Evolution Of Dwarf Galaxy Properties In Local Group Environments
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Evolution Of Dwarf Galaxy Properties In Local Group Environments
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Author : Kenza Sigrid Arraki
language : en
Publisher:
Release Date : 2016
Evolution Of Dwarf Galaxy Properties In Local Group Environments written by Kenza Sigrid Arraki and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Dwarf galaxies categories.
Understanding galaxy evolution depends on connecting large-scale structures determined by the [Lambda]CDM model with, at minimum, the small-scale physics of gas, star formation, and stellar feedback. Formation of galaxies within dark matter halos is sensitive to the physical phenomena occurring within and around the halo. This is especially true for dwarf galaxies, which have smaller potential wells and are more susceptible to the effects of tidal stripping and gas ionization and removal than larger galaxies. At dwarf galaxies scales comparisons of dark matter-only simulations with observations has unveiled various differences such as the core-cusp, the missing satellites, and the too big to fail problems. We have run suites of collisionless and hydrodynamical simulations of dwarf galaxies evolution in massive host environments to address these issues. We performed controlled, numerical simulations, which mimic the effects of baryons, in order to examine the assumptions implicitly made by dark matter-only simulations. The too big to fail problem is due to the overabundance of relatively massive, dense satellite galaxies found in simulations of Milky Way-like environments. We found that the removal of a small baryonic component from the central region of forming dwarf spheroidal galaxies and the inclusion of a disk component in the host galaxy can substantially reduce the central dark matter density of satellites, bringing simulations and observations of satellites into agreement. Additionally, we studied hydrodynamical simulations of massive host galaxies and their surrounding dwarf galaxy populations. The VELA simulation suite of cosmological zoom-in simulations is run with the ART code, stochastic star formation, and stellar feedback (supernovae feedback, stellar winds, radiation pressure, and photoionization pressure). The suite includes host galaxies with M[subscript vir](z = 0 ) = 1011 - 1012 M[sol] and their satellite dwarf galaxies and local isolated dwarf galaxies around each primary galaxy. We found that the inclusion of these relevant physical processes aligned the velocity functions and star formation histories of the dwarf galaxy populations closer to observations of the Local Group dwarf galaxies. By reproducing observations of dwarf galaxies we show how the inclusion of baryons in simulations relieves many of the discovered tensions between dark matter-only simulations and observations.
Observational Evidence Of The Large Scale Environmental Influence On Dwarf Galaxy Evolution
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Author : Kelly Ann Douglass
language : en
Publisher:
Release Date : 2017
Observational Evidence Of The Large Scale Environmental Influence On Dwarf Galaxy Evolution written by Kelly Ann Douglass and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Astrophysics categories.
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.
Constraints On Environmental And Secular Effects On The Chemodynamical Evolution Of Dwarf Galaxies
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Author : Ryan Leaman
language : en
Publisher:
Release Date : 2012
Constraints On Environmental And Secular Effects On The Chemodynamical Evolution Of Dwarf Galaxies written by Ryan Leaman and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
This thesis presents observations and analysis relating to the understanding of processes that govern the formation and evolution of low mass galactic systems. In particular we have focused on separating out the contribution to the chemical and dynamical evolution of dwarf galaxies due to solely secular (internal) processes compared to external effects from the local environment a galaxy resides in. Our observational data focus on an extremely isolated dwarf galaxy, WLM, which we demonstrate has had a uniquely quiescent tidal history, thereby making it an excellent test case for such a study. With spectroscopic and photometric observations of the resolved stars and neutral gas in WLM we have been able to characterize the chemical, structural and kinematic properties of this gas rich dwarf galaxy. As WLM has not been subject to strong tidal or ram-pressure stripping of its stellar and gaseous populations, we have been able to compare the dynamical evolution and chemical history of WLM to theoretical models which are environment independent. A differential comparison of WLM to more environmentally processed dwarf galaxies in the Local Group has revealed that WLM's structural and dynamical state is far from the idealized picture of dIrrs as thin gas-rich rotating systems. The stellar component of WLM shows equal parts rotation and dispersion, and both the gaseous and stellar structural properties show an intrinsically thick axisymmetric configuration. The time evolution of the random (dispersion) component of the stellar orbital energy shows an increase with stellar age, which we show is consistent with secular processes alone - such as disk heating from giant molecular clouds and dark matter substructure. While the degree to which the thick structural and dynamically hot configuration for WLM is surprising, its chemical properties show remarkably consistent values with other galaxies of the same halo mass. Comparing the spatial chemical trends in WLM with other dwarf galaxies we identify a correlation between the strength of the radial abundance gradients and the angular momentum content of dwarf galaxies in the Local Group. Finally using a large sample of chemical abundance measurements in the literature for dwarf galaxies and star clusters, we demonstrate that their distributions of chemical elements all exhibit a binomial form, and use the statistical properties of the distributions to identify a new metric for differentiating low luminosity stellar systems. We further apply a simple binomial chemical evolution model to describe the self-enrichment and pre-enrichment in the two classes of objects, and suggest how this may be used to place constraints on the formation environments of globular clusters in particular.
