Measurements of Cosmic Microwave Background (CMB) anisotropy have served as the best experimental probe of the early universe to date. The inflationary paradigm, inspired in part by the extreme isotropy of the CMB, is now a cornerstone in modern cosm
ology. Inflation has passed a series of rigorous experimental tests, but we still do not understand the physical mechanism or energy scale behind inflation. A general prediction of inflation and one that can provide certain insights into inflationary physics is a background of primordial gravitational waves. These perturbations leave a distinct signature in the CMB B-modes of polarization. The EPIC (Experimental Probe of Inflationary Cosmology) study team has investigated several CMB polarization mission concepts to carry out a definitive measurement of the inflationary B-mode polarization spectrum. In this report we study a mission with an aperture intermediate between the two missions discussed in our previous report. EPIC-IMs increased aperture allows access to a broader science case than the small EPIC-Low Cost mission. In addition to the search for inflationary gravitational waves, the increase aperture allows us to mine the scale polarization and lensing shear polarization signals down to cosmological limits, so that we extract virtually all the cosmological information available from the CMB. In addition, a modest number of channels operating at higher frequencies allows for an all-sky measurement of polarized Galactic dust, which will provide a rich dataset for Galactic science related to magnetic fields. Using a combination of a large sensitivity focal plane with a new optical design, and an efficient 4K mechanical cooler, EPIC-IM realizes higher sensitivity than EPIC-Comprehensive Science mission.
The Cosmic Infrared Background ExpeRiment (CIBER) is a rocket-borne absolute photometry imaging and spectroscopy experiment optimized to detect signatures of first-light galaxies present during reionization in the unresolved IR background. CIBER-I co
nsists of a wide-field two-color camera for fluctuation measurements, a low-resolution absolute spectrometer for absolute EBL measurements, and a narrow-band imaging spectrometer to measure and correct scattered emission from the foreground zodiacal cloud. CIBER-I was successfully flown on February 25th, 2009 and has one more planned flight in early 2010. We propose, after several additional flights of CIBER-I, an improved CIBER-II camera consisting of a wide-field 30 cm imager operating in 4 bands between 0.5 and 2.1 microns. It is designed for a high significance detection of unresolved IR background fluctuations at the minimum level necessary for reionization. With a FOV 50 to 2000 times largerthan existing IR instruments on satellites, CIBER-II will carry out the definitive study to establish the surface density of sources responsible for reionization.
The cosmic dark ages are the mysterious epoch during which the pristine gas began to condense and ultimately form the first stars. Although these beginnings have long been a topic of theoretical interest, technology has only recently allowed the begi
nnings of observational insight into this epoch. Many questions surround the formation of stars in metal-free gas and the history of the build-up of metals in the intergalactic medium: (1) What were the properties of the first stellar and galactic sources to form in pristine (metal-free) gas? (2) When did the epoch of Population III (metal-free) star formation take place and how long did it last? (3) Was the stellar initial mass function dramatically different for the first stars and galaxies? These questions are all active areas of theoretical research. However, new observational constraints via the direct detection of Population III star formation are vital to making progress in answering the broader questions surrounding how galaxies formed and how the cosmological properties of the universe have affected the objects it contains.
(Brief Summary) What is the total radiative content of the Universe since the epoch of recombination? The extragalactic background light (EBL) spectrum captures the redshifted energy released from the first stellar objects, protogalaxies, and galaxie
s throughout cosmic history. Yet, we have not determined the brightness of the extragalactic sky from UV/optical to far-infrared wavelengths with sufficient accuracy to establish the radiative content of the Universe to better than an order of magnitude. Among many science topics, an accurate measurement of the EBL spectrum from optical to far-IR wavelengths, will address: What is the total energy released by stellar nucleosynthesis over cosmic history? Was significant energy released by non-stellar processes? Is there a diffuse component to the EBL anywhere from optical to sub-millimeter? When did first stars appear and how luminous was the reionization epoch? Absolute optical to mid-IR EBL spectrum to an astrophysically interesting accuracy can be established by wide field imagingat a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is reduced by more than two orders of magnitude.
The gravitational lensing distortion of distant sources by the large-scale distribution of matter in the Universe has been extensively studied. In contrast, very little is known about the effects due to the large-scale distribution of dark energy. We
discuss the use of Type Ia supernovae as probes of the spatial inhomogeneity and anisotropy of dark energy. We show that a shallow, almost all-sky survey can limit rms dark energy fluctuations at the horizon scale down to a fractional energy density of ~10^-4
Our ignorance of the dark energy is generally described by a two-parameter equation of state. In these approaches a particular {it ad hoc} functional form is assumed, and only two independent parameters are incorporated. We propose a model-independen
t, multi-parameter approach to fitting the dark energy, and show that next-generation surveys will constrain the equation of state in three or more independent redshift bins to better than 10%. Future knowledge of the dark energy will surpass two numbers (e.g., [$w_0$,$w_1$] or [$w_0$,$w_a$]), and we propose a more flexible approach to the analysis of present and future data.
This is the Phase 1 Report on the Experimental Probe of Inflationary Cosmology (EPIC), a mission concept study for NASAs Einstein Inflation Probe. When we began our study we sought to answer five fundamental implementation questions: 1) can foregroun
ds be measured and subtracted to a sufficiently low level?; 2) can systematic errors be controlled?; 3) can we develop optics with sufficiently large throughput, low polarization, and frequency coverage from 30 to 300 GHz?; 4) is there a technical path to realizing the sensitivity and systematic error requirements?; and 5) what are the specific mission architecture parameters, including cost? Detailed answers to these questions are contained in this report. Currently in Phase 2, we are exploring a mission concept targeting a ~2m aperture, in between the two options described in the current report with a small (~30 cm) and large (~4m) missions.
The 21-cm anisotropies from the neutral hydrogen distribution prior to the era of reionization is a sensitive probe of primordial non-Gaussianity. Unlike the case with cosmic microwave background, 21-cm anisotropies provide multi-redshift information
with frequency selection and is not damped at arcminute angular scales. We discuss the angular trispectrum of the 21-cm background anisotropies and discuss how the trispectrum signal generated by the primordial non-Gaussianity can be measured with the three-to-one correlator and the corresponding angular power spectrum. We also discuss the separation of primordial non-Gaussian information in the trispectrum with that generated by the subsequent non-linear gravitational evolution of the density field. While with the angular bispectrum of 21-cm anisotropies one can limit the second order corrections to the primordial fluctuations below f_NL< 1, using the trispectrum information we suggest that the third order coupling term, f_2 or g_NL, can be constrained to be arounde 10 with future 21-cm observations over the redshift interval of 50 to 100.
