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Letizia Stanghellini
NOAO
lstanghellini@noao.edu

Science Themes

  • Resolved stellar populations and their environments
  • Galaxy Evolution

Capabilities

  • Extremely Large Telescopes (>20m apertures)

Radial metallicity gradients in star-forming galaxies

Additional Authors: Danielle Berg (CCAPP, Ohio State University) Fabio Bresolin (Institute for Astronomy, University of Hawaii) Katia Cunha (Steward Observatory, University of Arizona) Laura Magrini (Osservatorio Astrofisico di Arcetri, INAF Italy)

Spiral star-forming galaxies are complex astrophysical objects whose baryonic component is dominated by the disk, where most of the star formation resides. The metallicity in the disk is not uniform, and it usually decreases with the distance to the galaxy center, in the so-called radial metallicity gradient. Radial metallicity gradients have been successfully used to set important constraints on galaxy formation and their chemical evolution. This paper focuses on the implications of radial metallicity gradients for a variety of galaxies and stellar populations, and on the foreseen advances in this field in the astronomical landscape of the 2020s.

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Chien-Hsiu Lee
NOAO
lee@noao.edu

Science Themes

  • Planetary Systems

Capabilities

  • Extremely Large Telescopes (>20m apertures)

Identification and characterization of the host stars in planetary microlensing

Additional Authors: Rachel Street (LCOGT), Kailash Sahu (STScI), Eliad Peretz (NASA/GSFC)

Microlensing offers a uniquie opportunity to probe exoplanets that are temperate and beyond the snow line, as small as Jovian satellites, at extragalactic distance, and even free floating exoplanets, which are not detected by other methods. This is because the microlensing does not depend on the brightness of the host star of the planets. Here we propose to robustly and routinely measure the mass of exoplanets beyond 1 AU from their host stars with the microlensing method; our experiment relies on directly imaging and resolving the host star (namely the lens) from the background source of the microlensing events, which requires high spatial resolution delivered by the ELTs. An immediate result from this project will be planet occurrence rate beyond the snow line, which will enable us to discern different planet formation mechanisms.

Link to draft or additional information: https://www.overleaf.com/read/zrmcxtncmdjc.

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Michael Pierce
University of Wyoming
mpierce@uwyo.edu

Science Themes

  • Cosmology and Fundamental Physics

Capabilities

  • Extremely Large Telescopes (>20m apertures)
  • Other: upgraded ALMA, NGVLA

Cosmological Constraints from Strong Gravitational Lensing

Additional Authors: Ian Dell'antonio (Brown University) Adam Myers (University of Wyoming)

The current tension between the best-fit cosmological models from measurements of the cosmic expansion history (Type Ia supernovae (SN) and Baryon Acoustic Oscillations (BAO) combined with the CMB) and local measurements of Ho has reached the point where a consideration of non-standard cosmographic techniques seems prudent. The geometrical nature of strong lensing can provide an independent constraint, specifically through the modeling of multiple-arc systems where the details of a specific lens model may be minimized (e.g., Link & Pierce 1998, Julio et al. 2010, Magana et al. 2018). Furthermore, over the next decade, high resolution imaging via interferometers, such as ALMA, and the next generation of large ground-based telescopes will provide the capability to measure transverse co-moving distances, for strongly lensed systems that results from our secular motion with respect to the CMB (this is the "Cosmological Parallax"). This measurement is interesting in that it is: independent of both SN and BAO, is geometrical, and the secular signal increases with time. A focused effort to model both known multiple arc systems and to investigate the possibility of measuring secular, cosmological parallaxes is proposed.

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Maruša Bradac
UCDavis
marusa@ucdavis.edu

Science Themes

  • Galaxy Evolution
  • Cosmology and Fundamental Physics

Capabilities

  • Extremely Large Telescopes (>20m apertures)
  • Wide-field multi-object spectroscopy

Spectroscopic Probes of Galaxies at the Epoch of Reionization

Additional Authors: A. Hoag (UCLA), B. Lemaux (UCDavis), C. Mason (UC Davis), T. Treu (UCLA), V. Strait (UCDavis) et al.

The epoch of reionization, which signified the transformation of the universe from opaque to
transparent, is poorly understood. When did it start/end? Was it patchy or smooth? How did
galaxies reionize the universe (if they did)? What are the properties of the earliest galaxies? To
answer these questions, over the last decades, several surveys have explored the high redshift
universe at progressively increasing depth. However, they still either lack the sample size or depth (or both). What emerges from these surveys is that the answers to these questions are likely tied
to the properties of even fainter galaxies. Future large spectroscopic studies of a large sample of
previously unexplored faint galaxy populations at redshifts z > 6 is needed to answer these fundamental questions. This can be achieved by a concerted efforts of using galaxy clusters that
serve as cosmic telescopes and ground-based telescopes enabling high resolution follow up of
galaxies deep into the epoch of reionization.

