# QUIJOTE Scientific results. III. Microwave spectrum of intensity and polarization in the Taurus molecular cloud Complex and L1527

## TL;DR

This study presents new microwave intensity and polarization data of the Taurus molecular cloud, detecting anomalous microwave emission and constraining its polarization, thereby improving understanding of emission components in molecular clouds.

## Contribution

The paper provides new 10-20 GHz polarization measurements of the TMC and L1527, detecting AME and setting upper limits on its polarization, enhancing component separation in microwave observations.

## Key findings

- Detected AME with flux densities of 43.0 Jy in TMC and 10.7 Jy in L1527.
- Constrained AME polarization to less than 4.2% in TMC and 5.3% in L1527.
- Identified that about 80% of HII gas is mixed with thermal dust in these regions.

## 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 $S_{\rm AME, peak} = 43.0 \pm 7.9\,$Jy in the Taurus Molecular Cloud (TMC) and $S_{\rm AME, peak} = 10.7 \pm 2.7\,$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 polarisation is obtained at the Planck channel of 28.4 GHz, with an upper limit $\pi_{\rm AME}<$4.2$\,\%$ (95$\,\%$ C. L.), which reduces to $\pi_{\rm AME} <$3.8$\,\%$ (95$\,\%$ C.L.) if the intensity of all the free-free, synchrotron and thermal dust components are negligible at this frequency. The same analysis in L1527 leads to $\pi_{\rm AME}<$5.3$\%$ (95$\,\%$C.L.), or $\pi_{\rm 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.