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Title: Line-of-sight extrapolation noise in dust polarization

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1358647
Grant/Contract Number:
FG02-95ER40896
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 95; Journal Issue: 10; Related Information: CHORUS Timestamp: 2017-05-19 22:13:10; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Poh, Jason, and Dodelson, Scott. Line-of-sight extrapolation noise in dust polarization. United States: N. p., 2017. Web. doi:10.1103/PhysRevD.95.103511.
Poh, Jason, & Dodelson, Scott. Line-of-sight extrapolation noise in dust polarization. United States. doi:10.1103/PhysRevD.95.103511.
Poh, Jason, and Dodelson, Scott. Fri . "Line-of-sight extrapolation noise in dust polarization". United States. doi:10.1103/PhysRevD.95.103511.
@article{osti_1358647,
title = {Line-of-sight extrapolation noise in dust polarization},
author = {Poh, Jason and Dodelson, Scott},
abstractNote = {},
doi = {10.1103/PhysRevD.95.103511},
journal = {Physical Review D},
number = 10,
volume = 95,
place = {United States},
year = {Fri May 19 00:00:00 EDT 2017},
month = {Fri May 19 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevD.95.103511

Citation Metrics:
Cited by: 3works
Citation information provided by
Web of Science

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  • The B-modes of polarization at frequencies ranging from 50-1000 GHz are produced by Galactic dust, lensing of primordial E-modes in the cosmic microwave background (CMB) by intervening large scale structure, and possibly by primordial B-modes in the CMB imprinted by gravitational waves produced during inflation. The conventional method used to separate the dust component of the signal is to assume that the signal at high frequencies (e.g., 350 GHz) is due solely to dust and then extrapolate the signal down to lower frequency (e.g., 150 GHz) using the measured scaling of the polarized dust signal amplitude with frequency. For typicalmore » Galactic thermal dust temperatures of about 20K, these frequencies are not fully in the Rayleigh-Jeans limit. Therefore, deviations in the dust cloud temperatures from cloud to cloud will lead to different scaling factors for clouds of different temperatures. Hence, when multiple clouds of different temperatures and polarization angles contribute to the integrated line-of-sight polarization signal, the relative contribution of individual clouds to the integrated signal can change between frequencies. This can cause the integrated signal to be decorrelated in both amplitude and direction when extrapolating in frequency. Here we carry out a Monte Carlo analysis on the impact of this line-of-sight extrapolation noise, enabling us to quantify its effect. Using results from the Planck experiment, we find that this effect is small, more than an order of magnitude smaller than the current uncertainties. However, line-of-sight extrapolation noise may be a significant source of uncertainty in future low-noise primordial B-mode experiments. Scaling from Planck results, we find that accounting for this uncertainty becomes potentially important when experiments are sensitive to primordial B-mode signals with amplitude r < 0.0015 .« less
  • We investigate the effect of line-of-sight temperature variations and noise on two commonly used methods to determine dust properties from dust-continuum observations of dense cores. One method employs a direct fit to a modified blackbody spectral energy distribution (SED); the other involves a comparison of flux ratios to an analytical prediction. Fitting fluxes near the SED peak produces inaccurate temperature and dust spectral index estimates due to the line-of-sight temperature (and density) variations. Longer wavelength fluxes in the Rayleigh-Jeans part of the spectrum ({approx}> 600 {mu}m for typical cores) may more accurately recover the spectral index, but both methods aremore » very sensitive to noise. The temperature estimate approaches the density-weighted temperature, or 'column temperature', of the source as short wavelength fluxes are excluded. An inverse temperature-spectral index correlation naturally results from SED fitting, due to the inaccurate isothermal assumption, as well as noise uncertainties. We show that above some 'threshold' temperature, the temperatures estimated through the flux ratio method can be highly inaccurate. In general, observations with widely separated wavelengths, and including shorter wavelengths, result in higher threshold temperatures; such observations thus allow for more accurate temperature estimates of sources with temperatures less than the threshold temperature. When only three fluxes are available, a constrained fit, where the spectral index is fixed, produces less scatter in the temperature estimate when compared to the estimate from the flux ratio method.« less
  • Multifluid C-type shock models are presented for the gas on the line of sight toward Zeta Oph and compared with observational data. A shock model of a 9 km/s-shock propagating into diffuse molecular gas with n(H) of 20/cm, and H/sub 2//H of 3 is in good agreement with the observed column density and radial velocity of the CH(+) and is consistent with observational limits of column densities of the OH and CH. The preferred shock model predicts that a large fraction of the J = 3-5 H/sub 2/ on this line of sight is due to collisional excitation in themore » shock-heated gas. The dominant molecular component present on this line of sight is interpreted as shock-compressed material behind the shock front. It is considered to be likely that the shock wave is driven by the pressure of the Zeta Oph H II region. 53 references.« less