#### Event Title

### The Absolute Magnitude Distribution of F-Turnoff Stars

#### Location

CSU 202

#### Start Date

21-4-2008 10:00 AM

#### End Date

21-4-2008 12:00 PM

#### Student's Major

Physics and Astronomy

#### Student's College

Science, Engineering and Technology

#### Mentor's Name

Paul Eskridge

#### Mentor's Department

Physics and Astronomy

#### Mentor's College

Science, Engineering and Technology

#### Description

In the past, F-turnoff stars have been used to discover structure in the Milky Way, such as the Sagittarius dwarf tidal stream, and are being used to trace the brightness distribution of stars in the halo. Some studies have assumed a single average absolute brightness (magnitude) for all halo stars with SDSS colors 0.1 < (gr) < 0.3 and others have assumed a Gaussian distribution of absolute magnitudes. This is particularly important as we use more sophisticated methods, including maximum likelihood methods to measure model parameters for the Milky Way more precisely. An absolute magnitude histogram of halo stars from the Besanc;on Galactic model was produced to show the brightness distribution for F-turnoff stars in that model. Comparison of the histogram with the assumed distribution shows that, at least for the model stars, absolute magnitude is not sufficiently described by a simple Gaussian curve. Rather, the model shows a linear increase from ~3.4 in absolute magnitude to the modal value, ~5.7, and falls off quickly to ~6.2. To test the accuracy of this result, data from the Sloan Digital Sky Survey were used to create histograms for ten halo globular clusters. Qualitative comparisons show that the absolute magnitude distributions for these clusters resemble the currently assumed Gaussian distribution more closely than that obtained from the Besançon model. Furthermore, preliminary data suggest that the globular cluster histograms can be adequately described by a skewed Gaussian distribution peaking at ~4.6 with corresponding left- and right-side standard deviations ~0.6 and~ 1.0.

The Absolute Magnitude Distribution of F-Turnoff Stars

CSU 202

In the past, F-turnoff stars have been used to discover structure in the Milky Way, such as the Sagittarius dwarf tidal stream, and are being used to trace the brightness distribution of stars in the halo. Some studies have assumed a single average absolute brightness (magnitude) for all halo stars with SDSS colors 0.1 < (gr) < 0.3 and others have assumed a Gaussian distribution of absolute magnitudes. This is particularly important as we use more sophisticated methods, including maximum likelihood methods to measure model parameters for the Milky Way more precisely. An absolute magnitude histogram of halo stars from the Besanc;on Galactic model was produced to show the brightness distribution for F-turnoff stars in that model. Comparison of the histogram with the assumed distribution shows that, at least for the model stars, absolute magnitude is not sufficiently described by a simple Gaussian curve. Rather, the model shows a linear increase from ~3.4 in absolute magnitude to the modal value, ~5.7, and falls off quickly to ~6.2. To test the accuracy of this result, data from the Sloan Digital Sky Survey were used to create histograms for ten halo globular clusters. Qualitative comparisons show that the absolute magnitude distributions for these clusters resemble the currently assumed Gaussian distribution more closely than that obtained from the Besançon model. Furthermore, preliminary data suggest that the globular cluster histograms can be adequately described by a skewed Gaussian distribution peaking at ~4.6 with corresponding left- and right-side standard deviations ~0.6 and~ 1.0.

#### Recommended Citation

Simones, Jacob. "The Absolute Magnitude Distribution of F-Turnoff Stars." *Undergraduate Research Symposium*, Mankato, MN, April 21, 2008.

https://cornerstone.lib.mnsu.edu/urs/2008/oral-session-04/2