Pub Date : 2018-07-17DOI: 10.1146/annurev-astro-081817-052028
D. Nesvorný
Several properties of the Solar System, including the wide radial spacing of the giant planets, can be explained if planets radially migrated by exchanging orbital energy and momentum with outer disk planetesimals. Neptune's planetesimal-driven migration, in particular, has a strong advocate in the dynamical structure of the Kuiper belt. A dynamical instability is thought to have occurred during the early stages with Jupiter having close encounters with a Neptune-class planet. As a result of the encounters, Jupiter acquired its current orbital eccentricity and jumped inward by a fraction of an astronomical unit, as required for the survival of the terrestrial planets and from asteroid belt constraints. Planetary encounters also contributed to capture of Jupiter Trojans and irregular satellites of the giant planets. Here we discuss the dynamical evolution of the early Solar System with an eye to determining how models of planetary migration/instability can be constrained from its present architecture. Specifically, we review arguments suggesting that the Solar System may have originally contained a third ice giant on a resonant orbit between Saturn and Uranus. This hypothesized planet was presumably ejected into interstellar space during the instability. The Kuiper belt kernel and other dynamical structures in the trans-Neptunian region may provide evidence for the ejected planet. We favor the early version of the instability where Neptune migrated into the outer planetesimal disk within a few tens of millions of years after the dispersal of the protosolar nebula. If so, the planetary migration/instability was not the cause of the Late Heavy Bombardment. Mercury's orbit may have been excited during the instability.
{"title":"Dynamical Evolution of the Early Solar System","authors":"D. Nesvorný","doi":"10.1146/annurev-astro-081817-052028","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-052028","url":null,"abstract":"Several properties of the Solar System, including the wide radial spacing of the giant planets, can be explained if planets radially migrated by exchanging orbital energy and momentum with outer disk planetesimals. Neptune's planetesimal-driven migration, in particular, has a strong advocate in the dynamical structure of the Kuiper belt. A dynamical instability is thought to have occurred during the early stages with Jupiter having close encounters with a Neptune-class planet. As a result of the encounters, Jupiter acquired its current orbital eccentricity and jumped inward by a fraction of an astronomical unit, as required for the survival of the terrestrial planets and from asteroid belt constraints. Planetary encounters also contributed to capture of Jupiter Trojans and irregular satellites of the giant planets. Here we discuss the dynamical evolution of the early Solar System with an eye to determining how models of planetary migration/instability can be constrained from its present architecture. Specifically, we review arguments suggesting that the Solar System may have originally contained a third ice giant on a resonant orbit between Saturn and Uranus. This hypothesized planet was presumably ejected into interstellar space during the instability. The Kuiper belt kernel and other dynamical structures in the trans-Neptunian region may provide evidence for the ejected planet. We favor the early version of the instability where Neptune migrated into the outer planetesimal disk within a few tens of millions of years after the dispersal of the protosolar nebula. If so, the planetary migration/instability was not the cause of the Late Heavy Bombardment. Mercury's orbit may have been excited during the instability.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2018-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-052028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42542366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-12DOI: 10.1146/annurev-astro-081817-051803
R. Hickox, D. Alexander
Active galactic nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH) and are among the most luminous objects in the Universe. However, the huge radiative power of most AGN cannot be seen directly, as the accretion is hidden behind gas and dust that absorb many of the characteristic observational signatures. This obscuration presents an important challenge for uncovering the complete AGN population and understanding the cosmic evolution of SMBHs. In this review, we describe a broad range of multiwavelength techniques that are currently being employed to identify obscured AGN, and we assess the reliability and completeness of each technique. We follow with a discussion of the demographics of obscured AGN activity, explore the nature and physical scales of the obscuring material, and assess the implications of obscured AGN for observational cosmology. We conclude with an outline of the prospects for future progress from both observations and theoretical models, and we highlight some of the key outstanding questions.
