[Yt-dev] Simulated Observations: Request for Corrections

Tue Mar 1 13:52:01 PST 2011

Hi John, Jeff, Britton,

That sounds awesome!  I'd be really happy if the 21cm and ALMA methods
got put in, and I'd be delighted if the light_ray were documented up a
bit.

The idea of PSFs, which came up on yt-users last week, is also really,
really cool.  I'd love it if these were just a layer or add-on to an
image, like Dave had suggested for callbacks.  I think there's a lot
of room here for fun stuff.

Thanks again; I've added all these to my list.

Best,

Matt

On Tue, Mar 1, 2011 at 12:08 PM, Britton Smith <brittonsmith at gmail.com> wrote:
> P.S. - the light ray tool, is currently undocumented.  I will add the
> documentation in the next day or so.
>
> On Tue, Mar 1, 2011 at 12:08 PM, Britton Smith <brittonsmith at gmail.com>
> wrote:
>>
>> We also have the light cone generator for simulated observations out to
>> cosmological distances.  This works particularly well with the SZ fields.
>> There is also the light ray tool for synthetic QSO sight lines that span
>> cosmological epochs.  These can be used for absorption/emission line
>> statistics and stats on distances of absorbers/emitters to galaxies (halos).
>>
>> Britton
>>
>> On Tue, Mar 1, 2011 at 10:49 AM, j s oishi <jsoishi at gmail.com> wrote:
>>>
>>> While we're on radio maps, I think we could also very easily add Mark
>>> Krumholz's ALMA tools for generating molecular emission maps from cold
>>> molecular gas for present-day star formation. I'd be happy to lead
>>> that effort once I dig out from the backlog of work piled up while I
>>> have been preparing for upcoming talks...
>>>
>>> On Tue, Mar 1, 2011 at 7:38 AM, John Wise <jwise at astro.princeton.edu>
>>> wrote:
>>> > Hi Matt,
>>> >
>>> > This is great that you sketched out the plan to make simulated
>>> > observations through yt.  I think another addition would be 21cm maps.  I
>>> > implemented these in enzo's projection tool (version 2), but I can add these
>>> > to yt soon.
>>> >
>>> > Also, we can probably put some pre-defined PSFs for various telescopes
>>> > / detectors when the user wants to make an image.  Conversions from physical
>>> > scales to angles would be handy as well, i.e. making a 1 arcmin^2 image.
>>> >
>>> > John
>>> >
>>> > On 1 Mar 2011, at 10:08, Eric Hallman 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
>>> >>> _______________________________________________
>>> >>> Yt-dev mailing list
>>> >>> Yt-dev at lists.spacepope.org
>>> >>> http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org
>>> >>
>>> >> Eric Hallman
>>> >> Google Voice: (774) 469-0278
>>> >> hallman13 at gmail.com
>>> >>
>>> >>
>>> >>
>>> >>
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