Environmental Influences On Dwarf Galaxy Evolution
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Author : Sabrina Renee Stierwalt
language : en
Publisher:
Release Date : 2010
Environmental Influences On Dwarf Galaxy Evolution written by Sabrina Renee Stierwalt and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
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.
Dwarf Galaxy Star Formation Histories In Local Group Cosmological Simulations
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Author : Ruth A. R. Digby
language : en
Publisher:
Release Date : 2019
Dwarf Galaxy Star Formation Histories In Local Group Cosmological Simulations written by Ruth A. R. Digby and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Dwarf galaxies are powerful tools in the study of galactic evolution. As the most numerous galaxies in the universe, they probe a diverse range of environments: some exist in near-isolation, allowing us to study how a galaxy's evolution depends on its intrinsic properties. Others have been accreted by larger galaxies and show the impact of environmental processes such as tidal stripping. Because dwarf galaxies have shallow potential wells, these processes leave strong signatures in their star formation histories (SFHs). We use state-of-the-art cosmological hydrodynamical simulations to study the evolution of dwarf galaxies in Local Group analogues. Their SFHs are remarkably diverse, but also show robust average trends with stellar mass and environment. Low- mass isolated dwarfs (10^5
Dwarf Galaxies Keys To Galaxy Formation And Evolution
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Author : Polychronis Papaderos
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-04-23
Dwarf Galaxies Keys To Galaxy Formation And Evolution written by Polychronis Papaderos and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-04-23 with Science categories.
Dwarf galaxy research constitutes an extremely vibrant field of astrophysical research, with many long-standing questions still unsettled and new ones constantly arising. The intriguing diversity of the dwarf galaxy population, observed with advanced ground-based and space-borne observatories over a wide spectral window providing an unprecedented level of detail, poses new challenges for both observers and theoreticians. The aim of this symposium was to bring together these two groups to exchange ideas and new results on the many evolutionary aspects of and open issues concerning dwarf galaxies. The main topics addressed include: the birth of dwarf galaxies: theoretical concepts and observable relics across wavelengths and time, the morphological, structural and chemical evolution of dwarf galaxies, possible evolutionary connections between early-type and late-type dwarfs, the star formation history of dwarf galaxies and its dependence on intrinsic and environmental properties, the origin and implications of starburst activity in dwarf galaxies, the fate of dwarfish systems born out of tidally ejected matter in galaxy collisions.
Dwarfs Among Giants
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Author : Clare Higgs
language : en
Publisher:
Release Date : 2021
Dwarfs Among Giants written by Clare Higgs and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
This thesis attempts to untangle, as best as possible, the importance of internally-driven evolutionary mechanisms relative to externally-driven effects, in shaping the structure and properties of the smallest observable galaxies. All galaxies are influenced by internal processes, such as feedback from star formation and the infall of gas or lack thereof, as well as environmental processes, like tides and ram pressure stripping. The smallest galaxies - dwarfs - are highly susceptible to all such processes, and their resulting structure is the summation of all prior events. I use nearby dwarf galaxies of the Local Group as test cases, focusing on those which are separated from the massive galaxies (like the Milky Way) and can be considered as "isolated''. These dwarfs are observed as part of the Solitary Local (Solo) Dwarf Galaxy Survey. Solo dwarfs will have spent the majority of their time as isolated systems, hence their properties should generally reflect their "intrinsic nature", unperturbed and unaffected by interactions with other systems. This survey was designed to focus on the old stellar populations present in these galaxies, in order to characterize their faint and extended structures. These old stellar populations should carry the hallmarks of the dwarfs' histories. By comparing the observed properties of Solo dwarfs with dwarfs currently in close proximity to a large host galaxy (i.e., the M 31 and Milky Way satellites), it should be possible to determine what aspects of the properties of dwarfs are most affected by environmentally-driven processes. The Local Group is the ideal regime in which to study these faint features, as the dwarfs' close proximity to us presents an opportunity to fully characterize these galaxies. However, the number of dwarfs in the Local Group is limited, with several galaxies (e.g. IC 10 or Sag dSph) being the unique example of their "type" locally observable. This limited sample emphasizes the need for careful, homogeneous observations and analysis, such that comparisons between this small, yet highly diverse, snapshot of galaxies accurately reflects the true nature of these dwarfs. I have homogeneously analyzed the 12 closest Solo dwarfs observable from the northern hemisphere, resulting in a consistently derived dataset. I determine fundamental properties, like distances, and characterize the structure of the dwarfs. I explore the possibility that the dwarfs may be more consistent with a two component profile, rather than one, finding that they are largely well characterized by a single Sérsic profile. I then compare these isolated dwarfs with the well-studied satellites of the Milky Way and M 31, primarily using two other homogeneous surveys; the MegaCam Survey of Outer Halo Objects and the Pan-Andromeda Archaeological Survey respectively. Examining each property (e.g. ellipticity, central surface brightness, or Sérsic radius) individually, we find no statistically significant differences between each group. However, when considering parameters in combination (e.g. absolute magnitude as a function of Sérsic radius), we see increased scatter in the satellite population, indicative of the impact of a massive host galaxy on the dwarfs, likely via tidal effects. The comparison between satellites and isolated dwarfs hones in on the impact of a massive galaxy in close proximity. Of course, processes within and surrounding the dwarf itself can also alter the dwarf. I look at the star formation histories and gas content of the dwarfs to explore the connection between internal and external processes in these small galaxies. Finally, I search for substructure in the form of satellites of dwarf galaxies, globular clusters and extended tidal features, all which inform about the dwarf's isolation, environment and history. Collectively, I generate comprehensive and detailed inspections of Local Group dwarfs and aim to understand them as products of their environment.
