Prospects for Measuring Cosmic Microwave Background Spectral Distortions in the Presence of Foregrounds

Measurements of cosmic microwave background spectral distortions have profound implications for our understanding of physical processes taking place over a vast window in cosmological history. Foreground contamination is unavoidable in such measurements and detailed signal-foreground separation will be necessary to extract cosmological science. We present MCMC-based spectral distortion detection forecasts in the presence of Galactic and extragalactic foregrounds for a range of possible experimental configurations, focusing on the Primordial Inflation Explorer (PIXIE) as a fiducial concept. We consider modifications to the baseline PIXIE mission (operating 12 months in distortion mode), searching for optimal configurations using a Fisher approach. Using only spectral information, we forecast an extended PIXIE mission to detect the expected average non-relativistic and relativistic thermal Sunyaev-Zeldovich distortions at high significance (194$\sigma$ and 11$\sigma$, respectively), even in the presence of foregrounds. The $\Lambda$CDM Silk damping $\mu$-type distortion is not detected without additional modifications of the instrument or external data. Galactic synchrotron radiation is the most problematic source of contamination in this respect, an issue that could be mitigated by combining PIXIE data with future ground-based observations at low frequencies ($\nu < 15-30$GHz). Assuming moderate external information on the synchrotron spectrum, we project an upper limit of $|\mu| < 3.6\times 10^{-7}$ (95\% c.l.), slightly more than one order of magnitude above the fiducial $\Lambda$CDM signal from the damping of small-scale primordial fluctuations, but a factor of $\simeq 250$ improvement over the current upper limit from COBE/FIRAS. This limit could be further reduced to $|\mu| < 9.4\times 10^{-8}$ (95\% c.l.) with more optimistic assumptions about low-frequency information. (Abridged)Comment: (16 pages, 11 figures, submitted to MNRAS. Fisher code available at https://github.com/mabitbol/sd_foregrounds. Updated with published version.

Constraining the Anomalous Microwave Emission Mechanism in the S140 Star Forming Region with Spectroscopic Observations Between 4 and 8 GHz at the Green Bank Telescope

Anomalous microwave emission (AME) is a category of Galactic signals that cannot be explained by synchrotron radiation, thermal dust emission, or optically thin free-free radiation. Spinning dust is one variety of AME that could be partially polarized and therefore relevant for ongoing and future cosmic microwave background polarization studies. The Planck satellite mission identified candidate AME regions in approximately $1^\circ$ patches that were found to have spectra generally consistent with spinning dust grain models. The spectra for one of these regions, G107.2+5.2, was also consistent with optically thick free-free emission because of a lack of measurements between 2 and 20 GHz. Follow-up observations were needed. Therefore, we used the C-band receiver (4 to 8 GHz) and the VEGAS spectrometer at the Green Bank Telescope to constrain the AME mechanism. For the study described in this paper, we produced three band averaged maps at 4.575, 5.625, and 6.125 GHz and used aperture photometry to measure the spectral flux density in the region relative to the background. We found if the spinning dust description is correct, then the spinning dust signal peaks at $30.9 \pm 1.4$ GHz, and it explains the excess emission. The morphology and spectrum together suggest the spinning dust grains are concentrated near S140, which is a star forming region inside our chosen photometry aperture. If the AME is sourced by optically thick free-free radiation, then the region would have to contain HII with an emission measure of $5.27^{+2.5}_{-1.5}\times 10^8$ $\rm{cm^{-6}\,pc}$ and a physical extent of $1.01^{+0.21}_{-0.20} \times 10^{-2}\,\rm{pc}$. This result suggests the HII would have to be ultra or hyper compact to remain an AME candidate.Comment: 21 pages, 14 figures. Submitted to Ap

Geology and Ground-Water Hydrology of the Valleys of the Republican and Frenchman Rivers Nebraska

