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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Paving the Way for Electroweak Baryogenesis

A detail look at the ingredients needed for creating the observed matter anomaly of the universe at the electroweak scale: new particles related to the Higgs boson, new sources of CP violation, and possibly new forces, all manifesting during the electroweak phase transition in the early universe. I will discuss three examples of plausible scenarios, two focused on the problem of preserving an asymmetry once created, and the third exhibiting a new mechanism where the source of both CP violation and the resulting asymmetry comes from the dark matter sector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2001

Far-Infrared Extragalactic Surveys: Past, Present, and Future

As much as one third of the luminosity of the local universe is emitted in the far infrared. In order to understand the history of energy release in the universe, it is crucial to characterize this rest-frame far-infrared contribution from the present back to the era of initial galaxy formation. Over the redshift range from 0 to 10, this energy is received in the 80 micrometers to 1 mm spectral region. In the 1980's the Infrared Astronomy Satellite (IRAS) all-sky survey provided the first comprehensive view of the far infrared emission from the local universe. The diffuse background measurements by Cosmic Background Explorer Satellite (COBE) have provided constraints on the integral contributions from the high redshift universe. In the past five years, submillimeter measurements made using the SCUBA instrument have revealed powerful high redshift sources. To develop a clear history of energy release in the universe, we need numbers and redshifts of representative populations of energetically important objects. The near future will bring the Space Infrared Telescope Facility Multiband Imaging Photometer (SIRTF)(MIPS) survey, which will cover about 100 square degrees at wavelengths out to 160 micrometers, providing a large sample of energetically important galaxies out to z of approx.3. In 2005, the Japanese IRIS survey will provide a 160 micrometers full sky survey, which will provide larger samples of the high z galaxy populations and will find intrinsically rare high luminosity objects. The SPIRE instrument on the FIRST facility will extend these surveys to longer wavelengths, providing a view of the universe at higher redshifts in three spectral bands. A concept for an all-sky submillimeter survey is under development, called the Survey of Infrared Cosmic Evolution (SIRCE). With a 2 m cryogenic telescope, it can map the entire sky to the confusion limit in the 100 to 500 micrometers range in six months. This survey will provide photometric redshifts, number counts, and will find the most luminous objects in the universe. In the next decade, the opening of the submillimeter, combined with the near infrared capability of NGST will provide us with a clear picture of energy release in the early universe.

Moseley, Samuel H., Jr.↗
NASA NTRS2009

Taking the Measure of the Universe

The cosmic microwave background (CMB) radiation is the oldest light in the universe - it is literally the remnant heat left over from the Big Bang. This fossil relic has survived largely intact and it provides us with a unique probe of conditions in the early universe, long before any stars or galaxies had formed. NASA has now flown two satellites devoted to studying the CMB: 'COBE' and 'WMAP'. In this lecture I will describe what we have learned from these missions including: evidence for the Big Bang itself; new measurements of the age, shape, and content of the universe; and new evidence that all structure in the universe emerged from microscopic quantum fluctuations in the primordial soup.

Hinshaw, Gary↗
NASA NTRS2010

James Webb Space Telescope Project Overview and Status for the SPIE

Often described as the successor to the Hubble Space Telescope, the JWST will serve astronomers world-wide in much the same way: Science & mission operations managed by the Space Telescope Science Institute The science investigations performed by the JWST will be determined by the General Observer community. Observing time allocated through annual peer-reviewed proposal cycles Four science themes have been defined by a succession of international community working groups to guide engineering development of the JWST: a) Identify the first bright objects that formed in the early Universe, and follow the ionization history. b) Determine how galaxies and dark matter, including gas, stars, metals, overall morphology and active nuclei evolved to the present day. c) Observe the birth and early development of stars and the formation of planets. d) Study the physical and chemical properties of solar systems (including our own) and where the building blocks of life may be present.

