Synthetic observations of simulated pillars of creation

TL;DR

This paper presents synthetic observations of simulated star-forming pillars, demonstrating their morphological and spectral similarities to real regions, and highlights the complexities in interpreting diagnostic diagrams due to 3D effects.

Contribution

It introduces hydrodynamic simulations with ionising radiation to produce realistic synthetic observations, revealing limitations of traditional diagnostic methods in complex 3D structures.

Findings

Simulated pillars resemble observed structures in optical emission lines.

Line profiles show typical FWHM of 2-4 km/s.

Diagnostic diagrams exhibit spatial variations, cautioning against simple interpretation.

Abstract

We present synthetic observations of star-forming interstellar medium structures obtained by hydrodynamic calculations of a turbulent box under the influence of an ionising radiation field. The morphological appearance of the pillar-like structures in optical emission lines is found to be very similar to observations of nearby star forming regions. We calculate line profiles as a function of position along the pillars for collisionally excited [OIII]5007, [NII]6584 and [SII]6717, which show typical FWHM of 2--4 km/s. Spatially resolved emission line diagnostic diagrams are also presented which show values in general agreement with observations of similar regions. The diagrams, however, also highlight significant spatial variations in the line ratios, including values that would be classically interpreted as shocked regions based on one-dimensional photoionisation calculations. These values tend to be instead the result of lines of sight intersecting which intersect for large portions of their lenghts the ionised-to-neutral transition regions in the gas. We caution therefore against a straightforward application of classical diagnostic diagrams and one--dimensional photoionisation calculations to spatially resolved observations of complex three-dimensional star forming regions.