Structure analysis of simulated molecular clouds with the Δ-variance

Bertram, Erik; Klessen, Ralf S.; Glover, Simon C. O.

doi:10.1093/mnras/stv948

Title: Structure analysis of simulated molecular clouds with the Δ-variance

Journal Article · Wed May 27 00:00:00 EDT 2015 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stv948· OSTI ID:1329377

Bertram, Erik ^[1]; Klessen, Ralf S. ^[2]; Glover, Simon C. O. ^[1]

Univ. Heidelberg, Heidelberg (Germany)
Univ. Heidelberg, Heidelberg (Germany); Univ. of California, Santa Cruz, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

Here, we employ the Δ-variance analysis and study the turbulent gas dynamics of simulated molecular clouds (MCs). Our models account for a simplified treatment of time-dependent chemistry and the non-isothermal nature of the gas. We investigate simulations using three different initial mean number densities of n₀ = 30, 100 and 300 cm^-3 that span the range of values typical for MCs in the solar neighbourhood. Furthermore, we model the CO line emission in a post-processing step using a radiative transfer code. We evaluate Δ-variance spectra for centroid velocity (CV) maps as well as for integrated intensity and column density maps for various chemical components: the total, H₂ and ¹²CO number density and the integrated intensity of both the ¹²CO and ¹³CO (J = 1 → 0) lines. The spectral slopes of the Δ-variance computed on the CV maps for the total and H₂ number density are significantly steeper compared to the different CO tracers. We find slopes for the linewidth–size relation ranging from 0.4 to 0.7 for the total and H₂ density models, while the slopes for the various CO tracers range from 0.2 to 0.4 and underestimate the values for the total and H₂ density by a factor of 1.5–3.0. We demonstrate that optical depth effects can significantly alter the Δ-variance spectra. Furthermore, we report a critical density threshold of 100 cm^-3 at which the Δ-variance slopes of the various CO tracers change sign. We thus conclude that carbon monoxide traces the total cloud structure well only if the average cloud density lies above this limit.

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Research Organization:: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC02-76SF00515

OSTI ID:: 1329377

Report Number(s):: SLAC-PUB-16732

Journal Information:: Monthly Notices of the Royal Astronomical Society, Vol. 451, Issue 1; ISSN 0035-8711

Publisher:: Royal Astronomical SocietyCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 9 works

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