Mapping the imprints of stellar and AGN feedback in the circumgalactic medium with X-ray microcalorimeters

TL;DR

This paper demonstrates that future X-ray microcalorimeters will enable detailed mapping of the circumgalactic medium around galaxies, revealing its structure, dynamics, and feedback processes, which current instruments cannot achieve.

Contribution

It shows how large grasp X-ray microcalorimeters can uniquely characterize the CGM in galaxy halos through realistic simulations and mock observations, highlighting their advantages over current detectors.

Findings

Microcalorimeters can distinguish faint CGM emission from Milky Way foreground.

Emission lines can trace halo extent up to R500 and R200 for larger galaxies.

Spectral fitting can reveal temperature, velocity, and enrichment maps of galaxy halos.

Abstract

The Astro2020 Decadal Survey has identified the mapping of the circumgalactic medium (CGM, gaseous plasma around galaxies) as a key objective. We explore the prospects for characterizing the CGM in and around nearby galaxy halos with a future, large grasp X-ray microcalorimeter. We create realistic mock observations from hydrodynamical simulations (EAGLE, IllustrisTNG, and Simba) that demonstrate a wide range of potential measurements, which will address the open questions in galaxy formation and evolution. By including all background and foreground components in our mock observations, we show why it is impossible to perform these measurements with current instruments, such as X-ray CCDs, and only microcalorimeters will allow us to distinguish the faint CGM emission from the bright Milky Way (MW) foreground emission lines. We find that individual halos of MW mass can, on average and depending on star formation rate, be traced out to large radii, around R500, and for larger galaxies even out to R200, using prominent emission lines, such as OVII, or OVIII. Furthermore, we show that emission line ratios for individual halos can reveal the radial temperature structure. Substructure measurements show that it will be possible to relate azimuthal variations to the feedback mode of the galaxy. We demonstrate the ability to construct temperature, velocity, and abundance ratio maps from spectral fitting for individual galaxy halos, which reveal rotation features, AGN outbursts, and enrichment.