12,844 research outputs found

    HI Epoch of Reionization Arrays

    Full text link
    There are few data available with which to constrain the thermal history of the intergalactic medium (IGM) following global recombination. Thus far, most constraints flow from analyses of the Cosmic Microwave Background and optical spectroscopy along a few lines of sight. However, direct study of the IGM in emission or absorption against the CMB via the 1S hyperfine transition of Hydrogen would enable broad characterization thermal history and source populations. New generations of radio arrays are in development to measure this line signature. Bright foreground emission and the complexity of instrument calibration models are significant hurdles. How to optimize these is uncertain, resulting in a diversity in approaches. We discuss recent limits on line brightness, array efforts including the new Large Aperture Experiment to Detect the Dark Ages (LEDA), and the next generation Hydrogen Reionization Array (HERA) concept.Comment: 8 pages, 4 figures, 1 table. Invited review to the 11th Asian-Pacific Regional IAU Meeting 2011, NARIT Conference Series, Vol. 1 eds. S. Komonjinda, Y. Kovalev, and D. Ruffolo (2012

    B-Mode contamination by synchrotron emission from 3-years WMAP data

    Full text link
    We study the contamination of the B-mode of the Cosmic Microwave Background Polarization (CMBP) by Galactic synchrotron in the lowest emission regions of the sky. The 22.8-GHz polarization map of the 3-years WMAP data release is used to identify and analyse such regions. Two areas are selected with signal-to-noise ratio S/N<2 and S/N<3, covering ~16% and ~26% fraction of the sky, respectively. The polarization power spectra of these two areas are dominated by the sky signal on large angular scales (multipoles l < 15), while the noise prevails on degree scales. Angular extrapolations show that the synchrotron emission competes with the CMBP B-mode signal for tensor-to-scalar perturbation power ratio T/S=103T/S = 10^{-3} -- 10210^{-2} at 70-GHz in the 16% lowest emission sky (S/N<2 area). These values worsen by a factor ~5 in the S/N<3 region. The novelty is that our estimates regard the whole lowest emission regions and outline a contamination better than that of the whole high Galactic latitude sky found by the WMAP team (T/S>0.3). Such regions allow T/S103T/S \sim 10^{-3} to be measured directly which approximately corresponds to the limit imposed by using a sky coverage of 15%. This opens interesting perspectives to investigate the inflationary model space in lowest emission regions.Comment: 5 pages, 3 figures, accepted for publication in MNRAS Letter

    Close kin influences on fertility behavior

    Get PDF
    Family members are uniquely situated to influence the decision-making of their kin in nearly every facet of life. We examine the importance of social interactions in fertility outcomes by assessing family members’ scope of influence on their fellow kin’s fertility behavior. With the unique KASS genealogical dataset from eight countries in Europe, we study the effects of family members’ fertility outcomes on individual fertility to assess the presence and the extent of inter-generational transmission of fertility behaviors and siblings’ influences on fertility outcomes. We find only limited evidence of the inter-generational transmission of fertility behaviors, but a relatively important effect of siblings for individual fertility. Rather than parents, siblings’ influences appear to constitute the largest share of familial influences on fertility outcomes. We also find that among siblings, women’s fertility is more subject to the influences of their sisters. These findings indicate the relative importance of close kin influences on individual fertility and demonstrate the consequences of family structure for fertility change.Europe, family demography, family size, fertility, kinship, sisters

    Office of the Legislative Analyst

    Get PDF

    The synchrotron foreground and CMB temperature-polarization cross correlation power spectrum from the first year WMAP data

    Full text link
    We analyse the temperature-polarization cross-correlation in the Galactic synchrotron template that we have recently developed, and between the template and CMB temperature maps derived from WMAP data. Since the polarized synchrotron template itself uses WMAP data, we can estimate residual synchrotron contamination in the CMB CTEC_\ell^{TE} angular spectrum. While C2TEC_2^{TE} appears to be contamined by synchrotron, no evidence for contamination is found in the multipole range which is most relevant for the fit of the cosmological optical depth.Comment: Accepted for pubblication on MNRAS Lette

    Post-correlation radio frequency interference classification methods

    Get PDF
    We describe and compare several post-correlation radio frequency interference classification methods. As data sizes of observations grow with new and improved telescopes, the need for completely automated, robust methods for radio frequency interference mitigation is pressing. We investigated several classification methods and find that, for the data sets we used, the most accurate among them is the SumThreshold method. This is a new method formed from a combination of existing techniques, including a new way of thresholding. This iterative method estimates the astronomical signal by carrying out a surface fit in the time-frequency plane. With a theoretical accuracy of 95% recognition and an approximately 0.1% false probability rate in simple simulated cases, the method is in practice as good as the human eye in finding RFI. In addition it is fast, robust, does not need a data model before it can be executed and works in almost all configurations with its default parameters. The method has been compared using simulated data with several other mitigation techniques, including one based upon the singular value decomposition of the time-frequency matrix, and has shown better results than the rest.Comment: 14 pages, 12 figures (11 in colour). The software that was used in the article can be downloaded from http://www.astro.rug.nl/rfi-software
    corecore