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Vertical structures of late-type edge-on disk galaxies

Berg, O. van den (2006) Vertical structures of late-type edge-on disk galaxies. Master's Thesis / Essay, Astronomy.

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The study of the vertical structures of the disks of late-type spiral galaxies is very important as it holds the key to unravelling the formation and evolution of disk galaxies. For example, the uncertainty if all late-type galaxies possess a thick disk, a faint extended disk component containing old stars, plays an important role in this discussion. To address this question, we collected a pilot sample of 11 late-type disk galaxies, observed in the near-infrared J- and or K'-lter, creating images with high S/N and very at backgrounds. Various kinds of structure decomposition was done on vertical surface brightness proles to discover if the galaxies contained thick disks or not and what their parameters would be. We create vertical colour prole sets for six galaxies available in the J- and K'-band to determine their colour gradients and hence insight in their stellar population. Our 2D two disk (thin+thick) ts conrm the results of Yoachim & Dalcanton (2006) as we nd clear thick disk components in all our sample galaxies except for one case, where the possible existence of a thick disk cannot be excluded. However, our results show clear dierences. We only nd thick disk components in our high-mass galaxies (vrot > 120 km s1). For two low-mass galaxies added to our sample we conrm a distinct vertical structure but those could not be tted as a superposition of thin+thick disk. Our thick disk parameter values show also fainter and atter thick disks than their high-mass galaxies, with an average dierence between n and k (the central surface brightness for the thin and thick disk) of 4.5 0.7 mag arcsec2 and an average scaleheight ratio of 5.6 1.8. Tests of our tting methods on articial galaxies showed that truncated galaxies, a commonly observed phenomenon, will show various deviations from the input parameters, making it dicult to assess the quality of the individual results. Our (J K) colour gradients show distinct blueing at larger distance from the plane. This is in contrast to the (B I) results of De Grijs & Peletier (2000) who nd no clear gradient and even a slight reddening at larger scaleheight. Their result is probably aected by star formation near the plane. Our results stay within the Bruzual-Charlot models, showing dust has little influence even close to the galactic plane on our colour proles. This in contrast to the (R K) results by Dalcanton & Bernstein (2002) who address their inner reddening to dust in uence.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Astronomy
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:28
Last Modified: 15 Feb 2018 07:28

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