||West Virginia University
|| HII Regions and the Warm Ionized Medium
||Plasma of temperature 10,000K is created by OB stars and takes the form of discrete HII regions and diffuse gas. It is the key to determining the impact of massive stars on the interstellar medium (ISM) and the lifecycle of ISM gas. We review research this plasma, highlight outstanding questions, and provide recommendations for future facilities.
|| Radar Astronomy for Planetary Surface Studies
||This paper addresses future use of ground-based radar facilities for studies of the surfaces of planets and satellites.
||Institute for Advanced Study
|| Magnetic Fields and Polarization in the Diffuse Interstellar Medium
||Magnetism is one of the most important forces on interstellar gas dynamics, star formation, and Galactic evolution. The next decade will transform our understanding of interstellar magnetism if we invest in polarimetry: surveys of polarized dust emission, starlight polarization, and single-dish measurements of Zeeman splitting.
|| Gravitational Waves, Extreme Astrophysics, and Fundamental Physics with Precision Pulsar Timing
||This white paper outlines a pulsar timing program that will provide precision masses of neutron stars, stringent tests of General Relativity, and the detectors for light-year wavelength gravitational wave astronomy and astrophysics: millisecond pulsars, nature's most precise clocks.
||University of California, Berkeley
|| Observing the Earth as a Communicating Exoplanet
||This white paper highlights an observing project that aims to advance and refine our search for life in the Universe, measure the Earth’s technosignature over time, and foster collaborations between radio astronomers and the wider astrobiology community. This paper highlights the Moonbounce Project and opportunities for project expansion.
||NASA Goddard Space Flight Center
|| Life Beyond the Solar System: Remotely Detectable Biosignatures
||This white paper reviews the scientific community’s ability to use data from future telescopes to search for life on exoplanets. It summarizes products from the Exoplanet Biosignatures Workshop Without Walls (EBWWW). This effort led to papers that constituted the Exoplanet Analysis Group's (ExoPAG) 16th Science Assessment Group (SAG 16).
||The Planetary Society
|| Thinking Big: How Large Aperture Space Telescopes Can Aid the Search for Life in Our Lifetimes
||We discuss the capabilities needed to conduct the most scientifically compelling endeavor currently facing space science: the successful search for life elsewhere. We provide the context for NASA’s search for life beyond the Earth, report our assessment of public support for this science, and ways for the Astro2020 process to address this goal.
||Center for Astrophysics | Harvard & Smithsonian
|| Increasing the Discovery Space in Astrophysics The Exploration Question for Planetary Systems
||Exploration can be the central question for Astro2020. Major astronomical discoveries were not driven by known questions, but by increasing discovery space via new telescopes and instruments, & now archive mining. Revolutionary facilities and supporting archives will open new discoveries. Here we focus on exploration for planetary systems.
||Space Telescope Science Institute
|| The Magellanic Stream as a Probe of Astrophysics
||The Magellanic Stream is the most spectacular example of a gaseous stream in the local Universe. In this white paper, we emphasize the Stream’s importance for many areas of Galactic astronomy, summarize key unanswered questions, and identify future observations and simulations needed to resolve them.
||Green Bank Observatory, WV
|| Radio Spectral Line Probe of Evolution of Fundamental Constants
||Comparisons between the redshifts of multiple spectral transitions from distant galaxies provide a sensitive probe of secular evolution in fundamental constants over cosmological epochs. We summarizes the current status of the field and the directions for progress with large radio telescopes and their new and improved instrumentation.
||Blue Marble Space Institute of Science
|| Searching for Technosignatures: Implications of Detection and Non-Detection
||The search for technosignatures from the Galaxy or the nearby universe raises two main questions: What are the possible characteristics of technosignatures? and How can future searches be optimized to enhance the probability of detection? Addressing these questions requires an interdisciplinary approach, which is described in this white paper.
||university of california at berkeley
|| Galactic and Extragalactic Astrochemisry: Heavy-Molecule Precursors to Life?