{"title":"Obscured Active Galactic Nuclei","authors":"R. Hickox, D. Alexander","doi":"10.1146/annurev-astro-081817-051803","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051803","url":null,"abstract":"Active galactic nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH) and are among the most luminous objects in the Universe. However, the huge radiative power of most AGN cannot be seen directly, as the accretion is hidden behind gas and dust that absorb many of the characteristic observational signatures. This obscuration presents an important challenge for uncovering the complete AGN population and understanding the cosmic evolution of SMBHs. In this review, we describe a broad range of multiwavelength techniques that are currently being employed to identify obscured AGN, and we assess the reliability and completeness of each technique. We follow with a discussion of the demographics of obscured AGN activity, explore the nature and physical scales of the obscuring material, and assess the implications of obscured AGN for observational cosmology. We conclude with an outline of the prospects for future progress from both observations and theoretical models, and we highlight some of the key outstanding questions.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2018-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051803","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47077816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-03DOI: 10.1146/annurev-astro-081817-051826
B. Barbuy, C. Chiappini, Ortwin Gerhard
The Galactic Bulge can uniquely be studied from large samples of individual stars and is therefore of prime importance for understanding the stellar population structure of bulges in general. Here the observational evidence on the kinematics, chemical composition, and ages of Bulge stellar populations based on photometric and spectroscopic data is reviewed. The bulk of Bulge stars are old and span a metallicity range of −1.5≲[Fe/H]≲+0.5. Stellar populations and chemical properties suggest a star-formation timescale below ∼2 Gyr. The overall Bulge is barred and follows cylindrical rotation, and the more metal-rich stars trace a box/peanut (B/P) structure. Dyna-mical models demonstrate the different spatial and orbital distributions of metal-rich and metal-poor stars. We discuss current Bulge-formation scenarios based on dynamical, chemical, chemodynamical, and cosmological models. Despite impressive progress, we do not yet have a successful fully self-consistent chemodynamical Bulge model in the cosmological framework, and we will also need a more extensive chrono-chemical-kinematic 3D map of stars to better constrain such models.
{"title":"Chemodynamical History of the Galactic Bulge","authors":"B. Barbuy, C. Chiappini, Ortwin Gerhard","doi":"10.1146/annurev-astro-081817-051826","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051826","url":null,"abstract":"The Galactic Bulge can uniquely be studied from large samples of individual stars and is therefore of prime importance for understanding the stellar population structure of bulges in general. Here the observational evidence on the kinematics, chemical composition, and ages of Bulge stellar populations based on photometric and spectroscopic data is reviewed. The bulk of Bulge stars are old and span a metallicity range of −1.5≲[Fe/H]≲+0.5. Stellar populations and chemical properties suggest a star-formation timescale below ∼2 Gyr. The overall Bulge is barred and follows cylindrical rotation, and the more metal-rich stars trace a box/peanut (B/P) structure. Dyna-mical models demonstrate the different spatial and orbital distributions of metal-rich and metal-poor stars. We discuss current Bulge-formation scenarios based on dynamical, chemical, chemodynamical, and cosmological models. Despite impressive progress, we do not yet have a successful fully self-consistent chemodynamical Bulge model in the cosmological framework, and we will also need a more extensive chrono-chemical-kinematic 3D map of stars to better constrain such models.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2018-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051826","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44612390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-04-09DOI: 10.1146/annurev-astro-081817-051756
R. Wechsler, J. Tinker
In our modern understanding of galaxy formation, every galaxy forms within a dark matter halo. The formation and growth of galaxies over time is connected to the growth of the halos in which they form. The advent of large galaxy surveys as well as high-resolution cosmological simulations has provided a new window into the statistical relationship between galaxies and halos and its evolution. Here, we define this galaxy–halo connection as the multivariate distribution of galaxy and halo properties that can be derived from observations and simulations. This galaxy–halo connection provides a key test of physical galaxy-formation models; it also plays an essential role in constraints of cosmological models using galaxy surveys and in elucidating the properties of dark matter using galaxies. We review techniques for inferring the galaxy–halo connection and the insights that have arisen from these approaches. Some things we have learned are that galaxy-formation efficiency is a strong function of halo mass; at its peak in halos around a pivot halo mass of 1012M⊙, less than 20% of the available baryons have turned into stars by the present day; the intrinsic scatter in galaxy stellar mass is small, less than 0.2 dex at a given halo mass above this pivot mass; below this pivot mass galaxy stellar mass is a strong function of halo mass; the majority of stars over cosmic time were formed in a narrow region around this pivot mass. We also highlight key open questions about how galaxies and halos are connected, including understanding the correlations with secondary properties and the connection of these properties to galaxy clustering.