The geology and ground-water resources of the upper Republican River valley west of the town of Alma, Nebr., to the Nebraska-Colorado State line and of the Frenchman River valley from its confluence with the Republican River to a point about 12 miles upstream from Wauneta, Nebr., were studied from January 1950 to April 1951. The purpose of the study was to relate the occurrence of ground water to irrigation and flood control and to aid in the evaluation of the effects of irrigation on the land in the area. The area included in this study consists of 370 square miles of flat or gently sloping terraces and bottom land that border the Republican and Frenchman Rivers on either side. The Republican River is a comparatively shallow stream, ranging in width from about 150 feet at the western end of the area to about 300 feet at the eastern end. The channel banks are low, except where the river cuts into bordering terraces. In many places, natural levees of loose sand and gravel have been formed adjacent to the river banks. The bedrock formations exposed in the area are the Niobrara formation and the Pierre shale of Cretaceous age and the Ogallala formation of Tertiary age. Deposits of sand and gravel, of early Pleistocene age, are present in the bottom of the ancestral Republican River valley and along the north side of the present valley. These coarse deposits are mantled by finer sediments of later Pleistocene and Recent age. Large quantities of ground water are available from the Pleistocene and Recent deposits throughout most of the Republican River valley. In the center of the valley as much as 40 to 60 feet of the deposits are saturated. The ground-water reservoir is recharged principally by precipitation. Ground water also enters the Republican River valley by underflow through the fill of tributary valleys. Ground water is discharged by evaporation, transpiration, and effluent streams; ground water also is drawn upon extensively for irrigation, for municipal supplies, and for domestic and stock use in rural areas

Geology and Ground-Water Hydrology of the Valleys of the Republican and Frenchman Rivers Nebraska

The geology and ground-water resources of the upper Republican River valley west of the town of Alma, Nebr., to the Nebraska-Colorado State line and of the Frenchman River valley from its confluence with the Republican River to a point about 12 miles upstream from Wauneta, Nebr., were studied from January 1950 to April 1951. The purpose of the study was to relate the occurrence of ground water to irrigation and flood control and to aid in the evaluation of the effects of irrigation on the land in the area. The area included in this study consists of 370 square miles of flat or gently sloping terraces and bottom land that border the Republican and Frenchman Rivers on either side. The Republican River is a comparatively shallow stream, ranging in width from about 150 feet at the western end of the area to about 300 feet at the eastern end. The channel banks are low, except where the river cuts into bordering terraces. In many places, natural levees of loose sand and gravel have been formed adjacent to the river banks. The bedrock formations exposed in the area are the Niobrara formation and the Pierre shale of Cretaceous age and the Ogallala formation of Tertiary age. Deposits of sand and gravel, of early Pleistocene age, are present in the bottom of the ancestral Republican River valley and along the north side of the present valley. These coarse deposits are mantled by finer sediments of later Pleistocene and Recent age. Large quantities of ground water are available from the Pleistocene and Recent deposits throughout most of the Republican River valley. In the center of the valley as much as 40 to 60 feet of the deposits are saturated. The ground-water reservoir is recharged principally by precipitation. Ground water also enters the Republican River valley by underflow through the fill of tributary valleys. Ground water is discharged by evaporation, transpiration, and effluent streams; ground water also is drawn upon extensively for irrigation, for municipal supplies, and for domestic and stock use in rural areas

An Assessment of Grass Regeneration Nurseries at the Western Regional Plant Introduction Station, 1994-1997

The Western Regional Plant Introduction Station (WRPIS), Pullman, WA, USA, maintains over 17,000 accessions of forage and turf grasses that are mostly wind cross-pollinated and highly heterogenic. Regeneration procedures have been refined over the past nine years to include improved isolation distance and increased plant populations for regeneration. The grass regeneration nurseries planted from 1994 through 1997 were evaluated using data recorded in the Germplasm Resources Information Network (GRIN) and it was found that approximately 78% of the regenerations were successful. Reasons for failures were contributed to inadequate plant number, presence of disease, seed shattering, and unsuitable growing environment. Several solutions have been identified and implemented

POLOCALC: a Novel Method to Measure the Absolute Polarization Orientation of the Cosmic Microwave Background

