[Yt-dev] Simulated Observations: Request for Corrections

Matthew Turk matthewturk at gmail.com
Tue Mar 1 07:16:05 PST 2011


Hi Eric,

Thanks, I totally forgot about those.  I'll add them to the list.

-Matt

On Tue, Mar 1, 2011 at 10:08 AM, Eric Hallman <hallman13 at gmail.com> wrote:
> 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
> Google Voice: (774) 469-0278
> hallman13 at gmail.com
>
>
>
>
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