Pathways to Discovery in Astronomy and Astrophysics for the 2020s (2023) / Chapter Skim
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Appendix F: Report of the Panel on the Interstellar Medium and Star and Planet Formation
Appendix F: Report of the Panel on the Interstellar Medium and Star and Planet Formation
Pages 311-329
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From page 311... ...
In this complex, turbulent, and dynamic environment, clouds of dense molecular gas are produced that are the sites of star formation. Within these molecular clouds, dense cores form that eventually gravitationally collapse and often fragment further to form stars with a wide range of masses.
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From page 312... ...
In particular, comparisons of ALMA CO maps to tracers of massive star formation on matched scales have revealed systematic variations in the star formation efficiency of molecular clouds, as well as the breakdown of star formation laws on cloud scales where the life cycles of star-forming clouds set by feedback or dynamics dominate. Observations with ALMA, Herschel, and optical integral field units (IFUs)
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From page 313... ...
have substantially improved estimates of young star luminosities and thereby ages, an essential aspect of characterizing the star formation histories of molecular clouds as well as for establishing protoplanetary disk lifetimes. Additional measurements of precise kinematics of young stellar populations from Gaia have increased the number of known nearby clusters and moving groups, facilitating more robust investigations of their initial mass functions, chemical homogeneity, and multiplicity statistics as a function of age.
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From page 314... ...
Laboratory experiments, including microgravity studies of dust particle collisions, chemical measurements of ice mantle formation and sublimation, and analyses of meteorites, provide critical inputs for both theoretical models and the interpretation of astronomical data. Building on these many achievements over the past decade, this appendix discusses the opportunities for making further progress in characterizing and understanding the state of the ISM in the Milky Way and nearby galaxies, star formation, and planet formation, greatly assisted and informed by the contributions of more than 150 science white papers from the broader community.
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From page 315... ...
Enabling the full diagnostic potential of these lines requires high-velocity resolution far-infrared (IR) observations coupled with matched resolution diagnostics of the ionized, atomic, and molecular gas phases (e.g., Hα, HI, and CO)
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From page 316... ...
(Right) Three-phase Interstellar Medium in Galaxies Resolving Evolution with Star Formation and Supernova Feedback (TIGRESS)
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From page 317... ...
The densest gas, in which stars form, generally comprises only a few percent of the total cloud mass, leading to low global star formation efficiencies. An observational census of the dense gas as a function of interstellar environment, and understanding how dense structures form and evolve, has important implica
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From page 318... ...
While filaments likely dominate the mass budget of the dense molecular gas where stars form, the understanding of their formation, fragmentation, as well as the degree to which they contain sub-structure remain controversial. Furthermore, it is not clear whether filaments are a widespread and critical step in star formation across galaxies of different properties.
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From page 319... ...
radio and millimeter spectroscopy of large samples of nearby galaxies to detect HCN, HCO+, CO isotopologues, and different excitation lines (>10× fainter than CO) are crucial to measuring the physical state of dense gas, and then to relate that to environment and the star formation efficiency.
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From page 320... ...
The initial phase of star formation is controlled by the collapse and fragmentation of dense molecular gas onto a disk, which then transports mass inward and angular momentum outward. This process is dictated by the density structures of dense molecular gas "cores," which are yet to be well resolved observationally.
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From page 321... ...
To characterize mass functions in extremely dense, massive regions requires the study of clusters -- in which most stars form -- and associations nearer the galactic center and in nearby galaxies. The Magellanic Clouds offer an especially compelling opportunity to probe the effects of metallicity, which has been shown in local samples to have an impact on stellar multiplicity.
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From page 322... ...
, disentangle photospheric emission from hot accretion continua and lines, measure nonthermal line profiles, and uncover distant, heavily extinct, star formation. To optimally synchronize these capabilities with time-domain surveys will also require a sophisticated alert system to trigger and prioritize follow-up.
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From page 323... ...
The metamorphosis of disk material into planetary systems involves a complex set of physical processes. Models for those processes are always limited by imperfect knowledge of the planet formation environment -- the spatial variations of temperatures, densities (for gas and solids)
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From page 324... ...
in disks. Aside from better characterizing the different potential transport process, continued efforts to measure turbulence are highly desirable because of the diverse roles it plays in planet formation -- from limiting the collisional growth of solids, to affecting the formation of planetesimals, and beyond to regulating the structures of gaps and the migration of protoplanets in gas disks.
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From page 325... ...
The physical conditions, spatial structures, and dynamics of CPDs are controlled by the combined gravitational potential of the protoplanet and host star, the local heating, and the mechanics of mass transfer from the circumstellar disk reservoir. Direct imaging measurements of the CPD spectral energy distribution (SED)
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From page 326... ...
Then, by empirically characterizing how these planets perturb their disks as a function of their mass, we could extrapolate to indirectly infer constraints on the mass function into the super-Earth regime by measuring more subtle disk substructures. These young planetary architectures could then be compared with their more evolved counterparts around main-sequence hosts found from microlensing surveys and direct imaging campaigns.
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From page 327... ...
The ISM, star formation, and planet formation also involve key physical processes that are less commonly encountered elsewhere, including non-ideal MHD and multiple-fluid effects, complex timedependent chemistry and dust evolution, and planetary growth processes (F-Q1, F-Q2, F-Q3, F-Q4)
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From page 328... ...
F-Q3c: Is the stellar initial mass function universal? F-Q4: Is planet formation fast or slow?
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From page 329... ...
resolution measurements of molecular gas and dust in circumstellar and circumplanetary disks (F-Q4, F-DA) MHD + radiation hydro F-Q1, F-Q2, F-Q3, XSEDE, NASA and Department Multiphase galaxy simulations with simulations, algorithm F-Q4, F-DA of Energy (DOE)
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