Imagerie à haute résolution des amas R136 et NGC3603 dévoilent la nature de leurs populations ...

292 Pages·2016·20.74 MB·English

by  Zeinab Khorrami

´
UNIVERSITE DE NICE-SOPHIA ANTIPOLIS
UFR Sciences
Ecole Doctorale des Sciences Fondamentales et Appliqu´ees
`
T H E S E
pour obtenir le titre de
Docteur en Sciences
de l’UNIVERSITE de Nice-Sophia Antipolis
Sp´ecialit´e: Astrophysique Relativiste
pr´esent´ee et soutenue par
Zeinab KHORRAMI
Laboratoire Lagrange - UMR7293, Observatoire de la Coˆte d’Azur
T I T R E
A sharpened close-up of R136 and NGC3603:
unshrouding the nature of their stellar population
Soutenue le 22 Juin 2016 `a l’Observatoire de la Cˆote dAzur
Membres du jury :
M. Farrokh Vakili Directeur de th`ese
M. Thierry Lanz Co-directeur de th`ese
M. Mathias SCHULTHEIS Pr´esident du jury
M. Fabrice MARTINS Rapporteur
M. David MOUILLET Rapporteur
Mme Caroline SOUBIRAN Examinateur
M. Richard WUNSCH Examinateur
M. Pascal CHARDONNET Examinateur

In memory of
Olivier

Abstract
The aim of this thesis is to understand the different aspects of the dynamical and
stellar evolution of very massive clusters. These newly formed massive clusters are
the most important link between the formation of the massive star clusters and
their evolution. We chose two young massive clusters, located in the most mas-
sive Galactic/extra-Galactic HII regions, NGC3603 and R136 which hosts the most
massive stars in the local universe.
This thesis contains the photometric analysis of the core of R136 and NGC3603 using
the Hubble Space Telescope (HST) data in the visible and the Very Large Telescope
(VLT/SPHERE) in the infrared. Thanks to SPHERE extreme AO system, I detected
manyfaintlow-massstarsforthefirsttimeinthecoreofbothclustersinthevicinityof
massive bright objects. Comparing the results of the HST and SPHERE photometry
analysis, NGC3603 shows no signature of mass segregation in its core for two main
reasons: First, the MF slope in the very core is not flatter than the next radial bin.
Second, both slopes are similar to the MF values found in previous works for the
outer regions. R136 is partially resolved in SPHERE/IRDIS data. The majority
(above 90%) of massive stars (brighter than 17 mag in K and 16 mag in J) have
visual companions closer than 0.2”. Among them, R136a1 and R136c have visual
companions detected for the first time. R136a3 is resolved as two stars (PSF fitting).
Consideringthespectroscopicandphotometricerrorsontheextinction(AJ = 1.3±0.5
and AK = 0.4±0.5) and the age (1.8+−01..28 Myr) of the cluster members, we estimate a
mass range for each detected star. The generalized histogram of stellar masses (MF)
was plotted at different ages with given errors on each stellar mass. We created series
of simulated images of R136 from the output of Nbody6 code, to be compared with
the HST/WFPC2 data of R136. These numerical simulations are done in order to
check the effect of initial binarities, mass segregation and stellar evolution on the
dynamical evolution of R136-like clusters at the early stages of their life (4 Myr).
The analysis of the bright stellar population (spectroscopic and photometry), shows
thatweneedmoreresolutiontogofurtheronstudyingR136whichis7-8timesfurther
thanNGC3603. ThespectroscopicanalysisfindverymassivestarsinthecoreofR136
where, for some of them SPHERE data has resolved them visually.
Future instruments with higher angular resolution (milliarcsec) like E-ELT (MI-
CADO), JWST and VLTI/GRAVITY can resolve the compact core of R136 and
similar objects at further distances. The kinematics of the core of these compact
clusters can be studied by using astrometric analysis with µarcsec accuracy with
GRAVITY in near future.
Keywords: Star clusters: individual (R136, NGC3603)- Stars: imaging- Stars: lumi-
nosity function, mass function- Stars: massive- Stars: pre-main sequence- Instrumen-
tation: high angular resolution- Methods: numerical- Methods: observational

