Tomography of Galactic star-forming regions and spiral arms with the Square Kilometer Array

TL;DR

The paper discusses how the Square Kilometer Array (SKA) will enable high-precision VLBI astrometry of star-forming regions and spiral arms, providing detailed 3D maps and kinematic data crucial for understanding galactic structure and dynamics.

Contribution

It introduces the potential of SKA's sensitivity to extend VLBI astrometry to distant galactic regions, enhancing our understanding of spiral arms and star formation.

Findings

VLBI can achieve 10 micro-arcsecond accuracy, surpassing Gaia.

SKA will enable tomographic mapping of regions several kpc away.

This will improve models of galactic structure and dynamics.

Abstract

Very Long Baseline Interferometry (VLBI) at radio wavelengths can provide astrometry accurate to 10 micro-arcseconds or better (i.e. better than the target GAIA accuracy) without being limited by dust obscuration. This means that unlike GAIA, VLBI can be applied to star-forming regions independently of their internal and line-of-sight extinction. Low-mass young stellar objects (particularly T Tauri stars) are often non-thermal compact radio emitters, ideal for astrometric VLBI radio continuum experiments. Existing observations for nearby regions (e.g. Taurus, Ophiuchus, or Orion) demonstrate that VLBI astrometry of such active T Tauri stars enables the reconstruction of both the regions' 3D structure (through parallax measurements) and their internal kinematics (through proper motions, combined with radial velocities). The extraordinary sensitivity of the SKA telescope will enable similar "tomographic mappings" to be extended to regions located several kpc from Earth, in particular to nearby spiral arm segments. This will have important implications for Galactic science, galactic dynamics and spiral structure theories.