud. These radio sources are interpreted as HII regions powered by $\sim$B0.5 ZAMS stars. We conclude that although G0.253+0.016 does not show evidence of O-type star formation, there are certainly early B-type stars embedded in it. We detect three more sources in the periphery of G0.253+0.016 with non-thermal spectral indices. We suggest that these sources may be related to the galactic center region and deserve further study.