J/ApJ/855/140ivo://CDS.VizieR/J/ApJ/855/140doi:10.26093/cds/vizier.18550140CDSLong K.S.Blair W.P.Milisavljevic D.Raymond J.C.Winkler P.F.2019-03-20T08:54:33Z2019-02-20T14:51:13ZCDS support team

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

cds-question@unistra.frsupernova-remnantsvisible-astronomyspectroscopyx-ray-sourcesastronomical-object-identificationTo date, over 220 emission nebulae in M33 have been identified as supernova remnants (SNRs) or SNR candidates, principally through [SII]:H{alpha} line ratios that are elevated compared to those in HII regions. In many cases, the determination of a high [SII]:H{alpha} line ratio was made using narrow-band interference filter images and has not been confirmed spectroscopically. Here, we present MMT 6.5m optical spectra that we use to measure [SII]:H{alpha} and other line ratios in an attempt to determine the nature of these suggested candidates. Of the 197 objects in our sample, 120 have no previously published spectroscopic observations. We confirm that the majority of candidate SNRs have emission line ratios characteristic of SNRs. While no candidates show Doppler-broadened lines expected from young, ejecta-dominated SNRs (>~1000km/s), a substantial number do exhibit lines that are broader than HII regions. We argue that the majority of the objects with high [SII]:H{alpha} line ratios (>0.4) are indeed SNRs, but the distinction between HII regions and SNRs becomes less obvious at low surface brightness, and additional criteria, such as X-ray detection, are needed. We discuss the properties of the sample as a whole and compare it with similar samples in other nearby galaxies.2018ApJ...855..140Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/855/140CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+AS/114/215 : New SNR candidates in M31 (Magnier+, 1995)J/ApJS/120/247 : Supernova remnants in M33 (Gordon+, 1999)J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)J/AJ/134/2474 : H{alpha} em. stars in 7 dwarfs galaxies (Massey+, 2007)J/ApJ/675/1213 : Abundances in M33 HII regions (Rosolowsky+, 2008)J/ApJS/187/495 : SNRs in M33 from optical and X-ray (Long+, 2010)J/A+A/512/A63 : Abundances of M33 HII regions (Magrini+, 2010)J/ApJS/193/31 : M33 Chandra ACIS survey: final catalog (Tullmann+, 2011)J/ApJS/203/8 : Optical SNR candidates in M83 (Blair+, 2012)J/ApJ/758/133 : HII regions & PNe metallicity profiles (Sanders+, 2012)J/MNRAS/429/189 : SNRs in six nearby galaxies (Leonidaki+, 2013)J/ApJ/788/55 : HST/WFC3 SNR discoveries in M83 (NGC5236) (Blair+, 2014)J/ApJ/786/130 : Catalog of M31 SNR candidates (Lee+, 2014)J/ApJ/793/134 : M33 SNR candidates properties (Lee+, 2014)J/ApJS/212/21 : A deep Chandra ACIS survey of M83 (Long+, 2014)J/ApJS/218/9 : Deep XMM-Newton survey of M33 (Williams+, 2015)J/MNRAS/460/1739 : Giant HII regions BOND abundances (Vale Asari+, 2016)J/MNRAS/472/308 : SNRs in M33: X-ray properties (Garofali+, 2017)J/ApJ/842/97 : Spectroscopic obs. of 413 HII regions in M33 (Lin+, 2017)J/ApJ/839/83 : GMOS spectroscopy of SNR candidates in M83 (Winkler+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/855/140https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/855/140http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/855/140https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/855/140https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/855/140http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/855/140GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/855/140/table1 (SNR Candidates in M33)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/855/140/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/855/140/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/855/140/table1?GETtext/xml+votable180.050000true23.126541730.46302780.0055555555555555566/2154 2155 2241https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/855/140?format=asciiX-rayOpticaldefaultJ/ApJ/855/140/table1SNR Candidates in M33SimbadNameSimbad column added by the CDSmeta.idcharIDSource identifier used in this papermeta.id;instr.setup;meta.maincharprimary[LL2014b]? Lee & Lee 2014, J/ApJ/793/134 identifiermeta.id.crossintnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[1] Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000[30/31] Degree of Declination (J2000)pos.eq.dec;meta.mainDiam[11/183] Apparent diameterpcpos.distanceintrho[0.2/8.1] Galactocentric distancekpcpos.distance;pos.galactocentricfloat[LBW2010]? Long+ 2010, J/ApJS/187/495 identifiermeta.id.crossintnullable[GWP2017]XMM identifier from Garofali+, 2017, J/MNRAS/472/308meta.id.crosscharX-rayX-ray detected? (1)meta.codecharPrevLiterature code of a previous spectrum (2)meta.codecharNewNew spectrum from MMT observations?meta.codecharConfA [SII]/H{alpha}>=0.4 confirmation? (3)meta.codecharJ/ApJ/855/140/table2Emission line fluxes of SNR candidatesu_[SII]/Ha[~] Approximation flag on [SII]/Hameta.code.errorcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDSource identifier used in this papermeta.id;instr.setupcharFHa[2/2485] H{alpha} flux (1)1e-20W.m**-2phot.fluxintu_Hb[~] Approximation flag on Hbmeta.code.errorcharHb[19/126]? H{beta} emission line strength (2)spect.line.intensity;em.line.Hbetaintnullableu_[OIII][~] Approximation flag on [OIII]meta.code.errorchar[OIII][13/693]? The [OIII]5007{AA} emission line strength (2)spect.line.intensity;em.line.OIIIintnullableu_[OI][~] Approximation flag on [OI]meta.code.errorchar[OI][8/151]? The [OI]6300{AA} emission line strength (2)spect.line.intensityintnullableHa[300] Halpha emission line strength (2)spect.line.intensityintu_[NII][~] Approximation flag on [NII]meta.code.errorchar[NII][-8/190]? The [NII]6584A emission line strength (2)spect.line.intensityintnullableu_[SII]6717[~] Approximation flag on [SII]6717meta.code.errorchar[SII]6717[28/253]? The [SII]6717A emission line strength (2)spect.line.intensityintnullableu_[SII]6731[~] Approximation flag on [SII]6731meta.code.errorchar[SII]6731[19/195]? The [SII]6731{AA} emission line strength (2)spect.line.intensityintnullable[SII]/Ha[0.1/1.5]? Ratio of [SII] to Halpha linesmeta.notefloatnullableFWHM[4.2/9.1] Full-Width at Half-Maximum of H{alpha} line in Angstroms0.1nmspect.line.widthfloat