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julywater / WeakLensing

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outline the introduction #12

Open davidwhogg opened 11 years ago

davidwhogg commented 11 years ago

Now write a bullet-point or telegraphic summary of the introduction argument. This should touch on

davidwhogg commented 11 years ago

ps. you have written a bit of this in the other documents, but let's get serious now.

julywater commented 11 years ago

I collected a bunch of papers and tried to write an introduction out line,it's in ms.tex file.But I don't know what to write about the last point:How it's related to galaxy-galaxy lensing.In the papers I read they just treat galaxy-galaxy lensing a kind of weak lensing They don't have specific discussion on galaxy-galaxy lensing.

在 2013年3月14日星期四，David W. Hogg 写道：

ps. you have written a bit of this in the other documents, but let's get serious now.

— Reply to this email directly or view it on GitHubhttps://github.com/julywater/WeakLensing/issues/12#issuecomment-14940356 .

davidwhogg commented 11 years ago

do a little reading about galaxy-galaxy weak lensing. There is a Sheldon et al paper that is pretty good, if I remember correctly

drphilmarshall commented 11 years ago

Yes - also Johnston's follow-up paper.

The key thing for us is their treatment of the observed ellipticities. The basic idea is to take each lens galaxy's shear catalog (a few sources per lens), recenter them on the lens, and then concatenate them all together - although there will be technical wrinkles to this procedure. Simply averaging together the ellipticities in annuli gives a "shear profile" which they then fit with various models for the average galaxy. It's a crude way of doing inference, but it makes the signal jump out.

A hierarchical inference would involve parameterising the mass distributions of galaxies, and then inferring the hyperparameters governing those parameters' correlated distributions while marginalising over the individual galaxy properties.

On Sun, Mar 17, 2013 at 1:04 AM, David W. Hogg notifications@github.comwrote:

do a little reading about galaxy-galaxy weak lensing. There is a Sheldon et al paper that is pretty good, if I remember correctly

— Reply to this email directly or view it on GitHubhttps://github.com/julywater/WeakLensing/issues/12#issuecomment-15015245 .