J/A+A/711/A37ivo://CDS.VizieR/J/A+A/711/A37CDSZerjal M.Dominguez-Tagle C.Vitas N.Sedighi N.Martin E.L.,Zapatero Osorio M.R.Olivares J.Munoz Torres S.Tsilia S.Zhang J.-Y.,Barrado D.Bejar V.J.S.Bouy H.Burgasser A.Cruz P.Lodieu N.,Mas Buitrago P.Phan-Bao N.Solano E.Tata R.Goldman B.Mohandasan A.,Reyle C.Smart R.L.Aghanim N.Altieri B.Amara A.Andreon S.,Auricchio N.Baccigalupi C.Baldi M.Balestra A.Bardelli S.,Battaglia P.Biviano A.Bonchi A.Branchini E.Brescia M.,Brinchmann J.Camera S.Canas-Herrera G.Capobianco V.Carbone C.,Carretero J.Casas S.Castellano M.Castignani G.Cavuoti S.,Chambers K.C.Cimatti A.Colodro-Conde C.Congedo G.Conselice C.J.,Conversi L.Copin Y.Courbin F.Courtois H.M.Cropper M.Cuby J.-G.,Da Silva A.Degaudenzi H.De Lucia G.Dolding C.Dole H.Douspis M.,Dubath F.Dupac X.Dusini S.Escoffier S.Farina M.Faustini F.,Ferriol S.Fotopoulou S.Frailis M.Franceschi E.Galeotta S.,George K.Gillis B.Giocoli C.Gomez-Alvarez P.Gracia-Carpio J.,Granett B.R.Grazian A.Grupp F.Haugan S.V.H.Hoar J.Holmes W.,Hormuth F.Hornstrup A.Jahnke K.Jhabvala M.Keihaenen E.Kermiche S.,Kiessling A.Kubik B.Kuijken K.Kuemmel M.Kunz M.Kurki-Suonio H.,Le Boulc'h Q.Le Brun A.M.C.Ligori S.Lilje P.B.Lindholm V.Lloro I.,Mainetti G.Maino D.Maiorano E.Mansutti O.Marggraf O.Martinelli M.,Martinet N.Marulli F.Massey R.Medinaceli E.Mei S.Mellier Y.,Meneghetti M.Merlin E.Meylan G.Mora A.Moresco M.Moscardini L.,Nakajima R.Neissner C.Niemi S.-M.Padilla C.Paltani S.Pasian F.,Pedersen K.Percival W.J.Pettorino V.Pires S.Polenta G.Poncet M.,Popa L.A.Pozzetti L.Raison F.Rebolo R.Renzi A.Rhodes J.,Riccio G.Romelli E.Roncarelli M.Saglia R.Sakr Z.Sapone D.,Sartoris B.Schewtschenko J.A.Schirmer M.Schneider P.Secroun A.,Seidel G.Seiffert M.Serrano S.Simon P.Sirignano C.Sirri G.,Stanco L.Steinwagner J.Tallada-Crespi P.Taylor A.N.Tereno I.,Toft S.Toledo-Moreo R.Torradeflot F.Tsyganov A.Tutusaus I.,Valenziano L.Valiviita J.Vassallo T.Verdoes Kleijn G.Veropalumbo A.,Wang Y.Weller J.Zacchei A.Zamorani G.Zerbi F.M.Zucca E.,Martin-Fleitas J.Scottez V.2026-06-30T15:44:59Z2026-06-30T16:40:45ZCDS support team

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

cds-question@unistra.frbrown-dwarfsinfrared-photometryWe present a catalogue of 5306 new ultracool dwarf (UCD) candidates in the three Euclid Deep Fields in the Q1 data release. They range from late M to late T dwarfs, and include 1200 L and T dwarfs. A total of 546 objects have been spectroscopically confirmed, including 329 L dwarfs and 26 T dwarfs. We also provide empirical Euclid colours as a function of spectral type. Our UCD selection criteria are based only on colour (I_E-Y_E>2.5). The combined requirement for optical detection and stringent signal-to-noise ratio threshold ensure a high purity of the sample, but at the expense of completeness, especially for T dwarfs. The detections range from magnitudes 19 and 24 in the near-infrared bands, and extend down to 26 in the optical band. We discuss Euclid's capability to identify UCD candidates based on its photometric passbands. The average surface density of detected UCDs on the sky is approximately 100 