Showing papers by "Steven R. Furlanetto published in 2019"
TL;DR: The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) signal was recently reported to have a strong 21 cm absorption signal relative to the cosmic microwave background as discussed by the authors.
Abstract: The Experiment to Detect the Global Epoch of Reionization Signature (EDGES)
recently reported a strong 21-cm absorption signal relative to the cosmic
microwave background at $z \sim 18$. While its anomalous amplitude may indicate
new physics, in this work we focus on the timing of the signal, as it alone
provides an important constraint on galaxy formation models. Whereas rest-frame
ultraviolet luminosity functions (UVLFs) over a broad range of redshifts are
well fit by simple models in which galaxy star formation histories track the
assembly of dark matter halos, we find that these same models, with reasonable
assumptions about X-ray production in star-forming galaxies, cannot generate a
narrow absorption trough at $z \sim 18$. If verified, the EDGES signal
therefore requires the fundamental inputs of galaxy formation models to evolve
rapidly at $z \gtrsim 10$. Unless extremely faint sources residing in halos
below the atomic cooling threshold are responsible for the EDGES signal, star
formation in $\sim 10^8$-$10^{10} \ M_{\odot}$ halos must be more efficient
than expected, implying that the faint-end of the UVLF at $M_{\mathrm{UV}}
\lesssim -12$ must steepen at the highest redshifts. This steepening provides a
concrete test for future galaxy surveys with the James Webb Space Telescope and
ongoing efforts in lensed fields, and is required regardless of whether the
amplitude of the EDGES signal is due to new cooling channels or a strong radio
background in the early Universe. However, the radio background solution
requires that galaxies at $z > 15$ emit 1-2 GHz photons with an efficiency
$\sim 10^3$ times greater than local star-forming galaxies, posing a challenge
for models of low-frequency photon production in the early Universe.
133 citations
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California Institute of Technology1, Las Cumbres Observatory Global Telescope Network2, Goddard Space Flight Center3, Space Telescope Science Institute4, University of Maryland, College Park5, University of Salerno6, Ohio State University7, University of Groningen8, Carnegie Institution for Science9, University of Arizona10, University of California, Berkeley11, University of Texas at Austin12, University of California, Santa Cruz13, University of California, Los Angeles14, Johns Hopkins University Applied Physics Laboratory15, Princeton University16, University of Toronto17, Max Planck Society18, Arizona State University19, Rutgers University20, University of Minnesota21, Gordon and Betty Moore Foundation22, Cornell University23, Stanford University24, University of Cambridge25, University of South Carolina26, Duke University27, University of Utah28, Vanderbilt University29, Johns Hopkins University30, Search for extraterrestrial intelligence31, Stony Brook University32, University of Washington33, Harvard University34
TL;DR: The Wide Field Infrared Survey Telescope (WFIRST) as discussed by the authors is a 2.4m space telescope with a 0.281 deg^2 field of view for near-IR imaging and slitless spectroscopy and a coronagraph designed for > 10^8 starlight suppresion.
Abstract: The Wide Field Infrared Survey Telescope (WFIRST) is a 2.4m space telescope with a 0.281 deg^2 field of view for near-IR imaging and slitless spectroscopy and a coronagraph designed for > 10^8 starlight suppresion. As background information for Astro2020 white papers, this article summarizes the current design and anticipated performance of WFIRST. While WFIRST does not have the UV imaging/spectroscopic capabilities of the Hubble Space Telescope, for wide field near-IR surveys WFIRST is hundreds of times more efficient. Some of the most ambitious multi-cycle HST Treasury programs could be executed as routine General Observer (GO) programs on WFIRST. The large area and time-domain surveys planned for the cosmology and exoplanet microlensing programs will produce extraordinarily rich data sets that enable an enormous range of Archival Research (AR) investigations. Requirements for the coronagraph are defined based on its status as a technology demonstration, but its expected performance will enable unprecedented observations of nearby giant exoplanets and circumstellar disks. WFIRST is currently in the Preliminary Design and Technology Completion phase (Phase B), on schedule for launch in 2025, with several of its critical components already in production.
111 citations
TL;DR: In this paper, the effects of Population III (Pop III) stars and their remnants on the cosmological 21-cm global signal were investigated by combining a semi-analytic model of Pop III star formation with a global 21cm simulation code.
