The Use of Brightest Cluster Galaxies as Standard Candles Since z~1

<p>Finding a new way to measure distances to galaxy clusters would allow currentcosmological models to be tested and/or constrained. We propose to accomplish this byusing a distance indicator that was investigated by Postman and Lauer (1995). They useda relationship discovered by Hoessel (1980) that compares the metric luminosity, withinthe inner 10 h^-1 kpc, of a brightest cluster galaxy (BCG) to the logarithmic slope of itssurface brightness profile (α = d log L / d log r). Postman and Lauer proved that thisrelationship did provide a standard candle based on BCG’s for distances to a redshift of z~ 0.05. With new data from the HST, we now have images of much more distant galaxyclusters than ever before (z~1). With this data, we can test to see if the relationship holdstrue over much larger distances. A problem that is always present within this work is theprocess of deciding how much light comes from the actual galaxy and how much comesfrom nearby galaxies.</p><p>We use a program called GALFIT (Peng 2009) to fit the galaxies and remove thelight that comes from objects other than the BCG within the cluster’s core. This providesan even clearer look into the galaxy cluster, allowing our measurements to be that muchmore precise. Using images from the HST ACS provided in the ESO Distant ClusterSurver (EdisCS), we have reduced data for ten different clusters. Of the original ten,alpha parameters could be found for seven of these clusters. We also got alpha values for12 additional clusters from the HST Archive Galaxy-Scale Gravitational Lens Survey(HAGGLeS). We used the exact same equation that Postman and Lauer created to fittheir data, simply adjusting the intercept to account for our F814W bandpass. Our best χ²fit is of the form: M_m = -20.809 – 4.397α + 2.738α². This fit increases the scatter of themagnitudes from 0.198 mag (intrinsic) to 0.270 mag (corrected). A possible redshift-αrelation was found to exist and warrents more investigation. K- and evolution correctionsactually decrease the effectiveness of the plot. We also discovered that the passbandplays no effective role in the change of the α parameter. We therefore conclude thatthere must be some sort of change that is occurring at high redshifts that affects theluminosity distribution, whether it be structural or a need to have different evolutionassumptions for different galaxies.</p>

Name thesis:degree_name

Bachelor of Sciences

Level thesis:degree_level

bachelors

Discipline thesis:degree_discipline

Physics and Astronomy

Grantor dc:publisher

Ohio University Art and Sciences Honors Theses

Year dc:date

2010

Author dc:creator

• Peery, Tyler Robert

Contributors dc:contributor

• Clowe, Douglas

• Astronomy
• Astrophysics
• Physics
• galaxy clusters
• brightest cluster galaxy
• standard candle

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276623279

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ouashonors1276623279