Sabelhaus, Phillip A.↗
DOE OSTI2022

A comparative analysis of the chemical compositions of Gaia-Enceladus/Sausage and Milky Way satellites using APOGEE

ABSTRACT We use data from the 17th data release of the Apache Point Observatory Galactic Evolution Experiment (APOGEE 2) to contrast the chemical composition of the recently discovered Gaia Enceladus/Sausage system (GE/S) to those of 10 Milky Way (MW) dwarf satellite galaxies: LMC, SMC, Boötes I, Carina, Draco, Fornax, Sagittarius, Sculptor, Sextans, and Ursa Minor. Our main focus is on the distributions of the stellar populations of those systems in the [Mg/Fe]–[Fe/H] and [Mg/Mn]–[Al/Fe] planes, which are commonly employed in the literature for chemical diagnosis and where dwarf galaxies can be distinguished from in situ populations. We show that, unlike MW satellites, a GE/S sample defined purely on the basis of orbital parameters falls almost entirely within the locus of ‘accreted’ stellar populations in chemical space, which is likely caused by an early quenching of star formation in GE/S. Due to a more protracted history of star formation, stars in the metal-rich end of the MW satellite populations are characterized by lower [Mg/Mn] than those of their GE/S counterparts. The chemical compositions of GE/S stars are consistent with a higher early star formation rate (SFR) than MW satellites of comparable and even higher mass, suggesting that star formation in the early universe was strongly influenced by other parameters in addition to mass. We find that the direction of the metallicity gradient in the [Mg/Mn]–[Al/Fe] plane of dwarf galaxies is an indicator of the early SFR of the system.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2019

CMB Spectral Distortions: Status and Prospects

Departures of the energy spectrum of the cosmic microwave background (CMB) from a perfect blackbody probe a fundamental property of the universe - its thermal history. Current upper limits, dating back some 25 years, limit such spectral distortions to 50 parts per million and provide a foundation for the Hot Big Bang model of the early universe. Modern upgrades to the 1980's-era technology behind these limits enable three orders of magnitude or greater improvement in sensitivity. The standard cosmological model provides compelling targets at this sensitivity, spanning cosmic history from the decay of primordial density perturbations to the role of baryonic feedback in structure formation. Fully utilizing this sensitivity requires concurrent improvements in our understanding of competing astrophysical foregrounds. We outline a program using proven technologies capable of detecting the minimal predicted distortions even for worst-case foreground scenarios.

Kogut, A.↗
DOE OSTI2022

Cannibalism's lingering imprint on the matter power spectrum

The early universe may have contained internally thermalized dark sectors that were decoupled from the Standard Model. In such scenarios, the relic dark thermal bath, composed of the lightest particle in the dark sector, can give rise to an epoch of early matter domination prior to Big Bang Nucleosynthesis, which has a potentially observable impact on the smallest dark matter structures. This lightest dark particle can easily and generically have number-changing self-interactions that give rise to “cannibal” behavior. We consider cosmologies where an initially sub-dominant cannibal species comes to temporarily drive the expansion of the universe, and we provide a simple map between the particle properties of the cannibal species and the key features of the enhanced dark matter perturbation growth in such cosmologies. Finally, we further demonstrate that cannibal self-interactions can determine the small-scale cutoff in the matter power spectrum even when the cannibal self-interactions freeze out prior to cannibal domination.

cosmological perturbation theory↗
NASA NTRS1999

Clustering of the Diffuse Infrared Light from the COBE DIRBE Maps: Power Spectrum Analysis and Excess Isotropic Component of Fluctuations - 3

The cosmic infrared background (CIB) radiation is the cosmic repository for energy release throughout the history of the universe. The spatial fluctuations of the CIB resulting from galaxy clustering are expected to be at least a few percent on scales of a degree, depending on the luminosity and clustering history of the early universe. Using the all-sky data from the COBE DIRBE instrument at wavelengths 1.25 - 100 microns we attempt to measure the CIB fluctuations. In the near-IR, foreground emission is dominated by small scale structure due to stars in the Galaxy. There we find a strong correlation between the amplitude of the fluctuations and Galactic latitude after removing bright foreground stars. Using data outside the Galactic plane (absolute value of b > 20 deg) and away from the center (90 deg < l < 270 deg) we extrapolate the amplitude of the fluctuations to cosec absolute value of b = 0. We find a positive intercept of delta.F(sub rms) = 15.5(sup +3.7, sub -7.0), 5.9(sup +1.6, sub -3.7), 2.4(sup +0.5, sub -0.9), 2.0(sup +0.25, sub -0.5) nW/sq m.sr at 1.25, 2.2, 3.5 and 4.9 microns respectively, where the errors are the range of 92% confidence limits. For color subtracted maps between band 1 and 2 we find the isotropic part of the fluctuations at 7.6(sup +1.2, sub -2.4) nW/sq m.sr. Based on detailed numerical and analytic models, this residual is not likely to originate from the Galaxy, our clipping algorithm, or instrumental noise. We demonstrate that the residuals from the fit used in the extrapolation are distributed isotropically and suggest that this extra variance may result from structure in the CIB. We also obtain a positive intercept from a linear combination of maps at 1.25 and 2.2 microns. For 2 deg < theta < 15 deg, a power-spectrum analysis yields limits of (theta/5 deg) x delta.F(sub rms)(theta) < 6, 2.5, 0.8, 0.5 nW/sq m.sr at 1.25, 2.2, 3.5 and 4.9 microns respectively. From 10 - 100 microns, the dominant foregrounds are emission by dust in the Solar system and the Galaxy. There the upper limits on the CIB fluctuations are below 1 nW/sq m.sr and are lowest (< equal 0.5 nW/sq m.sr) at 25 microns.

