62 research outputs found
Kinematics of the Outer Stellar Halo
We have tested whether the simple model for the kinematics of the Galactic
stellar halo (in particular the outer halo) proposed by Sommer-Larsen, Flynn
and Christensen (SLFC) is physically realizable, by directly integrating
particles in a 3-D model of the Galactic potential. We are able to show that
the SLFC solution can be realized in terms of a distribution of particles with
stationary statistical properties in phase-space. Hence, the SLFC model, which
shows a notable change in the anisotropy from markedly radial at the sun to
markedly tangential beyond about Galactocentric radius r=20 kpc, seems a
tenable description of outer halo kinematics.Comment: 13 pages, 6 figures, accepted for publication in MNRAS. also
available at http://astro.utu.fi/~cflynn/papers/fslc4/fslc4.htm
CMB map derived from the WMAP data through Harmonic Internal Linear Combination
We are presenting an Internal Linear Combination (ILC) CMB map, in which the
foreground is reduced through harmonic variance minimization. We have derived
our method by converting a general form of pixel-space approach into spherical
harmonic space, maintaining full correspondence. By working in spherical
harmonic space, spatial variability of linear weights is incorporated in a
self-contained manner and our linear weights are continuous functions of
position over the entire sky. The full correspondence to pixel-space approach
enables straightforward physical interpretation on our approach. In variance
minimization of a linear combination map, the existence of a cross term between
residual foregrounds and CMB makes the linear combination of minimum variance
differ from that of minimum foreground. We have developed an iterative
foreground reduction method, where perturbative correction is made for the
cross term. Our CMB map derived from the WMAP data is in better agreement with
the WMAP best-fit CDM model than the WMAP team's Internal Linear
Combination map. We find that our method's capacity to clean foreground is
limited by the availability of enough spherical harmonic coefficients of good
Signal-to-Noise Ratio (SNR).Comment: The whole sky CMB map, which is derived from the WMAP 5 year data
through our method, is available in HEALPix FITS format at
http://www.nbi.dk/~jkim/hilc The paper with higher resolution images also
available at http://www.nbi.dk/~jkim/hil
CMB polarization map derived from the WMAP 5 year data through Harmonic Internal Linear Combination
We have derived whole-sky CMB polarization maps from the WMAP 5 year
polarization data, using the Harmonic Internal Linear Combination (HILC)
method. Our HILC method incorporates spatial variability of linear weights in a
natural way and yields continuous linear weights over the entire sky. To
estimate the power spectrum of HILC maps, we have derived a unbiased quadratic
estimator, which is similar to the WMAP team's cross power estimator, but in a
more convenient form for HILC maps. From our CMB polarization map, we have
obtained TE correlation and E mode power spectra without applying any mask.
They are similar to the WMAP team's estimation and consistent with the WMAP
best-fit CDM model. Foreground reduction by HILC method is more
effective for high resolution and low noise data. Hence, our HILC method will
enable effective foreground reduction in polarization data from the Planck
surveyor.Comment: The whole sky CMB polarization map derived from the WMAP 5 year data
is available in the HEALPix FITS format at http://www.nbi.dk/~jkim/hilc v3:
matched with the accepted version, to appear in PRD. v4: fixed some pdf file
proble
Spectroscopy of Hot Stars in the Galactic Halo. III. Analysis of a Large Sample of Field Horizontal-branch and other A-type Stars
Planck early results. XI. Calibration of the local galaxy cluster Sunyaev-Zeldovich scaling relations
Statistics of CMB polarization angles
We study the distribution functions of the CMB polarization angle ,
focusing on the Planck 2018 CMB maps. We extend the model of Preece & Battye
(2014) of Gaussian correlated and Stokes parameters to allow nonzero
means. When the variances of and are equal and their covariance and
means are zero, the polarization angle is uniformly distributed. Otherwise the
uniform distribution will be modulated by harmonics with and
phases. These modulations are visible in the Planck 2018 CMB maps. Furthermore,
the mean value of is peculiar compared to the power spectrum.Comment: 14 pages, 6 figure
Planck early results. XXVI. Detection with Planck and confirmation by XMM-Newton of PLCK G266.6-27.3, an exceptionally X-ray luminous and massive galaxy cluster at z similar to 1
Planck early results. XVIII. The power spectrum of cosmic infrared background anisotropies
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