WorldCat Identities

Abel, Tom G. 1970-

Works: 32 works in 49 publications in 1 language and 382 library holdings
Genres: Conference papers and proceedings  Observations 
Roles: Author, Thesis advisor, Editor, Creator
Publication Timeline
Most widely held works by Tom G Abel
The first stars : proceedings of the MPA/ESO Workshop held at Garching, Germany, 4-6 August 1999 by MPA/ESO Workshop( Book )

9 editions published between 2000 and 2014 in English and held by 175 WorldCat member libraries worldwide

Neither the formation process of "The First Stars" nor their existence in the present universe is known with any certainty. The authors of this volume address all open questions presenting an abundance of interesting data at the same time as giving an exhaustive overview of our present-day knowledge. This covers research from spectroscopic observations, stellar evolution, nucleosynthesis, structure and galaxy formation. The contributions shed new light on past views, often questioning traditional interpretations. Dealing with problems at the crossroads of cosmology, star formation and galactochemical evolution in stars, the book addresses researchers graduate students in astrophysics, nuclear physics and astrochemistry
First stars III : Santa Fe, New Mexico, 15-20 July 2007 by First stars III( Book )

4 editions published in 2008 in English and held by 104 WorldCat member libraries worldwide

The first structures in the universe a theoretical study of their formation, evolution, and impact on subsequent structure formation( )

2 editions published in 1999 in English and held by 34 WorldCat member libraries worldwide

The first stars : proceedings of the MPA/ESO Symposium held at Garching, Germany, 4-6 August 1999 by MPA/ESO Workshop( Book )

2 editions published in 2000 in English and held by 10 WorldCat member libraries worldwide

The Formation of Primordial Luminous Objects( )

1 edition published in 2005 in English and held by 6 WorldCat member libraries worldwide

The scientific belief that the universe evolves in time is one of the legacies of the theory of the Big Bang. The concept that the universe has an history started to attract the interest of cosmologists soon after the first formulation of the theory: already Gamow (1948; 1949) investigated how and when galaxies could have been formed in the context of the expanding Universe. However, the specific topic of the formation (and of the fate) of the first objects dates to two decades later, when no objects with metallicities as low as those predicted by primordial nucleosynthesis (Z {approx}<10{sup -10} {approx} 10{sup -8}Z{sub {circle_dot}}) were found. Such concerns were addressed in two seminal papers by Peebles & Dicke (1968; hereafter PD68) and by Doroshkevich, Zel'Dovich & Novikov (1967; hereafter DZN67), introducing the idea that some objects could have formed before the stars we presently observe. (1) Both PD68 and DZN67 suggest a mass of {approx} 10{sup 5} M{sub {circle_dot}} for the first generation of bound systems, based on the considerations on the cosmological Jeans length (Gamow 1948; Peebles 1965) and the possible shape of the power spectrum. (2) They point out the role of thermal instabilities in the formation of the proto-galactic bound object, and of the cooling of the gas inside it; in particular, PD68 introduces H{sub 2} cooling and chemistry in the calculations about the contraction of the gas. (3) Even if they do not specifically address the occurrence of fragmentation, these papers make two very different assumptions: PD68 assumes that the gas will fragment into ''normal'' stars to form globular clusters, while DZN67 assumes that fragmentation does not occur, and that a single ''super-star'' forms. (4) Finally, some feedback effects as considered (e.g. Peebles & Dicke considered the effects of supernovae). Today most of the research focuses on the issues when fragmentation may occur, what objects are formed and how they influence subsequent structure formation. In these notes we will leave the discussion of feedback to lecture notes by Ferrara & Salvaterra and by Madau & Haardt in this same book and focus only on the aspects of the formation of the first objects. The advent of cosmological numerical hydrodynamics in particular allow a fresh new look at these questions. Hence, these notes will touch on aspects of theoretical cosmology to chemistry, computer science, hydrodynamics and atomic physics. For further reading and more references on the subject we refer the reader to other relevant reviews such as Barkana & Loeb 2001, and more recently Ciardi & Ferrara 2004, Glover 2004 and Bromm & Larson 2004. In these notes, we try to give a brief introduction to only the most relevant aspects. We will start with a brief overview of the relevant cosmological concepts in section 2, followed by a discussion of the properties of primordial material (with particular emphasis to its cooling and its chemistry) in section 3. We will then review the technique and the results of numerical simulations in sections 4 and 5: the former will deal with detailed 3D simulations of the formation of gaseous clouds which are likely to transform into luminous objects, while the latter will examine results (mostly from 1D codes) about the modalities of such transformation. Finally, in section 6 we will critically discuss the results of the previous sections, examining their consequences and comparing them to our present knowledge of the universe
Dynamical Expansion of HII Regions From Ultracompact to Compact Sizes in Turbulent, Self-Gravitating Molecular Clouds( )

