4 research outputs found
CMB anisotropies from acausal scaling seeds
We investigate models where structure formation is initiated by scaling
seeds: We consider rapidly expanding relativistic shells of energy and show
that they can fit current CMB and large scale structure data if they expand
with super-luminal velocities. These acausally expanding shells provide a
viable alternative to inflation for cosmological structure formation with the
same minimal number of parameters to characterize the initial fluctuations.
Causally expanding shells alone cannot fit present data. Hybrid models where
causal shells and inflation are mixed also provide good fits.Comment: 9 pages,13 figures, revised version accepted for publication in PR
Detection of new point sources in WMAP 7 year data using internal templates and needlets
We have developed a new needlet based method to detect point sources in
cosmic microwave background (CMB) maps and have applied it to the WMAP 7 year
data. We use both the individual frequency channels as well as internal
templates, the difference between pairs of frequency channels, with the
advantage that the CMB component is eliminated. Using the area of the sky
outside the Kq85 galactic mask, we detect a total of 2102 point sources at the
level in either the frequency maps or the internal templates. Of
these, 1116 are detected either at directly in the frequency channels
or at in the internal templates and at the
corresponding position in the frequency channels. Of the 1116 sources, 603 are
detections which have not been reported so far in WMAP data. We have made a
catalogue of these sources available with position and flux estimated in the
WMAP channels where they are seen. In total, we identified 1029 of the 1116
sources with counterparts at 5GHz and 69 at other frequencies.Comment: Accepted version, added integral number counts, 29 pages (+16 pages
for the catalogue),10 figure
Masking versus removing point sources in CMB data: the source corrected WMAP power spectrum from new extended catalogue
In (Scodeller et al.) a new and extended point source catalogue obtained from
the WMAP 7-year data was presented. It includes most of the sources included in
the standard WMAP 7-year point source catalogues as well as a large number of
new detections. Here we study the effects on the estimated CMB power spectrum
when taking the newly detected point sources into consideration. We create
point source masks for all the 2102 sources that we detected as well as a
smaller one for the 665 sources detected in the Q, V and W bands. We also
create WMAP7 maps with point sources subtracted in order to compare with the
spectrum obtained with source masks. The extended point source masks and point
source cleaned WMAP7 maps are made publicly available. Using the proper
residual correction, we find that the CMB power spectrum obtained from the
point source cleaned map without any source mask is fully consistent with the
spectrum obtained from the masked map. We further find that the spectrum
obtained masking all 2102 sources is consistent with the results obtained using
the standard WMAP 7-year point source mask (KQ85y7). We also verify that the
removal of point sources does not introduce any skewness.Comment: 26 pages and 11 figures; accepted version, published in Ap
Testing for foreground residuals in the Planck foreground cleaned maps: A new method for designing confidence masks
We test for foreground residuals in the foreground-cleaned Planck cosmic microwave background (CMB) maps outside and inside the U73 mask commonly used for cosmological analysis. The aim of this paper is to introduce a new method of validating masks by looking at the differences in cleaned maps obtained by different component-separation methods. By analyzing the power spectrum, as well as the mean, rms, and skewness of needlet coefficients on separate equatorial bands running from the poles to the equator outside and inside the U73 mask, we first confirm that the pixels already masked by U73 are highly contaminated and cannot be used for cosmological analysis. We further find that the U73 mask needs extension in order to reduce large-scale foreground residuals to a level of less than 20% of the standard deviation of CMB fluctuations within the bands closest to the galactic equator. We also find 276 point-like residuals in the cleaned foreground maps that are currently not masked by the U73 mask. About 80 of these are identified as sz clusters that have not been properly subtracted by the component separation methods, and the rest are strongly correlated with the Planck dust map, indicating point-like dust residuals. Our final publicly available extended mask leaves 65.9% of the sky for cosmological analysis. This extended mask may be important for analyses on local sky patches; for the full sky power spectrum, we have shown that the unmasked residuals have very little impact.
Reproduced with permission from Astronomy & Astrophysics, © ES