Download or read book Observational Evidence of the Large scale Environmental Influence on Dwarf Galaxy Evolution written by Kelly Ann Douglass and published by . This book was released on 2017 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Environmental Influences on Dwarf Galaxy Evolution written by Sabrina Renee Stierwalt and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Constraints on Environmental and Secular Effects on the Chemodynamical Evolution of Dwarf Galaxies written by Ryan Leaman and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Solo Dwarf Galaxy Survey written by Clare Higgs and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxy evolution depends on a diverse suite of factors, from the environment in which the galaxy exists to the number of supernovae that explode throughout its history. The structure and stellar populations present will also be altered by a galaxy's merger history, stellar mass, star formation rate, among other influences. Some factors, like mergers, are dependent on the environment of the galaxy, while others, like feedback from star formation, are intrinsic to the galaxy themselves. Dwarf galaxies are sensitive to many of these factors due to their smaller masses, hence shallower potential wells. Dwarfs are also interesting in themselves as the least massive structures that can form stars, forming the faint limit of galaxy types. There is some indication that the evolutionary pathway of dwarfs might be different than their more massive counterparts. Indeed, some dwarfs may be the stripped remnants of larger galaxy after a major interaction. Regardless, dwarfs are thought to be the building blocks of larger galaxies via hierarchical galaxy formation and understanding these small dwarfs helps us build a more complete picture of galaxy formation and evolution at all masses. As dwarfs generally have low stellar mass, they are very faint. Our most complete sample of dwarfs is therefore restricted to those that are nearby. These nearby systems are dominated by dwarfs satellite to the Milky Way and M31. However, the evolution of these satellites will be greatly influenced by their massive host. By studying nearby isolated dwarfs, we can try to separate the secular evolutionary processes of dwarfs from the influence of their larger host. Additionally, stellar populations can be resolved in these nearby galaxies, and so their structures can be probed to much fainter regimes than integrated light studies allow.The Sagittarius Dwarf Irregular Galaxy (Sag DIG) is one of the most isolated, low mass galaxies, located at the edge of the Local Group. Its isolation from other galaxies coupled with its relative proximity provide an excellent opportunity to study the intrinsic properties of this low mass system. We preform an in-depth analysis of its resolved stellar populations and its structural properties as the first galaxy in the larger dataset, Solitary Local Dwarfs Survey (Solo). Solo is a wide field photometric study targeting every isolated dwarf galaxy within 3 Mpc of the Milky Way. Solo is based on (u)gi multi-band imaging from CFHT/MegaCam for northern targets, and Magellan/Megacam for southern targets. All galaxies fainter than M ~ -18 (in the V band) situated beyond the nominal virial radius of the Milky Way and M31 (> 300 kpc) are included in this volume-limited sample, for a total of 42 targets. For Sag DIG, we provide updated estimates of its central surface brightness and integrated luminosity, and trace its surface brightness profile to a level fainter than 30 mag./sq.arcsec. Sag DIG is well described by a highly elliptical (disk-like) system following a single component Sersic model. However, a low-level distortion is present at the outer edges of the galaxy that, were Sag DIG not so isolated, would likely be attributed to some kind of previous tidal interaction. Further, we find evidence of an extremely low level, extended distribution of stars beyond ~5 arcmins (> 1.5 kpc) that suggests Sag DIG may be embedded in a very low density stellar halo. We compare the stellar and HI structures of Sag DIG, and discuss results for this galaxy in relation to other isolated, dwarf irregular galaxies in the Local Group. Sag DIG, and the similarly isolated dwarf Aquarius, both have HI distributions that are more circular than their stellar components. In contrast, Wolf - Lundmark - Mellote (WLM), another isolated but slightly more massive dwarf, has stellar and HI components that trace each other well. Sag DIG and Aquarius also differ in that there is no signature of rotation in the HI of Sag DIG, while there is clear rotation in both the HI and stellar component for Aquarius. These preliminary comparisons demonstrate some of the potential analysis which will be possible on a much larger scale with the full Solo Survey.

Download or read book Environmental Effects on Dwarf Galaxy Evolution written by Rory Smith and published by . This book was released on 2009 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evolution of Dwarf Galaxy Properties in Local Group Environments written by Kenza Sigrid Arraki and published by . This book was released on 2016 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Origin and Evolution of the Elements Volume 4 Carnegie Observatories Astrophysics Series written by Andrew McWilliam and published by Cambridge University Press. This book was released on 2004-09-23 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Carnegie volume discusses the origin and evolution of elements in our galaxy and others.

Download or read book Observational and Physical Cosmology written by F. Sánchez and published by Cambridge University Press. This book was released on 1992-02-27 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of a very exciting and successful conference on observational and physical cosmology.