Abstract: We investigate the effects of Population III (Pop III) stars and their remnants on the cosmological 21-cm global signal. By combining a semi-analytic model of Pop III star formation with a global 21-cm simulation code, we investigate how X-ray and radio emission from accreting Pop III black holes may affect both the timing and depth of the 21-cm absorption feature that follows the initial onset of star formation during the Cosmic Dawn. We compare our results to the findings of the EDGES experiment, which has reported the first detection of a cosmic 21-cm signal. In general, we find that our fiducial Pop III models, which have peak star formation rate densities of $\sim 10^{-4}$ M$_\odot$ yr$^{-1}$ Mpc$^{-3}$ between $z \sim 10$ and $z \sim 15$, are able to match the timing of the EDGES signal quite well, in contrast to models that ignore Pop III stars. To match the unexpectedly large depth of the EDGES signal without recourse to exotic physics, we vary the parameters of emission from accreting black holes (formed as Pop III remnants) including the intrinsic strength of X-ray and radio emission as well as the local column density of neutral gas. We find that models with strong radio emission and relatively weak X-ray emission can self-consistently match the EDGES signal, though this solution requires fine-tuning. We are only able to produce signals with sharp features similar to the EDGES signal if the Pop~III IMF is peaked narrowly around $140 \, M_\odot$.
42 citations
University of Pennsylvania1, San Diego State University2, California State University, Los Angeles3, University of California, Berkeley4, Rhodes University5, Queen Mary University of London6, McGill University7, University of Cambridge8, Arizona State University9, INAF10, National Radio Astronomy Observatory11, University of Toronto12, California Institute of Technology13, University of California, Los Angeles14, University of Melbourne15, University of Washington16, Massachusetts Institute of Technology17, Scuola Normale Superiore di Pisa18, Brown University19, Harvard University20, American Astronomical Society21
TL;DR: Kohn et al. as discussed by the authors performed a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and showed that it achieves qualitative redundancy between the nominally redundant baselines of the array and reasonable amplitude accuracy.
Abstract: Author(s): Kohn, SA; Aguirre, JE; La Plante, P; Billings, TS; Chichura, PM; Fortino, AF; Igarashi, AS; Benefo, RK; Gallardo, S; Martinot, ZE; Nunhokee, CD; Kern, NS; Bull, P; Liu, A; Alexander, P; Ali, ZS; Beardsley, AP; Bernardi, G; Bowman, JD; Bradley, RF; Carilli, CL; Cheng, C; Deboer, DR; Acedo, EDL; Dillon, JS; Ewall-Wice, A; Fadana, G; Fagnoni, N; Fritz, R; Furlanetto, SR; Glendenning, B; Greig, B; Grobbelaar, J; Hazelton, BJ; Hewitt, JN; Hickish, J; Jacobs, DC; Julius, A; Kariseb, M; Kolopanis, M; Lekalake, T; Loots, A; Macmahon, D; Malan, L; Malgas, C; Maree, M; Mathison, N; Matsetela, E; Mesinger, A; Morales, MF; Neben, AR; Nikolic, B; Parsons, AR; Patra, N; Pieterse, S; Pober, JC; Razavi-Ghods, N; Ringuette, J; Robnett, J; Rosie, K; Sell, R; Smith, C; Syce, A; Tegmark, M; Thyagarajan, N; Williams, PKG; Zheng, H | Abstract: Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted H i emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to k ∥) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from H i in the EoR (the "EoR window"). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. For instruments pursuing a "foreground avoidance" strategy of simply measuring in the EoR window, and not attempting to model and remove foregrounds, as is the plan for the first stage of the Hydrogen Epoch of Reionization Array (HERA), characterizing the intrinsic instrument polarization response is particularly important. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power-spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters, and discuss the achieved isolation of foreground power due to the intrinsic spectral smoothness of the foregrounds, the instrument chromaticity, and the calibration. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond that expected from the interferometer array configuration and the modeled primary beam response. Furthermore, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters, which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration.
28 citations
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TL;DR: In the early universe, most of the baryonic matter was in the form of neutral hydrogen (HI), detectable via its ground state's spin-flip transition as mentioned in this paper, and a measurement of the redshifted 21cm spectrum maps the history of the HI gas through the Dark Ages and Cosmic Dawn and up to the Epoch of Reionization (EoR).