Kashlinsky, A.↗
DOE OSTI2024

New horizons in the holographic conformal phase transition

Abstract We describe 5D dynamical cosmological solutions of the stabilized holographic dilaton and their role in completion of the conformal phase transition. This analysis corresponds, via the AdS/CFT dictionary, to a study of out-of-equilibrium dynamics where trajectories of the dilaton do not depend solely on thermodynamic quantities in the early universe, but have sensitivity also to initial conditions. Unlike the well-studied thermal transition, which requires quantum tunneling of an infrared brane through the surface of an AdS-Schwarzschild horizon, our approach instead invokes an early epoch in which the cosmology is fully 5-dimensional, with highly relativistic brane motion and with Rindler horizons obscuring the infrared brane at early times. In this context, we demonstrate the existence of a large class of natural initial conditions that seed trajectories where the brane simply passes through the Rindler horizon and into the basin of attraction of the stabilized dilaton potential. This corresponds to successful completion of the phase transition without sacrificing perturbativity of the 5D theory.

Physics↗
NASA NTRS2004

Theoretical Astrophysics at Fermilab

The Theoretical Astrophysics Group works on a broad range of topics ranging from string theory to data analysis in the Sloan Digital Sky Survey. The group is motivated by the belief that a deep understanding of fundamental physics is necessary to explain a wide variety of phenomena in the universe. During the three years 2001-2003 of our previous NASA grant, over 120 papers were written; ten of our postdocs went on to faculty positions; and we hosted or organized many workshops and conferences. Kolb and collaborators focused on the early universe, in particular and models and ramifications of the theory of inflation. They also studied models with extra dimensions, new types of dark matter, and the second order effects of super-horizon perturbations. S tebbins, Frieman, Hui, and Dodelson worked on phenomenological cosmology, extracting cosmological constraints from surveys such as the Sloan Digital Sky Survey. They also worked on theoretical topics such as weak lensing, reionization, and dark energy. This work has proved important to a number of experimental groups [including those at Fermilab] planning future observations. In general, the work of the Theoretical Astrophysics Group has served as a catalyst for experimental projects at Fennilab. An example of this is the Joint Dark Energy Mission. Fennilab is now a member of SNAP, and much of the work done here is by people formerly working on the accelerator. We have created an environment where many of these people made transition from physics to astronomy. We also worked on many other topics related to NASA s focus: cosmic rays, dark matter, the Sunyaev-Zel dovich effect, the galaxy distribution in the universe, and the Lyman alpha forest. The group organized and hosted a number of conferences and workshop over the years covered by the grant. Among them were:

Source record↗
DOE OSTI2021

A Lunar Farside Low Radio Frequency Array for Dark Ages 21-cm Cosmology

An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 kmx10 km area on the lunar surface. The antenna nodes are tethered to the lander for central data processing, power, and data transmission to a relay satellite. The array, named FARSIDE, would provide the capability to image the entire sky in 1400 channels spanning frequencies from 100 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, the Earth's auroral kilometric radiation, and plasma noise from the solar wind. It is thus the only location within the inner solar system from which sky noise limited observations can be carried out at sub-MHz frequencies. Through precision calibration via an orbiting beacon and exquisite foreground characterization, the farside array would measure the Dark Ages global 21-cm signal at redshifts z~35-200. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2010

