90 research outputs found
Absolute polarization angle calibration using polarized diffuse Galactic emission observed by BICEP
We present a method of cross-calibrating the polarization angle of a
polarimeter using BICEP Galactic observations. \bicep\ was a ground based
experiment using an array of 49 pairs of polarization sensitive bolometers
observing from the geographic South Pole at 100 and 150 GHz. The BICEP
polarimeter is calibrated to +/-0.01 in cross-polarization and less than +/-0.7
degrees in absolute polarization orientation. BICEP observed the temperature
and polarization of the Galactic plane (R.A= 100 degrees ~ 270 degrees and Dec.
= -67 degrees ~ -48 degrees). We show that the statistical error in the 100 GHz
BICEP Galaxy map can constrain the polarization angle offset of WMAP Wband to
0.6 degrees +\- 1.4 degrees. The expected 1 sigma errors on the polarization
angle cross-calibration for Planck or EPIC are 1.3 degrees and 0.3 degrees at
100 and 150 GHz, respectively. We also discuss the expected improvement of the
BICEP Galactic field observations with forthcoming BICEP2 and Keck
observations.Comment: 13 pages, 10 figures and 2 tables. To appear in Proceedings of SPIE
Astronomical Telescopes and Instrumentation 201
End-to-End Modeling of the TDM Readout System for CMB-S4
The CMB-S4 experiment is developing next-generation ground-based microwave
telescopes to observe the Cosmic Microwave Background with unprecedented
sensitivity. This will require an order of magnitude increase in the 100 mK
detector count, which in turn increases the demands on the readout system. The
CMB-S4 readout will use time division multiplexing (TDM), taking advantage of
faster switches and amplifiers in order to achieve an increased multiplexing
factor. To facilitate the design of the new readout system, we have developed a
model that predicts the bandwidth and noise performance of this circuity and
its interconnections. This is then used to set requirements on individual
components in order to meet the performance necessary for the full system. We
present an overview of this model and compare the model results to the
performance of both legacy and prototype readout hardware.Comment: This manuscript was submitted to the Journal of Low Temperature
Physics as part of the special issue "LTD20", supporting the conference
contribution RP-00
Constraints on axion-like polarization oscillations in the cosmic microwave background with POLARBEAR
Very light pseudoscalar fields, often referred to as axions, are compelling
dark matter candidates and can potentially be detected through their coupling
to the electromagnetic field. Recently a novel detection technique using the
cosmic microwave background (CMB) was proposed, which relies on the fact that
the axion field oscillates at a frequency equal to its mass in appropriate
units, leading to a time-dependent birefringence. For appropriate oscillation
periods this allows the axion field at the telescope to be detected via the
induced sinusoidal oscillation of the CMB linear polarization. We search for
this effect in two years of POLARBEAR data. We do not detect a signal, and
place a median upper limit of on the sinusoid amplitude
for oscillation frequencies between and
, which corresponds to axion masses between and . Under the
assumptions that 1) the axion constitutes all the dark matter and 2) the axion
field amplitude is a Rayleigh-distributed stochastic variable, this translates
to a limit on the axion-photon coupling .Comment: 17 pages, 5 figures, 2 tables. Published in Physical Review
Astro2020 APC White Paper: The Early Career Perspective on the Coming Decade, Astrophysics Career Paths, and the Decadal Survey Process
In response to the need for the Astro2020 Decadal Survey to explicitly engage
early career astronomers, the National Academies of Sciences, Engineering, and
Medicine hosted the Early Career Astronomer and Astrophysicist Focus Session
(ECFS) on October 8-9, 2018 under the auspices of Committee of Astronomy and
Astrophysics. The meeting was attended by fifty six pre-tenure faculty,
research scientists, postdoctoral scholars, and senior graduate students, as
well as eight former decadal survey committee members, who acted as
facilitators. The event was designed to educate early career astronomers about
the decadal survey process, to solicit their feedback on the role that early
career astronomers should play in Astro2020, and to provide a forum for the
discussion of a wide range of topics regarding the astrophysics career path.
This white paper presents highlights and themes that emerged during two days
of discussion. In Section 1, we discuss concerns that emerged regarding the
coming decade and the astrophysics career path, as well as specific
recommendations from participants regarding how to address them. We have
organized these concerns and suggestions into five broad themes. These include
(sequentially): (1) adequately training astronomers in the statistical and
computational techniques necessary in an era of "big data", (2) responses to
the growth of collaborations and telescopes, (3) concerns about the adequacy of
graduate and postdoctoral training, (4) the need for improvements in equity and
inclusion in astronomy, and (5) smoothing and facilitating transitions between
early career stages. Section 2 is focused on ideas regarding the decadal survey
itself, including: incorporating early career voices, ensuring diverse input
from a variety of stakeholders, and successfully and broadly disseminating the
results of the survey
Science from an Ultra-Deep, High-Resolution Millimeter-Wave Survey
Opening up a new window of millimeter-wave observations that span frequency
bands in the range of 30 to 500 GHz, survey half the sky, and are both an order
of magnitude deeper (about 0.5 uK-arcmin) and of higher-resolution (about 10
arcseconds) than currently funded surveys would yield an enormous gain in
understanding of both fundamental physics and astrophysics. In particular, such
a survey would allow for major advances in measuring the distribution of dark
matter and gas on small-scales, and yield needed insight on 1.) dark matter
particle properties, 2.) the evolution of gas and galaxies, 3.) new light
particle species, 4.) the epoch of inflation, and 5.) the census of bodies
orbiting in the outer Solar System.Comment: 5 pages + references; Submitted to the Astro2020 call for science
white paper
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