Abstract: The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard LCDM cosmological model. Divergences from that model would indicate new physics, such as dark matter decay (heating) or baryonic cooling beyond that expected from adiabatic expansion of the Universe. In the early Universe, most of the baryonic matter was in the form of neutral hydrogen (HI), detectable via its ground state's spin-flip transition. A measurement of the redshifted 21-cm spectrum maps the history of the HI gas through the Dark Ages and Cosmic Dawn and up to the Epoch of Reionization (EoR). The Experiment to Detect the Global EoR Signature (EDGES) recently reported an absorption trough at 78 MHz (redshift z of 17), similar in frequency to expectations for Cosmic Dawn, but about 3 times deeper than was thought possible from standard cosmology and adiabatic cooling of HI. Interactions between baryons and slightly-charged dark matter particles with electron-like mass provide a potential explanation of this difference but other cooling mechanisms are also being investigated to explain these results. The Cosmic Dawn trough is affected by cosmology and the complex astrophysical history of the first luminous objects. Another trough is expected during the Dark Ages, prior to the formation of the first stars and thus determined entirely by cosmological phenomena (including dark matter). Observations on or in orbit above the Moon's farside can investigate this pristine epoch (15-40 MHz; z=100-35), which is inaccessible from Earth. A single cross-dipole antenna or compact array can measure the amplitude of the 21-cm spectrum to the level required to distinguish (at >5$\sigma$}) the standard cosmological model from that of additional cooling derived from current EDGES results. This observation constitutes a powerful, clean probe of exotic physics in the Dark Ages.
21 citations
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TL;DR: The only known way to measure fluctuations in this era is through the 21-cm line of neutral hydrogen as discussed by the authors, which has enormous potential for cosmology, because they span a large volume while the fluctuations remain linear even on small scales.
Abstract: The Dark Ages are the period between the last scattering of the cosmic microwave background and the appearance of the first luminous sources, spanning approximately 1100 < z < 30. The only known way to measure fluctuations in this era is through the 21-cm line of neutral hydrogen. Such observations have enormous potential for cosmology, because they span a large volume while the fluctuations remain linear even on small scales. Observations of 21-cm fluctuations during this era can therefore constrain fundamental aspects of our Universe, including inflation and any exotic physics of dark matter. While the observational challenges to these low-frequency 21-cm observations are enormous, especially from the terrestrial environment, they represent an important goal for cosmology.
15 citations
Journal Article•
TL;DR: The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard ΛCDM cosmological model as mentioned in this paper.
Abstract: The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard ΛCDM cosmological model. Divergences from that model would indicate new physics, such as dark matter decay (heating) or baryonic cooling beyond that expected from adiabatic expansion of the Universe.
14 citations
Journal Article•
University of California, Irvine1, New York University2, California Institute of Technology3, Jet Propulsion Laboratory4, INAF5, McGill University6, University of Nottingham7, Lam Research8, University of California, Santa Barbara9, University of Texas at Austin10, University of California, Los Angeles11, Massachusetts Institute of Technology12, Imperial College London13, University of Massachusetts Amherst14, Institute for Advanced Study15, Sapienza University of Rome16, Carnegie Mellon University17, Rochester Institute of Technology18
TL;DR: The cosmic dawn and epoch of reionization mark the time period in the universe when stars, galaxies, and black hole seeds first formed and the intergalactic medium changed from neutral to an ionized one.
Abstract: The cosmic dawn and epoch of reionization mark the time period in the universe when stars, galaxies, and black hole seeds first formed and the intergalactic medium changed from neutral to an ionized one. This white paper outlines the current state of knowledge, anticipated scientific outcomes in the 2020s and scientific goals for new facilities
13 citations
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University of California, Irvine1, New York University2, California Institute of Technology3, Jet Propulsion Laboratory4, INAF5, McGill University6, University of Nottingham7, Lam Research8, University of California, Santa Barbara9, University of Texas at Austin10, University of California, Los Angeles11, Massachusetts Institute of Technology12, Imperial College London13, University of Massachusetts Amherst14, Institute for Advanced Study15, Sapienza University of Rome16, Carnegie Mellon University17, Rochester Institute of Technology18
TL;DR: In this paper, the current state of knowledge and anticipated scientific outcomes with ground and space-based astronomical facilities in the 2020s are outlined and a number of scientific goals and objectives for new facilities in late 2020s to mid 2030s are proposed.