objects per deg^2, including 20 L and T dwarfs per deg^2^. This leads to an expectation of at least 1.4 million ultracool dwarfs in the final data release of the Euclid Wide Survey, including at least 300000 L dwarfs, and more than 2600 T dwarfs, using the strict selection criteria from this work.2026A&A...711A..37Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/711/A37CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/388 : Euclid final merged catalog. Q1 data releaseJ/A+A/711/A10 : Euclid (Q1). Census of dwarf galaxies (Euclid Coll., 2026)J/A+A/711/A16 : X-ray point-like sources of Euclid (Q1) (Euclid Coll.+, 2026)J/A+A/711/A37 : Ultracool dwarfs in Euclid Deep Fields (Zerjal+, 2026)J/A+A/711/A38 : Euclid Q1. Photometric studies of known transientsJ/A+A/711/A39 : Euclid Q1. Secondary nuclei in ET galaxies (Fabricius+, 2026)J/A+A/711/A20 : Galaxies of Euclid (Q1) (Euclid Coll.+, 2026)J/A+A/711/A24 : Euclid Q1. Little red dots properties (Euclid Coll., 2026)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/711/A37https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/711/A37http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/711/A37https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/711/A37https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/711/A37http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/711/A37GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/711/A37/tablea1 (A table of 60 benchmark objects)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/711/A37/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/711/A37/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/711/A37/tablea1?GETtext/xml+votable180.050000true65.4087774271452-47.74794285715230.005555555555555556Cone search capability for table J/A+A/711/A37/tablea3 (A table of 5306 ultracool dwarf candidates in Euclid's Q1 data release)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/711/A37/tablea3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/711/A37/tablea3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/711/A37/tablea3?GETtext/xml+votable180.050000true67.0049939754188-47.8214513070940.0055555555555555564/2145 5/2557 2559 2901 2903 3839 4010-4011 8506 8579 8592 8982-8983 8989 6/10235 11601 11603 11609 15353-15355 16034-16035 16038-16039 16056 16058 33981-33983 34028 34030 34307 34309-34311 34313-34315 34337 34339-34342 34352 34372 34374 34376-34377 35926-35927 35953 35955 35964 36098 36104 36106-36107 36128-36130https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/711/A37?format=asciiInfrareddefaultJ/A+A/711/A37/tablea1A table of 60 benchmark objectsObjectIdObject ID in Euclid Q1meta.id;meta.mainSpTypeSpectral type from Dominguez-Tagle et al. (2025ApJ...991...84D)src.spTypecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right ascension (J2000) in Euclid Q1degpos.eq.ra;meta.mainDEJ2000Declination (J2000) in Euclid Q1degpos.eq.dec;meta.mainImagMagnitude computed from flux_vis_2fwhm_apermagphot.mag;em.opt.IdoubleYmag? Magnitude computed from flux_y_2fwhm_apermagphot.mag;em.IR.JdoublenullableJmag? Magnitude computed