{"title":"The Connection Between Galaxies and Their Dark Matter Halos","authors":"R. Wechsler, J. Tinker","doi":"10.1146/annurev-astro-081817-051756","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051756","url":null,"abstract":"In our modern understanding of galaxy formation, every galaxy forms within a dark matter halo. The formation and growth of galaxies over time is connected to the growth of the halos in which they form. The advent of large galaxy surveys as well as high-resolution cosmological simulations has provided a new window into the statistical relationship between galaxies and halos and its evolution. Here, we define this galaxy–halo connection as the multivariate distribution of galaxy and halo properties that can be derived from observations and simulations. This galaxy–halo connection provides a key test of physical galaxy-formation models; it also plays an essential role in constraints of cosmological models using galaxy surveys and in elucidating the properties of dark matter using galaxies. We review techniques for inferring the galaxy–halo connection and the insights that have arisen from these approaches. Some things we have learned are that galaxy-formation efficiency is a strong function of halo mass; at its peak in halos around a pivot halo mass of 1012M⊙, less than 20% of the available baryons have turned into stars by the present day; the intrinsic scatter in galaxy stellar mass is small, less than 0.2 dex at a given halo mass above this pivot mass; below this pivot mass galaxy stellar mass is a strong function of halo mass; the majority of stars over cosmic time were formed in a narrow region around this pivot mass. We also highlight key open questions about how galaxies and halos are connected, including understanding the correlations with secondary properties and the connection of these properties to galaxy clustering.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051756","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47912049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-12DOI: 10.1146/annurev-astro-081817-052035
A. Hughes, G. Duchêne, G. Duchêne, B. Matthews, B. Matthews
Debris disks are tenuous, dust-dominated disks commonly observed around stars over a wide range of ages. Those around main sequence stars are analogous to the Solar System's Kuiper Belt and zodiacal light. The dust in debris disks is believed to be continuously regenerated, originating primarily with collisions of planetesimals. Observations of debris disks provide insight into the evolution of planetary systems; and the composition of dust, comets, and planetesimals outside the Solar System; as well as placing constraints on the orbital architecture and potentially the masses of exoplanets that are not otherwise detectable. This review highlights recent advances in multiwavelength, high-resolution scattered light and thermal imaging that have revealed a complex and intricate diversity of structures in debris disks and discusses how modeling methods are evolving with the breadth and depth of the available observations. Two rapidly advancing subfields highlighted in this review include observations of atomic and molecular gas around main sequence stars and variations in emission from debris disks on very short (days to years) timescales, providing evidence of non-steady-state collisional evolution particularly in young debris disks.
{"title":"Debris Disks: Structure, Composition, and Variability","authors":"A. Hughes, G. Duchêne, G. Duchêne, B. Matthews, B. Matthews","doi":"10.1146/annurev-astro-081817-052035","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-052035","url":null,"abstract":"Debris disks are tenuous, dust-dominated disks commonly observed around stars over a wide range of ages. Those around main sequence stars are analogous to the Solar System's Kuiper Belt and zodiacal light. The dust in debris disks is believed to be continuously regenerated, originating primarily with collisions of planetesimals. Observations of debris disks provide insight into the evolution of planetary systems; and the composition of dust, comets, and planetesimals outside the Solar System; as well as placing constraints on the orbital architecture and potentially the masses of exoplanets that are not otherwise detectable. This review highlights recent advances in multiwavelength, high-resolution scattered light and thermal imaging that have revealed a complex and intricate diversity of structures in debris disks and discusses how modeling methods are evolving with the breadth and depth of the available observations. Two rapidly advancing subfields highlighted in this review include observations of atomic and molecular gas around main sequence stars and variations in emission from debris disks on very short (days to years) timescales, providing evidence of non-steady-state collisional evolution particularly in young debris disks.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2018-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-052035","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44595112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-18DOI: 10.1146/annurev-astro-081817-051853
R. Dawson, J. Johnson
Hot Jupiters were the first exoplanets to be discovered around main sequence stars and astonished us with their close-in orbits. They are a prime example of how exoplanets have challenged our textbook, solar-system inspired story of how planetary systems form and evolve. More than twenty years after the discovery of the first hot Jupiter, there is no consensus on their predominant origin channel. Three classes of hot Jupiter creation hypotheses have been proposed: in situ formation, disk migration, and high-eccentricity tidal migration. Although no origin channel alone satisfactorily explains all the evidence, two major origin channels together plausibly account for properties of hot Jupiters themselves and their connections to other exoplanet populations.
