Data Mining: Sky Maps, Power Spectrum, etc.

Background:
BOOMERanG constraints on primordial non-Gaussianity from analytical Minkowski functionals: Subdegree Sunyaev-Zel'dovich signal from multifrequency BOOMERanG observations: Searching for non Gaussian signals in the BOOMERanG 2003 CMB maps:
    In De Troia et al.(2007), we analyze the BOOMERanG 2003 (B03) 145 GHz temperature map to constrain the amplitude of a non Gaussian, primordial contribution to CMB fluctuations. We perform a pixel space analysis restricted to a portion of the map chosen in view of high sensitivity, very low foreground contamination and tight control of systematic effects. We set up an estimator based on the three Minkowski functionals which relies on high quality simulated data, including non Gaussian CMB maps. We find good agreement with the Gaussian hypothesis and derive the first limits based on BOOMERanG data for the non linear coupling parameter f_NL as -300
CMB multipole measurements in the presence of foregrounds:
    Most analysis of Cosmic Microwave Background spherical harmonic coefficients a_lm has focused on estimating the power spectrum C(l)=<|a_lm|^2> rather than the coefficients themselves. We present a minimum-variance method for measuring a_lm given anisotropic noise, incomplete sky coverage and foreground contamination, and apply it to the WMAP data. Our method is shown to constitute lossless data compression in the sense that the widely used quadratic estimators of the power spectrum C(l) can be computed directly from our a_lm-estimators. As the Galactic cut is increased, the error bars &Delta-a_lm on low multipoles go from being dominated by foregrounds to being dominated by sample variance from other multipoles, with the intervening minimum defining the optimal cut. Applying our method to the WMAP quadrupole and octopole, we find that their previously reported "axis of evil" alignment appears to be rather robust to Galactic cut and foreground contamination. Details can be found in de Oliveira-Costa & Tegmark (2006).
BOOMERanG results:
    In Masi et al.(2006), we present the BOOMERanG-03 experiment and maps of the Stokes parameters I, Q, U of the microwave sky obtained during a 14 day balloon flight in 2003. Three regions of the southern sky were surveyed: a deep survey (~ 90 square degrees) and a shallow survey (~ 750 square degrees) at high Galactic latitudes (both centered at RA ~ 5.5 h, dec ~ -45 deg) and a survey of ~ 300 square degrees across the Galactic plane at RA ~ 9.1 h, dec ~ -47 deg. All three surveys were carried out in three wide frequency bands centered at 145, 245 and 345 GHz, with an angular resolution of ~ 10'. The 145 GHz maps of Stokes I are dominated by Cosmic Microwave Background (CMB) temperature anisotropy, which is mapped with high signal to noise ratio. The measured anisotropy pattern is consistent with the pattern measured in the same region by BOOMERanG-98 and by WMAP. The 145 GHz maps of Stokes Q and U provide a robust statistical detection of polarization of the CMB when subjected to a power spectrum analysis. This amplitude of the polarization is consistent with that of the CMB in the &Lambda-CDM cosmological scenario. At 145 GHz, in the CMB surveys, the intensity and polarization of the astrophysical foregrounds are found to be negligible with respect to the cosmological signal. At 245 and 345 GHz we detect ISD emission correlated to the 3000 GHz IRAS/DIRBE maps, and give upper limits for any other non-CMB component. We also present intensity maps of the surveyed section of the Galactic plane. These are compared to monitors of different interstellar components, showing that a variety of emission mechanisms is present in that region.

    In MacTavish et al.(2006), we present the cosmological parameters from the CMB intensity and polarization power spectra of the 2003 Antarctic flight of the BOOMERanG telescope. The BOOMERanG data alone constrains the parameters of the &Lambda-CDM model remarkably well and is consistent with constraints from a multi-experiment combined CMB data set. We add LSS data from the 2dF and SDSS redshift surveys to the combined CMB data set and test several extensions to the standard model including: running of the spectral index, curvature, tensor modes, the effect of massive neutrinos, and an effective equation of state for dark energy. We also include an analysis of constraints to a model which allows a CDM isocurvature admixture.

