SIMIO: Connecting SIMulatIons to Observations
The SIMIO package contains a suite of functions and wrappers for CASA 5.6.2, designed to take your radiative transfer image (for example, from RADMC3D) and return how your system would have looked if ALMA had observed it. The package aims to answer the question, "How would my system look if an existing observation had targeted it?".
Difference with simobserve and simanalyze:
The CASA tasks generate the synthetic observation based on the antenna configuration inputs, total exposure time, observation time, selected bandwidth, and other information needed to create the synthetic visibilities.
SIMIO, on the other hand, takes existing ALMA observations and replaces their data with your synthetic image. Therefore you automatically have the same uv-coverage, frequency coverage, bandwidth, exposure time, and all the properties of the actual observation. This comes in handy when you need to test if existing observations could have detected the features of your simulations.
With SIMIO, you do not need to worry about the observational details since the default parameters already mimic exactly the chosen observation. All the imaging parameters and routines are set to state-of-the-art knowledge. Just input your simulation, and get all the products.
Compare directly to any ALMA observation:
SIMIO has several templates that you can use for your synthetic observation, and you can also add templates by yourself. Each template will contain an actual observation of a protoplanetary disk and information about the source. By default, SIMIO will take your observation and simulate it as if it had the same geometry and distance as the template. Both the geometry and the distance to the source can be modified. You can also disable the source geometry and input your radiative transfer image with the desired geometry.
Better than Gaussian convolution, and as easy to run:
Gaussian convolution is just one of the steps of generating an image with the CLEAN. SIMIO will give you all the data products you could need:
- Measurement Set (ms file).
- Images in fits format (Beam convolved, PSF, model, residuals).
- Additional data figures, comparing your source to the template.
This work was possible thanks to the support of my Ph.D. advisor, Paola Pinilla. The original routines to extract and replace visibilities in measurement sets were written by Laura Perez and later modified to fit into SIMIO. The JvM correction routine is original from the MAPS collaboration. I also thank the ALMA helpdesk staff, especially Jackie Bertone, who helped fix the measurement set of TWHya to create its template.
I acknowledge the support provided by the Alexander von Humboldt Foundation in the framework of the Sofja Kovalevskaja Award endowed by the Federal Ministry of Education and Research.
Are you having issues to create a template?
Send me a message, some measurement sets can be a bit challenging, we will sort it out ;)