Completeness as a function of stellar density

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For those interested in the performance of the deblender on crowded stellar fields, may I draw your attention to section 4.1 of “The Saga of M81: Global View of a Massive Stellar Halo in Formation” (2020, ApJ accepted) by Adam Smercina et al., where we use fake sources to measure detection completeness as a function of stellar density. Adam found we get good completeness up to 100 arcmin-2, after which it starts to fall off (see Figure 4 from the paper, reproduced below). This number is certainly a function of seeing, depth and target brightness, but may serve as a useful benchmark.

Thanks to Song Huang for the original SynPipe implementation, and Sophie Reed for integrating it into the LSST stack.


Thanks for sharing this, @price. The M81 plots sample the regime in which you are mainly sampling upper-RGB stars, still unaffected by changes in the luminosity function coming from the old main sequence turn-offs, horizontal branch and red clump at r>27. What happens to completeness below that point depends on the detailed luminosity function, that changes from galaxy to galaxy and obviously change with their distances. So, these results could not be extrapolated to the Bulge, LMC, etc, by just using stellar density and seeing as parameters. Keeping this in mind, it is great to see there’s a SynPipe working for these estimates. I think the SMWLV science collaboration will need it a lot.

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@price Thank you for introducing this result!

Are you aware of any application of the new fake object pipeline on the galaxy side?

I believe @sophiereed and @dtaranu have played with fake galaxies.