Abstract: The cosmic dawn and epoch of reionization mark the time period in the universe when stars, galaxies, and blackhole seeds first formed and the intergalactic medium changed from neutral to an ionized one. Despite substantial progress with multi-wavelength observations, astrophysical process during this time period remain some of the least understood with large uncertainties on our existing models of galaxy, blackhole, and structure formation. This white paper outlines the current state of knowledge and anticipated scientific outcomes with ground and space-based astronomical facilities in the 2020s. We then propose a number of scientific goals and objectives for new facilities in late 2020s to mid 2030s that will lead to definitive measurements of key astrophysical processes in the epoch of reionization and cosmic dawn.
11 citations
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TL;DR: In this article, the authors describe how the 21-cm line of neutral hydrogen provides a powerful probe of the reionization process and therefore important constraints on both the galaxies and intergalactic absorbers at that time.
Abstract: The epoch of reionization, when photons from early galaxies ionized the intergalactic medium about a billion years after the Big Bang, is the last major phase transition in the Universe's history. Measuring the characteristics of the transition is important for understanding early galaxies and the cosmic web and for modeling dwarf galaxies in the later Universe. But such measurements require probes of the intergalactic medium itself. Here we describe how the 21-cm line of neutral hydrogen provides a powerful probe of the reionization process and therefore important constraints on both the galaxies and intergalactic absorbers at that time. While existing experiments will make precise statistical measurements over the next decade, we argue that improved 21-cm analysis techniques - allowing imaging of the neutral gas itself - as well as improved theoretical models, are crucial for testing our understanding of this important era.
8 citations
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TL;DR: A multitude of multi-wavelength intensity mapping measurements, ranging from the redshifted 21 cm background in the radio to the unresolved X-ray background, contain a plethora of synergistic information about this elusive era.
Abstract: Cosmic dawn and the Epoch of Reionization (EoR) are among the least explored observational eras in cosmology: a time at which the first galaxies and supermassive black holes formed and reionized the cold, neutral Universe of the post-recombination era. With current instruments, only a handful of the brightest galaxies and quasars from that time are detectable as individual objects, due to their extreme distances. Fortunately, a multitude of multi-wavelength intensity mapping measurements, ranging from the redshifted 21 cm background in the radio to the unresolved X-ray background, contain a plethora of synergistic information about this elusive era. The coming decade will likely see direct detections of inhomogenous reionization with CMB and 21 cm observations, and a slew of other probes covering overlapping areas and complementary physical processes will provide crucial additional information and cross-validation. To maximize scientific discovery and return on investment, coordinated survey planning and joint data analysis should be a high priority, closely coupled to computational models and theoretical predictions.
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TL;DR: The 21cm line at high redshifts is a powerful way to constrain cosmology as mentioned in this paper, and it is a probe of cosmic dawn and Epoch of Reionization astrophysics.
Abstract: In addition to being a probe of Cosmic Dawn and Epoch of Reionization astrophysics, the 21cm line at $z>6$ is also a powerful way to constrain cosmology. Its power derives from several unique capabilities. First, the 21cm line is sensitive to energy injections into the intergalactic medium at high redshifts. It also increases the number of measurable modes compared to existing cosmological probes by orders of magnitude. Many of these modes are on smaller scales than are accessible via the CMB, and moreover have the advantage of being firmly in the linear regime (making them easy to model theoretically). Finally, the 21cm line provides access to redshifts prior to the formation of luminous objects. Together, these features of 21cm cosmology at $z>6$ provide multiple pathways toward precise cosmological constraints. These include the "marginalizing out" of astrophysical effects, the utilization of redshift space distortions, the breaking of CMB degeneracies, the identification of signatures of relative velocities between baryons and dark matter, and the discovery of unexpected signs of physics beyond the $\Lambda$CDM paradigm at high redshifts.
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TL;DR: In this article, the early phases of galaxy formation were studied by combining observations of galaxies with direct measurements of the reionization process: the former will provide a detailed understanding of bright sources, while the latter will constrain the (substantial) faint source population.
Abstract: The early phases of galaxy formation constitute one of the most exciting frontiers in astrophysics. It is during this era that the first luminous sources reionize the intergalactic medium - the moment when structure formation affects every baryon in the Universe. Here we argue that we will obtain a complete picture of this era by combining observations of galaxies with direct measurements of the reionization process: the former will provide a detailed understanding of bright sources, while the latter will constrain the (substantial) faint source population. We further describe how optimizing the comparison of these two measurements requires near-infrared galaxy surveys covering large volumes and retaining redshift information and also improvements in 21-cm analysis, moving those experiments into the imaging regime.
