Abstract
We present the power spectrum methodology used for the first-season COMAP analysis, and assess the quality of the current data set. The main results are derived through the Feed–Feed ...Pseudo-Cross-Spectrum (FPXS) method, which is a robust estimator with respect to both noise modeling errors and experimental systematics. We use effective transfer functions to take into account the effects of instrumental beam smoothing and various filter operations applied during the low-level data processing. The power spectra estimated in this way have allowed us to identify a systematic error associated with one of our two scanning strategies, believed to be due to residual ground or atmospheric contamination. We omit these data from our analysis and no longer use this scanning technique for observations. We present the power spectra from our first season of observing, and demonstrate that the uncertainties are integrating as expected for uncorrelated noise, with any residual systematics suppressed to a level below the noise. Using the FPXS method, and combining data on scales
k
= 0.051–0.62 Mpc
−1
, we estimate
P
CO
(k) = −2. 7 ± 1.7 × 10
4
μ
K
2
Mpc
3
, the first direct 3D constraint on the clustering component of the CO(1–0) power spectrum in the literature.
Abstract
We present early results from the CO Mapping Array Project (COMAP) Galactic Plane Survey conducted between 2019 June and 2021 April, spanning 20° <
ℓ
< 40° in Galactic longitude and ∣
b
∣ < ...1.°5 in Galactic latitude with an angular resolution of 4.′5. We present initial results from the first part of the survey, including the diffuse emission and spectral energy distributions of H
ii
regions and supernova remnants (SNRs). Using low- and high-frequency surveys to constrain free–free and thermal dust emission contributions, we find evidence of excess flux density at 30 GHz in six regions, which we interpret as anomalous microwave emission. Furthermore we model ultracompact H
ii
contributions using data from the 5 GHz CORNISH catalog and reject these as the cause of the 30 GHz excess. Six known SNRs are detected at 30 GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at 30 GHz is consistent with a power-law extrapolation from lower frequencies with no indication of spectral steepening in contrast with recent results from the Sardinia Radio Telescope. We also extract five hydrogen radio recombination lines (RRLs) to map the warm ionized gas, which can be used to estimate electron temperatures or to constrain continuum free–free emission. The full COMAP Galactic Plane Survey, to be released in 2023/2024, will span
ℓ
∼ 20°–220° and will be the first large-scale radio continuum and RRL survey at 30 GHz with 4.′5 resolution.
In this letter, we propose a novel wideband subharmonically pumped fully differential I-Q resistive mixer architecture, which eliminates the necessity for on-chip dc-blocking capacitors to integrate ...IF amplifiers. The proposed differential subharmonic mixer topology is verified by presenting a CMOS millimeter-wave monolithic integrated circuit (MMIC), which includes the mixer and two on-chip differential IF amplifiers at the mixer's I- and Q-channels. The 3-dB IF frequency bandwidth is measured from 0.01 to 5 GHz with a peak conversion gain (CG) of −2 dB and an image rejection ratio (IRR) of more than 25 dB over the IF frequency range. The proposed mixer covers the input signal (RF) frequency from 170 to 185 GHz. The mixer has also been tested with an on-chip voltage-controlled oscillator (VCO) and shows −4.7-dB CG with a 3-dB IF bandwidth from 0.01 to 4.5 GHz.
COMAP Early Science. III. CO Data Processing Foss, Marie K.; Ihle, Håvard T.; Borowska, Jowita ...
Astrophysical journal/The Astrophysical journal,
07/2022, Letnik:
933, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
We describe the first-season CO Mapping Array Project (COMAP) analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain ...calibration, filtering, data selection, and mapmaking. Absolute gain calibration relies on a combination of instrumental and astrophysical sources, while relative gain calibration exploits real-time total-power variations. High-efficiency filtering is achieved through spectroscopic common-mode rejection within and across receivers, resulting in nearly uncorrelated white noise within single-frequency channels. Consequently, near-optimal but biased maps are produced by binning the filtered time stream into pixelized maps; the corresponding signal bias transfer function is estimated through simulations. Data selection is performed automatically through a series of goodness-of-fit statistics, including
χ
2
and multiscale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a data set with very low levels of correlated noise. We find that one of our two scanning strategies (the Lissajous type) is sensitive to residual instrumental systematics. As a result, we no longer use this type of scan and exclude data taken this way from our Season 1 power spectrum estimates. We perform a careful analysis of our data processing and observing efficiencies and take account of planned improvements to estimate our future performance. Power spectrum results derived from the first-season COMAP maps are presented and discussed in companion papers.
COMAP Early Science. II. Pathfinder Instrument Lamb, James W.; Cleary, Kieran A.; Woody, David P. ...
Astrophysical journal/The Astrophysical journal,
07/2022, Letnik:
933, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Line intensity mapping (LIM) is a new technique for tracing the global properties of galaxies over cosmic time. Detection of the very faint signals from redshifted carbon monoxide (CO), a ...tracer of star formation, pushes the limits of what is feasible with a total-power instrument. The CO Mapping Project Pathfinder is a first-generation instrument aiming to prove the concept and develop the technology for future experiments, as well as delivering early science products. With 19 receiver channels in a hexagonal focal plane arrangement on a 10.4 m antenna and an instantaneous 26–34 GHz frequency range with 2 MHz resolution, it is ideally suited to measuring CO (
J
= 1–0) from
z
∼ 3. In this paper we discuss strategies for designing and building the Pathfinder and the challenges that were encountered. The design of the instrument prioritized LIM requirements over those of ancillary science. After a couple of years of operation, the instrument is well understood, and the first year of data is already yielding useful science results. Experience with this Pathfinder will guide the design of the next generations of experiments.
An MMIC Low-Noise Amplifier Design Technique Varonen, Mikko; Reeves, Rodrigo; Kangaslahti, Pekka ...
IEEE transactions on microwave theory and techniques,
03/2016, Letnik:
64, Številka:
3
Journal Article
Recenzirano
In this paper we discuss the design of low-noise amplifiers (LNAs) for both cryogenic and room-temperature operation in general and take the stability and linearity of the amplifiers into special ...consideration. Oscillations that can occur within a multi-finger transistor are studied and verified with simulations and measurements. To overcome the stability problem related to the multi-finger transistor design approach a parallel two-finger unit transistor monolithic microwave integrated circuit LNA design technique, which enables the design of wideband and high-linearity LNAs with very stable, predictable, and repeatable operation, is proposed. The feasibility of the proposed design technique is proved by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26-33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K.
In this letter, a rectangular waveguide to conductor backed-coplanar waveguide electromagnetic transition suitable of operating at sub-millimeter wave frequencies is demonstrated. The dipole based ...transition is fabricated using InP monolithic microwave integrated circuit technology. The compact transition eliminates wire-bonding problems (return loss and insertion loss) and is suitable for direct integration of sub-millimeter wave monolithic integrated circuits. Measured transition loss of ~1 dB has been achieved in the frequency range of 340 to 380 GHz.
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