A multi-wavelength view of the Galactic center dust ridge reveals little star formation

TL;DR

This study investigates the Galactic center dust ridge using multi-wavelength observations, revealing a large reservoir of cold molecular material with limited evidence of ongoing high-mass star formation.

Contribution

The paper provides new submillimeter and radio observations that constrain star formation activity and stellar content within the Galactic center dust ridge.

Findings

The dust ridge contains a massive reservoir of cold molecular gas.

No stars earlier than B0.5 spectral type are present in the clouds.

Limited signs of high-mass star formation, with only a few methanol masers detected.

Abstract

The Galactic center dust ridge consists of a narrow string of massive condensations identified in submillimeter dust continuum emission. To determine whether new high-mass stars are forming in this region, we performed new observations at 870 $\mu$m with the Atacama Pathfinder Experiment telescope and at 8.4 GHz with the Very Large Array. We complement our data with recent maser and mid-infrared results. The ridge's clouds are dark at mid-infrared wavelengths, indicating the presence of cold, high column density material. In combination with existing temperature measurements in the dust ridge, we determined the masses of the largest clouds. The results show that the dust ridge contains a very massive reservoir of molecular material. We find five radio sources at 8.4 GHz in the general dust ridge vicinity but outside of the dust ridge clouds, which are probably all excited by massive young stars, whose properties we constrain. Our observations exclude the existence of zero age main sequence stars with spectral types earlier than B0.5 within the dust ridge clouds. The only indication of ongoing high-mass star formation inside the clouds are class II methanol masers that are found in two of the clouds. Except for a weak water maser, found in previous observations, no signs of star formation are detected in the massive cloud M0.25+0.012.