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Usually, the precipitable water vapor (PWV) is used as a conventional parameter to characterize the amount of water vapor, which is defined as the overall depth of water in a column of the atmosphere above the ground.

So far, we have also ignored the effects of foreground contamination, and it is to this we now turn. For more details about sky coverage, refer to [8].

4), we can see that the AliCPT site at B1 is not far from point A1: the distance between them is only about 1 km. 2003) – will soon provide polarized maps at CMB frequencies.

Together with the southern cleanest sky region covered by southern projects such as BICEP and the Simons Array, AliCPT will increase the chances of finding the B-mode and PGWs.

Note that our value differs from the value given in this reference as we use a different value for the pivot wavenumber, k0.

The temperature sensitivity of a PSB pair can be obtained by, When defining the sensitivity of a PSB, it is therefore important to state whether a sensitivity is an NET for a single detector, an NET for a pair of detectors, or an NEQ for a pair of detectors. 2 review of cmb polarization Detailed reviews of the CMB polarization are given by Zaldarriaga (2003) and Hu & White (1997) . 2003, hereafter B03). The poorest parameter improvement is for τ and A, which only improve by a factor of about 1.3.

w^{-1} = \frac{4\pi f_{\mathrm{sky}}\mathrm{NET}^2}{t_{\mathrm{obs}}N_{\mathrm{det}}} , Among all the components of air, water vapor plays a crucial role due to its strong absorption/emission and heavy time variation. Therefore, to achieve high-precision detection of the primordial B-mode signal, we shall perform a delensing procedure to remove the lensing effect from the data.

Exploring bouncing cosmologies with cosmological surveys.

This degeneracy is seen to be broken on large scales by the differences in the responses of the polarization power spectra.

After commissioning in 2019, the observation is expected to start in 2020.

Atmospheric conditions: For ground-based CMB telescopes, the atmosphere is a big concern.

For a ground-based experiment, it is not possible to make observations of the whole sky due to the limited sky coverage available from the ground.

However, as would be expected, increasing the minimum ℓ does affect the GW B-mode detection. Each year, we will install four modules and finish the 12 modules by the end of 2022.

So the sky coverage (both observable and low foreground contamination sky) of AliCPT is complementary to that of the experiments in Antarctic and Atacama. A possible observing patch for QUaD is also shown, in which the mean foreground amplitude is low. Therefore, measurement of the asymmetry of polarization maps is the key to distinguishing various theories and studying the related physical mechanisms in the early Universe. However, for simplicity, and as a prerequisite to the measurement of the polarization power spectra, we will maximize the S/N for the amplitude.

The S/N is close to 100 for survey areas over 300 deg2. Variation of S/N with survey area for the EE (left-hand panel) and total BB (right-hand panel) power spectra, with foregrounds (solid) and without foregrounds (dashed), for an observing time of 1 yr (light) and 2 yr (dark) for r= 0.01. Such an experiment could also directly detect the gravitational wave component of the B-mode spectrum if the amplitude of the signal is close to current upper limits. This produces local quadrupoles in the radiation field. However, for a ground-based experiment, the lower-ℓ cut-off is also limited by the stability of the atmosphere. © 2008-2020 ResearchGate GmbH. If the minimum ℓ is increased to 100, the GW is no longer detectable below the current upper limit of 0.36.

For an experiment with the sensitivity and multipole coverage of QUaD, an E-mode survey is sample-variance-limited, so that a larger area is preferable (>1000 deg2) for statistical purposes.

and prospects for the future detection of CMB polarization. The noise spectrum is given by, \begin{equation}

Forecast of the average polarization rotation angle. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only.

From Table 3, it is evident that QUaD cannot detect the GW B-mode component unless the tensor-to-scalar ratio is larger than the values considered so far. In the following section, we present our formalism for this procedure, based on the Fisher information matrix. A detailed description of QUaD is given in Church et al. F_{ij} = \sum _{\ell }\frac{2\ell +1}{2}f_{\mathrm{sky}}\mathrm{Tr}\left[\mathbf {C}^{-1}_{\ell }\frac{\partial \mathbf {C}_{\ell }}{\partial \theta _{i}}\mathbf {C}^{-1}_{\ell }\frac{\partial \mathbf {C}_{\ell }}{\partial \theta _{j}}\right], The residual foreground contamination used here therefore gives an upper limit on that which can be expected in the final cleaned maps, given that our foreground models are accurate.

We investigate the science goals achievable with the upcoming generation of ground-based cosmic microwave background polarization experiments, focusing on one particular experiment, QUaD [QUEST (Q and U Extragalactic Submillimetre Telescope) and DASI (Degree Angular Scale Interferometer)], a proposed bolometric polarimeter operating from the South Pole. Although this is suboptimal for both surveys, the drop to S/N = 90 for the E-mode survey is minimal and S/N = 4.5 for the B-mode survey is still a strong detection. Fig.

