We constrain the spectral index of polarized synchrotron emission,
β
s
, by correlating the recently released 2.3 GHz
S
-Band Polarization All Sky Survey (
S
-PASS) data with the 23 GHz 9-year
...Wilkinson
Microwave Anisotropy Probe (WMAP) sky maps. We subdivide the S-PASS field, which covers the southern ecliptic hemisphere, into 95 15° ×15° regions and estimate the spectral index of polarized synchrotron emission within each region using a simple but robust
T
–
T
plot technique. Three different versions of the S-PASS data are considered, corresponding to: no correction for Faraday rotation; Faraday correction based on the rotation measure model presented by the S-PASS team; or Faraday correction based on a rotation measure model presented by Hutschenreuter and Enßlin. We find that the correlation between S-PASS and WMAP is strongest when applying the S-PASS model. Adopting this correction model, we find that the mean spectral index of polarized synchrotron emission gradually steepens from
β
s
≈ −2.8 at low Galactic latitudes to
β
s
≈ −3.3 at high Galactic latitudes, in good agreement with previously published results. The flat spectral index at the low Galactic latitudes is likely partly due to depolarization effects. Finally, we consider two special cases defined by the BICEP2 and SPIDER fields and obtain mean estimates of
β
BICEP2
= −3.22 ± 0.06 and
β
SPIDER
= −3.21 ± 0.03, respectively. Adopting the bandpass filtered WMAP 23 GHz sky map to only include angular scales between 2° and 10° as a spatial template, we constrain the root-mean-square synchrotron polarization amplitude to be less than 0.03
μ
K (0.009
μ
K) at 90 GHz (150 GHz) for the BICEP2 field, corresponding roughly to a tensor-to-scalar ratio of
r
≲ 0.02 (
r
≲ 0.005). Very similar constraints are obtained for the SPIDER field. A comparison with a similar analysis performed in the 23–33 GHz range suggests a flattening of about Δ
β
s
∼ 0.1 ± 0.2 from low to higher frequencies, but with no statistical significance due to high uncertainties.
We present the first degree-scale tomography map of the dusty magnetized interstellar medium (ISM) from stellar polarimetry and distance measurements. We used the RoboPol polarimeter at Skinakas ...Observatory to conduct a survey of the polarization of starlight in a region of the sky of about four square degrees. We propose a Bayesian method to decompose the stellar-polarization source field along the distance to invert the three-dimensional (3D) volume occupied by the observed stars. We used this method to obtain the first 3D map of the dusty magnetized ISM. Specifically, we produced a tomography map of the orientation of the plane-of-sky component of the magnetic field threading the diffuse, dusty regions responsible for the stellar polarization. For the targeted region centered on Galactic coordinates ( l , b ) ≈ (103.3°, 22.3°), we identified several ISM clouds. Most of the lines of sight intersect more than one cloud. A very nearby component was detected in the foreground of a dominant component from which most of the polarization signal comes and which we identified as being an intersection of the wall of the Local Bubble and the Cepheus Flare. Farther clouds, with a distance of up to 2 kpc, were similarly detected. Some of them likely correspond to intermediate-velocity clouds seen in H I spectra in this region of the sky. We found that the orientation of the plane-of-sky component of the magnetic field changes along distance for most of the lines of sight. Our study demonstrates that starlight polarization data coupled to distance measures have the power to reveal the great complexity of the dusty magnetized ISM in 3D and, in particular, to provide local measurements of the plane-of-sky component of the magnetic field in dusty regions. This demonstrates that the inversion of large data volumes, as expected from the P ASIPHAE survey, will provide the necessary means to move forward in the modeling of the Galactic magnetic field and of the dusty magnetized ISM as a contaminant in observations of the cosmic microwave background polarization.