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Ian Roederer
U. Michigan
iur@umich.edu

Science Themes

  • Stars and Stellar Evolution

Capabilities

  • Extremely Large Telescopes (>20m apertures)

First Stars and the Origin of the Elements

Additional Authors: D. Buzasi (FGCU), A. Ji (Carnegie Obs), G. Mace (McDonald Obs and U Texas), V. Placco (U Notre Dame), I. Roederer (U Michigan), J. Sobeck (U Washington)

Adaptation of a US-ELT program Key Science Program concept that focuses on detecting metal-free stars or excluding their existence, as well as characterizing the nature and end states of the first stars that produced metals.

URL for draft coming soon.

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Peregrine McGehee
College of the Canyons
peregrine.mcgehee@gmail.com

Science Themes

  • Star and Planet Formation

Capabilities

  • Extremely Large Telescopes (>20m apertures)

Dynamical Processes in the Planet-Forming Environment

Metallic emission lines, along with the Balmer series of hydrogen, probe the chemistry and kinematics of gas within the planet-forming and central regions of circumstellar disks.
The transfer of circumstellar disk mass and momentum onto the protostar and out into the environment occurs via a variety of mechanisms including magnetospheric accretion, jets, outflows, and disk winds. The interplay of these processes determine both the conditions under which planet formation occurs and the lifetime of the disk. High-spectral resolution study of these emission lines provides critical information on
disk chemistry, mass and momentum loss, turbulence, and disk wind origins.

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Michael H. Wong
UC Berkeley
mikewong@astro.berkeley.edu

Science Themes

  • Planetary Systems

Capabilities

  • Extremely Large Telescopes (>20m apertures)
  • Time domain services

Solar system Deep Time-Surveys of atmospheres, surfaces, and rings

Additional Authors: (this initial list is comprised of participants from the US ELT KSP effort, Nov-Dec 2018) Michael H. Wong (UC Berkeley) Richard Cartwright (SETI Institute) Glenn Orton (JPL) Matthew Tiscareno (SETI Institute) Thomas Greathouse (SWRI) David Trilling (Northern Arizona Univeristy) Kunio Sayanagi (Hampton University) Nancy Chanover (NMSU) Al Conrad (LBTO) Imke de Pater (UC Berkeley) Eric Gaidos (University of Hawaii) Michael Lucas (UT Knoxville) Karen Meech (University of Hawaii) Noemi Pinilla-Alonso (University of Central Florida) Megan E. Schwamb (Gemini Observatory)

Observations at leading observatories reveal varying
environmental conditions in our dynamic solar system.
Observations conducted over decade-scale campaign durations
create a long-term legacy chronicling the evolution of dynamic
planetary atmospheres, surfaces, and rings, establishing a
permanent resource for comparison with other observations
conducted in past, contemporaneous, or future epochs.
Long-duration datasets address questions about potential
biosignatures, circulation and evolution of atmospheres from the
edge of the habitable zone to the ice giants, orbital dynamics
and planetary seismology with ring systems, exchange between
components in the planetary system, and the migration and
processing of volatiles on icy bodies, including Ocean Worlds.
The common factor uniting these scientifically diverse
investigations is the need for a very long campaign duration, and
temporal sampling at an annual cadence. The integrity of
long-duration programs requires an institutional-level commitment
beyond the scope of typical general observer cycles.

Link to draft or additional information: http://astro.berkeley.edu/~mikewong/papers/US_ELTP_KSP_SS01_cadence_20181218.pdf.

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Enrique Lopez-Rodriguez
SOFIA Science Center
enloro@gmail.com

Science Themes

  • Galaxy Evolution

Capabilities

  • Extremely Large Telescopes (>20m apertures)

Tracing the AGN feeding and feedback

Additional Authors: Robert Nikutta (NOAO), Nancy Levenson (STScI), Chris Packham (UTSA), Erin Hicks (University of Alaska), Kohei Ichikawa (Tohoku University), Vivian U. (UC Irvine), Sibasish Laha (UC San Diego).

