Anders Paaske Drachmann Master's Defense

Title: Dust production in late-type high-mass stars - the significance and contribution to the ISM

Supervisor: Anja C. Andersen


Cosmic dust, that dominate the solid phase of matter in the universe, not only shapes what we observe – observations of star formation, quasars, supernovae and hence dark energy –are all profoundly affected by dust, but the presence of dust also dictates the formation of low- and high-mass stars, the making of planets, and the formation of molecules in space. Yet, we do not know the formation site of most dust. Recent ob- servations by infrared (IR) space telescopes have made it easier to investigate proba- ble production sites of dust such as supernova remnants (SNR) which show promising results of dust production. However, recent observations and theoretical studies sug- gests that the reverse shock from the supernova (SN) might be destroying significant amounts of the dust.

Lately, a large population of dusty shells around high mass stars in our Galaxy has been found, which indicate that high mass stars could be contributing to the overall dust budget as well. From a sample of 10 Spitzer identified high mass stars with cir- cumstellar dust shells I use new photometric data from the Herschel Space Observatory to determine their spectral energy distribution (SED). By fitting each SED with a two- component black-body function I find the dust masses and temperature of the shells using silicate- and carbon- based models. With a dust minimum of 0.1 M⊙ per SN to explain for the majority of dust produced in early galaxies, the results suggests that late-type high mass stars indeed could be able to produce noticeable amounts of dust. It seems that high mass stars could be an important contributor to the dust budget of the ISM, perhaps on the same level as SNRs.

Censor: Max Striztinger, Aarhus University

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