{"title":"Origins of Hot Jupiters","authors":"R. Dawson, J. Johnson","doi":"10.1146/annurev-astro-081817-051853","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051853","url":null,"abstract":"Hot Jupiters were the first exoplanets to be discovered around main sequence stars and astonished us with their close-in orbits. They are a prime example of how exoplanets have challenged our textbook, solar-system inspired story of how planetary systems form and evolve. More than twenty years after the discovery of the first hot Jupiter, there is no consensus on their predominant origin channel. Three classes of hot Jupiter creation hypotheses have been proposed: in situ formation, disk migration, and high-eccentricity tidal migration. Although no origin channel alone satisfactorily explains all the evidence, two major origin channels together plausibly account for properties of hot Jupiters themselves and their connections to other exoplanet populations.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2018-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051853","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45101557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-04DOI: 10.1146/annurev-astro-081817-051839
N. Bastian, C. Lardo
Globular clusters (GCs) exhibit star-to-star variations in specific elements (e.g., He, C, N, O, Na, Al) that bear the hallmark of high-temperature H-burning. These abundance variations can be observed spectroscopically and also photometrically, with the appropriate choice of filters, due to the changing of spectral features within the band pass. This phenomenon is observed in nearly all of the ancient GCs, although, to date, it has not been found in any massive cluster younger than 2 Gyr. Many scenarios have been suggested to explain this phenomenon, with most invoking multiple epochs of star formation within the cluster; however, all have failed to reproduce various key observations, in particular when a global view of the GC population is taken. We review the state of current observations and outline the successes and failures of each of the main proposed models. The traditional idea of using the stellar ejecta from a first generation of stars to form a second generation of stars, while conceptually straightforward, has failed to reproduce an increasing number of observational constraints. We conclude that the puzzle of multiple populations remains unsolved, hence alternative theories are needed.
{"title":"Multiple Stellar Populations in Globular Clusters","authors":"N. Bastian, C. Lardo","doi":"10.1146/annurev-astro-081817-051839","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051839","url":null,"abstract":"Globular clusters (GCs) exhibit star-to-star variations in specific elements (e.g., He, C, N, O, Na, Al) that bear the hallmark of high-temperature H-burning. These abundance variations can be observed spectroscopically and also photometrically, with the appropriate choice of filters, due to the changing of spectral features within the band pass. This phenomenon is observed in nearly all of the ancient GCs, although, to date, it has not been found in any massive cluster younger than 2 Gyr. Many scenarios have been suggested to explain this phenomenon, with most invoking multiple epochs of star formation within the cluster; however, all have failed to reproduce various key observations, in particular when a global view of the GC population is taken. We review the state of current observations and outline the successes and failures of each of the main proposed models. The traditional idea of using the stellar ejecta from a first generation of stars to form a second generation of stars, while conceptually straightforward, has failed to reproduce an increasing number of observational constraints. We conclude that the puzzle of multiple populations remains unsolved, hence alternative theories are needed.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2017-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051839","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44271912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-11-20DOI: 10.1146/annurev-astro-081817-051900
F. Galliano, F. Galliano, M. Galametz, M. Galametz, A. Jones
This article gives an overview of the constitution, physical conditions, and observables of dust in the interstellar medium of nearby galaxies. We first review the macroscopic, spatial distribution of dust in these objects and its consequences for our ability to study grain physics. We also discuss the possibility of using dust tracers as diagnostic tools. We then survey the current understanding of the microscopic, intrinsic properties of dust in different environments, derived from different observables: emission, extinction, polarization, and depletions, over the whole electromagnetic spectrum. Finally, we summarize the clues about grain evolution, evidenced either on local scales or over cosmic time. We put in perspective the different evolution scenarios. We attempt a comprehensive presentation of the main observational constraints, analysis methods, and modeling frameworks of the distinct processes. We discuss neither the dust properties of the Milky Way and distant galaxies, nor circumstellar or active galactic nucleus torus dust.
