{"action":"created","issue":{"url":"https://api.github.com/repos/LSSTDESC/DC2_Repo/issues/150","repository_url":"https://api.github.com/repos/LSSTDESC/DC2_Repo","labels_url":"https://api.github.com/repos/LSSTDESC/DC2_Repo/issues/150/labels{/name}","comments_url":"https://api.github.com/repos/LSSTDESC/DC2_Repo/issues/150/comments","events_url":"https://api.github.com/repos/LSSTDESC/DC2_Repo/issues/150/events","html_url":"https://github.com/LSSTDESC/DC2_Repo/issues/150","id":314253417,"node_id":"MDU6SXNzdWUzMTQyNTM0MTc=","number":150,"title":"discrepancy in fluxes predicted by CatSim and PhoSim","user":{"login":"danielsf","id":1682854,"node_id":"MDQ6VXNlcjE2ODI4NTQ=","avatar_url":"https://avatars1.githubusercontent.com/u/1682854?v=4","gravatar_id":"","url":"https://api.github.com/users/danielsf","html_url":"https://github.com/danielsf","followers_url":"https://api.github.com/users/danielsf/followers","following_url":"https://api.github.com/users/danielsf/following{/other_user}","gists_url":"https://api.github.com/users/danielsf/gists{/gist_id}","starred_url":"https://api.github.com/users/danielsf/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/danielsf/subscriptions","organizations_url":"https://api.github.com/users/danielsf/orgs","repos_url":"https://api.github.com/users/danielsf/repos","events_url":"https://api.github.com/users/danielsf/events{/privacy}","received_events_url":"https://api.github.com/users/danielsf/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":25,"created_at":"2018-04-13T21:18:31Z","updated_at":"2018-06-01T00:09:33Z","closed_at":null,"author_association":"NONE","body":"This is copied from an issue in the ImSim repo\r\n\r\nhttps://github.com/LSSTDESC/imSim/issues/78#issuecomment-381262052\r\n\r\nCatSim has tools to predict the number of ADU counts from a source.  I noticed that  these tools wer giving significantly different values than what resulted from the `Nphotons` column in PhoSim's centroid files.  It looks like the result is that PhoSim and CatSim use different throughput data.  I'm not sure which is \"right\" (if that even has meaning at this point)?\r\n\r\nI would appreciate input from people such as @johnrpeterson @rhiannonlynne @ivezic \r\n\r\nHere is the detailed description of the situation:\r\n\r\nOkay. I think this is a discrepancy between PhoSim and CatSim.\r\n\r\nI used PhoSim to simulate 16 sources with a flat SED on the R22S11 chip. This simulation was run in opticsonlymode, which means that there is no atmosphere and no throughput due to the detector. I then compared the gain*ADU value predicted by CatSim with the median of the reported number of photons in the centroid file. The ratio of CatSimValue/PhoSimValue is, for each filter:\r\n\r\nu: 0.811\r\ng: 0.915\r\nr: 0.897\r\ni: 0.865\r\nz: 0.859\r\ny: 0.472 (more on this later)\r\n\r\nJust doing the most naive thing imaginable and replacing the CatSim `throughputs/baseline/filter_*.dat` data with the data in `$PHOSIM_DIR/data/lsst/filter_*.txt` (taking an angle of incidence=19 degrees, because that matters in PhoSim), I get ratios of CatSimValue/PhoSimValue\r\n\r\nu: 0.873\r\ng: 0.973\r\nr: 0.959\r\ni: 0.944\r\nz: 0.930\r\ny: 0.544\r\n\r\nPhoSim also has its own files specifying throughput for the lenses and mirrors. If I were being careful, I would try swapping those in as well to see if the ratios go to 1. Regardless: there is obviously a discrepancy between the throughputs being used by PhoSim and those being used by CatSim.\r\n\r\nWhat's up with the y filter?\r\n\r\nIf you look at `$PHOSIM_DIR/data/lsst/filters_5.txt`, the y-band as non-zero (in fact, almost unity) throughput all the way out to a wavelength of 1.2 microns. In CatSim, the y-band throughput goes to zero at 1.1 microns. Furthermore, I do not know what PhoSim does about the fact that the y-band throughput is unity at the end of the wavelength grid. The SED I simulated has flux out to 2 microns. Maybe PhoSim extrapolates the throughput, which is why CatSim and PhoSim still disagree by a factor of 2, even when I use the PhoSim throughput for y-band.\r\n\r\nIt seems like people with authority should discuss where the various throughput files are coming from and which is correct.