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TL;DR: The Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE) as mentioned in this paper is a low radio frequency interferometric array on the farside of the Moon.
Abstract: This is the final report submitted to NASA for a Probe-class concept study of the "Farside Array for Radio Science Investigations of the Dark ages and Exoplanets" (FARSIDE), a low radio frequency interferometric array on the farside of the Moon. The design study focused on the instrument, a deployment rover, the lander and base station, and delivered an architecture broadly consistent with the requirements for a Probe mission. This notional architecture consists of 128 dipole antennas deployed across a 10 km area by a rover, and tethered to a base station for central processing, power and data transmission to the Lunar Gateway, or an alternative relay satellite. FARSIDE would provide the capability to image the entire sky each minute in 1400 channels spanning frequencies from 150 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, auroral kilometric radiation, and plasma noise from the solar wind. This would enable near-continuous monitoring of the nearest stellar systems in the search for the radio signatures of coronal mass ejections and energetic particle events, and would also detect the magnetospheres for the nearest candidate habitable exoplanets. Simultaneously, FARSIDE would be used to characterize similar activity in our own solar system, from the Sun to the outer planets. Through precision calibration via an orbiting beacon, and exquisite foreground characterization, FARSIDE would also measure the Dark Ages global 21-cm signal at redshifts from 50-100. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range.
Journal Article•
TL;DR: Peeples et al. as discussed by the authors studied the relationship between the CGM and galactic star formation histories, internal kinematics, chemical evolution, quenching, satellite evolution, dark matter halo occupation, and the reionization of the larger-scale intergalactic medium in light of the advances that will be made on these topics in the 2020s.
Abstract: Author(s): Peeples, Molly S; Behroozi, Peter; Bordoloi, Rongmon; Brooks, Alyson; Bullock, James S; Burchett, Joseph N; Chen, Hsiao-Wen; Chisholm, John; Christensen, Charlotte; Coil, Alison; Corlies, Lauren; Diamond-Stanic, Aleksandar; Donahue, Megan; Faucher-Giguere, Claude-Andre; Ferguson, Henry; Fielding, Drummond; Fox, Andrew J; French, David M; Furlanetto, Steven R; Gennaro, Mario; Gilbert, Karoline M; Hamden, Erika; Hathi, Nimish; Hayes, Matthew; Henry, Alaina; Howk, J Christopher; Hummels, Cameron; Keres, Dusan; Kirby, Evan; Koekemoer, Anton M; Lan, Ting-Wen; Lanz, Lauranne; Law, David R; Lehner, Nicolas; Lotz, Jennifer M; Martin, Crystal L; McQuinn, Kristen; McQuinn, Matthew; Munshi, Ferah; Oh, S Peng; O'Meara, John M; O'Shea, Brian W; Pacifici, Camilla; Peek, JEG; Postman, Marc; Prescott, Moire; Putman, Mary; Quataert, Eliot; Rafelski, Marc; Ribaudo, Joseph; Rowlands, Kate; Rubin, Kate; Salmon, Brett; Scarlata, Claudia; Shapley, Alice E; Simons, Raymond; Snyder, Gregory F; Stern, Jonathan; Strom, Allison L; Tollerud, Erik; Torrey, Paul; Tremblay, Grant; Tripp, Todd M; Tumlinson, Jason; Tuttle, Sarah; Bosch, Frank C van den; Voit, G Mark; Wang, Q Daniel; Werk, Jessica K; Williams, Benjamin F; Zaritsky, Dennis; Zheng, Yong | Abstract: Galaxies evolve under the influence of gas flows between their interstellar medium and their surrounding gaseous halos known as the circumgalactic medium (CGM). The CGM is a major reservoir of galactic baryons and metals, and plays a key role in the long cycles of accretion, feedback, and recycling of gas that drive star formation. In order to fully understand the physical processes at work within galaxies, it is therefore essential to have a firm understanding of the composition, structure, kinematics, thermodynamics, and evolution of the CGM. In this white paper we outline connections between the CGM and galactic star formation histories, internal kinematics, chemical evolution, quenching, satellite evolution, dark matter halo occupation, and the reionization of the larger-scale intergalactic medium in light of the advances that will be made on these topics in the 2020s. We argue that, in the next decade, fundamental progress on all of these major issues depends critically on improved empirical characterization and theoretical understanding of the CGM. In particular, we discuss how future advances in spatially-resolved CGM observations at high spectral resolution, broader characterization of the CGM across galaxy mass and redshift, and expected breakthroughs in cosmological hydrodynamic simulations will help resolve these major problems in galaxy evolution.
