Environmental Influences on Dwarf Galaxy Evolution

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Total Pages : 0 pages
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Book Synopsis Environmental Influences on Dwarf Galaxy Evolution by : Sabrina Renee Stierwalt

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.

Observational Evidence of the Large-scale Environmental Influence on Dwarf Galaxy Evolution

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Total Pages : 322 pages
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Book Synopsis Observational Evidence of the Large-scale Environmental Influence on Dwarf Galaxy Evolution by : Kelly Ann Douglass

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.

Environmental Effects on Dwarf Galaxy Evolution

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Total Pages : 215 pages
Book Rating : 4.:/5 (87 download)

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Book Synopsis Environmental Effects on Dwarf Galaxy Evolution by : Rory Smith

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:

Environment and the Formation of Galaxies: 30 years later

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Publisher : Springer Science & Business Media
ISBN 13 : 3642202853
Total Pages : 236 pages
Book Rating : 4.6/5 (422 download)

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Book Synopsis Environment and the Formation of Galaxies: 30 years later by : Ignacio Ferreras

Download or read book Environment and the Formation of Galaxies: 30 years later written by Ignacio Ferreras and published by Springer Science & Business Media. This book was released on 2011-07-06 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Constraints on Environmental and Secular Effects on the Chemodynamical Evolution of Dwarf Galaxies

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Book Synopsis Constraints on Environmental and Secular Effects on the Chemodynamical Evolution of Dwarf Galaxies by : Ryan Leaman

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.

Dwarf Galaxies: Keys to Galaxy Formation and Evolution

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Publisher : Springer Science & Business Media
ISBN 13 : 3642220185
Total Pages : 347 pages
Book Rating : 4.6/5 (422 download)

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Book Synopsis Dwarf Galaxies: Keys to Galaxy Formation and Evolution by : Polychronis Papaderos

Download or read book Dwarf Galaxies: Keys to Galaxy Formation and Evolution written by Polychronis Papaderos and published by Springer Science & Business Media. This book was released on 2012-04-23 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

The Environmental Impact of the Virgo Cluster on the Evolution of Dwarf Irregular Galaxies

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ISBN 13 :
Total Pages : 252 pages
Book Rating : 4.:/5 (62 download)

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Book Synopsis The Environmental Impact of the Virgo Cluster on the Evolution of Dwarf Irregular Galaxies by : Henry Lee

Download or read book The Environmental Impact of the Virgo Cluster on the Evolution of Dwarf Irregular Galaxies written by Henry Lee and published by . This book was released on 2001 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Environmental Influences on Star Formation in Low-mass Galaxies

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ISBN 13 :
Total Pages : 144 pages
Book Rating : 4.:/5 (113 download)

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Book Synopsis Environmental Influences on Star Formation in Low-mass Galaxies by : Jing Sun

Download or read book Environmental Influences on Star Formation in Low-mass Galaxies written by Jing Sun and published by . This book was released on 2019 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interaction between galaxies is of critical importance to the growth and evolution of galaxies. I explore the environmental influences on the star formation in low-mass galaxies with stellar mass 8 ≤ log (M?/M) ≤ 10 at a redshift of 0.01

The Origin and Evolution of Dwarf Galaxies in the Cluster Environment

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)

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Book Synopsis The Origin and Evolution of Dwarf Galaxies in the Cluster Environment by : Samantha J. Penny

Download or read book The Origin and Evolution of Dwarf Galaxies in the Cluster Environment written by Samantha J. Penny and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

The environmental processing of late-type dwarf satellite galaxies

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ISBN 13 :
Total Pages : pages
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Book Synopsis The environmental processing of late-type dwarf satellite galaxies by : Cameron James Robert Yozin-Smith