1 edition published in 2006 in English and held by 6 WorldCat member libraries worldwide

The H II Region of a Primordial Star( )

1 edition published in 2006 in English and held by 6 WorldCat member libraries worldwide

The concordance model of cosmology and structure formation predicts the formation of isolated very massive stars at high redshifts in dark matter dominated halos of 10{sup 5} to 10{sup 6} Msun. These stars photo-ionize their host primordial molecular clouds, expelling all the baryons from their halos. When the stars die, a relic H II region is formed within which large amounts of molecular hydrogen form which will allow the gas to cool efficiently when gravity assembles it into larger dark matter halos. The filaments surrounding the first star hosting halo are largely shielded and provide the pathway for gas to stream into the halo when the star has died. We present the first fully three dimensional cosmological radiation hydrodynamical simulations that follow all these effects. A novel adaptive ray casting technique incorporates the time dependent radiative transfer around point sources. This approach is fast enough so that radiation transport, kinetic rate equations, and hydrodynamics are solved self-consistently. It retains the time derivative of the transfer equation and is explicitly photon conserving. This method is integrated with the cosmological adaptive mesh refinement code enzo, and runs on distributed and shared memory parallel architectures. Where applicable the three dimensional calculation not only confirm expectations from earlier one dimensional results but also illustrate the multi-fold hydrodynamic complexities of H II regions. In the absence of stellar winds the circumstellar environments of the first supernovae and putative early gamma-ray bursts will be of low density {approx}1 cm{sup -3}. Albeit marginally resolved, ionization front instabilities lead to cometary and elephant trunk like small scale structures reminiscent of nearby star forming regions
The first structures in the universe : a theoretical study of their formation, evolution, and impact on subsequent structure formation by Tom G Abel( Book )

2 editions published in 1999 in English and held by 5 WorldCat member libraries worldwide

Formation of Primordial Stars in a Lambda-CDM Universe( )

1 edition published in 2006 in English and held by 5 WorldCat member libraries worldwide

