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LSSTDESC / lsstdesc-diffsky

Library for differentiable generation of synthetic skies for LSST DESC
BSD 3-Clause "New" or "Revised" License
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Inspect excessively high peculiar velocities #104

Open aphearin opened 7 months ago

aphearin commented 7 months ago

As reported by Rick Kessler, our peculiar velocities are suspiciously high. In the plot below, a cut on stellar mass logsm>9.5 was made. The typical velocity is a bit north of 500 km/s, which is a bit uncomfortably high. The very first check would be to repeat this measurement separately for host halos and satellites.

Screenshot 2024-02-22 at 2 13 12 PM

evevkovacs commented 6 months ago

As a first pass, I compared the peculiar velocity distributions in cosmoDC2 and roman_rubin_v1.1.2_elais (in a singlr healpixel). Here are 2 plots: the first looks at all non synthetic galaxies, the second shows galaxies with log_10(M*) > 9.5. cosmoDC2_RR_pec_no_cuts cosmoDC2_RR_pec_Mstar_9 5 Apart from having more galaxies in roman-rubin, the distributions are similar.

evevkovacs commented 6 months ago

And now with the distributions separated by centrals and satellites: cosmoDC2_RR_pec_Mstar_9 5_cen_sat Again, they look very similar.

evevkovacs commented 6 months ago

These velocities are in comoving units.