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  • 2015-2019  (207.411)
  • Physik  (207.411)
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  • 1
    Online-Ressource
    Online-Ressource
    Annual Reviews ; 2015
    In:  Annual Review of Astronomy and Astrophysics Vol. 53, No. 1 ( 2015-08-18), p. 51-113
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 53, No. 1 ( 2015-08-18), p. 51-113
    Kurzfassung: Modeling galaxy formation in a cosmological context presents one of the greatest challenges in astrophysics today due to the vast range of scales and numerous physical processes involved. Here we review the current status of models that employ two leading techniques to simulate the physics of galaxy formation: semianalytic models and numerical hydrodynamic simulations. We focus on a set of observational targets that describe the evolution of the global and structural properties of galaxies from roughly cosmic high noon (z ∼ 2–3) to the present. Although minor discrepancies remain, overall, models show remarkable convergence among different methods and make predictions that are in qualitative agreement with observations. Modelers have converged on a core set of physical processes that are critical for shaping galaxy properties. This core set includes cosmological accretion, strong stellar-driven winds that are more efficient at low masses, black hole feedback that preferentially suppresses star formation at high masses, and structural and morphological evolution through merging and environmental processes. However, all cosmological models currently adopt phenomenological implementations of many of these core processes, which must be tuned to observations. Many details of how these diverse processes interact within a hierarchical structure formation setting remain poorly understood. Emerging multiscale simulations are helping to bridge the gap between stellar and cosmological scales, placing models on a firmer, more physically grounded footing. Concurrently, upcoming telescope facilities will provide new challenges and constraints for models, particularly by directly constraining inflows and outflows through observations of gas in and around galaxies.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2015
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    Annual Reviews ; 2015
    In:  Annual Review of Astronomy and Astrophysics Vol. 53, No. 1 ( 2015-08-18), p. 247-278
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 53, No. 1 ( 2015-08-18), p. 247-278
    Kurzfassung: We review the expanding, internet-enabled, and rapidly evolving field of citizen astronomy, focusing on research projects in stellar, extragalactic, and planetary science that have benefited from the participation of members of the public. These volunteers contribute in various ways: making and analyzing new observations, visually classifying features in images and light curves, exploring models constrained by astronomical data sets, and initiating new scientific enquiries. The most productive citizen astronomy projects involve close collaboration between the professionals and amateurs involved and occupy scientific niches not easily filled by great observatories or machine learning methods: Citizen astronomers are motivated by being of service to science, as well as by their interest in the subject. We expect participation and productivity in citizen astronomy to increase, as data sets get larger and citizen science platforms become more efficient. Opportunities include engaging citizens in ever-more advanced analyses and facilitating citizen-led enquiry through professional tools designed with citizens in mind.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2015
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
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  • 3
    Online-Ressource
    Online-Ressource
    Annual Reviews ; 2016
    In:  Annual Review of Astronomy and Astrophysics Vol. 54, No. 1 ( 2016-09-19), p. 761-803
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 54, No. 1 ( 2016-09-19), p. 761-803
    Kurzfassung: In the past five years, deep imaging campaigns conducted with the Hubble Space Telescope (HST) and ground-based observatories have delivered large samples of galaxies at 6.5 〈 z 〈 10, providing our first glimpse of the census of star formation activity in what is thought to be the heart of the reionization era. The space density of luminous galaxies has been shown to decrease by 15–20× over 4 〈 z 〈 8. Over this same redshift interval, the faint-end slope of the UV luminosity function becomes steeper (α≃−2.0 at z≃7−8), revealing a dominant population of low-luminosity galaxies. Analysis of multiwavelength imaging from HST and the Spitzer Space Telescope demonstrates that z 〉 6 UV-selected galaxies are relatively compact with blue UV continuum slopes, low stellar masses, and large specific star formation rates. In the last year, ALMA (the Atacama Large Millimeter Array) and ground-based infrared spectrographs have begun to complement this picture, revealing minimal dust obscuration and hard radiation fields, and providing evidence for metal-poor ionized gas. Weak low-ionization absorption lines suggest a patchy distribution of neutral gas surrounds O and B stars, possibly aiding in the escape of ionizing radiation. Gamma ray burst afterglows and Lyman-α surveys have provided evidence that the intergalactic medium (IGM) evolves from mostly ionized at z≃6−6.5 ([Formula: see text]) to considerably neutral at z≃7−8 ([Formula: see text] ). The reionization history that emerges from considering the UV output of galaxies over 6 〈 z 〈 10 is consistent with these constraints on the IGM ionization state. The latest measurements suggest that galaxies can complete reionization by z≃6 and reproduce the Thomson scattering optical depth faced by cosmic microwave background photons if the luminosity function extends ≃4 mag below current surveys and a moderate fraction ([Formula: see text]) of ionizing radiation escapes from galaxies.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2016
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
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  • 4
    Online-Ressource
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    Annual Reviews ; 2017
    In:  Annual Review of Astronomy and Astrophysics Vol. 55, No. 1 ( 2017-08-18), p. 343-387