from flux_j_2fwhm_apermagphot.mag;em.IR.JdoublenullableHmag? Magnitude computed from flux_h_2fwhm_apermagphot.mag;em.IR.HdoublenullableI-Y? I-Y colourmagphot.color;em.IR;em.IRdoublenullableI-J? I-J colourmagphot.color;em.IR;em.IRdoublenullableI-H? I-H colourmagphot.color;em.IR;em.IRdoublenullableY-J? Y-J colourmagphot.color;em.IR;em.IRdoublenullableY-H? Y-H colourmagphot.color;em.IR;em.IRdoublenullableJ-H? J-H colourmagphot.color;em.IR.J;em.IR.Hdoublenullablee_Imag? Lower I magnitude errormagstat.error;phot.magdoublenullableE_Imag? Upper I magnitude errormagstat.error;stat.maxdoublenullablee_Ymag? Lower Y magnitude errormagstat.error;phot.magdoublenullableE_Ymag? Upper Y magnitude errormagstat.error;stat.maxdoublenullablee_Jmag? Lower J magnitude errormagstat.error;phot.magdoublenullableE_Jmag? Upper J magnitude errormagstat.error;stat.maxdoublenullablee_Hmag? Lower H magnitude errormagstat.error;phot.magdoublenullableE_Hmag? Upper H magnitude errormagstat.error;stat.maxdoublenullablee_I-Y? Lower I-Y colour errormagstat.errordoublenullableE_I-Y? Upper I-Y colour errormagstat.error;stat.maxdoublenullablee_I-J? Lower I-J colour errormagstat.error;phot.color;em.opt.IdoublenullableE_I-J? Upper I-J colour errormagstat.error;stat.maxdoublenullablee_I-H? Lower I-H colour errormagstat.error;phot.color;em.opt.IdoublenullableE_I-H? Upper I-H colour errormagstat.error;stat.maxdoublenullablee_Y-J? Lower Y-J colour errormagstat.errordoublenullableE_Y-J? Upper Y-J colour errormagstat.error;stat.maxdoublenullablee_Y-H? Lower Y-H colour errormagstat.errordoublenullableE_Y-H? Upper Y-H colour errormagstat.error;stat.maxdoublenullablee_J-H? Lower J-H colour errormagstat.error;phot.color;em.IR.JdoublenullableE_J-H? Upper J-H colour errormagstat.error;stat.maxdoublenullableSNRISignal-to-noise of the I fluxphot.flux.density;em.opt.IdoubleSNRY? Signal-to-noise of the Y fluxstat.snrdoublenullableSNRJ? Signal-to-noise of the J fluxstat.snrdoublenullableSNRH? Signal-to-noise of the H fluxstat.snrdoublenullabledetQualFlagDetection quality flag, propagated from Euclid Q1meta.code.qualintFlagvis[0/2] Flag VIS, propagated from Euclid Q1meta.code.errorintFlagY[0/2] Flag Y, propagated from Euclid Q1meta.code.errorintFlagJ[0/2] Flag J, propagated from Euclid Q1meta.code.errorintFlagH[0/2] Flag H, propagated from Euclid Q1meta.code.errorintGaiaDR3? Gaia DR3 source_id, propagated from Euclid Q1meta.idnullableFWHMFWHM, propagated from Euclid Q1arcsecphys.angSizedoubleellEllipticity, propagated from Euclid Q1src.ellipticitydoublemumax-magMumax_minus_mag, propagated from Euclid Q1mag.arcsec**-2phot.mag.sbdoubleKronRadKron radius, propagated from Euclid Q1pixphys.angSizedoubleE(B-V)E(B-V), propagated from Euclid Q1magphot.color.excessdoublee_E(B-V)E(B-V), propagated from Euclid Q1magstat.errordoubleSpTnumNumerical spectral typesrc.spTypeintJ/A+A/711/A37/tablea3A table of 5306 ultracool dwarf candidates in Euclid's Q1 data releaserecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObjectIdObject ID in Euclid Q1meta.id;meta.mainRAJ2000Right ascension (J2000) in Euclid