The results show that the PWV of Ali has a very strong seasonal variation and the median PWV in the observing season (October to March) is about 1 mm (1.07 mm for MERRA-2, 0.92 mm for radiosondes), which is excellent for observation at 95/150 GHz. Comment: 8 pages, 3 figures, to appear in S. Cecchini et al., Astrophysical Polarized, The coming flood of CMB polarization experiments, spurred by the recent detection of CMB polarization by DASI and WMAP, will be confronted by many new analysis tasks specific to polarization. This represents the decomposition of the polarization field into different parity states: the E field is unchanged by a parity transformation, but the B field changes sign. The CMB polarization signal primarily arises from the Thomson scattering of the CMB photons during recombination.

Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This has become a key scientific goal of CMB observations in recent years. In this paper, we have given an introduction to the new ground-based CMB polarization project in China, AliCPT, including the observational conditions and scientific goals. 545 (2000) L5, Kosowsky, A., Annals Phys. We extend this work by considering the criteria for a measurement of the polarization spectra including the effects of gravitational lensing and foregrounds.

In this section, we describe the atmospheric conditions, sky coverage and infrastructure of the AliCPT site. In fact, there are motivations to speculate on the CPT violation in cosmology. Any violation, if found, would be a powerful and important clue for new physics beyond the standard model.

CMB photons are relics left after the Big Bang.

For clarity, we do not show the Planck measurements of the EE power spectrum. The AliCPT telescope plans to scan the cleanest sky regions at 95/150 GHz, in order to suppress the residual foreground as much as possible.

Although Planck will cover much more sky than QUaD, the QUaD observations would be at higher S/N than the average of those made by Planck.

All other parameters used are as per the ‘middle-of-the-road’ model in T00. The horizontal black dashed line is the current limit r < 0.07. Also, AliCPT plans to adopt the data of LSS tracers for the cross-correlation studies. \mathcal {L} = \frac{1}{\sqrt{|\mathbf {C(\theta )}|}} \exp \left(-\frac{1}{2}\mathbf {d^{\dagger }[\mathbf {C}(\theta )]^{-1}}\mathbf {d}\right), All of the structure in the high S/N QUaD map is real signal, while the Planck map (shown with the same pixelization) has much lower S/N per pixel. The intensity measured by the copolar (, For a bolometer, the noise-equivalent power due to photon noise (NEP) is given by (, In order to measure the polarization, we require a pair of PSBs.

However, as well as fluctuations in the CMB temperature field, there are also anisotropies in the linear polarization of the CMB. All rights reserved. ) We illustrate the difference between QUaD and the Planck satellite mission in Fig.

We plot spectra without gravitational lensing (dotted lines) and without reionization (dashed lines) and with both included (solid lines). In Section 3, we present the formalism used in the investigation, and in Section 4, we show how we have included the effects of foregrounds. Conversely, with only temperature information, h and ns are strongly degenerate, with much of the difference in response coming at very low modes, or modes beyond a few hundred.

This kind of contamination can be removed through multi-frequency surveys, since the frequency spectrum distributions of CMB and other components are different.

Middle panel: Sensitivity of r  with complete delensing. To estimate the S/N for the TE spectrum, we assume that a QUaD map could be combined with the portion of the expected 4-yr WMAP data covering the same area of sky. The yellow and green dashed lines are the predictions from inflation models with potential functions of φ2 [17] and φ2/3 [18], respectively.

2) is larger than the GL signal over most of the multipole range which can be covered from the ground.

The derivatives used in the calculation are shown in Figs 8 and 9.

Statistically averaging the data allows a high-significance measurement of the EE power spectrum over a range of multipoles from ℓ= 25 to 2500, with good sampling of the acoustic oscillations.

2002).

We review the science case for studying CMB polarization. 23 December 2013 •First direct detection of BB signal from lensing!

3). The new algorithm takes into account a possible cross- correlated noise component among the different detectors of a CMB experiment. Notice, Smithsonian Terms of It will also improve the ability of the experiment to remove low-lying systematic effects which would not be detectable in observations of lower S/N. 3 shows the region of sky which would be accessible to QUaD from the South Pole and the estimated levels of foreground contamination across this area from dust (Finkbeiner, Davis & Schlegel 1999) and synchrotron (Giardino et al.

Ground-based constraints on the B-mode GW signal will therefore also complement those obtainable from the current generation of satellite experiments.

Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. By preferentially selecting regions of sky with low foreground variance, it will also be possible for a ground-based experiment to reduce further the foreground contamination.

The main scientific goal of the AliCPT project is to probe the primordial gravitational waves (PGWs) originating from the very early Universe.

1998; Maino et al. Recent advances in foreground removal techniques (Baccigalupi 2003) indicate that it may be possible to remove some of the foreground noise from the signal. To find out more, see our Privacy and Cookies policy.

If it is possible to reduce the foreground contamination, the gravitational wave could also be detected for r≥ 0.14. Therefore, by integrating deeply on relatively small patches of sky (Jaffe, Kamionkowski & Wang 2000), it is possible to make a measurement of the polarization anisotropies with a comparable signal-to-noise (S/N) ratio to a satellite experiment on all but the largest angular scales. This is achieved by characterizing and removing the instrumental noise contribution in multipole space.

However, the error on r more than doubles if B-modes are not included. The best-fit value is A = 0.072 ± 0.022 for CMB power at l < 64, and pointing to (227°, −27°).

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