Primordial stars are formed from a chemically pristine gas consisting of hydrogen and helium. They are believed to have been born at some early epoch in the history of the Universe and to have enriched the interstellar medium with synthesized heavy elements before the emergence of ordinary stellar populations. We study the formation of the first generation of stars in the standard cold dark matter model. We follow the gravitational collapse and thermal evolution of primordial gas clouds within early cosmic structures using very high-resolution, cosmological hydrodynamic simulations. Our simulation achieves a dynamic range of {approx} 10{sup 10} in length scale. With accurate treatment of atomic and molecular physics, it allows us to study the chemo-thermal evolution of primordial gas clouds to densities up to {rho} {approx} 2 x 10{sup -8}g cm{sup -3} (n{sub H} {approx} 10{sup 16}cm{sup -3}) without assuming any a priori equation of state; a six orders of magnitudes improvement over previous three-dimensional calculations. We implement an extensive chemistry network for hydrogen, helium and deuterium. All the relevant atomic and molecular cooling and heating processes, including cooling by collision-induced continuum emission, are implemented. For calculating optically thick H{sub 2} cooling at high densities, we use the Sobolev method (Sobolev 1960) and evaluate the molecular line opacities for a few hundred lines. We validate the accuracy of the method by performing a spherical collapse test and comparing the results with those of accurate one-dimensional calculations that treat the line radiative transfer problem in a fully self-consistent manner. We then perform a cosmological simulation adopting the standard {Lambda}CDM model. Dense gas clumps are formed at the centers of low mass ({approx} 10{sup 5-6}M{sub {circle_dot}}) dark matter halos at redshifts z {approx} 20, and they collapse gravitationally when the cloud mass exceeds a few hundred solar masses. To examine possible gas fragmentation owing to thermal instability, we compute explicitly the growth rate of isobaric perturbations. We show that the cloud core does not fragment in either the low-density (n{sub H} {approx} 10{sup 10}cm{sup -3}) or high-density ({approx} 10{sup 15}cm{sup -3}) regimes, where gas cooling rate is increased owing to three-body molecule formation and collision-induced emission, respectively. The cloud core becomes marginally unstable against chemo-thermal instability in the low-density regime. However, since the core is already compact at that point and correspondingly the sound-crossing time as well as the free-fall time are short, or comparable to the perturbation growth timescale, it does not fragment. Run-away cooling simply leads to fast condensation of the core to form a single proto-stellar seed. We also show that the core remains stable against gravitational deformation and fragmentation throughout the evolution. We trace in Lagrangian space the gas elements that end up at the center of the cloud, and study the evolution of the specific angular momentum. We show that, during the final dynamical collapse, small angular momentum material collapses faster than the rest of the gas and selectively sinks inwards. Consequently, the central regions have little specific angular momentum, and rotation does not halt collapse. With the large physical dynamic range of our simulation, we, for the first time, obtain an accurate gas mass accretion rate within a 10M{sub {circle_dot}} innermost region around the protostar. The protostar is accreting the surrounding hot (T {approx} 2000K) gas at a rate of M> 10{sup -2}-10{sup -3}M{sub {circle_dot}}/yr. From these findings we conclude that primordial stars formed in early cosmological halos are massive. We carry out proto-stellar evolution calculations using the obtained accretion rate. For a particular gas cloud we simulate, the resulting mass of the first star is M{sub ZAMS} {approx} 60-100M{sub {circle_dot}}, with the exact mass dependent on the actual accretion rate
An Excursion Set Model of the Cosmic Web : the Abundance of Sheets, Filaments And Halos( )

1 edition published in 2006 in English and held by 5 WorldCat member libraries worldwide

We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of this approach, which we develop here, large scale structure shows a clear hierarchy of morphologies: the mass in large-scale sheets is partitioned up among lower mass filaments, which themselves are made-up of still lower mass halos. Our approach provides analytic estimates of the mass fraction in sheets, filaments and halos, and its evolution, for any background cosmological model and any initial fluctuation spectrum. In the currently popular {Lambda}CDM model, our analysis suggests that more than 99% of the mass in sheets, and 72% of the mass in filaments, is stored in objects more massive than 10{sup 10}M{sub {circle_dot}} at the present time. For halos, this number is only 46%. Our approach also provides analytic estimates of how halo abundances at any given time correlate with the morphology of the surrounding large-scale structure, and how halo evolution correlates with the morphology of large scale structure
Radiative transfer effects during photoheating of the intergalactic medium( )

1 edition published in 2000 in English and held by 2 WorldCat member libraries worldwide

Quasars: absorption lines, galaxies: formation, cosmology: theory
Intergalactic H2 photodissociation and the soft UV background produced by population III objects( )

1 edition published in 2000 in English and held by 2 WorldCat member libraries worldwide

Galaxies: formation, cosmology: theory
Photon conserving radiative transfer around point sources in multi-dimensional numerical cosmology( )

1 edition published in 2000 in English and held by 2 WorldCat member libraries worldwide

