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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Search for Dwarf Emission Line Galaxies in Galaxy Voids

Draper, Christian D 01 August 2019 (has links)
The population and formation of dwarf galaxies, Mr > −14, contain clues about the nature of dark matter. The best place to search for these dwarf galaxies without influence from nearby large galaxies is within galaxy voids, where no galaxies have yet been found. To search for this potential dwarf galaxy population we have developed and applied a new photometric technique. We use three redshifted Ha filters, designated Ha8, Ha12, and Ha16, along with the Sloan broadband filters, g', r', and i' to identify emission line galaxies. From the ratio of the object flux through the Ha filters, Ha12-Ha8 and Ha12-Ha16, we are able to determine the distance to these galaxies and the strength of the emission line captured in the filter set. One problem with using just the three Ha filters is that the system will be sensitive to any emission line which has been redshifted enough to fall within the set. Of particular concern are the [OII] and [OIII] lines which will contaminate the sample. To overcome this we use a color-color relation, g' - r' and r' - i', to help separate which type of emission has been detected. We have applied this method to search for galaxies within the void FN2 and FN8. From this we have found 23 candidate objects which could have Ha emission placing them inside of the void. To better understand the population density dwarf galaxies through voids we have also modeled the population of objects which we will detect having Ha emission compared to the contamination of back ground objects which we can then use to compare the density in the void with the mean galaxy density. We have also begun taking spectra of the emission objects, to ensure our method does detect emission line objects, to test how well the distance and emission strength determination is, and to begin identifying which type of emission we have detected. To date we have taken spectra on 6 objects. All 6 showed emission, 4 with [OII] and 2 with [OIII]. Though none was Ha we formed a “pseudo-redshift” to determine the accuracy of our measurements. This shows that our method is accurate to -127+-204 km/sec.

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