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A comprehensive study of the young star cluster HD 97950 in NGC 3603

Pang, Xiaoying

German Title: Eine umfassende Studie des jungen Sternhaufens HD 97950 in NGC 3603

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Abstract

I study the young massive star cluster HD,97950 located in the Galactic giant H,{sc ii} region NGC,3603. My goals are (1) to estimate the survival probability of the cluster, (2) to investigate the origin of its mass segregation, and (3) to investigate the interplay between the cluster and the surrounding interstellar medium (ISM). All the studies are done with data of the Hubble Space Telescope. I determine the cluster velocity dispersion from the stars' relative proper motions, and calculate the virial mass of the cluster. The cluster star formation efficiency is estimated to be about 50%, which suggests that the HD,97950 cluster will most likely survive as a bound cluster to gas expulsion. I apply the $Lambda$ minimum spanning tree technique to measure the mass segregation down to 30,M$_{odot}$. The high-mass stars are more segregated than low-mass stars, implying that the mass segregation in HD,97950 is mostly of dynamical origin. To improve the age determination for the cluster stars that are severely reddened by the surrounding dusty ISM, I compute a pixel-to-pixel distribution of the gas reddening, $E(B-V)_{rm g}$, associated with the cluster. The radial profiles of $E(B-V)_{rm g}$ show significant spatial variations around HD,97950. Using $UBVRI$ photometry, I estimate the stellar reddening of cluster stars. After correcting for foreground reddening, the total to selective extinction ratio in the cluster is $R_V=3.49pm0.79$. The extinction curve in the $UBVRI$ filters in the cluster is greyer than the average Galactic extinction laws, but close to the extinction law for starburst galaxies. This indicates that stellar feedback from massive stars changes the dust properties in the HD,97950 cluster in a similar way as in starburst galaxies.

Translation of abstract (German)

Ich studiere den jungen massereichen Sternhaufen HD,97950 in der Riesen-H,{sc ii}-Region NGC,3603 im Carina-Spiralarm. Ich sch"atze seine "Uberlebenswahrscheinlichkeit ab, untersuche die Ursachen seiner Massensegregation und studiere das Wechselspiel zwischen dem Sternhaufen und dem umgebenden interstellaren Medium (ISM). Alle Untersuchungen verwenden Daten des Hubble-Teleskops(HST). Ich bestimme die Geschwindigkeitsdispersion des Sternhaufens aus der relativen Eigenbewegung seiner Sterne und berechne seine Virialmasse. Die Sternenstehungseffizienz des Sternhaufens (SFE) sch"atze ich auf etwa 50%, was nahelegt, dass HD,97950 den Aussto{ss} seines Gases als gebundener Sternhaufen "ueberleben wird. Ich verwende die $Lambda$ minimum spanning tree Technik zur Messung der Segregation oberhalb 30,M$_{odot}$. Massive Sterne unterliegen st"arkerer Segregation, was nahelegt, dass die Massensegregation prim"ar dynamischer Natur ist. Um die Altersbestimmung f"ur Sterne zu verbessern, die durch das ISM starke Verf"arbung erfahren, berechne ich die Verteilung des Farbexzesses $E(B-V)_{rm g}$ des mit dem Sternhaufen assoziierten Gases Pixel f"ur Pixel. Die Radialprofile von $E(B-V)_{rm g}$ zeigen signifikante r"aumliche Variationen um HD,97950. Anhand von $UBVRI$-Photometrie erforsche ich die stellare Verf"arbung in der Region. Die Extinktionskurven in den $UBVRI$ Filtern sind grauer als die Gesetze der mittleren galaktischen Extinktion,"ahneln aber dem Extinktionsgesetz f"ur Starburstgalaxien. Dies deutet darauf hin, dass massive Sterne die Staubeigenschaften in HD,97950 durch R"uckkopplung ver"ndern, "ahnlich wie in Starburstgalaxien.

Item Type: Dissertation
Supervisor: Grebel, Prof. Dr. Eva
Date of thesis defense: 21 May 2012
Date Deposited: 05 Jun 2012 07:35
Date: 2012
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 520 Astronomy and allied sciences
Controlled Keywords: Astronomie
Uncontrolled Keywords: Sternhaufen , Extinktionen , HII Region , Hauptreihenstern , Vor Hauptreihenstern , StellardynamikStar cluster , Extinction , HII region , Main sequence stars , Pre-main sequence stars , stellar dynamics
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