A Scientific Revolution: The Hubble and James Webb Space Telescopes

Astronomy is going through a scientific revolution, responding to a flood of data from the Hubble Space Telescope, other space missions, and large telescopes on the ground. In this talk, I will discuss some of the important discoveries of the last decade, from dwarf planets in the outer Solar System to the mysterious dark energy that overcomes gravity to accelerate the expansion of the Universe. The next decade will be equally bright with the newly refurbished Hubble and the promise of its successor, the James Webb Space Telescope. An infrared-optimized 6.5m space telescope, Webb is designed to find the first galaxies that formed in the early universe and to peer into the dusty gas clouds where stars and planets are born. With MEMS technology, a deployed primary mirror and a tennis-court sized sunshield, the mission presents many technical challenges. I will describe Webb's scientific goals, its design and recent progress in constructing the observatory. Webb is scheduled for launch in 2014.

Gardner, Jonathan P.↗
DOE OSTI2024

A Large Sample of Extremely Metal-poor Galaxies at z < 1 Identified from the DESI Early Data

Extremely metal-poor galaxies (XMPGs) at relatively low redshift are excellent laboratories for studying galaxy formation and evolution in the early universe. Much effort has been spent on identifying them from large-scale spectroscopic surveys or spectroscopic follow-up observations. Previous work has identified a few hundred XMPGs. In this work, we obtain a large sample of 223 XMPGs at z < 1 from the early data of the Dark Energy Spectroscopic Instrument (DESI). The oxygen abundance is determined using the direct T e method based on the detection of the [O iii]λ4363 line. The sample includes 95 confirmed XMPGs based on the oxygen abundance uncertainty; the remaining 128 galaxies are regarded as XMPG candidates. These XMPGs are only 0.01% of the total DESI observed galaxies. Their coordinates and other properties are provided in the paper. The most XMPGs have an oxygen abundance of ~1/34 Z ⊙ , a stellar mass of about 1.5 × 10 7 M ⊙ , and a star formation rate of 0.22 M ⊙ yr –1 . The two most XMPGs present distinct morphologies suggesting different formation mechanisms. The local environmental investigation shows that XMPGs preferentially reside in relatively low-density regions. Many of them fall below the stellar mass–metallicity relations (MZRs) of normal star-forming galaxies. From a comparison of the MZR with theoretical simulations, it appears that XMPGs are good analogs to high-redshift star-forming galaxies. The nature of these XMPG populations will be further investigated in detail with larger and more complete samples from the ongoing DESI survey.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2006

Gamma Ray Bursts

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. There has been tremendous recent progress in our understanding of bursts with the new data from the Swift mission. Swift was launched in November 2004 and is a multiwave length observatory designed to determine the origin of bursts and use them to probe the early Universe. It was developed and is being operated by an international team of scientists from the US, UK and Italian. The first year of findings from the mission will be presented. A large step forward has been made in our understanding of the mysterious short GRBs. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

Gehrels, Neil↗
NASA NTRS2018

A Brief History of Space Climatology: From the Big Bang to the Present

This work presents a space climatology timeline ranging from the Big Bang to the present. It begins with a description of the early universe including the origin and abundances of particles significant for radiation effects. It continues to a transition period to modern times when the era of modern space climatology began to emerge due to discoveries of sunspots and the solar activity cycle, along with development of early astronomical methods. The timeline concludes in the modern era with a description of the radiation environments of galactic cosmic rays, solar particle events and the Van Allen Belts.

Galactic Cosmic Rays↗
NASA NTRS2018

A Brief History of Space Climatology: From the Big Bang to the Present

This work presents a space climatology timeline ranging from the Big Bang to the present. It began with a description of the early universe including the origin and abundances of particles significant for radiation effects. It continued to a transition period to modern times when the era of modern space climatology began to emerge due to discoveries of sunspots and the solar activity cycle, along with development of early astronomical methods. The timeline concluded in the modern era with a description of the radiation environments of galactic cosmic rays, solar particle events and the Van Allen Belts.

