An I-band calibration of the SBF method at blue colours

An I-band calibration of the SBF method at blue colours

Astronomy&Astrophysicsmanuscriptno.mieskeFebruary5,2008

cESO2008

AnI-bandcalibrationoftheSBFmethodatbluecolours

arXiv:astro-ph/0605660v1 26 May 2006

S.Mieske1,M.Hilker2,andL.Infante3

1

2

3

EuropeanSouthernObservatory,Karl-Schwarzschild-Strasse2,85748GarchingbeiM¨unchen,Germany

e-mail:smieske@ArgelanderInstitutf¨urAstronomie-AbteilungSternwarte,AufdemH¨ugel71,53121Bonn,Germanye-mail:mhilker@astro.uni-bonn.deDepartamentodeAstronom´ ayAstrof´ sica,Ponti ciaUniversidadCat´olicadeChile,Casilla306,Santiago22,Chilee-mail:linfante@astro.puc.cl

ABSTRACT

Context.Thesurfacebrightness uctuation(SBF)methodisapowerfultooltoderivedistancestogalaxiesforwhichsinglestarscannotberesolved.Uptonow,themethodhasbeencalibratedmainlyatredcoloursduetotheintrinsicfaintnessofblueearly-typegalaxies.Aims.InthispaperweaddresstheI-bandcalibrationoftheSBFmethodatbluecolours,theregimeofdwarfellipticalgalaxies(dEs).

Methods.Wepresentdeepandwide- eldVIphotometryofthecentralFornaxclusterobtainedatLasCampanasObservatory.WiththesedataweperformanSBFanalysisof25dEsintherange 16.5<MV< 11.2mag,0.8<(V I)0<1.10mag.Ourcolourcalibrationisaccuratetobetterthan2%.ForthecalibrationanalysisweexcludeeightdEswhoseSBFmeasurementwasa ectedbypoorseeing(FWHM 1′′).Results.OurSBFdataareinconsistentatthe3σlevelwithacolourindependentabsoluteSBFmagnitude

MI (V I)plane.Weobtainthefollowingone-branchempiricalSBFcalibration:

MI,whichissigni cantlylarger

thanfoundatreddercolours.ThisisinagreementwiththosetheoreticalSBFmodelsthatpredict

indicator.ThisnormalisedamplitudeconvertedtomagnitudeisintheframeworkofSBFinvestigationsreferredtoasappar-ent uctuationmagnitude

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