Skip to main content

Currently Skimming:


Pages 247-263

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 247...
... WHAT SEEDS SUPERMASSIVE BLACK HOLES AND HOW DO THEY GROW? While it is well established that SMBHs and galaxies grow together over cosmic time, the physics of both what seeded SMBHs in the first place and the processes that govern their growth remain poorly understood.
From page 248...
... B-Q4b. How Do Central Black Holes Grow?
From page 249...
... We have also seen the discovery of astrophysical high-energy neutrinos and a potential association with a specific astrophysical source. Last, we have obtained new constraints on cosmic rays within the Milky Way and extragalactic cosmic rays, including more precise measures of the spectrum and composition of UHECRs, the discovery of TeV halos, and the discovery of pevatrons (PeV cosmic ray sources)
From page 250...
... Combined with EM surveys of star formation and SNe, detection of the MeV neutrino background will provide a multi
From page 251...
... Direct diagnostics of the explosion mechanism and the properties of the neutron star in formation (e.g., rotation, convection) could be gleaned from simultaneous neutrino and GW detections in the first seconds after collapse.
From page 252...
... The specifics of the needed capabilities for the individual messengers and EM bands are discussed in previous sections and are summarized in Table B.2. TABLE B.1 Key Science Questions and Discovery Area Question Subquestions B-Q1: What are the mass and spin distributions of B-Q1a: What do the mass and spin distributions tell us about neutron star neutron stars and stellar-mass black holes?
From page 253...
... High-angular B-Q1: ULXs and other point sources in Chandra, XMM, High angular resolution (<1 arcsec @ 1 keV; resolution X-ray nearby galaxies NuSTAR, Athena <15 arcsec @ 20 keV)
From page 254...
... (EeV) cosmic rays B-DA: UHECR counterparts of neutrino >4× larger detector area.
From page 255...
... Using the well-understood physics of plasmas, we are able to map the temperature fluctuations seen in the CMB back to the primordial conditions imprinted in the Big Bang. The small primordial fluctuations are inferred to closely follow a specific statistical pattern: Gaussian correlations with no preferred scale and with all components (i.e., dark matter, nuclei, photons, etc.)
From page 256...
... effect. • Searches for inflationary gravitational waves have improved in precision by more than a factor of 10, to the point where they disfavor many of the simplest models of inflation.
From page 257...
... The observed travel time of gravitons resulted in an improvement of more than 10 orders of magnitude in the determination of the speed of propagation of gravitational waves. • The primordial deuterium-to-hydrogen ratio has been measured to 1 percent precision.
From page 258...
... (4) How will measurements of gravitational waves reshape our cosmological view?
From page 259...
... already rule out very interesting portions of the parameter space of models. A concerted effort over the next decade to improve the sensitivity to gravitational waves by a factor of 10–100 would cross important theoretical thresholds.
From page 260...
... WHAT ARE THE PROPERTIES OF DARK MATTER AND THE DARK SECTOR? Since the Astro2010 decadal survey, the field of dark matter theory and detection has undergone a paradigm shift.
From page 261...
... However, the clumpiness of dark matter on small scales is today only loosely constrained, save for the extreme case of objects compact enough to produce microlensing of stars. Many theories of dark matter beyond the WIMP paradigm feature modifications of the scale-invariant power spectrum -- for example, resulting in gravitational collapse in the early universe into dark matter mini halos, which can be thousands or even a million times more dense than Lambda cold dark matter (ΛCDM)
From page 262...
... A goal of the next decade is to solve this puzzle. A next-generation gamma-ray telescope with better angular resolution than the Fermi satellite to resolve point sources in the galactic bulge, or better sensitivity to photons from dark matter annihilation in dwarf galaxies, would be a powerful tool for doing so.
From page 263...
... Narrow-field observations would be particularly advanced by the next generation of large-aperture optical telescopes. The flexibility of the Roman Space Telescope mission will provide an important and powerful capability to investigate opportunities or questions raised by many of the funded upcoming wide-field survey facilities and CMB experiments, listed earlier in this appendix, that will begin earlier in the decade.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.