Big bang↗
NASA NTRS2014

James Webb Space Telescope: The First Light Machine

NASA James Webb Space Telescope (JWST) will search for the first luminous objects of the Universe to help answer fundamental questions about how the Universe came to look like it does today. At 6.5 meters in diameter, JWST will be the world's largest space telescope. Its architecture, e.g. aperture, wavelength range and operating temperature, is driven by JWST's science objectives. Introduction: Scheduled to start its 5 year mission after 2018, JWST will study the origin and evolution of galaxies, stars and planetary systems. Its science mission is to: Identify the first bright objects that formed in the early Universe, and follow the ionization history. Determine how galaxies form. Determine how galaxies and dark matter, including gas, stars, metals, overall morphology and active nuclei evolved to the present day. Observe the birth and early development of stars and the formation of planets. And, study the physical and chemical properties of solar systems for the building blocks of Life. Principle: To accomplish the JWST science objectives requires a larger aperture infrared cryogenic space telescope. A large aperture is required because the objects are very faint. The infrared spectral range is required because the objects are so far away that their ultraviolet and visible wavelength spectral lines are red-shifted into the infrared. Because the telescope is infrared, it needs to be cryogenic. And, because of the telescope is infrared, it must operate above the Earth's atmosphere, i.e. in space. JWST is probably the single most complicated mission that humanity has attempted. It is certainly the most difficult optical fabrication and testing challenge of our generation. The JWST 6.5 m diameter primary mirror is nearly a parabola with a conic constant of -0.9967 and radius of curvature at 30K of 15.880 m. The primary mirror is divided into 18 segments with 3 different prescriptions; each with its own off-axis distance and aspheric departure. The radius of curvature for all 18 segments must match to +/- 0.150 mm at 30K. JWST is diffraction limited at 2 micrometers which translates into a transmitted wavefront specification of 156 nm rms. Of that amount, 50 nm rms is allocated to the primary mirror. Each segment is allocated 22 nm rms surface error. At the start of the JWST program, the capability to make such a mirror did not exist. In 1996, NASA began a systematic and comprehensive mirror technology development effort which resulted in JWST. This program resulted in a qualified mirror fabrication process being approved in 2006. Today, all JWST primary mirror segments meet their requirements and are on schedule for a 2018 launch. The next step is system level assembly, integration and test. Ambient tests will be conducted at Goddard Space Flight Center and cryogenic system level testing will be performed in Chamber A at the Johnson Space Center.

Stahl, H. Philip↗
NASA NTRS2001

A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe. The major study of a sample of z=3 and its comparison with a sample of z=0.l quasars across the whole X-ray to radio spectrum was completed and accepted for publication in ApJ Supplements. This study comprises the thesis work of Olga Kuhn. The two samples are matched in evolved luminosity, and so should be sampling the same black hole population at different z, and in different accretion states. Despite this no strong differences were found between the samples, except in the 'small bump' region of the optical/UV. This region is dominated by FeII emission, and may indicate abundance evolution in quasars. The lack of overall spectral changes argues strongly against a single population of quasars fading over cosmic time, and for a multiple generation, or multiple outburst model for quasars. A study of the total luminosity absorbed from quasars and re-emitted in the infrared produced two results (reported in two papers): The minimum intrinsic luminosity/Gpc(3) from AGN compared with the measured mass density in supermassive black holes [Gpc(-3)] requires a conversion efficiency of accreted mass into luminosity of greater than 15%. Non-rotating black holes cannot exceed 5% efficiency, while rapidly rotating black holes can reach 47%. Hence our result requires that most supermassive black holes must be rapidly rotating. The second result comes from considering the contribution that the re-radiated quasar radiation makes to the far infrared background (FIRB). The effective temperature of the re radiation is tightly constrained, but the detailed shape (e.g. line emission, range of temperature) is only of second order importance. At least 15perhaps 20-25% of the FIR background must come from AGN. This contribution significantly relieves problems in galaxy evolution that come from trying to use only starlight to make the FIRB. The third paper addresses the origin of the dust obscuration that is so widespread in AGN. The standard assumption is that the dust comes from the normal star-formation processes in galaxies and is drawn close to the nucleus along with the gas that powers the accretion. In complete contrast, using a wind outflow model for the broad emission line (BEL) region (Elvis 2000) as a basis, we show that BEL clouds will expand, cool and form dust as they flow outward, in strict analogy to the stellar winds of red supergiants.

Elvis, M.↗