Drivers of Galaxy Fueling
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Stark, David. Drivers of Galaxy Fueling. Chapel Hill, NC: University of North Carolina at Chapel Hill Graduate School, 2015. https://doi.org/10.17615/wqgd-1b33APA
Stark, D. (2015). Drivers of Galaxy Fueling. Chapel Hill, NC: University of North Carolina at Chapel Hill Graduate School. https://doi.org/10.17615/wqgd-1b33Chicago
Stark, David. 2015. Drivers of Galaxy Fueling. Chapel Hill, NC: University of North Carolina at Chapel Hill Graduate School. https://doi.org/10.17615/wqgd-1b33- Last Modified
- March 19, 2019
- Creator
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Stark, David
- Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
- Abstract
- In an effort to clarify the connection between the evolution of galaxies and their surroundings, this work investigates how environment influences the fueling of galaxies. We explore when and where environmental mechanisms play a major role in both the conversion of gas into stars and the replenishment of galaxy gas reservoirs over time, as well as the loss of gas due to heating or stripping. We identify multiple connected evolutionary sequences in a fueling diagram that relates global molecular-to-atomic gas ratios and mass-corrected blue-centeredness, a metric tracing the degree to which galaxies have bluer centers than the average galaxy at their stellar mass. Most spiral galaxies follow a positive correlation between global molecular-to-atomic gas ratios and mass-corrected blue-centeredness, suggesting that minor mergers and interactions between galaxies play a systematic role in driving gas inflows that replenish star forming molecular gas. We also identify a population of blue-sequence E/S0 galaxies (with masses below key scales associated with transitions in gas richness) that occupy a distinct regime of the fueling diagram. These galaxies appear to be the result of gas-rich major mergers, and show signs of rebuilding their gas disks through fresh gas accretion as they emerge from their recent central starburst. We next investigate the potential for star formation in the Smith Cloud, a "high-velocity cloud" currently interacting with the Milky Way. This study explores whether low density clouds of gas that serve to refuel the gas reservoirs of galaxies like the Milky Way can themselves be sites of star formation prior to accretion (possibly driven by tidal interactions with their larger host). Finding star formation might also suggest that the Smith Cloud, and potentially other high-velocity clouds, are really dwarf galaxies. We do not identify a statistically significant number of candidate young stars in projection with the cloud. However, we note several striking similarities between the Smith Cloud and the recently discovered galaxy, Leo P, a high velocity cloud with a confirmed stellar population. The young stars in Leo P would not yield a statistically significant detection if Leo P were placed at the Smith Cloud's distance and projected location near the Milky Way, leaving open the possibility that the Smith Cloud may yet prove to be a dwarf galaxy. We conclude by analyzing how how different environmental scales influence the global atomic gas fractions and spectral profiles of galaxies, employing the new ~90% complete RESOLVE atomic gas census and a variety of metrics designed to characterize the local and large-scale environments of galaxies. We show that satellites below M*=10^10 Msun experience gas depletion in moderate-mass (~10^12 Msun) group dark matter halos, well below the scale of massive galaxy groups and clusters. We also identify a significant population of gas-depleted centrals in low mass (<10^11.4 Msun) dark matter halos that cluster around more massive groups. This population is consistent with being the result of flyby interactions, where galaxies fly into a more massive group dark matter halo, have their gas stripped, then fly back out. At fixed group halo mass, we identify systematically higher gas-to-stellar mass ratios in satellites within filaments compared to satellites within walls. The observed differences are too large to be explained by different stellar mass distributions, and are consistent with walls being in a more evolved state compared to present-day filaments. Lastly, we find no robust results linking HI profile asymmetries to gas accretion or tidal interactions, but we argue that revisiting this analysis will be worthwhile, as our existing data are affected by two competing biases that can be eliminated or quantified in future work.
- Date of publication
- May 2015
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- Rights statement
- In Copyright
- Advisor
- Kannappan, Sheila
- Henning, Reyco
- Reichart, Daniel
- Heitsch, Fabian
- Cecil, Gerald
- Degree
- Doctor of Philosophy
- Degree granting institution
- University of North Carolina at Chapel Hill Graduate School
- Graduation year
- 2015
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- Place of publication
- Chapel Hill, NC
- Access right
- There are no restrictions to this item.
- Date uploaded
- August 25, 2015
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