Journal Article•
TL;DR: The 21cm line at high redshifts is a powerful way to constrain cosmology as mentioned in this paper, and it is a probe of cosmic dawn and Epoch of Reionization astrophysics.
Abstract: In addition to being a probe of Cosmic Dawn and Epoch of Reionization astrophysics, the 21cm line at $z>6$ is also a powerful way to constrain cosmology. Its power derives from several unique capabilities. First, the 21cm line is sensitive to energy injections into the intergalactic medium at high redshifts. It also increases the number of measurable modes compared to existing cosmological probes by orders of magnitude. Many of these modes are on smaller scales than are accessible via the CMB, and moreover have the advantage of being firmly in the linear regime (making them easy to model theoretically). Finally, the 21cm line provides access to redshifts prior to the formation of luminous objects. Together, these features of 21cm cosmology at $z>6$ provide multiple pathways toward precise cosmological constraints. These include the "marginalizing out" of astrophysical effects, the utilization of redshift space distortions, the breaking of CMB degeneracies, the identification of signatures of relative velocities between baryons and dark matter, and the discovery of unexpected signs of physics beyond the $\Lambda$CDM paradigm at high redshifts.
Journal Article•
TL;DR: Finkelstein et al. as discussed by the authors presented a detailed map of the ionized intergalactic medium throughout the epoch of reionization by using Lyman-alpha emission from photometrically-identified galaxies.
Abstract: Author(s): Finkelstein, Steven L; Bradac, Marusa; Casey, Caitlin; Dickinson, Mark; Endsley, Ryan; Furlanetto, Steven; Hathi, Nimish; Hutchison, Taylor; Jung, Intae; Kartaltepe, Jeyhan; Koekemoer, Anton M; Larson, Rebecca L; Mason, Charlotte; Papovich, Casey; Ravindranath, Swara; Rigby, Jane; Stark, Dan; Wold, Isak | Abstract: The epoch of reionization (6 l z l 10) marks the period in our universe when the first large galaxies grew to fruition, and began to affect the universe around them Massive stars, and potentially accreting supermassive black holes, filled the universe with ionizing radiation, burning off the haze of neutral gas that had filled the intergalactic medium (IGM) since recombination (z~1000) The evolution of this process constrains key properties of these earliest luminous sources, thus observationally constraining reionization is a key science goal for the next decade The measurement of Lyman-alpha emission from photometrically-identified galaxies is a highly constraining probe of reionization, as a neutral IGM will resonantly scatter these photons, reducing detectability While significant work has been done with 8-10m telescopes, these observations require extremely large telescopes (ELTs); the flux limits available from today's 10m class telescopes are sufficient for only the brightest known galaxies (m l 26) Ultra-deep surveys with the Giant Magellan Telescope (GMT) and Thirty Meter Telescope (TMT) will be capable of detecting Lyman-alpha emission from galaxies 2-3 magnitudes fainter than today's deepest surveys Wide-field fiber spectroscopy on the GMT combined with narrow-field AO-assisted slit spectroscopy on the TMT will be able to probe the expected size of ionized bubbles throughout the epoch of reionization, following up degree scale deep imaging surveys with the Wide Field Infrared Space Telescope These data will provide the first resolved Lyman-alpha-based maps of the ionized intergalactic medium throughout the epoch of reionization, constraining models of both the temporal and spatial evolution of this phase change
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TL;DR: Furlanetto et al. as mentioned in this paper reviewed some of the fundamental physics necessary for computing the highly redshifted spin-flip background, including the radiative transfer of the 21-cm line and define the crucial quantities of interest.
Abstract: Author(s): Furlanetto, Steven R | Abstract: We review some of the fundamental physics necessary for computing the highly-redshifted spin-flip background. We first discuss the radiative transfer of the 21-cm line and define the crucial quantities of interest. We then review the processes that set the spin temperature of the transition, with a particular focus on Wouthuysen-Field coupling, which is likely to be the most important process during and after the Cosmic Dawn. Finally, we discuss processes that heat the intergalactic medium during the Cosmic Dawn, including the scattering of Lyman-alpha, cosmic microwave background, and X-ray photons.