BEYONDPLANCK Colombo, L. P. L.; Eskilt, J. R.; Paradiso, S. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
675
Journal Article
Recenzirano
Odprti dostop
We present posterior sample-based cosmic microwave background (CMB) constraints from
Planck
LFI and WMAP observations as derived through global end-to-end Bayesian processing within the B
EYOND
P
...LANCK
framework. We first used these samples to study correlations between CMB, foreground, and instrumental parameters. We identified a particularly strong degeneracy between CMB temperature fluctuations and free-free emission on intermediate angular scales (400 ≲
ℓ
≲ 600), mitigated through model reduction, masking, and resampling. We compared our posterior-based CMB results with previous
Planck
products and found a generally good agreement, however, with notably higher noise due to our exclusion of
Planck
HFI data. We found a best-fit CMB dipole amplitude of 3362.7 ± 1.4 μK, which is in excellent agreement with previous
Planck
results. The quoted dipole uncertainty is derived directly from the sampled posterior distribution and does not involve any ad hoc contributions for
Planck
instrumental systematic effects. Similarly, we find a temperature quadrupole amplitude of $ \sigma^{TT}_2=229\pm97\,\muup{\rm K}^2 $ , which is in good agreement with previous results in terms of the amplitude, but the uncertainty is one order of magnitude greater than the naive diagonal Fisher uncertainty. Concurrently, we find less evidence of a possible alignment between the quadrupole and octopole than previously reported, due to a much larger scatter in the individual quadrupole coefficients that is caused both by marginalizing over a more complete set of systematic effects – as well as by requiring a more conservative analysis mask to mitigate the free-free degeneracy. For higher multipoles, we find that the angular temperature power spectrum is generally in good agreement with both
Planck
and WMAP. At the same time, we note that this is the first time that the sample-based, asymptotically exact Blackwell-Rao estimator has been successfully established for multipoles up to
ℓ
≤ 600. It now accounts for the majority of the cosmologically important information. Overall, this analysis demonstrates the unique capabilities of the Bayesian approach with respect to end-to-end systematic uncertainty propagation and we believe it can and should play an important role in the analysis of future CMB experiments. Cosmological parameter constraints are presented in a companion paper.
Context.
Next-generation wide-field optical polarimeters such as Wide-Area Linear Optical Polarimeters (WALOPs) have a field of view (FoV) of tens of arcminutes. Wide-field polarimetric flat sources ...are essential to the efficient and accurate calibration of these instruments. However, no established wide-field polarimetric standard or flat sources exist at present.
Aims.
This study tests the feasibility of using the polarized sky patches of the size of around 10 × 10 arcminutes
2
, at a distance of up to 20° from the Moon, on bright-Moon nights as a wide-field linear polarimetric flat source.
Methods.
We observed 19 patches of the sky adjacent to the bright-Moon with the RoboPol instrument in the SDSS-
r
broadband filter. These patches were observed on five nights within two days of the full-Moon across two RoboPol observing seasons.
Results.
We find that for 18 of the 19 patches, the uniformity in the measured normalized Stokes parameters
q
and
u
is within 0.2%, with 12 patches exhibiting uniformity within 0.07% or better for both
q
and
u
simultaneously, making them reliable and stable wide-field linear polarization flats.
Conclusions.
We demonstrate that the sky on bright-Moon nights is an excellent wide-field linear polarization flat source. Various combinations of the normalized Stokes parameters
q
and
u
can be obtained by choosing suitable locations of the sky patch with respect to the Moon.
We present the first application of the C
OSMOGLOBE
analysis framework by analyzing nine-year WMAP time-ordered observations that uses similar machinery to that of B
EYOND
P
LANCK
for the
Planck
Low ...Frequency Instrument (LFI). We analyzed only the
Q
-band (41 GHz) data and report on the low-level analysis process based on uncalibrated time-ordered data to calibrated maps. Most of the existing B
EYOND
P
LANCK
pipeline may be reused for WMAP analysis with minimal changes to the existing codebase. The main modification is the implementation of the same preconditioned biconjugate gradient mapmaker used by the WMAP team. Producing a single WMAP
Q
1-band sample requires 22 CPU-hrs, which is slightly more than the cost of a
Planck
44 GHz sample of 17 CPU-hrs; this demonstrates that a full end-to-end Bayesian processing of the WMAP data is computationally feasible. In general, our recovered maps are very similar to the maps released by the WMAP team, although with two notable differences. In terms of temperature, we find a ∼2 μK quadrupole difference that most likely is caused by different gain modeling, while in polarization we find a distinct 2.5 μK signal that has been previously referred to as poorly measured modes by the WMAP team. In the C
OSMOGLOBE
processing, this pattern arises from temperature-to-polarization leakage from the coupling between the CMB Solar dipole, transmission imbalance, and sidelobes. No traces of this pattern are found in either the frequency map or TOD residual map, suggesting that the current processing has succeeded in modeling these poorly measured modes within the assumed parametric model by using
Planck
information to break the sky-synchronous degeneracies inherent in the WMAP scanning strategy.
COSMOGLOBE DR1 results Watts, D. J.; Basyrov, A.; Eskilt, J. R. ...
