J/A+A/678/A44ivo://CDS.VizieR/J/A+A/678/A44doi:10.26093/cds/vizier.36780044CDSCsoernyei G.Anderson R.I.Vogl C.Taubenberger S.Blondin S.,Leibundgut B.Hillebrandt W.2025-06-24T20:01:10Z2023-10-02T08:02:18ZCDS support team

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

cds-question@unistra.frvariable-starsastrometryhst-photometryvisible-astronomygalaxiesThe distance to the Whirlpool galaxy, M 51, is still debated, even though the galaxy has been studied in great detail. Current estimates range from 6.02 to 9.09Mpc, and different methods yield discrepant results. No Cepheid distance has been published for M 51 to date. We aim to estimate a more reliable distance to M 51 through two independent methods: Cepheid variables and their period-luminosity relation, and an augmented version of the expanding photosphere method (EPM) on the type IIP supernova SN 2005cs, which exploded in this galaxy. For the Cepheid variables, we analysed a recently published Hubble Space Telescope catalogue of stars in M 51. By applying filtering based on the light curve and colour-magnitude diagram, we selected a high-quality sample of M 51 Cepheids to estimate the distance through the period-luminosity relation. For SN 2005cs, an emulator-based spectral fitting technique was applied, which allows for the fast and reliable estimation of the physical parameters of the supernova atmosphere. We augmented the established framework of EPM with these spectral models to obtain a precise distance to M 51. The two resulting distance estimates are D_Cep_=7.59+/-0.30Mpc and D_2005cs_=7.34+/-0.39Mpc using the Cepheid period-luminosity relation and the spectral modelling of SN 2005cs, respectively. This is the first published Cepheid distance for this galaxy. The obtained values are precise to 4-5% and are fully consistent within 1{sigma} uncertainties. Because these two estimates are completely independent, they can be combined for an even more precise estimate, which yields D_M51_=7.50+/-0.24Mpc (3.2% uncertainty). Our distance estimates agree with most of the results obtained previously for M 51, but they are more precise than the earlier counterparts. However, they are significantly lower than the TRGB estimates, which are often adopted for the distance to this galaxy. The results highlight the importance of direct cross-checks between independent distance estimates so that systematic uncertainties can be quantified. Because of the large discrepancy, this finding can also affect distance-sensitive studies and their discussion for objects within M 51, as well as the estimation of the Hubble constant through the type IIP standardizable candle method, for which SN 2005cs is a calibrator object.2023A&A...678A..44Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/678/A44CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/715/277 : Insights into the Cepheid distance scale (Bono+, 2010)J/ApJ/730/119 : HST/WFC3 obs. of Cepheids in SN Ia hosts (Riess+, 2011)J/ApJ/733/124 : Cepheids in M101 observed with HST (Shappee+, 2011)J/AJ/144/113 : Cepheids and companions in M33 from HST images (Chavez+, 2012)J/ApJ/748/107 : A global model for MC and Galactic Cepheids (Pejcha+, 2012)J/ApJ/777/79 : HST photometry of Cepheid candidates in M101 (Mager+, 2013)J/AJ/145/106 : M31 Cepheid disk sample of 1st year of PS1 (Kodric+, 2013)J/AJ/149/183 : gri photometry of variables in NGC 4258 (Hoffmann+, 2015)J/AJ/149/117 : LMC infrared survey. I. Photometry of Cepheids (Macri+, 2015)J/ApJ/799/144 : M31 Cepheids in near-IR (Kodric+, 2015)J/ApJ/830/10 : >20yrs of HST obs. of Cepheids in SNIa host gal.J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016)J/A+A/587/A70 : CALIFA face-on spiral gal. oxygen (Sanchez-Menguiano+, 2016)J/AJ/156/30 : Cepheids in M31 - PAndromeda Cepheid sample (Kodric+, 2018)J/ApJ/864/111 : HST/ACS one-year observations of M51 stars (Conroy+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/678/A44https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/678/A44http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/678/A44https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/678/A44https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/678/A44http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/678/A44GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/678/A44/ceps (Catalogue of M 51 Cepheid variables)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/678/A44/ceps?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/678/A44/ceps?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/678/A44/ceps?GETtext/xml+votable180.050000true202.4678138947.178066110.0055555555555555566/110272.0401237512456292e-19 4.2441532724171825e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/678/A44?format=asciiOpticaldefaultJ/A+A/678/A44/cepsCatalogue of M 51 Cepheid variablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainPFourier period at maximum power in F814Wdtime.perioddoubleF555WHST/F555W band (V) flux averaged brightnessmagphot.mag;em.opt.Vdoublee_F555WUncertainty in F555Wmagmagstat.errordoubleF606WHST/F606W band (V) flux averaged brightnessmagphot.mag;em.opt.Rdoublee_F606WUncertainty in F606Wmagmagstat.errordoubleF814WHST/F814W band (I) flux averaged brightnessmagphot.mag;em.opt.Idoublee_F814WUncertainty in F814Wmagmagstat.errordoubleWVI-555Wesenheit magnitude inferred based on F555W and F814Wmagphot.magdoublee_WVI-555Uncertainty in the Wesenheit magnitudemagstat.errordoubleZZaritsky et al. (1994ApJ...420...87Z) metallicity valuesphys.abund.Zdoublesig-clip[+] Boolean value for the Cepheid being included in the final PL relation fit. If '+', it was included, otherwise was discarded by the sigma clippingmeta.codechar