R´esum´e
Cette th`ese a pour objectif de comprendre les diff´erents aspects de l’´evolution des
amas d’´etoiles massives NGC3603 et R136 qui poss`edent les ´etoiles les plus mas-
sives connues de l’univers local. L’analyse photom´etrique des noyaux de R136 et
NGC3603 utilisant l’imagerie infrarouge de l’instrument SPHERE sur VLT et son
syst`eme d’optique adaptative extrˆeme de SPHERE, m’a permis de d´etecter pour la
1i`ere fois un grand nombre d’´etoiles de faible masse et luminosit´e au coeur de ces
amas et pour la plupart au voisinage des ´etoiles les plus lumineuses et massives. La
comparaison des donn´ees de SPHERE de NGC3603 a` celles du HST montre l’absence
de s´egr´egation de masse dans le noyau de cet amas. De plus la pente de la fonction
de masse de cette r´egion est la mˆeme que celle de la r´egion suivante et similaire aux
valeurs de la MF correspondant aux r´egions ext´erieures de l’amas connues jusqu’ici.
L’amas R136 est partiellement r´esolu par SPHERE/IRDIS dans l’IR. La majorit´e de
ses´etoilesmassivesontdescompagnonsvisuels. Enprenantcomptedesmesuresspec-
troscopiques et photom´etriques et leurs erreurs sur l’extinction et l’ˆage des membres
del’amas, j’aiestim´eunegammedemassespourchaque´etoileidentifi´ee. LaMFa´et´e
calcul´ee pour diff´erents ˆages ainsi que les erreurs sur les masses stellaires. J’ai simul´e
des s´eries d’images de R136 graˆce au code Nbody6, et les ai compar´ees aux observa-
tions du HST/WFPC2. Ces simulations permettent de v´erifier l’effet de la binarit´e
initiale des ´etoiles de l’amas, la s´egr´egation de masse et l’´evolution des ´etoiles sur
l’´evolution dynamique propre a` R136. Ces analyses d´emontrent l’importance d’une
r´esolution angulaire encore plus fine pour mieux comprendre la nature physique de
R136, qui se trouve a` une distance 7-8 fois plus loin que NGC3603. Les ´etudes spec-
troscopiques ont trouv´e des ´etoiles super massives dans le noyau de R136, alors que
notre pr´esent travail avec SPHERE r´esoud clairement certaines d’entre elles comme
multiples visuelles.
Mots-cl´es: Lesamasstellaires: individuel(R136,NGC3603)-Etoiles: ´etoilesmassives
- Imagerie-: fonction de masse-luminosit´e, fonction de masse - Etoiles : pr´es´equence
principale Etoiles: s´equenceprincipale-Instrumentation: hauter´esolutionangulaire
M´ethodes: num´erique M´ethodes : observationnelle

ACKNOWLEDGMENTS
Itismygreatpleasuretowritetheacknowledgementsafterallthehardworkwritingmythesis.
Firstly, I would like to express my sincere gratitude to my supervisor, Farrokh Vakili, for his
continuoussupportduringmyPh.Dstudy,withhispatience,motivationandconsiderablefreedom
fordevelopingmyideas. IwouldliketocordiallythankThierryLanz,whohasbeenatremendous
mentorforme. IamreallygratefultoThierryforencouragingmyresearchandforallowingmeto
growasaresearchscientist. IamgladthatIstartedmydoctoraljourneyunderthesupervisionof
Olivier Chesneau. He was a prolific scientist, full of energy, who helped me taking the first steps
onmyproject. HisuntimelydeparturewasatragiclossandweallmissOlivieratOCA.
Besides my supervisors, I would like to thank the rest of my thesis committee: Dr. Mathias
Schultheis, Dr. Fabrice Martins, Prof. David Mouillet, Dr. Richard Wunsch, Prof. Caroline
SoubiranandProf. PascalChardonnet,fortheirinsightfulcomments.
I am also grateful to many collaborators for their contributions to this thesis. I would like
to thank Djamel Mekarnia for his help on using IDL photometric packages and Marcel Carbillet
for teaching me how to work with CAOS. I am grateful to Armando Domiciano De Souza and
Florentin Millour for teaching me how to handle interferometric data (AMBER and MATISSE)
andcreateOBs. IamreallythankfultoMartinVannier,whowasagreatofficemateandfriend,for
numerousdiscussionsonscientificmatters.
My deepest gratitude goes to Richard Wunsch and Jan Palous for the joyful collaboration on
cluster’s formation and evolution, and all their support during my visits to Prague. I am really
thankful to Andreas Kuepper, Pavel Kroupa and Sambaran Banerjee for the helpful discussions
and comments on Nbody6 simulations. I also want to thank Maud Langlois and Hans-Martin
Schmid for their help on IRDIS and ZIMPOL data reduction. I thank Michael Meyer for his
helpfulcommentsanddiscussionsonR136andhissupportduringmyvisittoETH-Zurich.
IthankChrisEvansforprovidingMADcatalogandreduceddataonR136,andAaronDotter
forusefuldiscussionsonthebolometric-correctionsandzero-points.
Inparticular, IwouldliketothankWolfgangBrandnerforhisusefulcommentsonNGC3603
SPHEREresultsandalsoarrangingmyfirstobservationaltriptoParanaltoachieveanexceptional
experienceoffivenightsobservationswithNACO.
I thank Antti Tamm and Jaan Einasto for their warm hospitality on Tartu Observatory during
mymobility.
I want to express my deep acknowledgement to all my colleagues, officemates and friends at
OCAfortheirsupports.
I would have difficulty to complete all the administrative work without the help of Pascal
Chardonnet,PinaBarbaro,EmmanuelLosero,GildasTchibozofromIRAPandallthesecretaries
in Lagrange. I appreciate the help of directors of OCA and Lagrange during my PhD: Farrokh
Vakili, Thierry Lanz and Philippe Stee, and also people in the computational center especially
ArielleWillmandAlainMiniussi.
A special thanks to my dear family, my mother and father, my amazing sister Zahra, Amir,
Sama, Human and my parents-in-law. Words cannot express how grateful I am to my family, for
allofthesacrificesthattheyhavemadeonmybehalf.
At the end I would like to express appreciation to my beloved Samir for his constant love,
supportandfaithinmethroughallthosehardtimestogether.