J/ApJS/280/29ivo://CDS.VizieR/J/ApJS/280/29CDSAngulo R.Rest A.Blair W.P.Jencson J.Coulter D.A.Wang Q.,Foley R.J.Kilpatrick C.D.Li X.Piro A.L.Rojas-Bravo C.2026-07-22T08:38:57Z2026-07-22T09:36:58ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frinfrared-photometryvisible-astronomybroad-band-photometrysupernovaeDifference image analysis (DIA) is a powerful tool for studying time-variable phenomena, and has been used by many time-domain surveys. Most DIA algorithms involve matching the spatially varying point-spread function shape between science and template images, and then convolving that shape in one image to match the other. The wrong choice of which image to convolve can introduce one of the largest sources of artifacts in the final difference image. We introduce a quantitative metric to determine the optimal convolution direction that depends not only on the sharpness of the images measured by their FWHM, but also on their exposure depths. With this metric, the optimal convolution direction can be determined a priori, depending only on the FWHM and depth of the images. This not only simplifies the process, but also makes it more robust and less prone to creating suboptimal difference images due to the wrong choice of the convolution direction. As an additional benefit, for a large set of images, we define a Figure-of-Merit based on this metric, which allows us to rank a list of images and determine the ones best suited to be used as templates, thus streamlining and automating the data reduction process.2025ApJS..280...29Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/280/29CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/795/44 : PS1 SNe Ia (0.02<z<0.7) griz light curves (Rest+, 2014)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/280/29https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/280/29http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/280/29https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/280/29https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/280/29http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/280/29GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/280/29/table3 (Blanco/DECam fields)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/280/29/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/280/29/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/280/29/table3?GETtext/xml+votable180.050000true86.3517-24.37110.005555555555555556Cone search capability for table J/ApJS/280/29/table4 (Swope fields)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/280/29/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/280/29/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/280/29/table4?GETtext/xml+votable180.050000true76.4801-11.76830.0055555555555555566/18354 20713 21242 23084 37331 38016https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/280/29?format=asciiOpticalInfrareddefaultJ/ApJS/280/29/table3Blanco/DECam fieldsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldName of fieldobs.fieldcharID[155041/1094432] Exposure IDmeta.id;meta.mainintDateObservation Datestime.epoch;obsnullableRAJ2000[53/161.4] Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-61/-4.2] Declination (J2000)degpos.eq.dec;meta.mainExp[50/300] Exposure timestime.duration;obs.exposurefloatFilt[griz] Filter usedinstr.setup;instr.filtercharFWHM[2.47/11.16] Full-width at half-maximumpixinstr.bandwidthdoublemag[17.61/24.16] Apparent magnitude, m_5{sigma}_, in Filt (G1)magphot.magfloatJ/ApJS/280/29/table4Swope fieldsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldName of fieldobs.fieldcharID[1047/9166] Exposure IDmeta.id;meta.mainintDateObservation Date; YYYY-MM-DD Thh:mm:ssstime.epoch;obsnullableRAJ2000[16/76.5] Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-12/10.8] Declination (J2000)degpos.eq.dec;meta.mainExp[45/1200] Exposure timestime.duration;obs.exposurefloatFilt[gri] Filter usedinstr.setup;instr.filtercharFWHM[2.26/7.9] Full-width at half-maximumpixinstr.bandwidthdoublemag[19.84/23.6] Apparent magnitude, m_5{sigma}_, in Filt (G1)magphot.magfloat