    In Jones et al.(2006), we report on observations of the Cosmic Microwave Background (CMB) obtained during the January 2003 flight of BOOMERanG . These results are derived from 195 hours of observation with four 145 GHz Polarization Sensitive Bolometer (PSB) pairs, identical in design to the four 143 GHz Planck HFI polarized pixels. The data include 75 hours of observations distributed over 1.84% of the sky with an additional 120 hours concentrated on the central portion of the field, itself representing 0.22% of the full sky. From these data we derive an estimate of the angular power spectrum of temperature fluctuations of the CMB in 24 bands over the multipole range (50 < l < 1500). A series of features, consistent with those expected from acoustic oscillations in the primordial photon-baryon fluid, are clearly evident in the power spectrum, as is the exponential damping of power on scales smaller than the photon mean free path at the epoch of last scattering (l > 900). As a consistency check, the collaboration has performed two fully independent analyses of the time ordered data, which are found to be in excellent agreement.

    In Montroy et al.(2006), we report measurements of the CMB polarization power spectra from the January 2003 Antarctic flight of BOOMERanG. The primary results come from six days of observation of a patch covering 0.22% of the sky centered near R.A. = 82.5 deg., Dec= -45 deg. The observations were made using four pairs of polarization sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a non-zero signal in the range 100< l <1000 with a significance 4.8-sigma, a 2-sigma upper limit of 8.6 uK^2 for any contribution, and a 2-sigma upper limit of 7.0 uK^2 for the spectrum. Estimates of foreground intensity fluctuations and the non-detection of and signals rule out any significant contribution from galactic foregrounds. The results are consistent with a &Lambda-CDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.

    In Piacentini et al.(2006), we present a measurement of the temperature-polarization angular cross power spectrum, TE, of the Cosmic Microwave Background. The result is based on ~ 200 hours of data from 8 polarization sensitive bolometers operating at 145 GHz during the 2003 flight of BOOMERanG. We detect a significant correlation in the l-range between 50 and 950 with a statistical significance > 3.5 sigma. Contamination by polarized foreground emission and systematic effects are negligible in comparison with statistical uncertainty. The spectrum is consistent with previous detections and with the "concordance model" that assumes adiabatic initial conditions. This is the first measurement of using bolometric detectors.

How accurately can suborbital experiments measure the CMB?
    Great efforts are currently being channeled into ground- and balloon-based CMB experiments, mainly to explore polarization and anisotropy on small angular scales. To optimize instrumental design and assess experimental prospects, it is important to understand in detail the atmosphere-related systematic errors that limit the science achievable with new instruments. For this purpose, we spatially compare the 648 square degree ground- and balloon-based QMASK map with the atmosphere-free WMAP map, finding beautiful agreement on all angular scales where both are sensitive. This is a reassuring quantitative assessment of the power of the state-of-the-art FFT- and matrix-based mapmaking techniques that have been used for QMASK and virtually all subsequent experiments. Details can be found in de Oliveira-Costa et al.(2005). For the QMASK data and covariance matrix please go to the QMASK page at LAMBDA.
The significance of the largest scale CMB fluctuations in WMAP:
    In de Oliveira-Costa et al.(2004), We investigate anomalies reported in the Cosmic Microwave Background maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite on very large angular scales and discuss possible interpretations. Three independent anomalies involve the quadrupole and octopole:

    (1.) The cosmic quadrupole on its own is anomalous at the 1-in-20 level by being low (the cut-sky quadrupole measured by the WMAP team is more strikingly low, apparently due to a coincidence in the orientation of our Galaxy of no cosmological significance); (2.) The cosmic octopole on its own is anomalous at the 1-in-20 level by being very planar; (3.) The alignment between the quadrupole and octopole is anomalous at the 1-in-60 level.

    Although the a priori chance of all three occurring is 1 in 24000, the multitude of alternative anomalies one could have looked for dilutes the significance of such a posteriori statistics. The simplest small universe model where the universe has toroidal topology with one small dimension of order half the horizon scale, in the direction towards Virgo, could explain the three items above. However, we rule this model out using two topological tests: the S-statistic and the matched circle test.

