[Yt-dev] Simulated Observations: Request for Corrections

[Eric Hallman]

Matt,
   if we're being generous, we can include the capability to make SZ  
Compton y maps.  Also Kinematic SZ.  I think those are fields in yt  
now are they not (SZY and SZ_Kinetic)? Or are those user-derived  
fields not in public yt?

cheers,

On Mar 1, 2011, at 10:02 AM, Matthew Turk wrote:

> Hi all,
>
> I've been taking stock of where we are for simulated observations, and
> I wanted to run this past everyone to make sure I'm not missing
> anything.  I think we have four mechanisms for generating something
> that could *generously* be called a "Simulated Observation," but for
> each approach there are caveats.  If someone has something to add, in
> terms of capability or caveats, I would be eager to hear.  I have not
> included any methods for generating spectra from galaxies, but I
> believe this may have been done using the second method below.
>
> = X-ray Observations =
>
> Under the assumption of optically thin gas, projections can be made
> using emissivity to generated simulated observations.  yt includes a
> method for handling output from CLOUDY in the ROCO (Smith et al 2008)
> format, and generating integrated emissivity over given energy ranges.
>
> Caveats: The ROCO format for input requires some non-trivial handling
> of CLOUDY output.
>
> = SED Generation and Deposition =
>
> Using BC03 models for stellar population synthesis, star particles in
> a given calculation can be assigned an integrated flux for a specific
> bandpass.  These fluxes can then be combined using either projections
> or volume rendering.  This can use CIC interpolation to deposit a
> total flux into each cell (which should be flux-conserving, modulo a
> multiplicative factor not currently included) which is then either
> projected or volume rendered.
>
> Caveats: The deposition method produces far too washed out and murky
> results.  The multiplicative factor is not currently set correctly
> universally.
>
> = Thermal Gas Emission =
>
> Applying a black body spectrum to the thermal content of the gas, we
> can volume render the domain and apply absorption based on broad
> arguments of scattering.  One could theoretically include star
> particles as point sources in this, using recent changes to the volume
> renderer.
>
> Caveats: Scattering that results in re-emission is completely
> neglected, such as Halpha emission.  Scattering that results in just
> attenuating the emission is set in an ad hoc fashion.  Emission from
> point sources, if included at all, is included in a non-conservative
> fashion.
>
> = Export to Sunrise =
>
> Data can be exported to Sunrise for simulated observation generation.
>
> Caveats: This process is poorly documented.
>
>
>
> Does that all sound about right?  Does anybody have any additions or
> corrections to this?
>
> Thanks,
>
> Matt
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Eric Hallman
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hallman13 at gmail.com