A Limit on the Polarized Anomalous Microwave Emission of Lynds 1622

TL;DR

This study sets an upper limit on the linear polarization of anomalous microwave emission from Lynds 1622, aiding in understanding its nature and impact on cosmic microwave background polarization measurements.

Contribution

The paper provides the first polarization constraints on the anomalous microwave emission from Lynds 1622 using the Green Bank Telescope.

Findings

Upper limit of 88 micro-Kelvin on linear polarization at 9.65 GHz.

Fractional linear polarization constrained to less than 3.5%.

Results help refine models of microwave emission in dark clouds.

Abstract

The dark cloud Lynds 1622 is one of a few specific sites in the Galaxy where, relative to observed free-free and vibrational dust emission, there is a clear excess of microwave emission. In order to constrain models for this microwave emission, and to better establish the contribution which it might make to ongoing and near-future microwave background polarization experiments, we have used the Green Bank Telescope to search for linear polarization at 9.65 Ghz towards Lynds 1622. We place a 95.4% upper limit of 88 micro-Kelvin (123 micro-Kelvin at 99.7 confidence) on the total linear polarization of this source averaged over a 1'.3 FWHM beam. Relative to the observed level of anomalous emission in Stokes I these limits correspond to fractional linear polarizations of 2.7% and 3.5%.