The Influence of Environment on Galaxy Evolution PDF Download

Author: Dennis William Just
Publisher:
ISBN:
Category : Galaxies
Languages : en
Pages : 153

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Author: Ignacio Ferreras
Publisher: Springer Science & Business Media
ISBN: 3642202853
Category : Science
Languages : en
Pages : 236

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The publication of the morphology - density relation by Alan Dressler in 1980 brought into the limelight the role played by environment in the formation and evolution of galaxies. The symposium Environment and the Formation of Galaxies: 30 years later, was organised with the purpose of establishing the environmental impact on the evolution of galaxies and its dependence on look-back time. Special emphasis was placed on the physical mechanisms that are responsible for transforming galaxies once they are accreted by a group or a cluster, including the observable imprint left in the galaxy HI distribution. Other major topics of the symposium were the environmental dependence of galaxy properties at z ≥ 1 and the implementation of environmental effects in cosmological models of galaxy formation and evolution. This book presents the edited proceedings of this stimulating meeting.

Author: Sabrina Renee Stierwalt
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Galaxy groups are a rich source of information concerning galaxy evolution as they represent a fundamental link between individual galaxies and large scale structures. Nearby groups probe the low end of the galaxy mass function for the dwarf systems that constitute the most numerous extragalactic population in the local universe [Karachentsev et al., 2004]. Inspired by recent progress in our understanding of the Local Group, this dissertation addresses how much of this knowledge can be applied to other nearby groups by focusing on the Leo I Group at 11 Mpc. Gas-deficient, early-type dwarfs dominate the Local Group (Mateo [1998]; Belokurov et al. [2007]), but a few faint, HI-bearing dwarfs have been discovered in the outskirts of the Milky Way's influence (e.g. Leo T; Irwin et al. [2007]). We use the wide areal coverage of the Arecibo Legacy Fast ALFA (ALFALFA) HI survey to search the full extent of Leo I and exploit the survey's superior sensitivity, spatial and spectral resolution to probe lower HI masses than previous HI surveys. ALFALFA finds in Leo I a significant population of low surface brightness dwarfs missed by optical surveys which suggests similar systems in the Local Group may represent a so far poorly studied population of widely distributed, optically faint yet gas-bearing dwarfs. The morphological segregation seen in the Local Group is also reflected in Leo I and further suggests a significant population of gas-bearing dwarfs may be missed by surveys narrowly focused around more massive systems. The Leo I HI mass function is dominated by low mass objects yielding a steeper low-mass slope than found for luminosity functions of the group. However, the slope still falls short of that predicted by simulations of structure formation. Further contributors to this gap may be dwarf systems formed from tidal material (TDGs), the fraction of which, even in the Local Group, remains unknown. We find that TDGs can be identified from the ALFALFA survey based on their proximity to tidal remnants and from optical spectroscopic followup via their high gas fractions and high metallicities given their luminosities. However, despite the two large tidal remnants found in Leo I, our search results in only two TDGs for the group. If most dwarfs are instead formed from small dark matter haloes as suggested by the [LAMDA]CDM framework, different classes of dwarf may reflect early versus late stages of evolution. Dwarfs of mixed morphologies, like the six so-called transition dwarfs in the Local Group, may represent the evolutionary link between gas-rich and gas-poor classes, but when constrained by the requirement of HII regions, we find only one such candidate in Leo I. The work presented here lays the groundwork for future HI-based group studies which will be made possible with rich ALFALFA dataset.

