J/A+A/707/A91ivo://CDS.VizieR/J/A+A/707/A91CDSAlburai A.Galbany L.Burgaz U.Dimitriadis G.Johansson J.Smith M.,Sanfeliu R.Guerra S.Mueller-Bravo T.Goobar A.Dhawan S.Kim Y.-L.,Nordin J.Townsend A.Sollerman J.Ginolin M.Rigault M.Terwel J.H.,Smith R.Wold A.Chen T.X.Jegou du Laz T.2026-04-02T06:28:33Z2026-02-27T08:45:52ZCDS support team

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

cds-question@unistra.frsupernovaephotometryvisible-astronomyspectroscopyThe Zwicky Transient Facility Data Release 2 (ZTF DR2) includes a total of 3628 Type Ia supernovae (SNe Ia), providing the largest and most complete sample of spectroscopically confirmed SNe Ia at low redshift to date. In this paper, we present a photometric and spectroscopic analysis of 124 subluminous SNe Ia, the largest sample of spectroscopically classified subluminous type Ia supernova observed with a single instrument, comprising 87 91bg-like, 12 86G-like, 18 04gs-like, and 7 02es-like events. We complement the published DR2 SALT2 light-curve parameters with new parameters obtained using template-based fits from SNooPy. Expansion velocities and pseudo-equivalent widths pEW of key spectral features are measured using Spextractor, and spectral averages are constructed for each subluminous subtype, binned by phase. We also analyze the host galaxy environments, both global and local, in terms of g-z color, stellar mass, and directional light radius d_DLR_. We find that all subluminous SNe~Ia (except the 02es-like subtype) are intrinsically red. This is evident by separating extrinsic from intrinsic color components. Since SALT2 is not trained on subluminous SNe Ia, it compensates for their redder colors by inflating the c parameter, thus extending the luminosity- width relation to negative values of x1. As expected, all subluminous SNe Ia fall within the Cool region of the Branch et al. (2006PASP..118..560B) diagram, with the exception of 02es-like events, which show lower SiII 5972 pEW values. All subluminous subtypes tend to occur in more massive, redder host galaxies, and in the reddest local environments within their stellar mass bins. Notably, 91bg- and 86G-like SNe Ia explode at significantly larger normalized galactocentric distances. Finally, we identify the $pEW$ of the blended TiII+ SiII+MgII absorption feature at 4300{AA}, along with s_BV_, as robust and sufficient indicators for subclassifying subluminous SNe Ia.2026A&A...707A..91Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/707/A91CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/694/A9 : Spectral Measurements of ZTF SN Ia DR2 (Burgaz+, 2025)J/A+A/694/A10 : ZTF SN Ia DR2 (Dimitriadis+, 2025)J/A+A/694/A11 : SN 2020alm spectrum (Terwel+, 2025)J/A+A/694/A12 : ZTF SN Ia DR2. Secondary maximum in Type Ia SNJ/A+A/695/A264 : ZTF SN Ia DR2. SiII6355 high-velocity comp. (Harvey+, 2025)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/707/A91https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/707/A91http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/707/A91https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/707/A91https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/707/A91http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/707/A91GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/707/A91/tablea1 (SN Ia light-curve parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/707/A91/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/707/A91/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/707/A91/tablea1?GETtext/xml+votable180.050000true175.283291724.81955560.0055555555555555566/176 216 2372 2384 2418 3106 5204 5701 6131 6234 7275 7355 8203 8254 8345 8378 8537 9098 9122 9424 9454 9543 9666 9812 9891 10115 10202 10207 10322 10379 10409 10446 10534 10817 10995 11379 11854 12372 12497 12507 14069 14764 15244 15292 18354 19501 19533 20194 20865 21772 22566 23078 24954 25076 26422 26742 28458 28490 30074 31679 36761https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/707/A91?format=asciiOpticaldefaultJ/A+A/707/A91/tablea1SN Ia light-curve parametersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintZTFZTF Namemeta.id;meta.maincharIAUIAU Namemeta.idcharMJDBSALT2 time of maximum B brightnessdtime.epochdoublee_MJDBSALT2 time of maximum B brightness errordstat.errorfloatBmaxSALT2 maximum B brightnessmagphot.mag;em.opt.Bfloate_BmaxSALT2 maximum B brightness errormagstat.errorfloatx1SALT2 x1 stretch parameterstat.fit.paramfloate_x1SALT2 x1 stretch parameter errorstat.errorfloatcSALT2 color parametermagstat.fit.paramfloatSimbadNameSimbad column added by the CDSmeta.idcharnullablee_cSALT2 color parameter errormagstat.errorfloatMJDG? SNooPy time of maximum G brightnessdtime.epochdoublenullablee_MJDG? SNooPy time of maximum G brightness errordstat.errorfloatnullableGmax? SNooPy maximum G brightnessmagphot.mag;em.optfloatnullablee_Gmax? SNooPy maximum G brightness errormagstat.errorfloatnullablesBV? Reddest point in the B-V color curve normalized by 30 days, sBV=(tmax/30days)stat.fit.paramfloatnullablee_sBV? Reddest point in the B-V color curve normalized by 30 days, sBV=(tmax/30days) errorstat.errorfloatnullableE(B-V)? Extinction E(B-V)magphot.color.excessfloatnullablee_E(B-V)? Extinction E(B-V) errormagstat.errorfloatnullableSourceSource from which the values of the time of maximum light are obtainedmeta.id;instrchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.mainnullable_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainnullableJ/A+A/707/A91/tablea2Spectroscopic properties of all 124 SNe in the initial sampleZTFZTF namemeta.id;meta.maincharpEWCaIINIR? CaII NIR pseudo-equivalent width0.1nmspect.line.eqWidthfloatnullablee_pEWCaIINIR? CaII NIR pseudo-equivalent width error0.1nmstat.errorfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIAUIAU namemeta.idcharsubtypeSpectroscopic classificationsrc.classcharPhaseSpectral phasedtime.phasefloatVSiII {lambda}6355 velocity1000lm.s**-1spect.dopplerVelocfloate_VSiII {lambda}6355 velocity error1000lm.s**-1stat.error;pos.cartesian.yfloatpEWSiII6355SiII {lambda}6355 pseudo-equivalent width0.1nmspect.line.eqWidthfloate_pEWSiII6355SiII {lambda}6355 pseudo-equivalent width error0.1nmstat.errorfloatpEWSiII5972? SiII {lambda}5972 pseudo-equivalent width0.1nmspect.line.eqWidthfloatnullablee_pEWSiII5972? SiII {lambda}5972 pseudo-equivalent width error0.1nmstat.errorfloatnullablepEWMgII4000? MgII {lambda}4000 pseudo-equivalent width0.1nmspect.line.eqWidthfloatnullablee_pEWMgII4000? MgII {lambda}4000 pseudo-equivalent width error0.1nmstat.errorfloatnullablepEWOI7774? OI {lambda}7774 pseudo-equivalent width0.1nmspect.line.eqWidthfloatnullablee_pEWOI7774? OI {lambda}7774 pseudo-equivalent width error0.1nmstat.errorfloatnullable