Q1degpos.eq.ra;meta.mainDEJ2000Declination (J2000) in Euclid Q1degpos.eq.dec;meta.mainImagMagnitude computed from flux_vis_2fwhm_apermagphot.mag;em.opt.IdoubleYmagMagnitude computed from flux_y_2fwhm_apermagphot.mag;em.IR.JdoubleJmag? Magnitude computed from flux_j_2fwhm_apermagphot.mag;em.IR.JdoublenullableHmagMagnitude computed from flux_h_2fwhm_apermagphot.mag;em.IR.HdoubleI-YI-Y colourmagphot.color;em.IR;em.IRdoubleI-J? I-J colourmagphot.color;em.IR;em.IRdoublenullableI-HI-H colourmagphot.color;em.IR;em.IRdoubleY-J? Y-J colourmagphot.color;em.IR;em.IRdoublenullableY-H? Y-H colourmagphot.color;em.IR;em.IRdoublenullableJ-H? J-H colourmagphot.color;em.IR.J;em.IR.Hdoublenullablee_ImagLower I magnitude errormagstat.error;phot.magdoubleE_ImagUpper I magnitude errormagstat.error;stat.maxdoublee_YmagLower Y magnitude errormagstat.error;phot.magdoubleE_YmagUpper Y magnitude errormagstat.error;stat.maxdoublee_Jmag? Lower magnitude errormagstat.error;phot.magdoublenullableE_Jmag? Upper magnitude errormagstat.error;stat.maxdoublenullablee_HmagLower H magnitude errormagstat.error;phot.magdoubleE_HmagUpper H magnitude errormagstat.error;stat.maxdoublee_I-YLower I-Y colour errormagstat.errordoubleE_I-YUpper I-Y colour errormagstat.error;stat.maxdoublee_I-J? Lower I-J colour errormagstat.error;phot.color;em.opt.IdoublenullableE_I-J? Upper I-J colour errormagstat.error;stat.maxdoublenullablee_I-HLower I-H colour errormagstat.error;phot.color;em.opt.IdoubleE_I-HUpper I-H colour errormagstat.error;stat.maxdoublee_Y-J? Lower Y-J colour errormagstat.errordoublenullableE_Y-J? Upper Y-J colour errormagstat.error;stat.maxdoublenullablee_Y-HLower Y-H colour errormagstat.errordoubleE_Y-HUpper Y-H colour errormagstat.error;stat.maxdoublee_J-H? Lower J-H colour errormagstat.error;phot.color;em.IR.JdoublenullableE_J-H? Upper J-H colour errormagstat.error;stat.maxdoublenullableSNRISignal-to-noise of the I fluxphot.flux.density;em.opt.IdoubleSNRYSignal-to-noise of the Y fluxstat.snrdoubleSNRJ? Signal-to-noise of the J fluxstat.snrdoublenullableSNRHSignal-to-noise of the H fluxstat.snrdoubledetQualFlag[0/2] Detection quality flag, propagated from Euclid Q1meta.code.qualintFlagvisFlag VIS, propagated from Euclid Q1meta.code.errorintFlagYFlag Y, propagated from Euclid Q1meta.code.errorintFlagJFlag J, propagated from Euclid Q1meta.code.errorintFlagHFlag H, propagated from Euclid Q1meta.code.errorintGaiaDR3? Gaia DR3 source_id, propagated from Euclid Q1meta.idnullablevisdet[0/1]? VIS detection, propagated from Euclid Q1meta.codeintnullableFWHMFWHM, propagated from Euclid Q1arcsecphys.angSizedoubleellEllipticity, propagated from Euclid Q1src.ellipticitydoublemumax-magMumax_minus_mag, propagated from Euclid Q1mag.arcsec**-2phot.mag.sbdoubleKronRadKron radius, propagated from Euclid Q1pixphys.angSizedoubleE(B-V)E(B-V), propagated from Euclid Q1magphot.color.excessdoublee_E(B-V)E(B-V) error, propagated from Euclid Q1magstat.errordoubleSpTypeSpectral type from Dominguez-Tagle et al. (2025ApJ...991...84D)src.spTypecharSpTnum[67/87]? Numerical spectral typesrc.spTypeintnullableClassClass (1)meta.code.classchar