Radiative transfer, galaxies: formation, cosmology: theory, galaxies: intergalactic medium, galaxies: ISM
SPECS: The Kilometer-baseline Far-IR Interferometer in NASA's Space Science Roadmap( Book )

2 editions published in 2004 in English and held by 2 WorldCat member libraries worldwide

Ultimately, after the Single Aperture Far-IR (SAFIR) telescope, astrophysicists will need a far-IR observatory that provides angular resolution comparable to that of the Hubble Space Telescope. At such resolution galaxies at high redshift, protostars, and nascent planetary systems will be resolved, and theoretical models for galaxy, star, and planet formation and evolution can be subjected to important observational tests. This paper updates information provided in a 2000 SPIE paper on the scientific motivation and design concepts for interferometric missions SPIRIT (the Space Infrared Interferometric Telescope) and SPECS (the Submillimeter Probe of the Evolution of Cosmic Structure). SPECS is a kilometer baseline far-IR/submillimeter imaging and spectral interferometer that depends on formation flying, and SPIRIT is a highly-capable pathfinder interferometer on a boom with a maximum baseline in the 30 - 50 m range. We describe recent community planning activities, remind readers of the scientific rationale for space-based far-infrared imaging interferometry, present updated design concepts for the SPIRIT and SPECS missions, and describe the main issues currently under study. The engineering and technology requirements for SPIRIT and SPECS, additional design details, recent technology developments, and technology roadmaps are given in a companion paper in the Proceedings of the conference on New Frontiers in Stellar Interferometry
The first stars by Brian W O'Shea( )

3 editions published between 2003 and 2008 in English and held by 2 WorldCat member libraries worldwide

Novel methods and applications for kinetic plasma simulation by Samuel Richard Totorica( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Understanding the behavior of plasma is important for a broad range of applications, such as understanding the production of energetic particles in astrophysics, developing predictive models for space weather, and harnessing the potential of nuclear fusion power. Due to limitations such as noise from numerical collisions and the large number of simulation particles required to capture the development of nonthermal tails in the particle distribution, multiscale plasma simulations are extremely challenging. In this thesis the simplex-in-cell algorithm is presented, which holds promise for overcoming these difficulties by interpreting the simulation particles as the vertices of a mesh that traces the evolution of the distribution function in phase space. This enables a discretization using deformable phase space volume elements rather than fixed-shape clouds of charge. Using test problems including Landau damping and the Weibel instability it is shown how this new view retains fine-scale structure in the distribution function and can drastically reduce the number of simulation particles required to reach a given noise level. Magnetic reconnection is a promising candidate mechanism for accelerating the nonthermal particles associated with explosive phenomena in astrophysics. Laboratory experiments with high-power lasers can play an important role in the study of the detailed microphysics of reconnection and the dominant particle acceleration mechanisms. In this thesis the results of particle-in-cell simulations used to explore particle acceleration in conditions relevant for current and future laser-driven reconnection experiments are presented. These simulations indicate that laser-driven plasmas offer a promising platform for studying particle acceleration from reconnection, with the potential to reach multi-plasmoid regimes of strong astrophysical interest. These results provide new insight into the physics of reconnection and particle acceleration and are now helping to guide experimental campaigns
The co-evolution of galaxies and their surrounding environments in massive galaxy clusters by Steven Ehlert( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

