idl version of lens galaxy simulation

[WentaoLuo]

The idl version of lens galaxy simulation is ready now. Please feel free to curse that idl version of code.

[WentaoLuo]

It is under the directory of images.

[WentaoLuo]

Nan,

I am thinking that if you convert the CCD value into magnitude, then the image must look strange due to the fact that the brighter pixels has smaller mag values. Is that the requirement of ray-tracing code?

Why don't just work on CCD pixel value? Yes, of course I will add a function to "pixcos2pixsdss.py".

[linan7788626]

Do not worry about that, after ray-tracing, we will convert magnitude to number counting, so the final images are with “reasonable” values then. The reason we use magnitude is that it is universal for different telescopes and observations, if we use CCD pixel Values, we have to be very careful about the zero point , pixelization, exposure time, and so on. So I prefer to use magnitude.

—— Nan Li Postdoctoral Fellow University of Chicago & Argonne National Lab

linan7788626.github.io

On Feb 2, 2016, at 1:21 PM, Wentao Luo notifications@github.com wrote:

Nan,

I am thinking that if you convert the CCD value into magnitude, then the image must look strange due to the fact that the brighter pixels has smaller mag values. Is that the requirement of ray-tracing code?

Why don't just work on CCD pixel value? Yes, of course I will add a function to "pixcos2pixsdss.py".

— Reply to this email directly or view it on GitHub https://github.com/linan7788626/Arc_Finding_CNN/issues/8#issuecomment-178769024.

[WentaoLuo]

I have update and push the new conversion function. It can: 1, convert cosmos ccd value in unit of electron/sec to ccd counts in sdss 2, sdss ccd counts to Pogson Magnitude 3, Pogson Magnitude to sdss ccd counts

[WentaoLuo]

If we arbitrarily magnify the sdss ccd value converted from cosmos ccd given a Poisson noise with SDSS variance. Then it looks like above.

[WentaoLuo]

5 times sdss CCD value converted from cosmos with sdss sky variance.

[WentaoLuo]

Alas, SDSS does not have such deep observation and highly resolved CCD.

[WentaoLuo]

The zero point of ACS F814W is 26.786 and no airmass and atmospheric extinction kk, while SDSS zeropoint is 24.148. I we set magnitude to be the same as in SDSS observation, the counts from ACS CCD have to be multiplied by a factor of 100. Problem solved guys!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[WentaoLuo]

But the question now it is getting too bright. Still something need to be corrected.

[WentaoLuo]

Sorry, SDSS zero point is in AB magnitude and zero point of F814W in AB is 25.523. So again, problem solved.

[WentaoLuo]

See the updated figure. More reasonable.

[linan7788626]

good job man, I will merge them into the pipeline. thanks.

[WentaoLuo]

With color bar.

[WentaoLuo]

Thanks. We could proceed.

[WentaoLuo]

the figure above, I include softbias, noise and galaxy.

[WentaoLuo]

Nan,

I have pushed the conversion functions, please tell me those function are enough for your next work.

Cheers,

Wentao

[linan7788626]

Thanks wentao, I will check it today, and will close this issue, if it works. :-)

[WentaoLuo]

I thought we wanted to unify all the units, so I took SDSS zeropoint but have cosmos ccd count/second. That makes sense if we want to make the mag meaningful as far as I understand.

[WentaoLuo]

I have pushed the modified conversion functions. Cheers,

Wentao

[linan7788626]

Thanks Wentao.

[linan7788626]

Done, I will close it.