The relation between the masses of galaxies' central super massive black holes and their host galaxies implies an evolutionary connection. Thus, the buildup of the central black hole mass is a fundamental facet of galaxy growth and evolution, which occurs at least in part through accretion. However, the global physical processes by which this occurs is uncertain. For few decades, the best picture of the feeding material surrounding the super massive black hole in active galaxies has been a static structure re-processing the emission from the central engine (black hole and accretion disk). The cause of this picture is mainly due to the small physical scales, $le 10$ pc, of this structure and our limited instrumental capabilities to fully characterize it. Recent ALMA and IR interferometric observations using VLTI have provided new insights towards our understanding on this structure from a dynamical framework-- the feeding material is the central structure in a gas flow cycle in which gas is brought in from the host galaxy disk (inflow) and then driven out by the AGN in a wind (outflow) that can be explained by radiation-driven outflow models and/or magnetic disk-wind models. However, the limited sensitivity and the impossibility to obtain images using IR interferometry, and the limited AGN sample due to that both ALMA and VLTI are in the Southern hemisphere, make the dynamical framework unclear. This white paper discusses key open questions on our understanding about AGN feedback/feeding that can be addressed with a multiwavelength analysis using the next generation of extremely large telescopes, X-ray and radio facilities.

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Jeyhan Kartaltepe
Rochester Institute of Technology
jeyhan@astro.rit.edu

Science Themes

  • Galaxy Evolution

Capabilities

  • Extremely Large Telescopes (>20m apertures)
  • Wide-field multi-object spectroscopy
  • Wide-field imaging

Protocluster Evolution

Additional Authors: Gregory Rudnick, University of Kansas Caitlin Casey, University of Texas Nimish Hathi, Space Telescope Science Institute Steve Finkelstein, University of Texas Jeff Newman, University of Pittsburgh Mark Dickinson, NOAO

This white paper will discuss key open questions that can be addressed by detailed study of protoclusters at at ”Cosmic noon“, the key redshift range of z∼2−3 where galaxies were at the peak of their star formation rates and black hole growth and where protoclusters were forming into the most massive structures in today’s universe. We will particularly focus on the vast improvements that can be made with targeted spectroscopic surveys with a range of depths and area coverage in order to provide unprecedented characterization of galaxies over the full dynamic range of environmental densities at cosmic noon across a wide-range in cluster progenitor mass. These open science questions include:

1) What governed the cessation of star formation in present-day massive cluster galaxies?

2) How did environment regulate or enhance star formation during the epoch when the first large (~Mpc scale) structures were collapsing?

3) How did gas flows in and out of galaxies proceed at these epochs?

4)Were galaxies in early structures merely “accelerated” in their evolution, or did the environment actively affect their evolution?

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Joan Najita
NOAO
najita@noao.edu

Science Themes

  • Planetary Systems
  • Star and Planet Formation
  • Stars and Stellar Evolution
  • Formation and evolution of compact objects
  • Resolved stellar populations and their environments
  • Galaxy Evolution
  • Cosmology and Fundamental Physics
  • Multi-Messenger Astronomy and Astrophysics

Capabilities

  • Extremely Large Telescopes (>20m apertures)
  • Wide-field multi-object spectroscopy
  • Wide-field imaging
  • Optical interferometry
  • Astronomical data science
  • Time domain services

Investing for Discovery and Sustainability in Astronomy in the 2020s

As the next decade approaches, it is once again time for the US astronomical community to assess its investment priorities on the ground and in space in the coming decade. This report, created to aid NOAO in its planning for the 2020 Decadal Survey on Astronomy and Astrophysics, reviews the outcome of the previous Decadal Survey (Astro2010); describes the themes that emerged from the 2018 NOAO Community planning workshop "NOAO Community Needs for Science in the 2020s"; and based on the above, offers thoughts for the coming review. We find that a balanced set of investments in small- to large-scale initiatives is essential to a sustainable future, based on the experience of previous decades. While large facilities are the "value" investments that are guaranteed to produce compelling science and discoveries, smaller facilities are the "growth stocks" that are likely to deliver the biggest science bang per buck, sometimes with outsize returns. Investments in data-intensive missions also have benefits to society beyond the science they deliver. By training scientists who are well equipped to use their data science skills to solve problems in the public or private sector, astronomy can provide a valuable service to society by contributing to a data-capable workforce.

[Note: This white paper considers broad issues that are relevant for the 2020 Decadal Survey, rather than a focused science topic. It may be submitted in response to a future call for white papers on the state of the profession. In addition to the link below, it is also available at https://arxiv.org/abs/1901.08605]

Link to draft or additional information: http://ast.noao.edu/sites/default/files/Investing4Discovery.pdf.

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