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Producing LSST-like simulated images #19

Open linan7788626 opened 8 years ago

linan7788626 commented 8 years ago

Hi @WentaoLuo ,

Here is the list of tasks we would like to figure out today. And I will check the completed one as soon as we finish it.

WentaoLuo commented 8 years ago

figure_1

An LSST image without sky and noise. Given a de Vaucouleurs profile, with R_eff=3 arcsecs.

WentaoLuo commented 8 years ago

Here the unit of each pixel is number of photon-electrons.

linan7788626 commented 8 years ago

PSF has been convolved ?

WentaoLuo commented 8 years ago

There are no module at hand to generate co-added images for DES. LSST provides simple codes for co-added images.

WentaoLuo commented 8 years ago

Yes, the PSF is convolved with the galaxy image. PSF is simulated Komogorov model with the size of 0.7", typical LSST seeing FWHM.

linan7788626 commented 8 years ago

Does it make much difference for co-added images and un-co-added images?

WentaoLuo commented 8 years ago

i need to go through the instrumentation part of the LSST science book, and figure out the zero-point, gain and other stuff to convert the pixel value to data number or AB magnitude, which is more physical.

WentaoLuo commented 8 years ago

Co-added images are deeper, of course. And if we want to convince people we simulate DES like survey, we need to take the co-adding procedure into consideration.

linan7788626 commented 8 years ago

_Do not_ go too far away from the final goal, we are trying to produce simulated images which are similar as real observations, it _does not_ mean we have to produce these images following the really camera procedure exactly.

WentaoLuo commented 8 years ago

Alright, let's discuss it later this evening and see how to make things easier while reasonable as well.

linan7788626 commented 8 years ago

Hi @WentaoLuo ,

Enclosed link is of a test lensing system with lensed galaxy and lensed supernova, if possible, could you please try to convolve PSFs and add noise onto it (for both DES and LSST)? Let's see what will happen.

BTW, the pixel size is 0.919 arcsec.

https://www.dropbox.com/s/qrwuzrm4fodnkk8/all.fits?dl=0

Thanks

Nan

WentaoLuo commented 8 years ago

Hi,

I have pushed the code: cos2lsst_des.py, containing functions to convert cosmos image to ABmagnitude map.

I need to further modify to convert ABmag to DES and LSST pixel values.

But try the ABmag map first.

Cheers.

Wentao

WentaoLuo commented 8 years ago

cosimage_in_abmag

An example of AB mag map.

WentaoLuo commented 8 years ago

ABmag=-2.5*log10(flux/3631) flux here is in unit of Jy. 1 Jy=10^{-23} ergs sec^-1 cm^-2 Hz^-1 1 Jy=photons sec^-1 m^-2 (deltaLambda/Lambda)^-1 Where deltaLambda is the bandwith and Lambda is the central wavelenght of the band.

linan7788626 commented 8 years ago

good, I have marked the first task checked. thanks.

WentaoLuo commented 8 years ago

Still working on CCD values, later I will list the parameters that transfer ABmag to CCD value of DES and LSST respectively. So that we do not have to google and read the entire science book.

WentaoLuo commented 8 years ago

http://articles.adsabs.harvard.edu//full/1996AJ....111.1748F/0001749.000.html

On Tue, Mar 1, 2016 at 2:57 PM, Nan Li notifications@github.com wrote:

good, I have marked the first task checked. thanks.

— Reply to this email directly or view it on GitHub https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_linan7788626_Arc-5FFinding-5FCNN_issues_19-23issuecomment-2D190878012&d=AwMCaQ&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=tusHy7hx9eF1S7qAhofQhdSLXT3jkM3KlI15Md2kTPQ&m=fpKUgLCpVLhfOjKum5KdUgf_nLyVR_h6BXnAcoXhYcw&s=v7nfEL7TLx8isITB-8AVgS5nX6KaqdNCdlSQmmkQ02U&e= .

WentaoLuo commented 8 years ago

figure_lsst figure_des figure_sdss

top figure: LSST like image middle figure: DES like image bottom figure: SDSS like image

WentaoLuo commented 8 years ago

Looks like the same but please be aware of the colorbar value.

linan7788626 commented 8 years ago

Hi @WentaoLuo ,

It looks great, talk to you later, if this function for converting pixel values is fair enough, we can close this issue and push the project to the next step. Thank you.

-Nan

WentaoLuo commented 8 years ago

Sure, I am now at UChicago and I can see you name tag outside your office. I will be back to Pittsburgh tomorrow. Talk to you later.

WentaoLuo commented 8 years ago

Sorry guys for my late update due to personal stuff.

The new function in branch LSST contains the function to convert a cosmos image to SDSS, DES and LSST. It is sort of preliminary, but for the purpose of arc simulation. It is enough.

Cheers,

Wentao