{"title":"The Interstellar Dust Properties of Nearby Galaxies","authors":"F. Galliano, F. Galliano, M. Galametz, M. Galametz, A. Jones","doi":"10.1146/annurev-astro-081817-051900","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051900","url":null,"abstract":"This article gives an overview of the constitution, physical conditions, and observables of dust in the interstellar medium of nearby galaxies. We first review the macroscopic, spatial distribution of dust in these objects and its consequences for our ability to study grain physics. We also discuss the possibility of using dust tracers as diagnostic tools. We then survey the current understanding of the microscopic, intrinsic properties of dust in different environments, derived from different observables: emission, extinction, polarization, and depletions, over the whole electromagnetic spectrum. Finally, we summarize the clues about grain evolution, evidenced either on local scales or over cosmic time. We put in perspective the different evolution scenarios. We attempt a comprehensive presentation of the main observational constraints, analysis methods, and modeling frameworks of the distinct processes. We discuss neither the dust properties of the Milky Way and distant galaxies, nor circumstellar or active galactic nucleus torus dust.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2017-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051900","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48992198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-10-09DOI: 10.1146/annurev-astro-081817-051928
R. Mandelbaum
Weak gravitational lensing, the deflection of light by mass, is one of the best tools to constrain the growth of cosmic structure with time and reveal the nature of dark energy. I discuss the sources of systematic uncertainty in weak lensing measurements and their theoretical interpretation, including our current understanding and other options for future improvement. These include long-standing concerns such as the estimation of coherent shears from galaxy images or redshift distributions of galaxies selected on the basis of photometric redshifts, along with systematic uncertainties that have received less attention to date because they are subdominant contributors to the error budget in current surveys. I also discuss methods for automated systematics detection using survey data of the 2020s. The goal of this review is to describe the current state of the field and what must be done so that if weak lensing measurements lead toward surprising conclusions about key questions such as the nature of dark energy, those conclusions will be credible.
{"title":"Weak Lensing for Precision Cosmology","authors":"R. Mandelbaum","doi":"10.1146/annurev-astro-081817-051928","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051928","url":null,"abstract":"Weak gravitational lensing, the deflection of light by mass, is one of the best tools to constrain the growth of cosmic structure with time and reveal the nature of dark energy. I discuss the sources of systematic uncertainty in weak lensing measurements and their theoretical interpretation, including our current understanding and other options for future improvement. These include long-standing concerns such as the estimation of coherent shears from galaxy images or redshift distributions of galaxies selected on the basis of photometric redshifts, along with systematic uncertainties that have received less attention to date because they are subdominant contributors to the error budget in current surveys. I also discuss methods for automated systematics detection using survey data of the 2020s. The goal of this review is to describe the current state of the field and what must be done so that if weak lensing measurements lead toward surprising conclusions about key questions such as the nature of dark energy, those conclusions will be credible.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2017-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051928","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48827992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-08-18DOI: 10.1146/ANNUREV-ASTRO-091916-055221
Jinlin Han
Observational results of interstellar and intergalactic magnetic fields are reviewed, including the fields in supernova remnants and loops, interstellar filaments and clouds, Hii regions and bubbles, the Milky Way and nearby galaxies, galaxy clusters, and the cosmic web. A variety of approaches are used to investigate these fields. The orientations of magnetic fields in interstellar filaments and molecular clouds are traced by polarized thermal dust emission and starlight polarization. The field strengths and directions along the line of sight in dense clouds and cores are measured by Zeeman splitting of emission or absorption lines. The large-scale magnetic fields in the Milky Way have been best probed by Faraday rotation measures of a large number of pulsars and extragalactic radio sources. The coherent Galactic magnetic fields are found to follow the spiral arms and have their direction reversals in arms and interarm regions in the disk. The azimuthal fields in the halo reverse their directions below a...
{"title":"Observing Interstellar and Intergalactic Magnetic Fields","authors":"Jinlin Han","doi":"10.1146/ANNUREV-ASTRO-091916-055221","DOIUrl":"https://doi.org/10.1146/ANNUREV-ASTRO-091916-055221","url":null,"abstract":"Observational results of interstellar and intergalactic magnetic fields are reviewed, including the fields in supernova remnants and loops, interstellar filaments and clouds, Hii regions and bubbles, the Milky Way and nearby galaxies, galaxy clusters, and the cosmic web. A variety of approaches are used to investigate these fields. The orientations of magnetic fields in interstellar filaments and molecular clouds are traced by polarized thermal dust emission and starlight polarization. The field strengths and directions along the line of sight in dense clouds and cores are measured by Zeeman splitting of emission or absorption lines. The large-scale magnetic fields in the Milky Way have been best probed by Faraday rotation measures of a large number of pulsars and extragalactic radio sources. The coherent Galactic magnetic fields are found to follow the spiral arms and have their direction reversals in arms and interarm regions in the disk. The azimuthal fields in the halo reverse their directions below a...","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":null,"pages":null},"PeriodicalIF":33.3,"publicationDate":"2017-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/ANNUREV-ASTRO-091916-055221","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45187344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：