||Dense interstellar clouds contain an astonishingly rich collection of exotic molecules in various states of ionization and excitation, revealing complex astrochemistry. Charged molecules may moderate the magnetic field during star formation. The largest ones, which may be precursors to life, are best identified at 0.5-10 GHz with big telescopes.
|| Multi-Messenger Astrophysics With Pulsar Timing Arrays
||Pulsar timing arrays are on the verge of detecting low-frequency gravitational waves from supermassive black hole binaries. Multi-messenger observations will revolutionize our understanding of: 1. co-evolution of BHs with their hosts, 2. interactions of binaries with their environments, 3. fundamental physics of accretion, 4. cosmological distances
|| Radio Time-Domain Signatures of Magnetar Birth
||We consider the implications of an emerging consensus on the origin of a diverse set of luminous astrophysical transients, such as FRBs, SLSNe, and ULGRBs. Each of these classes could be interpreted as a signature of magnetar birth. We describe how radio transients from milliseconds to gigaseconds will be used to address diverse physical questions.
||Jet Propulsion Laboratory, California Institute of Technology
|| Magnetic Fields of Extrasolar Planets: Planetary Interiors and Habitability
||Generated by internal dynamos, magnetic fields are one of the few remote sensing means of constraining the properties of planetary interiors. The Earth's magnetic field has been speculated to be partially responsible for its habitability, and knowledge of an extrasolar planet’s magnetic field may be necessary to assess its habitability.
|| A Technosignature Carrying a Message Will Likely Inform us of Crucial Biological Details of Life Outside our Solar System
||We should search for interstellar messages because they probably contain a rich source of biological information about extraterrestrial life.
||West Virginia University
|| Radio Pulsar Populations
||We provide an overview of the radio pulsar population as it is currently understood, and give predictions for surveys with predominantly large single-dish radio facilities over the coming decade. Over 10,000 pulsars are expected to be found. Applications include tests of gravity and as natural laboratories for low-frequency gravitational waves.
||Agnes Scott College
|| Ground-based Observations of Small Solar System Bodies: Probing Our Local Debris Disk
||Comets and asteroids are a window into the formation, evolution, and dynamic environment of our solar system, an end-state of debris disks that we can only study from afar. Long-wavelength radio ground-based observations of asteroids and comets provide an excellent complement to shorter-wavelength observations both from the ground and from space.
||Green Bank Observatory
|| The Virtues of Time and Cadence for Pulsars and Fast Transients
||We summarize the scientific opportunities that can be realized using pulsars and fast radio transients with high-cadence, long duration observing programs and data sets, with a particular focus on gravitational waves, fundamental physics, pulsar emission, the dynamical interstellar and intergalactic media, and fast radio bursts.
||University of California, Los Angeles
|| Structure of terrestrial planets and ocean worlds
||Rotation studies provide a unique window on the interior structure of planetary bodies. The science can be accomplished only with facilities that enable many other astronomical observations. The Astro2020 decadal survey will make recommendations about the facilities that are critical to the realization of the science described in this white paper.
|| Emerging Capabilities for Detection and Characterization of Near-Earth Objects (NEOs)
||Here we describe the status for the detection and characterization of Near-Earth Objects (NEO) with current and future observatories. A summary of the capabilities, limitations, and obtainable NEO parameters is provided.
|| Invisible Structures in the Local Universe
||Neutral hydrogen surveys have revealed the existence of dark and almost-dark structures around nearby galaxies and in local groups and clusters. Understanding these structures will give us insights into how hydrogen cycles in and out of galaxies in different environments and will help us to understand the occupancy of low-mass dark matter subhalos.
||George Mason University
|| Community Endorsement of the National Academies Exoplanet Science Strategy and Astrobiology Strategy for the Search for Life in the Universe Reports
||The National Academies 'Exoplanet Science Strategy' and 'Astrobiology Strategy for the Search for Life in the Universe' reports present timely and consensus assessments of the priorities and recommendations of our science communities. We are signing our support for their findings and recommendations as input to the Astrophysics 2020 decadal survey.