Astronomy and astrophysics (Berlin),
11/2023, Letnik:
679
Journal Article
Recenzirano
Odprti dostop
We present C
OSMOGLOBE
Data Release 1, which implements the first joint analysis of WMAP and
Planck
LFI time-ordered data, processed within a single Bayesian end-to-end framework. This framework ...directly builds on a similar analysis of the LFI measurements by the B
EYOND
P
LANCK
collaboration, and approaches the cosmic microwave background (CMB) analysis challenge through Gibbs sampling of a global posterior distribution, simultaneously accounting for calibration, mapmaking, and component separation. The computational cost of producing one complete WMAP+LFI Gibbs sample is 812 CPU-h, of which 603 CPU-h are spent on WMAP low-level processing; this demonstrates that end-to-end Bayesian analysis of the WMAP data is computationally feasible. We find that our WMAP posterior mean temperature sky maps and CMB temperature power spectrum are largely consistent with the official WMAP9 results. Perhaps the most notable difference is that our CMB dipole amplitude is 3366.2 ± 1.4 μK, which is 11 μK higher than the WMAP9 estimate and 2.5
σ
higher than B
EYOND
P
LANCK
; however, it is in perfect agreement with the HFI-dominated
Planck
PR4 result. In contrast, our WMAP polarization maps differ more notably from the WMAP9 results, and in general exhibit significantly lower large-scale residuals. We attribute this to a better constrained gain and transmission imbalance model. It is particularly noteworthy that the
W
-band polarization sky map, which was excluded from the official WMAP cosmological analysis, for the first time appears visually consistent with the
V
-band sky map. Similarly, the long standing discrepancy between the WMAP
K
-band and LFI 30 GHz maps is finally resolved, and the difference between the two maps appears consistent with instrumental noise at high Galactic latitudes. Relatedly, these updated maps allowed us for the first time to combine WMAP and LFI polarization data into a single coherent model of large-scale polarized synchrotron emission. Still, we identified a few issues that require additional work, including (1) low-level noise modeling; (2) large-scale temperature residuals at the 1–2 μK level; and (3) a strong degeneracy between the absolute
K
-band calibration and the dipole of the anomalous microwave emission component. We conclude that leveraging the complementary strengths of WMAP and LFI has allowed the mitigation of both experiments’ weaknesses, and resulted in new state-of-the-art WMAP sky maps. All maps and the associated code are made publicly available through the C
OSMOGLOBE
web page.
COSMOGLOBE DR1 results Eskilt, J. R.; Watts, D. J.; Aurlien, R. ...
Astronomy and astrophysics (Berlin),
11/2023, Letnik:
679
Journal Article
Recenzirano
Odprti dostop
Cosmic birefringence is a parity-violating effect that might have rotated the plane of the linearly polarized light of the cosmic microwave background (CMB) by an angle
β
since its emission. This ...angle has recently been measured to be nonzero at a statistical significance of 3.6
σ
in the official
Planck
PR4 and 9-year WMAP data. In this work, we constrain
β
using the reprocessed B
EYOND
P
LANCK
LFI and C
OSMOGLOBE
DR1 WMAP polarization maps. These novel maps have both lower systematic residuals and a more complete error description than the corresponding official products. Foreground
EB
correlations could bias measurements of
β
, and while thermal dust
EB
emission has been argued to be statistically nonzero, no evidence for synchrotron
EB
power has been reported. Unlike the dust-dominated
Planck
HFI maps, the majority of the LFI and WMAP polarization maps are instead dominated by synchrotron emission. Simultaneously constraining
β
and the polarization miscalibration angle,
α
, of each channel, we find a best-fit value of
β
= 0.35° ±0.70° with LFI and WMAP data only. When including the
Planck
HFI PR4 maps, but fitting
β
separately for dust-dominated,
β
> 70 GHz
, and synchrotron-dominated channels,
β
≤70 GHz
, we find
β
≤70 GHz
= 0.53° ±0.28°. This differs from zero with a statistical significance of 1.9
σ
, and the main contribution to this value comes from the LFI 70 GHz channel. While the statistical significances of these results are low on their own, the measurement derived from the LFI and WMAP synchrotron-dominated maps agrees with the previously reported HFI-dominated constraints, despite the very different astrophysical and instrumental systematics involved in all these experiments.