Resolution Foreground Cleaned CMB Map from WMAP:
    We perform an independent foreground analysis of the WMAP maps to produce a cleaned CMB map (available online) useful for cross-correlation with, e.g., galaxy and X-ray maps. We use a variant of the Tegmark & Efstathiou (1996) technique that is completely blind, making no assumptions about the CMB power spectrum, the foregrounds, WMAP detector noise or external templates. Compared with the foreground-cleaned internal linear combination map produced by the WMAP team, our map has the advantage of containing less non-CMB power (from foregrounds and detector noise) outside the Galactic plane. The difference is most important on the the angular scale of the first acoustic peak and below, since our cleaned map is at the highest (13') rather than lowest (49') WMAP resolution. We also produce a Wiener filtered CMB map, representing our best guess as to what the CMB sky actually looks like, as well as CMB-free maps at the five WMAP frequencies useful for foreground studies. We argue that our CMB map is clean enough that the lowest multipoles can be measured without any galaxy cut, and obtain a quadrupole value that is slightly less low than that from the cut-sky WMAP team analysis. This can be understood from a map of the CMB quadrupole, which shows much of its power falling within the Galaxy cut region, seemingly coincidentally. Intriguingly, both the quadrupole and the octopole are seen to have power suppressed along a particular spatial axis, which lines up between the two, roughly towards (l,b) ~ (-80,60) in Virgo. Details about this analysis may be found in Tegmark et al.(2003).
The CMB power spectrum at l=30-200 from QMASK:
    We measure the cosmic microwave background (CMB) power spectrum on angular scales l~30-200 (1-6 degrees) from the QMASK map, which combines the data from the QMAP and Saskatoon experiments. Since the accuracy of recent measurements leftward of the first acoustic peak is limited by sample-variance, the large area of the QMASK map (648 square degrees) allows us to place among the sharpest constraints to date in this range, in good agreement with BOOMERanG and (on the largest scales) COBE/DMR. By band-pass-filtering the QMAP and Saskatoon maps, we are able to spatially compare them scale-by-scale to check for beam- and pointing-related systematic errors. Details can be found in Xu et al. (2002).
Comparing and combining the Saskatoon, QMAP and COBE CMB maps:
    We present a method for comparing and combining maps with different resolutions and beam shapes, and apply it to the Saskatoon, QMAP and COBE/DMR data sets. Although the Saskatoon and QMAP maps detect signal at the 21 sigma and 40 sigma levels, respectively, their difference is consistent with pure noise, placing strong limits on possible systematic errors. In particular, we obtain quantitative upper limits on relative calibration and pointing errors. Splitting the combined data by frequency shows similar consistency between the Ka- and Q-bands, placing limits on foreground contamination. The visual agreement between the maps is equally striking. Our combined QMAP+Saskatoon map, nicknamed QMASK, is publicly available in the QMASK page at LAMBDA, together with its 6495x6495 noise covariance matrix. This thoroughly tested data set covers a large enough area (648 square degrees) to allow a statistical comparison with COBE/DMR, showing good agreement. Details can be found in Xu et al.(2001).
Mapping the CMB: QMAP flights:
    We present results from the QMAP balloon experiment, which maps the Cosmic Microwave Background (CMB) and probes its angular power spectrum on degree scales. In two separate flights, data were taken in six channels at two frequency bands between 26 to 46 GHz. We describe our method for mapmaking (removal of 1/f-noise and scan-synchronous offsets) and power spectrum estimation, as well as the results of a joint analysis of the data from both flights. This produces a 527 square degree map of the CMB around the North Celestial Pole, allowing a wide variety of systematic cross-checks. The frequency dependence of the fluctuations is consistent with CMB and inconsistent with Galactic foreground emission. The anisotropy is measured in three multipole bands from l~40 to l~200, and the angular power spectrum shows a distinct rise which is consistent with the Saskatoon results. Details about this map-making process, as well as, the power spectrum extraction can be found in de Oliveira-Costa et al.(1998). For the QMAP data please go to the QMAP page at LAMBDA.
A spin modulated telescope to make two dimensional CMB maps:
    We present Cosmic Microwave Background (CMB) maps from the Santa Barbara HACME balloon experiment (Staren etal 1997), covering about 1150 square degrees split between two regions in the northern sky, near the stars gamma Ursae Minoris and alpha Leonis, respectively. The angular resolution FWHM of the beam is ~0.77 degrees in three frequency bands centered on 39, 41 and 43 GHz. The results demonstrate that the thoroughly interconnected scan strategy employed allows efficient removal of 1/f-noise. The maps display no striping, and the noise correlations are found to be virtually isotropic, decaying on an angular scale ~1 degree. The signal-to-noise ratio in the map is of order 0.5 and some individual hot and cold spots are significant at the 1 sigma-level, with many spatial features being consistent between the three channels. The results bode well for the planned follow-up experiments BEAST and ACE, since they show that even with the overly cautious assumption that 1/f-noise will be as dominant as for HACME, the problem it poses can be readily overcome with the mapmaking algorithm discussed. Details about this map-making process can be found in Tegmark et al.(1997).
A high-resolution map of the CMB around the NCP:
    Wiener filtering is a general method for estimating a signal from noise data. We made a Wiener-filtered map of the CMB fluctuations in a cap with 15 degrees of diameter, centered in the North Celestial Pole (NCP). The map was based on the 1993-1995 data from the Saskatoon experiment, with an angular resolution around 1 degree in the frequency range of 30-40 GHz. The signal-to-noise ratio in the map was the order of 2, and some individual hot and cold spots are significant at the 5 sigma level. The spatial features are found to be consistent from year to year, which reinforces the conclusion that Saskatoon results are not dominated by residual atmospheric contamination or other non-celestial signals. Details about this map-making process can be found in Tegmark et al.(1997).