||Center for Astrophysics | Harvard & Smithsonian; Caltech
|| Fast Radio Burst Tomography of the Unseen Universe
||The discovery of Fast Radio Bursts (FRBs) at cosmological distances has opened a powerful window on otherwise unseen matter in the Universe. Observations of >10^4 FRBs will assess the baryon contents and physical conditions in the hot/diffuse circumgalactic, intracluster, and intergalactic medium, and test extant compact-object dark matter models.
||Green Bank Observatory
|| Radio Scintillation Studies of Comet Ion Tails
||Future studies of comet ion tails using scintillation observations of the compact radio sources that they occult.
||Green Bank Observatory & Arecibo Observatory
|| Secular Transient Radio Sources
||The discovery and study of "secular transient radio sources" are reviewed via a number of examples. The continuing major contributions by large single-dish radio telescopes to the discovery, monitoring and VLBI follow-up studies of these transients are highlighted.
||University of Wisconsin -- Milwaukee
|| Physics Beyond the Standard Model With Pulsar Timing Arrays
||Pulsar timing arrays provide a rare opportunity to probe exotic physics. Potential sources of gravitational waves (GWs) in the nanohertz band include cosmic strings, inflation, and early universe phase transitions. GW observations will also make possible new tests of gravitational theories and provide a means to probe certain dark matter models.
|| Twelve Decades: Probing the Interstellar Medium from kiloparsec to sub-AU scales
||After a decade of great progress in understanding gas flow into, out of, and through the Milky Way, we are poised to merge observations with simulations to build a comprehensive picture of the multi-scale magnetized interstellar medium. These insights will also be crucial to four bold initiatives in the 2020s: GWs, FRBs, cosmic B-mode, and the EHT.
||Lunar and Planetary Institute
|| Planetary Radar Astronomy with Ground-Based Astrophysical Assets
||Planetary Radar with Ground-Based Astrophysical Assets
||California Institute of Technology
|| Supermassive Black-hole Demographics &Environments With Pulsar Timing Arrays
||Precision timing of large arrays (>50) of millisecond pulsars will detect the nanohertz gravitational-wave emission from supermassive binary black holes within the next 3-7 years. We review the scientific opportunities of these detections, the requirements for success, and the synergies with electromagnetic instruments operating in the 2020s.
||West Virginia University
|| Completing the Hydrogen Census in the Circumgalactic Medium at z?0
||Over the past decade, Lyman-? and metal line absorption observations have established the ubiquity of a gas-rich circumgalactic medium (CGM) around star-forming galaxies at z?0.2 potentially tracing half of the missing baryonic mass within galaxy halos. Unfortunately, these observations only provide a statistical measure of the gas in the CGM and do not constrain the spatial distribution and kinematics of the gas. Furthermore, we have limited sensitivity to Lyman-? at z?0 with existing instruments. As such, we remain ignorant of how this gas may flow from the CGM onto the disks of galaxies where it can fuel ongoing star-formation in the present day. Fortunately, 21-cm HI observations with radio telescopes can map HI emission providing both spatial and kinematic information for the CGM in galaxies at z=0. Observations with phased array feeds, radio cameras, on single-dish telescopes yield unmatched surface brightness sensitivity and survey speed. These observations can complete the census of HI in the CGM below NHI ?1017cm?2 and constrain how gas accretion is proceeding in the local universe. When used in concert with UV absorption line
||University of Vermont
|| A Plasma-Physical Understanding of Pulsar Radio Emission Physics
||The paper treats the longstanding problem of understanding pulsar radiation physically. It reports on progress in understanding both the radio and thermal X-ray emission, observationally and theoretically. It argues that recent progress has placed the emission problem on a plasma physics basis and that new efforts will have broad consequences.