Search Publications
Powerful Outflows and Feedback from Active Galactic Nuclei
Pounds, Ken; King, Andrew
Active galactic nuclei (AGNs) represent the growth phases of the supermassive black holes in the center of almost every galaxy. Powerful, highly ionized winds, with velocities â¼0.1-0.2c, are a common feature in X-ray spectra of luminous AGNs, offering a plausible physical origin for the well-known connections between the hole and properties of it…
Ideas for Citizen Science in Astronomy
Fletcher, Leigh N.; Marshall, Philip J.; Lintott, Chris J.
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 feat…
Short-Duration Gamma-Ray Bursts
Berger, Edo
Gamma-ray bursts (GRBs) display a bimodal duration distribution with a separation between the short- and long-duration bursts at about 2 s. The progenitors of long GRBs have been identified as massive stars based on their association with Type Ic core-collapse supernovae (SNe), their exclusive location in star-forming galaxies, and their strong co…
Far-Infrared Surveys of Galaxy Evolution
Lutz, Dieter
Roughly half of the radiation from evolving galaxies in the early Universe reaches us in the far-infrared and submillimeter wavelength ranges. Recent major advances in observing capabilities, in particular the launch of the Herschel Space Observatory in 2009, have dramatically enhanced our ability to use this information in the context of multiwav…
Star Formation in the Milky Way and Nearby Galaxies
Kennicutt, Robert C.; Evans, Neal J.
We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star form…
Cosmological Parameters from Observations of Galaxy Clusters
Allen, Steven W.; Evrard, August E.; Mantz, Adam B.
Studies of galaxy clusters have proved crucial in helping to establish the standard model of cosmology, with a Universe dominated by dark matter and dark energy. A theoretical basis that describes clusters as massive, multicomponent, quasi-equilibrium systems is growing in its capability to interpret multiwavelength observations of expanding scope…
The Chemical Composition of Comets—Emerging Taxonomies and Natal Heritage
Mumma, Michael J.; Charnley, Steven B.
Cometary nuclei contain the least modified material from the formative epoch of our planetary system, and their compositions reflect a range of processes experienced by material prior to its incorporation in the cometary nucleus. Dynamical models suggest that icy bodies in the main cometary reservoirs (Kuiper Belt, Oort Cloud) formed in a range of…
Relativistic X-Ray Lines from the Inner Accretion Disks Around Black Holes
Miller, J. M.
Relativistic X-ray emission lines from the inner accretion disks around black holes are reviewed. Recent observations with the Chandra X-ray Observatory, X-ray Multi-Mirror Mission-Newton, and Suzaku are revealing these lines to be good probes of strong gravitational effects. A number of important observational and theoretical developments are hig…
A New View of the Coupling of the Sun and the Heliosphere
Zurbuchen, Thomas H.
The structure of the global heliospheric field reflects the physical properties of the low corona. The implied connections between solar and heliospheric evolution have been analyzed by a powerful multisatellite solar and heliospheric observatory that includes the Ulysses and the Solar and Heliospheric Observatory (SOHO) spacecraft. This coordinat…
Standard Photometric Systems
Bessell, Michael S.
Standard star photometry dominated the latter half of the twentieth century reaching its zenith in the 1980s. It was introduced to take advantage of the high sensitivity and large dynamic range of photomultiplier tubes compared to photographic plates. As the quantum efficiency of photodetectors improved and the wavelength range extended further to…