Degree Year

1996

Document Type

Thesis

Degree Name

Bachelor of Arts

Department

Physics and Astronomy

Advisor(s)

Daniel Stinebring

Keywords

Disk galaxies, Galactic evolution, Galactic halos, Galactic structure, NGC891

Abstract

Understanding how galaxies evolve is a challenge for astronomers, given the very long timescales for such evolution to occur. Fortunately, the structure of a galaxy encodes a fossil record of its evolution. In particular, by decomposing this structure into a number of independent components, we can compare the results to theoretical predictions and begin to trace the history of mass accretion and star formation that have shaped the stellar systems we see today.

In this thesis, I present deep optical R-band surface photometry of the nearby edge-on spiral galaxy NGC891. This galaxy bears many similarities to the Milky Way, and thus exploring its structure can improve our understanding of our own Galaxy's evolution. Using a method developed by collaborators to carefully exposure-correct the image data and remove contributions of foreground stars, I am able to detect diffuse stellar light from NGC891 to a level 8 magnitudes (or 1500 times) fainter than the night sky background. Using one-dimensional surface brightness profiles extracted perpendicular to the galactic disk, I detect two vertically extended stellar disk components: a "thin disk" with scale height 0.6 kpc; and a "thick disk" with scale height of 1.7 kpc. The thin disk is considerably more extended than the corresponding component in the Milky Way, perhaps because of heating from the more massive molecular cloud layer in NGC891. The origin of the extended thick disk is not completely understood at this time and requires further two-dimensional modeling. Such modeling will also help constrain the presence of an extended stellar halo, which is not detected in this work.

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Physics Commons

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