www.univ-amu.fr
www.lam.fr
PhDThesis
PhDthesisdirectorname(HDR):P.Amram
Email:[email protected],phonenumber:+33495044109
Co-director:B.Epinat
PhDtitle:Kinematicsandmassdistributionofspiralandirregulargalaxies.
Subjectdescription:ThegoalofthisPhDistogobeyondactualissuesinspiralandirregularkinematicsandmassdistributionsusing
data as well as models and numerical simulations. The main goal is to study the mass distribution of galaxies using multiple
constrainsinordertocomputethemass-to-lightratioofthedifferentdiskpopulationsandtheshapeofdarkprofilehalos.Multiple
datasetsatdifferentwavelengthswillbeusedtoperformthisuniquemassmodelanalysisfrom2Dkinematicsoverlargesampleof
wellresolvednearbygalaxies.Highspatialandspectralresolutionstwo-dimensionalFabry-Perotspectro-imagerydata,allowingto
take into account inner disk non axi-symmetric structures (bars, spiral arms, …) and local motions (velocity dispersion,…),
complementedbyHIdatacubeandbroad-bandphotometry,willbeusedtostudythekinematicanddynamicsofthis sample of
galaxies.Inaddition,thePhDstudentwilltakeadvantageofthoseanalysestoconstraindarkmatterdistributioningalaxiesathigher
redshift in comparing with available data obtained with spectro-imagers and in the frame of the preparation of instrument of
further generations in the optical, the infra-red and the radio wavelength (First generation of spectro-imagers for the E-ELT:
HarmoniandMosaic;thirdgenerationspectro-imagerfortheVLTtobedefined;andSKA1forradioemissionlinesstudies).
Method:Inordertostudythekinematicandthemassdistributionofspiralandirregulargalaxies,largesampleofgalaxiesobserved
atdifferentwavelengthandusingdifferenttechnicsareneeded.2DKinematicaldataareobtainedfromionizedgaswithhighspatial
resolution(usuallyHalpha)intheinnerregionsofgalaxiesandfromneutralhydrogen(HI)intheoutergalacticdisk.Extensive2D
spectro-imageryhasbeenobtainedforalargenumberofspiralandirregulargalaxiesbyFabry-PerotHαobservations,withhighand
spectralspatialresolutions,openinganeweraofinparticularinnon-axisymmetricgalacticdynamics(e.g.GHASP,Epinatetal2008,
Dicaire et al 2008, Gomez-Lopez et al in preparation). Large HI surveys of spirals and irregular galaxies have also been led (e.g.
WHISP, http://wow.astron.nl/) allowing constraining large-scale kinematics as well as gas mass content. Multi-band photometry
dataarenowavailableformostofthegalaxiesforwhichwehavekinematicaldata,e.g.R-bandphotometry(Barbosaetal.2015)
andinfournearinfrared-bands(e.g.survey,Jarrettetal,2012).Galaxymodelingwillbecarriedoutusingdifferenttools.
Scientificcontext:Theexistenceofdarkhalosinspiralgalaxieshasbeenevidencedfromthewell-establisheddifferencebetween
thegalaxymasspredictedbytheluminosityandthemasspredictedbytherotationvelocities.Rotationcurvesoflate-typespiral
galaxiesmaybeusuallyfittedbytwocomponents,astellardiskandadarkhalo.Early-typespiralsneedathirdcomponent,abulge.
Theshapeofdarkhalosingalaxiesisstillsubjecttocusp/corecontroversy.Despitemajorsuccessesincosmologicalframeworks,
NFWdarkhalosstillfailtocorrectlyreproducetheinnershapeofrotationcurves.Thediskmassdistributioniscomputedfromthe
stellar light distribution. Nevertheless, despite the improvements in stellar mass distribution issued from spectral energy
distribution(SED)models,theestimationofthemass-to-light(M/L)ratiosofstellarcomponents(disk/sandbulge/s)ingalaxiesis
still an open issue. Kinematics of barred galaxies is complicated due to the non-circular streaming motion superposed on the
circular motion. Since interstellar gas is streaming along the bar, rotation velocities tend to show solid-body motion thus the
rotation curve is statistically underestimated along the bar but, depending on the orientation of the bar with respect to the
observational line-of-sight, barred galaxies might display faster rotation velocity within the inner disk. Nevertheless for barred
galaxies, more sophisticated modeling of non-circular motions is needed based on 2D velocity measurements and on numerical
methodbasedonN-bodysimulations.Sofar,galaxymassdistributionhasmainlybeenconstrainedforlatetypegalaxieswithno
bulge and for small samples of galaxies. The difficulty in studying galaxies with prominent bulges is that bulge and disk stellar
populationsaredifferent.Indeed,dependingonthecolorsusedtomakebulge/diskdecompositions,thebulgetodiskprominence
mayvary.
Rotationanddynamicsofhigh-redshiftgalaxiesareamongthemajorsubjectsinthegalaxyevolutionarea.Despitethedifficultyto
samplecorrectlytherotationofdistantspiralgalaxiestothelackofspatialresolution,uptoredshiftsz=3,theyappearsofarto
shownoparticulardifferenceinrotationcurveshapesfromthoseofnearbygalaxies.Thismightimplythatthedynamicalstructures
ofspiralgalaxieswerealreadyreachedattheseredshifts.However,theinnerrotationcurvesofhigh-redshiftgalaxiesarestillnot
preciseenoughtobecomparedwiththoseofnearbygalaxiesandinadditiontheirvelocitydispersionisusuallynotnegligiblysmall
compared to rotational velocity, which implies that the pressure term is not negligible. Higher resolution rotation curves at high
redshiftsarecrucialtoinvestigatedynamicalevolutionofdiskgalaxiesandtheirmergingprocesses.