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jennykim1016 / OM10

Tools for working with the Oguri & Marshall (2010) mock catalog of strong gravitational lenses
MIT License
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Calculating the size #18

Open jennykim1016 opened 7 years ago

jennykim1016 commented 7 years ago

veldisp vs redshift

This is the raw scatterplot of the data we have from Sonnenfeld's table. I expected to have data that looks like this (its a log-log graph):

real http://burro.case.edu/Academics/Astr222/Galaxies/Elliptical/kinematics.html

I think I can still try to fit in the curves onto the plot...

jennykim1016 commented 7 years ago

curve fit

Scipy optimize curve fit fails regardless of the initial value. I will just use numpy.polyfit to generate the data.

Thus I need to

jennykim1016 commented 7 years ago

painted

This is the final plot that I produced!

drphilmarshall commented 7 years ago

Nice work, Jenny! You did that super-fast :-) Let me just check real quick: are the sizes in the Sonnenfeld et al table in arcsec or in kpc? We expect a correlation in physical size (in kpc) but maybe not in apparent size (where the different redshifts cause the sizes to get mixed up). If the sizes are in arcsec, can you please convert to kpc (using lenspop angular diameter distances) and re-do your fit? Thanks!

Also - are you updating the OM10 notebook to include a section and a conclusion on lens galaxy sizes? You should! :-)

jennykim1016 commented 7 years ago

Hi @drphilmarshall ,

I used arcsecond -- I just fixed it to use kpc. From the virial theorem it seems reasonable to have a correlation between the size and the velocity dispersion, but it is not apparent in the non-logged graph, so I changed the graph to log-log graph and calculated the sizes from there.

It seems like, however, there are two columns in om10 - 'REFF' and 'REFF_T'. I have been updating REFF and would want to check that this is the right column. I also updated the columns.md, specifying that the REFF has a unit of kpc. However, if you think it is better to save REFF in arcseconds for consistency, I can fix it!

And yes, I have been updating the notebooks :) It is in the size_compute branch in this forked repository.

log-log real log-log

Final Plot) final image

drphilmarshall commented 7 years ago

I'm not sure what the _T stands for, but it might be "theta". I think you shoudl put the Reff in kpc in REFF and the Reff in arcsec in REFF_T - this way we won't need to recalculate either one!

Good idea to fit log size vs log vdsip, and also to define a Gaussian scatter in log size to draw from. I agree that there is not much of a correlation - but then, we are only looking at the most massive galaxies. One last thing - it's usual to use log_10 for these sorts of quantities, and then qhen you quote the width of the Gaussian distribution you say "a scatter of XX dex". Thanks!

jennykim1016 commented 7 years ago

I see! I fixed all the notebooks / codes to have log_10. I will finish updating the REFF_T and request the review soon. Thanks!