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Articles 1 - 7 of 7
Full-Text Articles in Stars, Interstellar Medium and the Galaxy
Response Of Galactic Disks To Dark Matter Halo Triaxiality, Alex J. Hutton
Response Of Galactic Disks To Dark Matter Halo Triaxiality, Alex J. Hutton
College of Graduate Studies: Theses & Dissertations
In this study we examine the influence of dark matter halo triaxiality on the evolution of galactic disks. We do this by running a series of collisionless N-body models. In a first set of models we place the galactic disk within an oblate halo at various orientations and examine the resulting evolution. In our second set we construct fully self-consistent models of a stellar disk embedded within a spherical halo, with an impacting external dark matter dwarf galaxy. After evolving the simulations for a Hubble time, we examine the disk orientation and warping along with other quantities such as bar …
Dipole Bound Excited States Of Polycyclic Aromatic Hydrocarbons Containing Nitrogen And Their Relation To The Interstellar Medium, Mallory L. Theis
Dipole Bound Excited States Of Polycyclic Aromatic Hydrocarbons Containing Nitrogen And Their Relation To The Interstellar Medium, Mallory L. Theis
Honors College Theses
Polycyclic aromatic hydrocarbons (PAHs) are the most abundant type of molecule present in the interstellar medium (ISM). It has been hypothesized that nitrogen replacement within a ring is likely for PAHs present in the ISM. Additionally, electrons, protons, and hydrogen atoms are readily added to or removed from PAHs creating a truly diverse set of chemistries in various interstellar regions. The presence of a nitrogen within a PAH (called a PANH herein) that is additionally dehydrogenated leads to a neutral radical with a large dipole moment. It has recently been shown through the use of high-level quantum chemical computations for …
Secular Damping Of Stellar Bars In Spinning Dark Matter Halos, Stacy Long, Isaac Shlosman, Clayton Heller
Secular Damping Of Stellar Bars In Spinning Dark Matter Halos, Stacy Long, Isaac Shlosman, Clayton Heller
Physics & Astronomy: Faculty Publications
We demonstrate using numerical simulations of isolated galaxies that growth of stellar bars in spinning dark matter halos is heavily suppressed in the secular phase of evolution. In a representative set of models, we show that for values of the cosmological spin parameter λ ≳ 0.03, bar growth (in strength and size) becomes increasingly quenched. Furthermore, the slowdown of the bar pattern speed weakens considerably with increasing λ until it ceases completely. The terminal structure of the bars is affected as well, including extent and shape of their boxy/peanut bulges. The essence of this effect lies in the modified angular …
Dissecting Galaxy Formation. Ii. Comparing Substructure In Pure Dark Matter And Baryonic Models, Emilio Romano-Diaz, Isaac Shlosman, Clayton Heller, Yehuda Hoffman
Dissecting Galaxy Formation. Ii. Comparing Substructure In Pure Dark Matter And Baryonic Models, Emilio Romano-Diaz, Isaac Shlosman, Clayton Heller, Yehuda Hoffman
Physics & Astronomy: Faculty Publications
We compare the substructure evolution in pure dark matter (DM) halos with those in the presence of baryons, hereafter PDM and BDM models, respectively. The prime halos have been analyzed in the previous work. Models have been evolved from identical initial conditions which have been constructed by means of the constrained realization method. The BDM model includes star formation and feedback from stellar evolution onto the gas. A comprehensive catalog of subhalo populations has been compiled and individual and statistical properties of subhalos analyzed, including their orbital differences. We find that subhalo population mass functions in PDM and BDM are …
Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Collisionless Models Revisited, Jorge Villa-Vargas, Isaac Shlosman, Clayton Heller
Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Collisionless Models Revisited, Jorge Villa-Vargas, Isaac Shlosman, Clayton Heller
Physics & Astronomy: Faculty Publications
We construct and evolve three one-parameter families and one two-parameter family of steady-state models of stellar disks embedded in live dark matter (DM) halos in order to study the dynamical and secular phases of bar evolution. These models are tested against those published in the literature in order to extend them and to include the gaseous component in the follow-up paper. Specifically, we are interested in the angular momentum, J, redistribution in the disk-halo system during these two evolutionary phases without distinguishing between the resonant and non-resonant effects. We confirm the previous results and quantify for the first time …
Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula
Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula
Physics & Astronomy: Faculty Publications
We investigate formation and evolution of galactic disks immersed in assembling live DM halos. Models have been evolved from cosmological initial conditions and represent the collapse of an isolated density perturbation. The baryons include gas participating in star formation (SF) and stars with the energy feedback onto the ISM. We find that (1) the triaxial halo figure tumbling is insignificant and the angular momentum (J) is channeled into the internal circulation, while the baryonic collapse is stopped by the centrifugal barrier; (2) density response of the (disk) baryons is out of phase with DM, thus washing out the …
Gas Feedback On Stellar Bar Evolution, Ingo Berentzen, Isaac Shlosman, Inma Martinez-Valpuesta, Clayton Heller
Gas Feedback On Stellar Bar Evolution, Ingo Berentzen, Isaac Shlosman, Inma Martinez-Valpuesta, Clayton Heller
Physics & Astronomy: Faculty Publications
We analyze evolution of live disk-halo systems with gas fractions, fgas ≤ 8% of the disk mass, for 5 Gyr. Specifically, we have addressed the issue of angular momentum (J) transfer from the gas to the stellar bar and its effect on the bar. We find that the bar weakening, reported in the literature, is not related to the gas, but is caused by the vertical buckling instability in the gas-poor disks and by a steep stellar heating by the central mass concentration (CMC) in the gas-rich disks. However, the gas has a profound effect on the …