Download or read book The environmental processing of late-type dwarf satellite galaxies written by Cameron James Robert Yozin-Smith and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The environmental mechanisms that drive late-type dwarf satellite galaxy evolution represent one of the key puzzles in astrophysics. In this thesis, we adopted numerical modelling of their dominant tidal and hydrodynamical interactions to reproduce observational constraints in the context of a CDM cosmology. Commencing with a holistic study of satellite galaxies with stellar mass M*?109 M?, we addressed the proposition that they are preferentially quenched in group-mass hosts (dynamical mass ?1013-13:5 M?), albeit inefficiently, with a quenching timescale of as much as 8 Gyr. Using cosmologically-motivated orbits and accounting for the stochastic influence of satellite harassment, our parameter study revealed their characteristic evolution tends towards a passive dS0 morphology, driven by strangulation (if assuming an efficiently stripped hot gas halo) and tidal torques acting on a gas-rich disc. Ram pressure stripping played an insignificant role for a spherically-symmetric model of the intragroup medium; however, we also demonstrated that satellites can be quenched within a single orbit if they encounter overdense substructure in the medium. In a second study, we examined a subset of these mechanisms in more detail with a suite of simulations that broadly replicate the wealth of multi-wavelength data for the Magellanic Clouds, a pair of M*?108:5-9:5 M? satellites of the Galaxy. The results support the tidal- dominated paradigm for the Clouds' morphology and recent enrichment, reproducing for the first time the metallicity and dust mass of the Stream (as a tidal arm of the small Cloud) and a young stellar population in the Bridge. This study also constitutes a valuable test of a novel subgrid dust lifecycle model; after modifying this model to accommodate a low-metallicity galaxy, we confirm the governing role of destructive stellar feedback in the dwarf-mass regime. There remain key features that were not reproduced, including the Stream's mass, gas- phase depletion and filamentary structure. A promising approach towards refining our model involves the adoption of larger pre-infall halo masses and a high energy orbit more consistent with recent proper motion measurements and Magellanic-analogues in the CDM model. In a third, related study, motivated by recent detections of ultra-faint dwarf galaxies (UFDs; M*?103-5 M?) in the Magellanic System, we test this scenario together with a further predic- tion of the CDM model which states that Magellanic-type galaxies should be accompanied by their own satellites. Accordingly, we showed how the locations of these UFDs are consistent with the recent (

Dwarf Galaxy Star Formation Histories in Local Group Cosmological Simulations

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ISBN 13 :
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Book Synopsis Dwarf Galaxy Star Formation Histories in Local Group Cosmological Simulations by : Ruth A. R. Digby

Download or read book Dwarf Galaxy Star Formation Histories in Local Group Cosmological Simulations written by Ruth A. R. Digby and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Dwarfs Among Giants

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Total Pages : pages
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Book Synopsis Dwarfs Among Giants by : Clare Higgs

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.

Near-Field Cosmology with Dwarf Elliptical Galaxies (IAU C198)

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Publisher : Cambridge University Press
ISBN 13 : 9780521852043
Total Pages : 456 pages
Book Rating : 4.8/5 (52 download)

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Book Synopsis Near-Field Cosmology with Dwarf Elliptical Galaxies (IAU C198) by : International Astronomical Union. Colloquium

Download or read book Near-Field Cosmology with Dwarf Elliptical Galaxies (IAU C198) written by International Astronomical Union. Colloquium and published by Cambridge University Press. This book was released on 2005 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of IAUC 198, covering important issues related to near-field cosmology with dwarf elliptical galaxies.

Solo Dwarf Galaxy Survey

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Total Pages : pages
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Book Synopsis Solo Dwarf Galaxy Survey by : Clare Higgs

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.

The Influence of Environment on Galaxy Evolution

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ISBN 13 :
Total Pages : 153 pages
Book Rating : 4.:/5 (881 download)

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Book Synopsis The Influence of Environment on Galaxy Evolution by : Dennis William Just

Download or read book The Influence of Environment on Galaxy Evolution written by Dennis William Just and published by . This book was released on 2012 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:

The Stellar Content and Star Formation Rates of Dwarf Irregular Galaxies

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (183 download)

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Book Synopsis The Stellar Content and Star Formation Rates of Dwarf Irregular Galaxies by : Jacqueline Michelle Dunn

Download or read book The Stellar Content and Star Formation Rates of Dwarf Irregular Galaxies written by Jacqueline Michelle Dunn and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

The Evolution of Galaxies

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Publisher : Springer Science & Business Media
ISBN 13 : 9401733139
Total Pages : 556 pages
Book Rating : 4.4/5 (17 download)

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Book Synopsis The Evolution of Galaxies by : José M. Vilchez

Download or read book The Evolution of Galaxies written by José M. Vilchez and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies have a history. This has become clear from recent sky surveys showing that distant galaxies, formed early in the life of the Universe, differ from the nearby ones. This book contains the proceedings of a 2000 conference addressing observational clues in this area.