    The 3 first pannels show maps gerated from the subsets of data that were taken in 1993, 1994 and 1995, respectively. The 1993 data seems to be rather featureless, reflecting the fact that the 1993 data set contains considerably less information than the other 2 years of data. Similarly, the 1995 map is seen to contain more small-scale structure than the 1994 map, which reflects the fact that the angular resolution was approximately doubled in 1995. Most potencial source problems with the experiment (as underestimation of atmospheric contamination, sidelobe pickup from celestial bodies, etc) would be expect to vary in timescales much shorter than 1 year. In addition, the beam patterns were quite different in the 3 years, as described in Netterfield et al.(1996). The visual similarity between these independent maps therefore provides evidence that the bulk of the signal being detected is in fact due to temperature fluctuations on the sky rather than to unknown systematic problems.


My papers on this subject:
  1. "BOOMERanG constraints on primordial non-Gaussianity from analytical Minkowski functionals" Natoli & the BOOMERanG Collaboration 2010, MNRAS, 408:1658.
  2. "Subdegree Sunyaev-Zel'dovich Signal from Multifrequency BOOMERANG Observations" Veneziani & the BOOMERanG Collaboration 2009, ApJ, 702:61.
  3. "Searching for non Gaussian signals in the BOOMERanG 2003 CMB maps" de Troia & the BOOMERanG Collaboration 2007, ApJ, 670:L36.
  4. "Searching for non-Gaussian signals in the BOOMERanG 2003 CMB map: Preliminary results" de Troia & the BOOMERanG Collaboration 2007, NewAR, v.51, p.250-255
  5. "CMB polarization with BOOMERanG 2003" Piacentini & the BOOMERanG Collaboration 2007, NewAR, v.51, p.244-249
  6. "The millimeter sky as seen with BOOMERanG" Masi & the BOOMERanG Collaboration 2007, NewAR, v.51, p.236-243
  7. "Observations of the temperature and polarization anisotropies with BOOMERanG 2003" Jones & the BOOMERanG Collaboration 2007, NewAR, v.50, p.945-950
  8. "CMB Multipole Measurements in the Presence of Foregrounds" de Oliveira-Costa & Tegmark 2006, Phys. Rev. D. 74:023005.
  9. "Instrument, Method, Brightness and Polarization Maps from the 2003 Flight of BOOMERanG" Masi & the BOOMERanG Collaboration 2006, A&A, 458:687.
  10. "A Measurement of the Polarization-Temperature Angular Cross Power Spectrum of the CMB from the 2003 Flight of BOOMERanG" Piacentini & the BOOMERanG Collaboration 2006, ApJ, 647:833.
  11. "A Measurement of the Angular Power Spectrum of the CMB Temperature Anisotropy from the 2003 Flight of BOOMERanG" Jones & the BOOMERanG Collaboration 2006, ApJ, 647:823.
  12. "A Measurement of the CMB EE Spectrum from the 2003 Flight of BOOMERanG" Montroy & the BOOMERanG Collaboration 2006, ApJ, 647:813.