A key yet poorly understood component to galaxy evolution models is the influence of the local environment, and is a particularly important aspect to understanding the evolution in galaxy clusters. Galaxy clusters are not only host to significant overdensities of galaxies, but these galaxies are embedded in a hot, diffuse Intracluster Medium (ICM). The ICM has long been observed to have important and lasting impacts on the properties of their constituent galaxies, which are commonly attributed to a number of unique astrophysical processes such as the stripping of galaxy gas by the ICM due to ram pressure and repeated tidal interactions. The galaxies in turn have also been observed to play an important role in the evolution of the ICM, especially near the centers of galaxy clusters where powerful outbursts from Active Galactic Nuclei (AGN) can provide a quasi-steady source of heating to the surrounding ICM, a process known as AGN feedback. Although great progress has been made in recent years to understand the connection between galaxies and the ICM, the precise influence of the ICM on cluster galaxies and the astrophysical processes that drive galaxy evolution in clusters are still subject to important uncertainties. It is clear from the data, however, that the predictions of the simplest models of ram pressure stripping, tidal encounters, and AGN feedback are inconsistent with observations; in particular observations taken with the modern generation of X-ray telescopes such as Chandra and XMM-Newton. These telescopes, with their superb angular resolution, large collecting areas, and wide fields of view, have revolutionized our understanding of galaxies in clusters, in particular for AGN. In this thesis, I will present a series of results regarding the nature of ram pressure stripping, harassment, and AGN feedback in cluster member galaxies driven primarily by X-ray observations. These results include multiwavelength observations of one of the most extreme cases of AGN feedback currently known, a mosaic of galaxies in the nearby Virgo Cluster which are all undergoing different variants of ramp pressure stripping, and the first set of results from one of the largest X-ray AGN surveys ever undertaken with Chandra. All of these results suggest an intricate choreography between the gas reservoirs initially hosted by galaxies and the surrounding ICM, with tests that investigate length scales ranging from 10 kpc to 1 Mpc
Computational modeling of stellar formation in molecular clouds by Ryan Raba( )

1 edition published in 2004 in English and held by 1 WorldCat member library worldwide

The formation of population III binaries from cosmological initial conditions by Matthew J Turk( Book )

1 edition published in 2009 in English and held by 1 WorldCat member library worldwide

"Previous high-resolution cosmological simulations predicted that the first stars to appear in the early universe were very massive and formed in isolation. Here, we discuss a cosmological simulation in which the central 50 M (where M is the mass of the Sun) clump breaks up into two cores having a mass ratio of two to one, with one fragment collapsing to densities of 10-8 grams per cubic centimeter. The second fragment, at a distance of ~800 astronomical units, is also optically thick to its own cooling radiation from molecular hydrogen lines but is still able to cool via collision-induced emission. The two dense peaks will continue to accrete from the surrounding cold gas reservoir over a period of ~105 years and will likely form a binary star system."
Star formation now and then by Tom G Abel( Visual )

1 edition published in 2009 in English and held by 1 WorldCat member library worldwide

Professor Tom Abel discusses that dramatic algorithmic breakthroughs over the last ten years enabled ab initio calculations of the formation of the first stars, their impact on their environment, early metal enrichment, dwarf galaxy formation, the build up of cosmological magnetic fields and many questions relating to the interplay between galaxies and the intergalactic medium in general. With these calculations of growing complexity in hand, detailed predictions for potential observables of the very high redshift universe have become feasible. In this talk he highlights some of interest for JWST, ALMA and the upcoming redshifted 21cm observatories. New simulations of local star forming regions explain the longevity of molecular clouds. A complete theory of star formation is needed to build confidence in any of the predictions about the so far unobserved very high redshift universe as well as our understanding of the formation of galaxies in general
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The first stars : proceedings of the MPA/ESO Workshop held at Garching, Germany, 4-6 August 1999 The first stars : proceedings of the MPA/ESO Symposium held at Garching, Germany, 4-6 August 1999
First stars III : Santa Fe, New Mexico, 15-20 July 2007The first stars : proceedings of the MPA/ESO Symposium held at Garching, Germany, 4-6 August 1999The first stars
Alternative Names
Abel, T.

Abel, Tom

Abel, Tom 1970-

Abel, Tom G.

Tom Abel American astronomer

Tom Abel astrònom estatunidenc

Tom Abel astronome américain

Tom Abel astrónomo estadounidense

Tom Abel deutscher Astrophysiker, Kosmologe und Hochschullehrer

Tom Abel Duits astronoom

توم هابيل عالم فلك أمريكي

汤姆·艾贝尔 美国物理学家

English (37)