The Atacama Cosmology Telescope: Microwave Intensity and Polarization Maps of the Galactic Center

TL;DR

This paper presents high-resolution intensity and polarization maps of the Galactic center using ACT and Planck data, revealing magnetic field structures and emission mechanisms across multiple frequencies.

Contribution

It provides the first combined high-resolution and large-scale polarization maps of the Galactic center, highlighting changes in emission mechanisms and magnetic field morphology.

Findings

Resolved known features of the Central Molecular Zone in intensity and polarization.

Mapped the Galactic magnetic field orientation and its frequency-dependent changes.

Identified key sources like Sgr A* and the Tornado remnant in detail.

Abstract

We present arcminute-resolution intensity and polarization maps of the Galactic center made with the Atacama Cosmology Telescope (ACT). The maps cover a 32 deg$^2$ field at 98, 150, and 224 GHz with $\vert l\vert\le4^\circ$, $\vert b\vert\le2^\circ$. We combine these data with Planck observations at similar frequencies to create coadded maps with increased sensitivity at large angular scales. With the coadded maps, we are able to resolve many known features of the Central Molecular Zone (CMZ) in both total intensity and polarization. We map the orientation of the plane-of-sky component of the Galactic magnetic field inferred from the polarization angle in the CMZ, finding significant changes in morphology in the three frequency bands as the underlying dominant emission mechanism changes from synchrotron to dust emission. Selected Galactic center sources, including Sgr A*, the Brick molecular cloud (G0.253+0.016), the Mouse pulsar wind nebula (G359.23-0.82), and the Tornado supernova remnant candidate (G357.7-0.1), are examined in detail. These data illustrate the potential for leveraging ground-based Cosmic Microwave Background polarization experiments for Galactic science.