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Isolating the dark matter component of these galaxies requires surface brightness profiles to quantify their stellar mass, rotation curves to derive their dynamical mass, and gas density profiles to quantify their gas mass. Obtaining a complete set of optical surface brightness profiles and a rotation curve for each galaxy provides the tools, lacking prior to our work, for studying the dark matter component of these galaxies. Because this thesis is a precursor to the dark matter measurments, the next steps that would bring us closer to that goal are to improve the quality of our photometric and kinematic data and to gather any missing data. For example, longer exposure times for D500-4, better spatial resolution for the IFU data, and 21-cm observations to map the extended gas disk of these galaxies would be useful.

each filter while all other galaxies were exposed for either 300 or 600 seconds, depending on the filter. Longer exposure times are necessary to obtain more detailed surface brightness profiles of this galaxy.

To improve the quality and accuracy of rotation curves, kinematic models that allow all parameters to vary are ideal. The rotation curves derived in this thesis were extracted from velocity maps containing few data points. The low number of data points required, for most best-fit kinematic models, that all geometry (ellipticity, position angle, center) parameters and the systemic velocity to be fixed to the average photometric values. The low number of data points used to map each galaxy results from the spatial resolution of the fibers used to obtain spectra. Compared to the small angular size of these galaxies, the 500 SparsePak fibers encompass large portions of the disk. Mapping velocity fields with smaller fibers would improve spatial resolution, making it possible to obtain more data points for DiskFit to use during fits, while allowing parameters to adjust.

The characteristic rotation curve flattening was only observed for D723-5, implying that optical observations of most of these galaxies are not enough to probe all of their dark matter content. LSB dwarfs have a gas to stellar mass fraction of about∼ 0.7 (Eder & Schombert 2000), indicating that they are gas rich. Their HI disks typically extend out ∼ 2.4 times that of their optical disks (van der Hulst et al. 1993), making HI observations necessary to probe these extended cold gas disks to infer a mass that encompasses all stellar, gas, and dark matter mass, from derived rotation curves.

Hα rotation curves for D500-4, D575-7, D631-7, and D723-5. The low surface brightness nature and small size of LSB dwarfs limits both the number of these galaxies that we can study and the quality of data, particularly kinematic data, that we can produce for them. Galaxies that are nearby and bright enough are typically selected for photometric and kine- matic analysis, but these characteristics are not enough to guarantee that their observed velocity fields will display well-ordered rotation; we started with 8 galaxies, all nearby and bright enough to observe, but we reduced our sample because half of the velocity fields did not show signs of organized rotation. In instances that we do see well-ordered rotation, obtaining good spatial resolution is a challenge because we are limited by the resolution of the available instruments; we mapped velocity fields with few data points because of the SparsePak fiber sizes, making the model fitting process more of a challenge.

Observing our galaxies with the the HexPak fiber bundle (WIYN telescope at KPNO) would improve the quality of our kinematic data. HexPak, a 4100x 3600 hexagon comprised of fibers with 100 and 300, provides the smaller fiber sizes that are needed to increase the spatial resolution of our velocity maps.

Additionally, Observing our galaxies with the Very Large Array (VLA) radio telescope (NRAO), comprised of 27 antennae, would provide the HI data we are currently missing. The VLA covers the submillimeter wavelength range that would allow us to obtain 21cm density profiles needed to measure gas mass and would make it possible to get a complete rotation curve of each galaxy by sampling velocities across the extended gas disk.

image objects as faint as 31 mag while avoiding interference from the earth’s atmosphere as a result of its space based nature. Our LSBs are faint objects with central surface brightnesses ranging between ∼21-23 mag arcsec−2_{, bright enough to be detected by HST. Observing} these galaxies outside of the earth’s atmosphere with WFC3 and applying longer exposure times would provide better quality images that would allow us to derive more detailed surface brightness profiles.

Despite this thesis being the first step in characterizing these photometric and kinematic properties of these galaxies, the information that we were able to extract from our data looks promising. These galaxies are consistent, well-behaved disk-only galaxies that display no warps, making them perfect candidates for dark matter halo studies.

Appendices

The following section presents the observed velocity fields of 4 galaxies in the original 8 galaxy sample. These galaxies were excluded from this study because their observed velocity fields obtained with the SparsePak IFU, did not show clear signs of rotation. Details are discussed below.

A Additional Galaxies

The same observation techniques and data reduction methods applied to D500-4, D575-7, D631-7, and D723-5 were also applied to D575-1, D646-7, D640-13, and D723-9; Hα, [SII], and [NII] emission were used to measure velocities and the same IDL code was applied to generate velocity maps. The observed velocity fields for these galaxies, seen in Figure A.1, did not display well-ordered rotation and were therefore excluded from the sample. Each pointing allows fibers to sit on a galaxy for 1800 seconds, gathering as many photons as possible for these faint objects. Only one pointing was applied to D646-7 and it was cut short in exposure time as a result of bad weather conditions. It did not produce conclusive results.

Figure A.1 Observed Velocity Fields for D575-1, D646-7, D640-13, D723-9

First row: SDSS g-band images. Second row: SparsePak Fiber placement over each galaxy. Third row: Observed velocity maps.

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