146 research outputs found
Searching for utopia
Professional project report submitted in partial fulfillment of the requirements for the degree of Masters of Arts in Journalism from the School of Journalism, University of Missouri--Columbia."Searching for Utopia" is a multimedia project about the Chautauqua gated community in western New York, which is perceived by people outside the gates as a utopian place. Through the use of multimedia I try to convey why people perceive Chautauqua as an ideal living space. Additionally, through photo-elicitation interviews with people from the Chautauqua community, respondents explain how they perceive Chautauqua, and if they find it a utopian place. The website of my project invites the audience to be immersed in a journey of Chautauqua.Includes bibliographic references
Galaxies with Shells in the Illustris Simulation: Metallicity Signatures
Stellar shells are low surface brightness arcs of overdense stellar regions,
extending to large galactocentric distances. In a companion study, we
identified 39 shell galaxies in a sample of 220 massive ellipticals
() from the
Illustris cosmological simulation. We used stellar history catalogs to trace
the history of each individual star particle inside the shell substructures,
and we found that shells in high-mass galaxies form through mergers with
massive satellites (stellar mass ratios ).
Using the same sample of shell galaxies, the current study extends the stellar
history catalogs in order to investigate the metallicity of stellar shells
around massive galaxies. Our results indicate that outer shells are often times
more metal-rich than the surrounding stellar material in a galaxy's halo. For a
galaxy with two different satellites forming shells, we find a
significant difference in the metallicity of the shells produced by each
progenitor. We also find that shell galaxies have higher mass-weighted
logarithmic metallicities ([Z/H]) at -
compared to galaxies without shells. Our results indicate that observations
comparing the metallicities of stars in tidal features, such as shells, to the
average metallicities in the stellar halo can provide information about the
assembly histories of galaxies.Comment: 15 pages, 5 figures. Article published in a special issue of MDPI
Galaxies after the conference "On the Origin (and Evolution) of Baryonic
Galaxy Halos", Galapagos Islands, 201
Formation and Incidence of Shell Galaxies in the Illustris Simulation
Shells are low surface brightness tidal debris that appear as interleaved
caustics with large opening angles, often situated on both sides of the galaxy
center. In this paper, we study the incidence and formation processes of shell
galaxies in the cosmological gravity+hydrodynamics Illustris simulation. We
identify shells at redshift z=0 using stellar surface density maps, and we use
stellar history catalogs to trace the birth, trajectory and progenitors of each
individual star particle contributing to the tidal feature. Out of a sample of
the 220 most massive galaxies in Illustris
(),
of the galaxies exhibit shells. This fraction increases with
increasing mass cut: higher mass galaxies are more likely to have stellar
shells. Furthermore, the fraction of massive galaxies that exhibit shells
decreases with increasing redshift. We find that shell galaxies observed at
redshift form preferentially through relatively major mergers
(1:10 in stellar mass ratio). Progenitors are accreted on low angular
momentum orbits, in a preferred time-window between 4 and 8 Gyrs ago. Our
study indicates that, due to dynamical friction, more massive satellites are
allowed to probe a wider range of impact parameters at accretion time, while
small companions need almost purely radial infall trajectories in order to
produce shells. We also find a number of special cases, as a consequence of the
additional complexity introduced by the cosmological setting. These include
galaxies with multiple shell-forming progenitors, satellite-of-satellites also
forming shells, or satellites that fail to produce shells due to multiple major
mergers happening in quick succession.Comment: 27 pages, 18 figures. Accepted for publication in MNRAS (new figures
3 and D1 + additional minor changes to match accepted version
Formation and Incidence of Shell Galaxies in the Illustris Simulation
Shells are low surface brightness tidal debris that appear as interleaved
caustics with large opening angles, often situated on both sides of the galaxy
center. In this paper, we study the incidence and formation processes of shell
galaxies in the cosmological gravity+hydrodynamics Illustris simulation. We
identify shells at redshift z=0 using stellar surface density maps, and we use
stellar history catalogs to trace the birth, trajectory and progenitors of each
individual star particle contributing to the tidal feature. Out of a sample of
the 220 most massive galaxies in Illustris
(),
of the galaxies exhibit shells. This fraction increases with
increasing mass cut: higher mass galaxies are more likely to have stellar
shells. Furthermore, the fraction of massive galaxies that exhibit shells
decreases with increasing redshift. We find that shell galaxies observed at
redshift form preferentially through relatively major mergers
(1:10 in stellar mass ratio). Progenitors are accreted on low angular
momentum orbits, in a preferred time-window between 4 and 8 Gyrs ago. Our
study indicates that, due to dynamical friction, more massive satellites are
allowed to probe a wider range of impact parameters at accretion time, while
small companions need almost purely radial infall trajectories in order to
produce shells. We also find a number of special cases, as a consequence of the
additional complexity introduced by the cosmological setting. These include
galaxies with multiple shell-forming progenitors, satellite-of-satellites also
forming shells, or satellites that fail to produce shells due to multiple major
mergers happening in quick succession.Comment: 27 pages, 18 figures. Accepted for publication in MNRAS (new figures
3 and D1 + additional minor changes to match accepted version
- …