Bridging simulations and observations via chemistry and radiative transfer

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Bridging simulations and observations via chemistry and radiative transfer

The goal of the CloudZoo project is to bring together modellers and observers, to address the open questions in ISM research. Although simulations can now be very advanced, capturing an increasing amount of physics, the raw data is not directly comparible to the data from observational studies. To address this, we have put together an ISM module that enables numerical simulations to capture the chemistry and thermodynamics of the ISM (e.g. Glover et al. 2010, Clark et al. 2011, Glover and Clark 2012a, and Glover and Clark 2012b). Using radiative transfer, this chemical and thermal information in the simulation data can then be used to make synthetic observational data, which can then be compared to the observations. This last step is done via Radiative Transfer.

This webpage hosts the synthetic observations that we have made from our simulations. On here you will find ppv cubes of line emission for a wide range of simulations of the ISM. All emission cubes are in the commonly used FITS format, and we also include some raw data from the simulation in this format too. Typically, the line emission will cover species such as CO (including various isotopologues), [CI], [CII] and HI emission (and sometimes absorption), depending on the simulation. Each simulation is accompanied with a description (or link to the journal article, if already published), along with a short decription of the caveats.

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The Simulations

Isolated clouds

The isolated cloud simulations start with a big ball of gas that has been stirred by turbulence. This turbulence will decay naturally in shock / compression events. Typically, we try to match the initial density to those observed in real clouds, and we cover cloud masses in the range from 10,000 to 100,000 solar masses. Our older suite of SPH simulations assume pure hydrodynamics, while our newer Arepo simulations cover both hydro and magnetohydrodynamics (with magnetic field strengths chose to match those in observations). All these clouds are exposed to different environmental conditions, such as different UV field strengths and/or cosmic-ray ionisation rates, and different types of initial turbulence. Due to the high initial densities, we tend to set the chemistry to fully molecular (in the hydrogen) at the start, however there are a few simulations that start from atomic gas. Click the above link to go the full list of available simulations.

Cloud-cloud collisions

Our cloud-coud collision simulations attempt to capture the more realistic scenario in which low-density, atomic / quasi-molecular clouds collide in spiral arms to produce high density molecular clouds. Although the inital clouds are seeded with some low-level turbulence, this does not decay as much as in the isolated clouds, as the collision pumps kinetic energy into the gas. These simulations are performed with Arepo, and thus cover both magnitised and non-magnitised clouds.

Useage Policy

For the moment, please get in touch with Paul Clark if you wish to use the simulation data hosted on this website. We are still working towards a more general useage policy.

Scripts and data tools

Many of the data products in this repository are in either peculiar units, non-standard formats, or a combination of both. To people make use of our data, we therefore provide several scrips to read the data, that make it easy to convert to standard formats. These scripts can be found here. If there is something you need in particular that isn't already here, then please ask!

Go to the scripts

Contact Details

Dr. Paul Clark

School of Physics and Astronomy

Cardiff University