BEYONDPLANCK Galloway, M.; Andersen, K. J.; Aurlien, R. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
675
Journal Article
Recenzirano
Odprti dostop
We describe the computational infrastructure for end-to-end Bayesian cosmic microwave background (CMB) analysis implemented by the BeyondPlanck Collaboration. The code is called
Commander3
. It ...provides a statistically consistent framework for global analysis of CMB and microwave observations and may be useful for a wide range of legacy, current, and future experiments. The paper has three main goals. Firstly, we provide a high-level overview of the existing code base, aiming to guide readers who wish to extend and adapt the code according to their own needs or re-implement it from scratch in a different programming language. Secondly, we discuss some critical computational challenges that arise within any global CMB analysis framework, for instance in-memory compression of time-ordered data, fast Fourier transform optimization, and parallelization and load-balancing. Thirdly, we quantify the CPU and RAM requirements for the current B
EYOND
P
LANCK
analysis, finding that a total of 1.5 TB of RAM is required for efficient analysis and that the total cost of a full Gibbs sample for LFI is 170 CPU-hrs, including both low-level processing and high-level component separation, which is well within the capabilities of current low-cost computing facilities. The existing code base is made publicly available under a GNU General Public Library (GPL) license.
BEYONDPLANCK Svalheim, T. L.; Zonca, A.; Andersen, K. J. ...
Astronomy and astrophysics (Berlin),
07/2023, Letnik:
675
Journal Article
Recenzirano
Odprti dostop
We discuss the treatment of bandpass and beam leakage corrections in the Bayesian B
EYOND
P
LANCK
cosmic microwave background (CMB) analysis pipeline as applied to the
Planck
LFI measurements. As a ...preparatory step, we first applied three corrections to the nominal LFI bandpass profiles, including the removal of a known systematic effect in the ground measuring equipment at 61 GHz, along with a smoothing of standing wave ripples and edge regularization. The main net impact of these modifications is an overall shift in the 70 GHz bandpass of +0.6 GHz. We argue that any analysis of LFI data products, either from
Planck
or B
EYOND
P
LANCK
, should use these new bandpasses. In addition, we fit a single free bandpass parameter for each radiometer of the form Δ
i
= Δ
0
+
δ
i
, where Δ
0
represents an absolute frequency shift per frequency band and
δ
i
is a relative shift per detector. The absolute correction is only fitted at 30 GHz, with a full
χ
2
-based likelihood, resulting in a correction of Δ
30
= 0.24 ± 0.03 GHz. The relative corrections were fitted using a spurious map approach that is fundamentally similar to the method pioneered by the WMAP team, but excluding the introduction of many additional degrees of freedom. All the bandpass parameters were sampled using a standard Metropolis sampler within the main B
EYOND
P
LANCK
Gibbs chain and the bandpass uncertainties were thus propagated to all other data products in the analysis. In summary, we find that our bandpass model significantly reduces leakage effects. For beam leakage corrections, we adopted the official
Planck
LFI beam estimates without any additional degrees of freedom and we only marginalized over the underlying sky model. We note that this is the first time that leakage from beam mismatch has been included for
Planck
LFI maps.
BEYONDPLANCK Svalheim, T. L.; Andersen, K. J.; Aurlien, R. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
675
Journal Article
Recenzirano
Odprti dostop
Using the
Planck
Low Frequency Instrument (LFI) and WMAP data within the global Bayesian B
EYOND
P
LANCK
framework, we constrained the polarized foreground emission between 30 and 70 GHz. We ...combined, for the first time, full-resolution
Planck
LFI time-ordered data with low-resolution WMAP sky maps at 33, 40, and 61 GHz. The spectral parameters were fit with a likelihood defined at the native resolution of each frequency channel. This analysis represents the first implementation of true multi-resolution component separation applied to CMB observations for both amplitude and spectral energy distribution (SED) parameters. For the synchrotron emission, we approximated the SED as a power-law in frequency and we find that the low signal-to-noise ratio of the current data strongly limits the number of free parameters that can be robustly constrained. We partitioned the sky into four large disjoint regions (High Latitude; Galactic Spur; Galactic Plane; and Galactic Center), each associated with its own power-law index. We find that the High Latitude region is prior-dominated, while the Galactic Center region is contaminated by residual instrumental systematics. The two remaining regions appear to be signal-dominated, and for these we derive spectral indices of
β
s
Spur
= −3.17 ± 0.06 and β
s
Plane
= −3.03 ± 0.07, which is in good agreement with previous results. For the thermal dust emission, we assumed a modified blackbody model and we fit a single power-law index across the full sky. We find
β
d
= 1.64 ± 0.03, which is slightly steeper than the value reported in
Planck
HFI data, but still statistically consistent at the 2
σ
confidence level.
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