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 55, No. 1 ( 2017-08-18), p. 343-387
    Kurzfassung: The dark energy plus cold dark matter (ΛCDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of the Universe and its evolution with time. Yet on length scales smaller than ∼1 Mpc and mass scales smaller than ∼10 11 M ⊙ , the theory faces a number of challenges. For example, the observed cores of many dark matter–dominated galaxies are both less dense and less cuspy than naïvely predicted in ΛCDM. The number of small galaxies and dwarf satellites in the Local Group is also far below the predicted count of low-mass dark matter halos and subhalos within similar volumes. These issues underlie the most well-documented problems with ΛCDM: cusp/core, missing satellites, and too-big-to-fail. The key question is whether a better understanding of baryon physics, dark matter physics, or both is required to meet these challenges. Other anomalies, including the observed planar and orbital configurations of Local Group satellites and the tight baryonic/dark matter scaling relations obeyed by the galaxy population, have been less thoroughly explored in the context of ΛCDM theory. Future surveys to discover faint, distant dwarf galaxies and to precisely measure their masses and density structure hold promising avenues for testing possible solutions to the small-scale challenges going forward. Observational programs to constrain or discover and characterize the number of truly dark low-mass halos are among the most important, and achievable, goals in this field over the next decade. These efforts will either further verify the ΛCDM paradigm or demand a substantial revision in our understanding of the nature of dark matter.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2017
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
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  • 5
    Online-Ressource
    Online-Ressource
    Annual Reviews ; 2017
    In:  Annual Review of Astronomy and Astrophysics Vol. 55, No. 1 ( 2017-08-18), p. 1-16
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 55, No. 1 ( 2017-08-18), p. 1-16
    Kurzfassung: This is an autobiographical account of my scientific career. My main research interest is the structure and assembly of galaxies. The assembly narrative has evolved from the monolithic and baryonic collapse picture of the early 1960s to the current hierarchical scenario underpinned by dark matter, and is still evolving. Technology has changed: CCDs replaced photographic plates and image tubes, large optical telescopes are much larger and instruments are much better, Galactic archaeology is supported by vast stellar surveys, and we have space astronomy and radio synthesis telescopes. The article describes the scientific areas in which I have worked and the colleagues who have influenced my progress. I have much to be grateful for: the people who have mentored and supported me over the years, the privilege of long-term collaborations, and the pleasure of advising many Ph.D. students and postdocs.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2017
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
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  • 6
    Online-Ressource
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    Annual Reviews ; 2019
    In:  Annual Review of Astronomy and Astrophysics Vol. 57, No. 1 ( 2019-08-18), p. 157-187
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 57, No. 1 ( 2019-08-18), p. 157-187
    Kurzfassung: The corona is a layer of hot plasma that surrounds the Sun, traces out its complex magnetic field, and ultimately expands into interplanetary space as the supersonic solar wind. Although much has been learned in recent decades from advances in observations, theory, and computer simulations, we still have not identified definitively the physical processes that heat the corona and accelerate the solar wind. In this review, we summarize these recent advances and speculate about what else is required to finally understand the fundamental physics of this complex system. Specifically: ▪ We discuss recent subarcsecond observations of the corona, some of which appear to provide evidence for tangled and braided magnetic fields and some of which do not. ▪ We review results from three-dimensional numerical simulations that, despite limitations in dynamic range, reliably contain sufficient heating to produce and maintain the corona. ▪ We provide a new tabulation of scaling relations for a number of proposed coronal heating theories that involve waves, turbulence, braiding, nanoflares, and helicity conservation. An understanding of these processes is important not only for improving our ability to forecast hazardous space-weather events but also for establishing a baseline of knowledge about a well-resolved star that is relevant to other astrophysical systems.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2019
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
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  • 7
    Online-Ressource
    Online-Ressource
    Annual Reviews ; 2015
    In:  Annual Review of Astronomy and Astrophysics Vol. 53, No. 1 ( 2015-08-18), p. 501-539
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 53, No. 1 ( 2015-08-18), p. 501-539
    Kurzfassung: Interstellar polarization at optical-to-infrared wavelengths is known to arise from asymmetric dust grains aligned with the magnetic field. This effect provides a potentially powerful probe of magnetic field structure and strength if the details of the grain alignment can be reliably understood. Theory and observations have recently converged on a quantitative, predictive description of interstellar grain alignment based on radiative processes. The development of a general, analytical model for this radiative alignment torque (RAT) theory has allowed specific, testable predictions for realistic interstellar conditions. We outline the theoretical and observational arguments in favor of RAT alignment, as well as reasons the “classical” paramagnetic alignment mechanism is unlikely to work, except possibly for the very smallest grains. With further detailed characterization of the RAT mechanism, grain alignment and polarimetry promise to not only better constrain the interstellar magnetic field but also provide new information on the dust characteristics.