\r\n\r\nI am using PhoSim version 3.7.9 and the version of the throughputs repository tagged 2017.01.31"},"comment":{"url":"https://api.github.com/repos/LSSTDESC/DC2_Repo/issues/comments/393720301","html_url":"https://github.com/LSSTDESC/DC2_Repo/issues/150#issuecomment-393720301","issue_url":"https://api.github.com/repos/LSSTDESC/DC2_Repo/issues/150","id":393720301,"node_id":"MDEyOklzc3VlQ29tbWVudDM5MzcyMDMwMQ==","user":{"login":"rhiannonlynne","id":1855711,"node_id":"MDQ6VXNlcjE4NTU3MTE=","avatar_url":"https://avatars3.githubusercontent.com/u/1855711?v=4","gravatar_id":"","url":"https://api.github.com/users/rhiannonlynne","html_url":"https://github.com/rhiannonlynne","followers_url":"https://api.github.com/users/rhiannonlynne/followers","following_url":"https://api.github.com/users/rhiannonlynne/following{/other_user}","gists_url":"https://api.github.com/users/rhiannonlynne/gists{/gist_id}","starred_url":"https://api.github.com/users/rhiannonlynne/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rhiannonlynne/subscriptions","organizations_url":"https://api.github.com/users/rhiannonlynne/orgs","repos_url":"https://api.github.com/users/rhiannonlynne/repos","events_url":"https://api.github.com/users/rhiannonlynne/events{/privacy}","received_events_url":"https://api.github.com/users/rhiannonlynne/received_events","type":"User","site_admin":false},"created_at":"2018-06-01T00:09:33Z","updated_at":"2018-06-01T00:09:33Z","author_association":"NONE","body":"Hi Scott,\n\nNice .. is there any correlation with location in the focal plane?\n\nLynne\n\nOn Thu, May 31, 2018 at 4:56 PM danielsf <notifications@github.com> wrote:\n\n> I just completed the following test:\n>\n> I generated and InstanceCatlaog with 68,229 objects whose SEDs were\n> randomly sampled from the ~ 1,000 galaxy SEDs shipped with CatSim. For each\n> object, a random redshift was chosen between 0 and 2. For each SED,\n> redshift combination, I set the magNorm so that CatSim predicted the object\n> should produce 20,000 photons in the r band. I then simulated this catalog\n> in all six LSST bands and compared the resulting centroid files to the\n> fluxes predicted by CatSim using the $THROUGHPUTS_DIR/imsim/goal/\n> bandpasses which seemed to produce the best agreement above. Note: this\n> simulation at altitude angle=56.2 degrees, or airmass ~ 1.2. No dust\n> extinction was applied. All sources were simulated as point source.\n> Comparing the number of photons predicted by CatSim to the number of\n> photons simulated by PhoSim gave the following distributions (color bars\n> are colored according to the faction of the total number of objects). Note\n> that the r-band plot will look a little odd, given that this is the band in\n> which I fixed magnorm to produce a set number of photons.\n>\n> [image: instcat_ratio_grid_0 txt]\n> <https://user-images.githubusercontent.com/1682854/40814118-373b2e54-64f3-11e8-8afd-7852ecef19f4.png>\n> [image: instcat_ratio_grid_1 txt]\n> <https://user-images.githubusercontent.com/1682854/40814119-3ace79ea-64f3-11e8-992f-eb506fe2af6c.png>\n> [image: instcat_ratio_grid_2 txt]\n> <https://user-images.githubusercontent.com/1682854/40814122-3f1dc230-64f3-11e8-87c5-c9df46ffbaf1.png>\n> [image: instcat_ratio_grid_3 txt]\n> <https://user-images.githubusercontent.com/1682854/40814125-41953188-64f3-11e8-8ee0-4bd9762d8dd0.png>\n> [image: instcat_ratio_grid_4 txt]\n> <https://user-images.githubusercontent.com/1682854/40814127-436c0130-64f3-11e8-9497-803c120eea2e.png>\n> [image: instcat_ratio_grid_5 txt]\n> <https://user-images.githubusercontent.com/1682854/40814129-455f05e6-64f3-11e8-8c66-4e9a070f619e.png>\n>\n> Comparing predicted colors gives the following plots.\n>\n> [image: u_g_color_plot]\n> <https://user-images.githubusercontent.com/1682854/40814148-65c89cac-64f3-11e8-9f5a-0e9b3736e951.png>\n> [image: g_r_color_plot]\n> <https://user-images.githubusercontent.com/1682854/40814151-68b2ae62-64f3-11e8-837b-c54878f29c7b.png>\n> [image: r_i_color_plot]\n> <https://user-images.githubusercontent.com/1682854/40814154-6b032e9e-64f3-11e8-8cba-9cc130a8a087.png>\n> [image: i_z_color_plot]\n> <https://user-images.githubusercontent.com/1682854/40814156-6d48e4f0-64f3-11e8-809c-f6645e12b03d.png>\n> [image: z_y_color_plot]\n> <https://user-images.githubusercontent.com/1682854/40814159-6f714c40-64f3-11e8-87c7-5bb5c2ba451c.png>\n>\n> I do not see any obvious structure in any of these plots, which, I\n> suspect, means that the difference between PhoSim and CatSim is due to a\n> difference in the throughputs used by CatSim as compared the effective\n> throughput used by PhoSim.\n>\n> —\n> You are receiving this because you were mentioned.\n> Reply to this email directly, view it on GitHub\n> <https://github.com/LSSTDESC/DC2_Repo/issues/150#issuecomment-393718362>,\n> or mute the thread\n> <https://github.com/notifications/unsubscribe-auth/ABxQ32FIKeubdtRviKtvONGMAf3Z0iCSks5t4INIgaJpZM4TUbuL>\n> .\n>\n"}}
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