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Dear Datalab colleague,

I am browsing the catalog, and find out that there is no uncertainty for the colors (mag_g, mag_r, mag_z, mag_w1, mag_w2, etc). Is it possible to include those info?

Also I noticed that the size info is quite limited. In SDSS, they provide r25, r50, r75, r90 (the number indicates the percentage of light included). Would it also be possible to include those info?

Thanks and have a good week,

Huanian
asked Dec 2, 2019 by anonymous | 18 views

1 Answer

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Hi Huinan, thanks for reaching out.

Regarding your first question on mag uncertainties: there are columns with SNR values, i.e. snr_g, snr_r, etc. To first order the uncertainties on the mag_g, mag_r are thus sigma_mag_g = 1/snr_g, sigma_mag_r = 1/snr_r, etc.

On your second question: the LS team does not compute the radii r25, r50, etc, but you can get something similar in the tables ls_dr8.apflux_n and ls_dr8.apflux_s; there you will find columns like apflux_g_1, apflux_g_2, ..., apflux_g_8, which are (circular) "Aperture fluxes on the co-added images in aperture of radius 0.5, 0.75, 1, 1.5, 2, 3.5, 5, 7 arcseconds".

Hope this is helpful.

Cheers,

Robert
answered Dec 2, 2019 by datalab (6,680 points)
Thank you very much, Robert. I will try those first.

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