Organizing Crowded Field Photometry Test Data Sets

Science Milky Way (Open)
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#1

This is a posting summarizing Stars, Milky Way & Local Volume emails earlier today: Members respond to @jbosch and @RHL 's call for test data and development of metrics. I’ve tried to tag people whose usernames I know. We’re still new to community

Knut Olsen: @knutago

I am swamped through June, but after that would like to help with 1), using DECam data from the SMASH survey. I developed a crowding metric as part of the cadence white paper work, which I could revise to address this problem.

Alex Drliva-Wagner @kadrlica

I’m also happy to contribute to (1). I think that we can identify a
fair amount of DECam data available in crowded fields.

Mike Rich:

Christian Johnson (Clay Fellow, CfA) has reduced all of the very crowded Blanco DECam Bulge Survey data, using Daophot. He is collaborating with me, and we would be happy to provide or to reduce a challenge dataset.

Jeffrey Carlin: @jeffcarlin

I would also be happy to contribute both data and effort. We have HSC data from an ongoing survey of Local Volume (D ~ 2-4 Mpc) galaxies. The HSC/LSST stack doesn’t yet detect/measure sources in the crowded central regions of these galaxies, or in the bodies of the dwarf galaxy satellites we have discovered. These would be great testbeds for improvements to crowded-field techniques.

Also interested in helping @willclarkson @jgizis …

Peregrine McGehee shared thoughts on developing requirements which I have not copied here because I want to have them in a separate post. @pmmcgehee

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Crowded field photometry and testing scarlet
#2

Very nice to see movement on simulating crowding stellar fields, and I agree with the earlier statements to try and simulate something like a globular cluster. This allows us to explore the range of crowding through a single system (i.e., by just moving radially out in the cluster) so the simulation can check off a good part of parameter space for Milky Way Science.

Although using DECam and HSC observations to feed the LSST simulation is fine, I believe it will be very important to have a “truth” image buried within such a simulation. Here, we need Hubble data. We want to know the precise photometry, astrometry, and morphology at a level deeper than ground-based seeing and 8-m sensitivity limits, and only HST can provide that. This then directly allows us tok directly characterize how well LSST is measuring photometry, astrometry, and completeness as a function of crowding. Such observations would also allow us to test how well we can establish the zero motion frame of reference for proper motion studies (i.e., how well we can find and centroid on galaxies behind the cluster). So, I suggest picking a cluster from the ACS treasury survey that is well centered on the HST field, and that has HSC or DECam data.

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#3

For folks that haven’t seen the slide deck already, we’ve posted @jbosch’s recent presentation about LSST’s crowded field plans to Zenodo:

#4

Am I correctly concluding that this effort didn’t get very far?
We need to decide how serious DM should be about crowded
fields processing very very soon!

#5

Sorry for the delay.

Not this effort exactly, but some things have happened. Colin Slater @ctslater can let you know what the current status is.

We did get a report from Veronica Dike (@vdike) at the blending meeting which happened in parallel with the all hands meeting last August for some tests from the UCLA+ group (i.e., Mike Rich, etc.).

What do you need to get serious?