2,149 research outputs found
Mapping the CMB III: combined analysis of 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.Comment: 4 pages, with 3 figures included. Submitted to ApJL. Window functions
are available at http://pupgg.princeton.edu/~cmb/welcome.html and color
figures and links at http://www.sns.ias.edu/~angelica/skymap.html#qma
Galactic emission at 19 GHz
We cross-correlate a 19 GHz full sky Cosmic Microwave Background (CMB) survey
with other maps to quantify the foreground contribution. Correlations are
detected with the Diffuse Infrared Background Experiment (DIRBE) 240, 140 and
100 micron maps at high latitudes (|b|>30degrees), and marginal correlations
are detected with the Haslam 408 MHz and the Reich & Reich 1420 MHz synchrotron
maps. The former agree well with extrapolations from higher frequencies probed
by the COBE DMR and Saskatoon experiments and are consistent with both
free-free and rotating dust grain emission.Comment: 4 pages, with 4 figures included. Accepted for publication in ApJL.
Color figure and links at http://www.sns.ias.edu/~angelica/foreground.html#19
or from [email protected]
Mapping the CMB I: the first flight of the QMAP experiment
We report on the first flight of the balloon-borne QMAP experiment. The
experiment is designed to make a map of the cosmic microwave background
anisotropy on angular scales from 0.7 to several degrees. Using the map we
determine the angular power spectrum of the anisotropy in multipole bands from
l~40 to l~140. The results are consistent with the Saskatoon (SK) measurements.
The frequency spectral index (measured at low l) is consistent with that of CMB
and inconsistent with either Galactic synchrotron or free-free emission. The
instrument, measurement, analysis of the angular power spectrum, and possible
systematic errors are discussed.Comment: 4 pages, with 5 figures included. Submitted to ApJL. Window functions
and color figures are available at
http://pupgg.princeton.edu/~cmb/welcome.htm
Mapping the CMB II: the second flight of the QMAP experiment
We report the results from the second flight of QMAP, an experiment to map
the cosmic microwave background near the North Celestial Pole. We present maps
of the sky at 31 and 42 GHz as well as a measurement of the angular power
spectrum covering the l-range 40-200. Anisotropy is detected at about 20 sigma
and is in agreement with previous results at these angular scales. We also
report details of the data reduction and analysis techniques which were used
for both flights of QMAP.Comment: 4 pages, with 5 figures included. Submitted to ApJL. Window functions
and color figures are available at
http://pupgg.princeton.edu/~cmb/welcome.htm
Galactic microwave emission at degree angular scales
We cross-correlate the Saskatoon Ka and Q-Band Cosmic Microwave Background
(CMB) data with different maps to quantify possible foreground contamination.
We detect a marginal correlation (2 sigma) with the Diffuse Infrared Background
Experiment (DIRBE) 240, 140 and 100 microm maps, but we find no significant
correlation with point sources, with the Haslam 408 MHz map or with the Reich
and Reich 1420 MHz map. The rms amplitude of the component correlated with
DIRBE is about 20% of the CMB signal. Interpreting this component as free-free
emission, this normalization agrees with that of Kogut et al. (1996a; 1996b)
and supports the hypothesis that the spatial correlation between dust and warm
ionized gas observed on large angular scales persists to smaller angular
scales. Subtracting this contribution from the CMB data reduces the
normalization of the Saskatoon power spectrum by only a few percent.Comment: Minor revisions to match published version. 14 pages, with 2 figures
included. Color figure and links at
http://www.sns.ias.edu/~angelica/foreground.htm
Galactic contamination in the QMAP experiment
We quantify the level of foreground contamination in the QMAP Cosmic
Microwave Background (CMB) data with two objectives: (a) measuring the level to
which the QMAP power spectrum measurements need to be corrected for foregrounds
and (b) using this data set to further refine current foreground models. We
cross-correlate the QMAP data with a variety of foreground templates. The 30
GHz Ka-band data is found to be significantly correlated with the Haslam 408
MHz and Reich and Reich 1420 MHz synchrotron maps, but not with the Diffuse
Infrared Background Experiment (DIRBE) 240, 140 and 100 micron maps or the
Wisconsin H-Alpha Mapper (WHAM) survey. The 40 GHz Q-band has no significant
template correlations. We discuss the constraints that this places on
synchrotron, free-free and dust emission. We also reanalyze the
foreground-cleaned Ka-band data and find that the two band power measurements
are lowered by 2.3% and 1.3%, respectively.Comment: 4 ApJL pages, including 4 figs. Color figures and data at
http://www.hep.upenn.edu/~angelica/foreground.html#qmap or from
[email protected]
How accurately can suborbital experiments measure the CMB?
Great efforts are currently being channeled into ground- and balloon-based
CMB experiments, mainly to explore anisotropy on small angular scales and
polarization. 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 suborbital
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.Comment: 4 pages, 2 figures. More info at
http://www.hep.upenn.edu/~angelica/skymap.html QMASK data and covariance
matrix at http://www.hep.upenn.edu/~xuyz/qmask.htm
- …