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2015
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Online-Ressource
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    Annual Reviews ; 2019
    In:  Annual Review of Astronomy and Astrophysics Vol. 57, No. 1 ( 2019-08-18), p. v-vii
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 57, No. 1 ( 2019-08-18), p. v-vii
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2019
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Online-Ressource
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    Annual Reviews ; 2019
    In:  Annual Review of Astronomy and Astrophysics Vol. 57, No. 1 ( 2019-08-18), p. 1-34
    In: Annual Review of Astronomy and Astrophysics, Annual Reviews, Vol. 57, No. 1 ( 2019-08-18), p. 1-34
    Kurzfassung: Dear readers: We are sad to report that, soon after submitting her draft manuscript for this prefatory chapter, Nancy Grace Roman passed away on December 25, 2018. This final version of her memoir has been lightly edited but remains very true to the original. However, an Abstract was missing. Rather than trying to synthesize one in Nancy Grace's inimitable style, we take this opportunity to comment briefly on her life and its significance. Nancy Grace Roman was born in 1925 and came of age scientifically in the United States during the 1940s and 1950s. Together with the equally fascinating prefatory by Vera Rubin ( ARAA, Vol. 49), which we also recommend to you, these two memoirs give us intimate insight into the obstacles faced by women astronomers trying to rise in the field during those years. Roman's memoir is bitingly candid, recounting numerous snubs by teachers, insultingly small salaries, and attempts by her thesis advisor to simultaneously exploit her scientific findings and smother her role in them. Discouragement at every turn from doing forefront research is what drove Roman into government service, where she found a niche and blossomed as one of the visionary founders of the US civilian space program. We do not know what impact Roman might have had as a researcher with access to the world's largest telescopes, but we do know that her influence as an enabler of other people's science was vast. Her sobriquet as the “Mother of Hubble,” bestowed by admirer Ed Weiler, is well deserved. Nancy Grace granted an audio interview to Joss Bland-Hawthorn on August 4, 2018, just a few months before her passing. It captures her persona more vividly than mere words on paper, and we recommend the online recording to you at https://www.annualreviews.org/r/nancy-grace-roman-interview .
    Materialart: Online-Ressource
    ISSN: 0066-4146 , 1545-4282
    RVK:
    Sprache: Englisch
    Verlag: Annual Reviews
    Publikationsdatum: 2019
    ZDB Id: 2160505-1
    ZDB Id: 2010305-0
    SSG: 16,12
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  • 10
    Online-Ressource
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    IOP Publishing ; 2015
    In:  Japanese Journal of Applied Physics Vol. 54, No. 1S ( 2015-01-01), p. 01AE01-
    In: Japanese Journal of Applied Physics, IOP Publishing, Vol. 54, No. 1S ( 2015-01-01), p. 01AE01-
    Materialart: Online-Ressource
    ISSN: 0021-4922 , 1347-4065
    RVK:
    RVK:
    RVK:
    Sprache: Unbekannt
    Verlag: IOP Publishing
    Publikationsdatum: 2015
    ZDB Id: 218223-3
    ZDB Id: 797294-5
    ZDB Id: 2006801-3
    ZDB Id: 797295-7
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