QUIJOTE scientific results – III. Microwave spectrum of intensity and polarization in the Taurus Molecular Cloud complex and L1527

Abstract

We present new intensity and polarization observations of the Taurus molecular cloud (TMC) region in the frequency range 10-20 GHz with the Multi-Frequency Instrument (MFI) mounted on the first telescope of the QUIJOTE experiment. From the combination of the QUIJOTE data with the WMAP 9-yr data release, the Planck second data release, the DIRBE maps and ancillary data, we detect an anomalous microwave emission (AME) component with flux density S AME,peak = 43.0 ± 7.9 Jy in the Taurus Molecular Cloud (TMC) and S AME,peak = 10.7 ± 2.7 Jy in the dark cloud nebula L1527, which is part of the TMC. In the TMC the diffuse AME emission peaks around a frequency of 19 GHz, compared with an emission peak about a frequency of 25 GHz in L1527. In the TMC, the best constraint on the level of AME polarization is obtained at the Planck channel of 28.4 GHz, with an upper limit π AME <4.2 % (95 % C. L.), which reduces to π AME <3.8 % (95 % C.L.) if the intensity of all the freefree, synchrotron and thermal dust components are negligible at this frequency. The same analysis in L1527 leads to π AME <5.3% (95 %C.L.), or π AME <4.5 % (95%C.L.) under the same assumption. We find that in the TMC and L1527 on average about 80% of the HII gas should be mixed with thermal dust. Our analysis shows how the QUIJOTE-MFI 10-20 GHz data provides key information to properly separate the synchrotron, free-free and AME components.

Detection of spectral variations of Anomalous Microwave Emission with QUIJOTE and C-BASS

“…Individual examples point to clear leakages of AME into free-free emission and vice versa, which can be seen by eye. However, leakages primarily occur from AME into free-free in this region, which is consistent with QUIJOTE studies of the Taurus region by Poidevin et al (2019) and observations of W43, W44, and W47 by Génova-Santos et al (2017). These leakages originate from degeneracies between components due to the limited multifrequency data available to the Planck Collaboration X (2016a) COMMANDER separation, and they were observed and discussed in Planck Collaboration XXV (2016c) and Planck Collaboration IV (2020b).…”

“…Finally, by using QUIJOTE and C-BASS, we have shown that the Planck Collaboration X (2016a) COMMANDER separation maps in the region suffer from degeneracies between free-free emission and AME due to the limited frequency coverage of the data used, highlighting the need for data below ≈ 20 GHz as discussed in Génova-Santos et al (2017) and Poidevin et al (2019). The addition of low frequencies emphasizes the importance of cross-collaborations at low frequencies such as QUIJOTE and C-BASS, where the overall outcome far exceeds the sum of their individual contributions.…”

“…For the purpose of this paper, it is assumed that the majority of AME originates from spinning dust grains. Observations suggest that AME is ubiquitous along the Galactic plane and that it accounts for up to half of the flux density in intensity at ∼ 30 GHz (Planck Collaboration XV 2014d, Planck Collaboration XXV 2016c), being strongest in photodissociation regions (PDRs) such as Perseus (Watson et al 2005;Tibbs et al 2010;Planck Collaboration XX 2011), ρ Ophiuchi (Casassus et al 2008;Planck Collaboration XX 2011), molecular clouds (Génova-Santos et al 2011;Planck Collaboration XV 2014d;Planck Collaboration XII 2014e;Poidevin et al 2019), and other dense environments associated with H II regions (Todorović et al 2010). A comprehensive review of AME is given in Dickinson et al (2018).…”

Polycyclic Aromatic Hydrocarbons, the Anomalous Microwave Emission, and Their Connection to the Cold Neutral Medium

“…The fidelity of our study is likely most limited by the reliability of the AME maps, which result from an extensive and challenging component separation analysis (Planck Collaboration X 2016). While additional multifrequency data have in general validated the Planck Collaboration X (2016) AME maps, systematic discrepancies have been noted at the ∼10-20% level (Dickinson et al 2019;Poidevin et al 2019;Cepeda-Arroita et al 2021). In particular, the AME is often underestimated and free-free emission overestimated.…”

Broadband polarimeter receivers at 30 and 40 GHz for cosmic microwave background measurement

“…The Thirty and Forty GHz polarimeters for the Q-U-I JOint TEnerife (QUIJOTE) CMB radio astronomy experiment, 1,2 are broadband very sensitive receivers to perform scientific sky observations of the Cosmic Microwave Background (CMB). The aim of the QUIJOTE experiment is the measurement of the linear polarization percentage of the received waves from the sky.…”