Author: Geert Sikkema
Publisher:
ISBN: 9789036737494
Category :
Languages : en
Pages : 174

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Author: Kelly Ann Douglass
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 322

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We investigate how the cosmic environment affects galaxy evolution in the Universe by studying gas-phase chemical abundances and other galaxy properties as a function of the large-scale environment and local density of galaxies. Using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, we estimate the oxygen and nitrogen abundances of 993 star-forming void dwarf galaxies and 759 star-forming dwarf galaxies in denser regions. We use the Direct Te method for calculating the gas-phase chemical abundances in the dwarf galaxies because it is best suited for low metallicity, low mass galaxies. A substitute for the [OII] 3727 doublet is developed, permitting oxygen abundance estimates of SDSS dwarf galaxies at all redshifts with the Direct Te method. We find that star-forming void dwarf galaxies have slightly higher oxygen abundances than star-forming dwarf galaxies in denser environments, but we find that void dwarf galaxies have slightly lower nitrogen abundances and lower N/O ratios than galaxies in denser regions. At smaller scales, we find that only the presence of a neighboring galaxy within 0.05 Mpc/h or 0.1 r_virial, or the presence of a group within 0.05 Mpc/h, influences a dwarf galaxy's evolution. Dwarf galaxies within 0.05 Mpc/h or 0.1 r_virial of another galaxy tend to be bluer, have higher sSFRs, have higher oxygen abundances, and have lower N/O ratios than average. In contrast, galaxies within 0.05 Mpc/h of the center of the closest group have lower oxygen and nitrogen abundances than average. We also investigate how a galaxy transitions through the color-magnitude diagram, evolving from a blue, star-forming spiral or irregular galaxy in the blue sequence to a red elliptical galaxy in the red cloud through the green valley. We discover that combining a galaxy's color, color gradient, and inverse concentration index determines a galaxy's location on the color-magnitude diagram. The results indicate that, in the green valley, there is a lower fraction of void dwarf galaxies than dwarf galaxies in denser regions. From these analyses, we surmise that void dwarf galaxies experience delayed star formation as predicted by the Lambda CDM cosmology. We also conjecture that cosmic downsizing corresponds to a shift towards star formation in both lower mass objects and void regions closer to the present epoch. We present evidence that void dwarf galaxies may have a higher ratio of dark matter halo mass to stellar mass when compared to dwarf galaxies in denser environments.

Author: Eric D. Feigelson
Publisher: Cambridge University Press
ISBN: 052176727X
Category : Science
Languages : en
Pages : 495

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Modern Statistical Methods for Astronomy: With R Applications.

Author: Riccardo Brunino
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Rosemary Theresa Coogan
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Jesús Falcón-Barroso
Publisher: Cambridge University Press
ISBN: 1107035279
Category : Science
Languages : en
Pages : 657

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The formation and evolution of galaxies is one of the most important topics in modern astrophysics. Secular evolution refers to the relatively slow dynamical evolution due to internal processes induced by a galaxy's spiral arms, bars, galactic winds, black holes and dark matter haloes. It plays an important role in the evolution of spiral galaxies with major consequences for galactic bulges, the transfer of angular momentum, and the distribution of a galaxy's constituent stars, gas and dust. This internal evolution is in turn the key to understanding and testing cosmological models of galaxy formation and evolution. Based on the twenty-third Winter School of the Canary Islands Institute of Astrophysics, this volume presents reviews from nine world-renowned experts on the observational and theoretical research into secular processes, and what these processes can tell us about the structure and formation of galaxies. The volume provides a firm grounding for graduate students and early career researchers working on galactic dynamics and galaxy evolution.

Author: J.M. Shull
Publisher: Springer Science & Business Media
ISBN: 9401118825
Category : Science
Languages : en
Pages : 597

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In July 1992, over 300 astronomers attended the Third Tetons Summer School on the subject of `The Environment and Evolution of Galaxies'. This book presents 28 papers based on invited review talks and a panel discussion on `The Nature of High Redshift Objects'. The major themes include: the Interstellar and Intergalactic Medium, Galaxy Formation and Evolution, Cooling Flows, Quasars and Radiation Backgrounds, and Interactions between Galaxies/AGNs and their Environment. Recent advances with the ROSAT, COBE and Hubble Space Telescope are discussed, together with current theoretical developments. The tutorial nature of the papers make this book a valuable supplement for professional astonomers, graduate students, and senior undergraduates. As with previous Tetons conferences, this book provides both the current state of observational and theoretical research and material complementary to courses in extragalactic and interstellar astrophysics.