PHANGS-JWST First Results: Duration of the early phase of massive star formation in NGC628

TL;DR

This study uses JWST's high-resolution infrared observations to measure the duration of the embedded phase of massive star formation in galaxy NGC628, significantly expanding the observable volume compared to previous telescopes.

Contribution

First measurement of the early star formation phase duration in NGC628 using JWST, demonstrating the potential for systematic studies across nearby galaxies.

Findings

Embedded phase lasts about 5.1 Myr, with 2.3 Myr heavily obscured.

This phase accounts for roughly 20% of the molecular cloud lifetime.

Measurement volume increased by over 100 times compared to previous telescopes.

Abstract

The earliest stages of star formation, when young stars are still deeply embedded in their natal clouds, represent a critical phase in the matter cycle between gas clouds and young stellar regions. Until now, the high-resolution infrared observations required for characterizing this heavily obscured phase (during which massive stars have formed, but optical emission is not detected) could only be obtained for a handful of the most nearby galaxies. One of the main hurdles has been the limited angular resolution of the Spitzer Space Telescope. With the revolutionary capabilities of the JWST, it is now possible to investigate the matter cycle during the earliest phases of star formation as a function of the galactic environment. In this Letter, we demonstrate this by measuring the duration of the embedded phase of star formation and the implied time over which molecular clouds remain inert in the galaxy NGC628 at a distance of 9.8Mpc, demonstrating that the cosmic volume where this measurement can be made has increased by a factor of $>100$ compared to Spitzer. We show that young massive stars remain embedded for $5.1_{-1.4}^{+2.7}$Myr ($2.3_{-1.4}^{+2.7}$Myr of which being heavily obscured), representing $\sim20\%$ of the total cloud lifetime. These values are in broad agreement with previous measurements in five nearby ($D < 3.5$Mpc) galaxies and constitute a proof of concept for the systematic characterization of the early phase of star formation across the nearby galaxy population with the PHANGS-JWST survey.