  13. "Cosmological Parameters from the 2003 Flight of BOOMERanG" MacTavish & the BOOMERanG Collaboration 2006, ApJ, 647:799.
  14. "BOOMERanG Results" Polenta & the BOOMERanG Collaboration 2005, AdSpR, 36(6):1064.
  15. "How accurately can suborbital experiments measure the CMB?" de Oliveira-Costa, Tegmark, Devlin, Page, Miller, Netterfield & Xu 2005, Phys. Rev. D. 71:043004.
  16. "Significance of the largest scale CMB fluctuations in WMAP" de Oliveira-Costa, Tegmark, Hamilton & Zaldarriaga 2004, Phys. Rev. D., 69:3516.
  17. "A High Resolution Foreground Cleaned CMB Map from WMAP" Tegmark, de Oliveira-Costa & Hamilton 2003, Phys. Rev. D., 68:123523.
  18. "Maps of the millimetre sky from the BOOMERanG experiment" de Bernardis & the BOOMERanG Collaboration 2003, Proceedings from "IAU Symposium 216: Maps of the Cosmos", Sydney, July 14-17.
  19. "The CMB power spectrum at l=30-200 from QMASK" Xu, Tegmark & de Oliveira-Costa 2002, Phy.Rev.D 65:083002
  20. "Comparing and combining the Saskatoon, QMAP and COBE CMB maps" Xu, Tegmark, de Oliveira-Costa, Devlin, Herbig, Miller, Netterfield & Page 2001, Phy.Rev.D, 63:103002.
  21. "Mapping the CMB III: combined analysis of QMAP flights" de Oliveira-Costa, Devlin, Herbig, Miller, Netterfield, Page & Tegmark 1998, ApJ, 509:L77.
  22. "Mapping the CMB II: the second flight of the QMAP experiment" Herbig, de Oliveira-Costa, Devlin, Miller, Netterfield, Page & Tegmark 1998, ApJ, 509:L73.
  23. "Mapping the CMB I: the first flight of the QMAP experiment" Devlin, de Oliveira-Costa, Herbig, Miller, Netterfield, Page & Tegmark 1998, ApJ, 509:L69.
  24. "New Techniques for Making CMB Maps" de Oliveira-Costa & Tegmark 1998, Proceedings from "Wide Field Surveys in Cosmology, 14th IAP meeting", Ed. F. Bouchet.
  25. "A Spin Modulated Telescope to Make Two Dimensional CMB Maps" Staren, Meinhold, Childers, Lim, Levy, Lubin, Seiffert, Gaier, Figueiredo, Villela, Wuensche, Tegmark & de Oliveira-Costa 2000, ApJ, 539:52.
  26. "Cosmic microwave background maps from the HACME experiment" Tegmark, de Oliveira-Costa, Staren, Meinhold, Lubin, Childers, Figueiredo, Gaier, Lim, Seiffert, Villela & Wuensche 2000, ApJ, 541:535.
  27. "A high-resolution map of the Cosmic Microwave Background around the North Celestial Pole" Tegmark, de Oliveira-Costa, Devlin, Netterfield, Page & Wollack 1997, ApJ, 474:L77.
  28. "Search for structures in the CMBR" de Oliveira-Costa & Villela 1993, Rev. Mex. Astron. Astrofis., 26:127 (Just Abstract).
  29. "Structures in the CMB: hot and cold spots in the microwave sky" de Oliveira-Costa 1993, M.Sc. Thesis published by INPE, INPE-5491-TDI/508 (Avaiable under request, in Portuguese).

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Last modified: Jan 4, 2014.