We describe a novel method to measure the absolute orientation of the polarization plane of the CMB with arcsecond accuracy, enabling unprecedented measurements for cosmology and fundamental physics. Existing and planned CMB polarization instruments looking for primordial B-mode signals need an independent, experimental method for systematics control on the absolute polarization orientation. The lack of such a method limits the accuracy of the detection of inflationary gravitational waves, the constraining power on the neutrino sector through measurements of gravitational lensing of the CMB, the possibility of detecting Cosmic Birefringence, and the ability to measure primordial magnetic fields. Sky signals used for calibration and direct measurements of the detector orientation cannot provide an accuracy better than 1 deg. Self-calibration methods provide better accuracy, but may be affected by foreground signals and rely heavily on model assumptions. The POLarization Orientation CALibrator for Cosmology, POLOCALC, will dramatically improve instrumental accuracy by means of an artificial calibration source flying on balloons and aerial drones. A balloon-borne calibrator will provide far-field source for larger telescopes, while a drone will be used for tests and smaller polarimeters. POLOCALC will also allow a unique method to measure the telescopes' polarized beam. It will use microwave emitters between 40 and 150 GHz coupled to precise polarizing filters. The orientation of the source polarization plane will be registered to sky coordinates by star cameras and gyroscopes with arcsecond accuracy. This project can become a rung in the calibration ladder for the field: any existing or future CMB polarization experiment observing our polarization calibrator will enable measurements of the polarization angle for each detector with respect to absolute sky coordinates.Comment: 15 pages, 5 figures, Accepted by Journal of Astronomical Instrumentatio

A CubeSat for Calibrating Ground-Based and Sub-Orbital Millimeter-Wave Polarimeters (CalSat)

We describe a low-cost, open-access, CubeSat-based calibration instrument that is designed to support ground-based and sub-orbital experiments searching for various polarization signals in the cosmic microwave background (CMB). All modern CMB polarization experiments require a robust calibration program that will allow the effects of instrument-induced signals to be mitigated during data analysis. A bright, compact, and linearly polarized astrophysical source with polarization properties known to adequate precision does not exist. Therefore, we designed a space-based millimeter-wave calibration instrument, called CalSat, to serve as an open-access calibrator, and this paper describes the results of our design study. The calibration source on board CalSat is composed of five "tones" with one each at 47.1, 80.0, 140, 249 and 309 GHz. The five tones we chose are well matched to (i) the observation windows in the atmospheric transmittance spectra, (ii) the spectral bands commonly used in polarimeters by the CMB community, and (iii) The Amateur Satellite Service bands in the Table of Frequency Allocations used by the Federal Communications Commission. CalSat would be placed in a polar orbit allowing visibility from observatories in the Northern Hemisphere, such as Mauna Kea in Hawaii and Summit Station in Greenland, and the Southern Hemisphere, such as the Atacama Desert in Chile and the South Pole. CalSat also would be observable by balloon-borne instruments launched from a range of locations around the world. This global visibility makes CalSat the only source that can be observed by all terrestrial and sub-orbital observatories, thereby providing a universal standard that permits comparison between experiments using appreciably different measurement approaches

Retention of low-fitness genotypes over six decades of admixture between native and introduced tiger salamanders

<p>Abstract</p> <p>Background</p> <p>Introductions of non-native tiger salamanders into the range of California tiger salamanders have provided a rare opportunity to study the early stages of secondary contact and hybridization. We produced first- and second-generation hybrid salamanders in the lab and measured viability among these early-generation hybrid crosses to determine the strength of the initial barrier to gene exchange. We also created contemporary-generation hybrids in the lab and evaluated the extent to which selection has affected fitness over approximately 20 generations of admixture. Additionally, we examined the inheritance of quantitative phenotypic variation to better understand how evolution has progressed since secondary contact.</p> <p>Results</p> <p>We found significant variation in the fitness of hybrids, with non-native backcrosses experiencing the highest survival and F2 hybrids the lowest. Contemporary-generation hybrids had similar survival to that of F2 families, contrary to our expectation that 20 generations of selection in the wild would eliminate unfit genotypes and increase survival. Hybrid survival clearly exhibited effects of epistasis, whereas size and growth showed mostly additive genetic variance, and time to metamorphosis showed substantial dominance.</p> <p>Conclusions</p> <p>Based on first- and second- generation cross types, our results suggest that the initial barrier to gene flow between these two species was relatively weak, and subsequent evolution has been generally slow. The persistence of low-viability recombinant hybrid genotypes in some contemporary populations illustrates that while hybridization can provide a potent source of genetic variation upon which natural selection can act, the sorting of fit from unfit gene combinations might be inefficient in highly admixed populations. Spatio-temporal fluctuation in selection or complex genetics has perhaps stalled adaptive evolution in this system despite selection for admixed genotypes within generations.</p