Download or read book Astronomical Data Analysis Software and Systems X written by Frank Roderic Harnden and published by . This book was released on 2001 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cosmic Velocity Fields written by François R. Bouchet and published by Atlantica Séguier Frontières. This book was released on 1993 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dwarfs Among Giants written by Clare Higgs and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Origins of Life written by Vlado Valkovic and published by CRC Press. This book was released on 2021-11-09 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary purpose of this book is to prepare the ground for coordinated efforts aiming to answer the question: where and when life originated. The appearance of life involves three successive stages: i) the formation of chemical elements and their combination to simple molecules, which is the concern of physicists; ii) the evolution of organized complexity in biomolecules and their reactions, which falls within the field of chemistry; iii) the onset of Darwinian evolution after the appearance of the first cell-like structure, which is studied by biologists. This book focuses on the first two steps of this process with chapters exploring topics such as chemical element abundances; galaxies, galactic magnetic fields and cosmic rays; galactic chemical evolution. Key Features: Contains extensive lists of reference and additional reading. Includes new hypotheses concerning the origin of life. Combines consideration from nuclear physics, astrophysics, astro- and geochemistry. Despite its interdisciplinary nature, this book remains accessible to nonexperts, and would be a valuable companion for both experts and laypeople.

Download or read book Nearly Normal Galaxies written by Sandra M. Faber and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is sometimes said that astronomy is the crossroads of physics. In the same spirit, it can forcefully be argued that galaxies are the crossroads of astronomy. Internal pro ces ses within galaxies involve all of the fundamental components of astrophysics: stellar evolution, star formation, low-density astrophysics, dynamics, hydrodynamics, and high-energy astrophysics. Indeed, one can hardly name an observational datum in any wavelength range on any kind of celestial object that does not provide a useful clue to galaxy formation and evolution. Although internal processes in galaxies until recently occupied most of our attention, we now know that it is also vital to relate galaxies to their environment. How galaxies congregate in larger structures and are in turn influenced by them are crucial questions for galactic evolution. On a grander level we have also come to regard galaxies as the basic building blocks of the universe, the basic units whereby the large scale structure of the universe is apprehended and quantified. On a grander level still, we also believe strongly that galaxies are the direct descendents of early density irregularities in the Big Bang. Galaxy properties are now viewed as providing a crucial constraint on the physics of the Big Bang and a vital link between the macroscopic and microscopic structure of the universe.

Download or read book NgVLA written by Eric James Murphy and published by . This book was released on 2018 with total page 830 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Literature 1987 Part 1 written by S. Böhme and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy and Astrophysics Abstracts aims to present a comprehensive documen tation of the literature concerning all aspects of astronomy, astrophysics, and their border fields. It is devoted to the recording, summarizing, and indexing of the relevant publications throughout the world. Astronomy and Astrophysics Abstracts is prepared by a special department of the Astronomisches Rechen-Institut under the auspices of the International Astronomical Union. Volume 43 records literature published in 1987 and received before August 15, 1987. Some older documents which we received late and which are not surveyed in earlier volumes are included too. We acknowledge with thanks contributions of our colleagues all over the world. We also express our gratitude to all organiza tions, observatories, and publishers which provide us with complimentary copies of their publications. Starting with Volume 33, all the recording, correction, and data processing work was done by means of computers. The recording was done by our technical staff members Ms. Helga Ballmann, Ms. Beate Gobel, Ms. Monika Kohl, Ms. Sylvia Matyssek, Ms. Doris Schmitz-Braunstein, Ms. Utta-Barbara Stegemann. Mr. Jochen Heidt and Mr. Kristopher Polzine supported our task by careful proof reading. It is a pleasure to thank them all for their encouragement. Heidelberg, October 1987 The Editors Contents Introduction . . . . . . . . . . . 1 Concordance Relation: PHYS-AAA 3 Abbreviations 5 Periodicals, Proceedings, Books, Activities 001 Periodicals . . . . . . . . . . . 10 002 Bibliographical Publications, Documentation, Catalogues, Data Bases 50 003 Books ...... .

Download or read book Feedback and Environmental Effect on Star Formation in Galaxies written by Taro Sato and published by ProQuest. This book was released on 2007 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies of galaxy evolution and formation have shown that both environment and gaseous "feedback" process are critical factors that give rise to the observed variety and richness in galaxy populations. This thesis presents research in these two seemingly disparate aspects of galaxy formation. One deals with a detailed study of the star-forming galaxy population in z = 0.4 galaxy cluster Abell 851, which describes how they may be the key population at an intermediate phase of environmentally-driven evolution, causing the Butcher-Oemler effect. The other is a study of host galaxies of gaseous outflows which are drawn from a large-scale galaxy survey. The census shows that starburst-driven outflows are ubiquitous in the galaxies in transition, suggesting the importance of feedback-driven evolution. We speculate on how these factors might play synergetic or even integral roles in transforming the star-forming property of galaxy, and propose a few directions of research that may help elucidate the significance of feedback and environment in galaxy formation and evolution.

Download or read book Clusters of Galaxies Volume 3 Carnegie Observatories Astrophysics Series written by John S. Mulchaey and published by Cambridge University Press. This book was released on 2004-09-23 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Series of review papers covering clusters of galaxies and related phenomena.