Sgr A* and its Environment: Low Mass Star Formation, the Origin of X-ray Gas and Collimated Outflow

TL;DR

This paper presents high-resolution multiwavelength radio images of Sgr A*'s environment, revealing new features, star formation evidence, and a proposed model for X-ray emission and outflows involving stellar winds and jets.

Contribution

It provides new high-resolution observations of Sgr A*'s surroundings, identifies star formation near Sgr A*, and proposes a model linking stellar winds and jets to observed X-ray and radio features.

Findings

Detection of a continuous east-west radio ridge linking Sgr A* and star clusters.

Evidence of star formation within 2" of Sgr A* from protoplanetary disk-like features.

Proposal that diffuse X-ray emission is due to hot winds from stellar mass loss and photoevaporating disks.

Abstract

We present high-resolution multiwavelength radio continuum images of the region within 150$"$ of Sgr A*, revealing a number of new extended features and stellar sources in this region. First, we detect a continuous 2" east-west ridge of radio emission, linking Sgr A* and a cluster of stars associated with IRS 13N and IRS 13E. The ridge suggests that an outflow of east-west blob-like structures is emerging from Sgr A*. We also find arc-like features within the ridge with morphologies suggestive of photoevaporative protoplanetary disks. We use near-IR fluxes to show that the emission has similar characteristics to those of a protoplanetary disk irradiated by the intense radiation field at the Galactic center. This suggests that star formation has taken place within the S cluster 2$"$ from Sgr A*. We suggest that the diffuse X-ray emission associated with Sgr A* is due to an expanding hot wind produced by the mass loss from B-type main sequence stars, and/or the disks of photoevaporation of low mass YSOs at a rate ~10^{-6} solar mass per year. The proposed model naturally reduces the inferred accretion rate and is an alternative to the inflow-outflow style models to explain the underluminous nature of Sgr A*. Second, we detect new cometary radio and nea-IR sources and a striking tower of radio emission suggesting that they are tracing interaction sites of a mildly relativistic jet from Sgr A* with the atmosphere of stars and the nonthermal Sgr A East shell at a PA$\sim50-60^\circ$ with ~10^{-7} solar mass per year, and opening angle 10 degrees.