The Stellar Content And Star Formation Rates Of Dwarf Irregular Galaxies
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Author : Jacqueline Michelle Dunn
language : en
Publisher:
Release Date : 2007
The Stellar Content And Star Formation Rates Of Dwarf Irregular Galaxies written by Jacqueline Michelle Dunn and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Astronomical photometry categories.
The star formation histories and evolution of 70 dwarf irregular galaxies that reside in differing local and global environments are investigated. Local environment is defined by the local galaxy number density, where high indicates at least one neighbor within 200 kpc and low indicates no neighbors within 1 Mpc. Global environment is classified as either the field or a galaxy group / cluster. The shallow gravitational potentials of these galaxies are more susceptible to changes in morphology and dynamics by external perturbations, making dwarf irregular galaxies ideal candidates for a study on the role of environment in galaxy evolution. Absolute magnitudes, colors, central surface brightnesses, and star formation rates were compared using UBVRIJHK and Halpha photometry. With a high degree of statistical significance, galaxies in local high density environments have brighter central and effective surface brightnesses, while those in global high density environments have brighter absolute magnitudes, central and effective surface brightnesses, and higher star formation rates. However, no difference is seen among the different environments when considering star formation rates normalized by HI mass. Sersic profiles were fit to the V and R band surface brightness profiles of the galaxies. No correlation exists between structural characteristics and environment. Spectral energy distribution models were generated by varying the rate of stellar formation and amplitude to replicate periodic burst and constant star formation rate scenarios. Of the 28 galaxies for which star formation history analysis was performed, roughly half were well fit by one of the models. Periodic burst systems account for roughly half of those galaxies, with the remaining galaxies being better represented by continuously star forming systems. The star formation histories are uncorrelated with both local and global environmental classifications. Numerical simulations provide insight into the effects of differing gravitational environments, and indicate global environment having a larger influence on the physical properties of a dwarf galaxy. The star formation histories and structural properties of dwarf irregular galaxies were found to be independent of environment, indicating that cluster membership and proximity to a neighboring galaxy have no systematic long-term effects on the evolution of the objects in this study.
Dwarf Galaxies Iau S344
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Author : Kristen B. W. McQuinn
language : en
Publisher: Cambridge University Press
Release Date : 2019-09-30
Dwarf Galaxies Iau S344 written by Kristen B. W. McQuinn and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-09-30 with Science categories.
Dwarf galaxies are important tools for understanding structure formation and galaxy evolution across cosmic time. These low-mass systems allow us to gain a detailed understanding of stellar, chemical, and dynamical properties in the nearby universe; they also provide a unique window into the complex physics of the early universe. The Proceedings of IAU Symposium 344 present our current understanding of dwarf galaxies, with sections dedicated to: Local Group dwarf galaxies; the interstellar medium and star formation in dwarfs; metallicity, massive stars, and chemical evolution; the dwarf galaxy-environment connection; low-mass galaxies at high redshift; and dwarfs as cosmological probes. Broad overviews from leaders in the field, detailed presentation of cutting-edge results, and short summaries of a wide range of work are included for each of these topics, suitable for both experts and newcomers to the field.
Groups Of Galaxies In The Nearby Universe
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Author : Ivo Saviane
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-08-01
Groups Of Galaxies In The Nearby Universe written by Ivo Saviane and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-08-01 with Science categories.
For every galaxy in the field or in clusters, there are about three galaxies in groups. The Milky Way itself resides in a group. Groups in the local universe offer the chance to study galaxies in environments characterized by strong interactions. In the cosmological context, groups trace large-scale structures better than clusters; the evolution of groups and clusters appears to be related. All these aspects of research are summarized in this book.