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TL;DR: Furlanetto et al. as mentioned in this paper describe how the high-redshift 21-cm background can be used to improve both our understanding of the fundamental cosmological parameters of our Universe and exotic processes originating in the dark sector.
Abstract: Author(s): Furlanetto, Steven R | Abstract: We describe how the high-redshift 21-cm background can be used to improve both our understanding of the fundamental cosmological parameters of our Universe and exotic processes originating in the dark sector. The 21-cm background emerging during the cosmological Dark Ages, the era between hydrogen recombination and the formation of the first luminous sources (likely at z ~ 30), is difficult to measure but provides several powerful advantages for these purposes: in addition to the lack of astrophysical contamination, it will allow probes of very small scale structure over a very large volume. Additionally, the 21-cm background is sensitive to the thermal state of the intergalactic hydrogen and therefore probes any exotic processes (including, e.g., dark matter scattering or decay and primordial black holes) during that era. After astrophysical sources have formed, cosmological information can be separated from astrophysical effects on the 21-cm background through methods such as redshift space distortions, joint modeling, and by searching for indirect effects on the astrophysical sources themselves.
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TL;DR: In this article, the authors outline connections between the CGM and galactic star formation histories, internal kinematics, chemical evolution, quenching, satellite evolution, dark matter halo occupation, and the reionization of the larger scale intergalactic medium in light of the advances that will be made on these topics in the 2020s.
Abstract: Galaxies evolve under the influence of gas flows between their interstellar medium and their surrounding gaseous halos known as the circumgalactic medium (CGM). The CGM is a major reservoir of galactic baryons and metals, and plays a key role in the long cycles of accretion, feedback, and recycling of gas that drive star formation. In order to fully understand the physical processes at work within galaxies, it is therefore essential to have a firm understanding of the composition, structure, kinematics, thermodynamics, and evolution of the CGM. In this white paper we outline connections between the CGM and galactic star formation histories, internal kinematics, chemical evolution, quenching, satellite evolution, dark matter halo occupation, and the reionization of the larger-scale intergalactic medium in light of the advances that will be made on these topics in the 2020s. We argue that, in the next decade, fundamental progress on all of these major issues depends critically on improved empirical characterization and theoretical understanding of the CGM. In particular, we discuss how future advances in spatially-resolved CGM observations at high spectral resolution, broader characterization of the CGM across galaxy mass and redshift, and expected breakthroughs in cosmological hydrodynamic simulations will help resolve these major problems in galaxy evolution.
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TL;DR: In this paper, the first resolved Lyman-alpha-based maps of the ionized intergalactic medium throughout the epoch of reionization were obtained using the massive Magellan Telescope (GMT) and Thirty Meter Telescope (TMT).
Abstract: The epoch of reionization (6 < z < 10) marks the period in our universe when the first large galaxies grew to fruition, and began to affect the universe around them. Massive stars, and potentially accreting supermassive black holes, filled the universe with ionizing radiation, burning off the haze of neutral gas that had filled the intergalactic medium (IGM) since recombination (z~1000). The evolution of this process constrains key properties of these earliest luminous sources, thus observationally constraining reionization is a key science goal for the next decade. The measurement of Lyman-alpha emission from photometrically-identified galaxies is a highly constraining probe of reionization, as a neutral IGM will resonantly scatter these photons, reducing detectability. While significant work has been done with 8-10m telescopes, these observations require extremely large telescopes (ELTs); the flux limits available from today's 10m class telescopes are sufficient for only the brightest known galaxies (m < 26). Ultra-deep surveys with the Giant Magellan Telescope (GMT) and Thirty Meter Telescope (TMT) will be capable of detecting Lyman-alpha emission from galaxies 2-3 magnitudes fainter than today's deepest surveys. Wide-field fiber spectroscopy on the GMT combined with narrow-field AO-assisted slit spectroscopy on the TMT will be able to probe the expected size of ionized bubbles throughout the epoch of reionization, following up degree scale deep imaging surveys with the Wide Field Infrared Space Telescope. These data will provide the first resolved Lyman-alpha-based maps of the ionized intergalactic medium throughout the epoch of reionization, constraining models of both the temporal and spatial evolution of this phase change.