Synthetic CO emission and the X-CO factor of young molecular clouds: a convergence study

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F22%3A00552022" target="_blank" >RIV/67985815:_____/22:00552022 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1093/mnras/stab3354" target="_blank" >https://doi.org/10.1093/mnras/stab3354</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1093/mnras/stab3354" target="_blank" >10.1093/mnras/stab3354</a>

Result language

angličtina

Original language name

Synthetic CO emission and the X-CO factor of young molecular clouds: a convergence study

Original language description

The properties of synthetic CO emission from 3D simulations of forming molecular clouds are studied within the SILCC-Zoom project. Since the time-scales of cloud evolution and molecule formation are comparable, the simulations include a live chemical network. Two sets of simulations with an increasing spatial resolution (dx = 3.9 pc to dx = 0.06 pc) are used to investigate the convergence of the synthetic CO emission, which is computed by post-processing the simulation data with the radmc-3d radiative transfer code. To determine the excitation conditions, it is necessary to include atomic hydrogen and helium alongside H-2, which increases the resulting CO emission by similar to 7-26 per cent. Combining the brightness temperature of (CO)-C-12 and (CO)-C-13, we compare different methods to estimate the excitation temperature, the optical depth of the CO line and hence, the CO column density. An intensity-weighted average excitation temperature results in the most accurate estimate of the total CO mass. When the pixel-based excitation temperature is used to calculate the CO mass, it is over-/underestimated at low/high CO column densities where the assumption that (CO)-C-12 is optically thick while (CO)-C-13 is optically thin is not valid. Further, in order to obtain a converged total CO luminosity and hence X-CO factor, the 3D simulation must have dx less than or similar to 0.1 pc. The X-CO evolves over time and differs for the two clouds: yet pronounced differences with numerical resolution are found. Since high column density regions with a visual extinction larger than 3 mag are not resolved for dx greater than or similar to 1 pc, in this case the H-2 mass and CO luminosity both differ significantly from the higher resolution results and the local X-CO is subject to strong noise. Our calculations suggest that synthetic CO emission maps are only converged for simulations with dx less than or similar to 0.1 pc.

Czech name

—

Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2022

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

e-ISSN

1365-2966

Volume of the periodical

510

Issue of the periodical within the volume

1

Country of publishing house

GB - UNITED KINGDOM

Number of pages

21

Pages from-to

753-773

UT code for WoS article

000736094100052

EID of the result in the Scopus database

2-s2.0-85126689410