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Active Galactic Nuclei at High Redshift: Prospects of the Line Emission Mapper Probe Mission

Presentation #110.26 in the session LEM.

Published onJul 01, 2023
Active Galactic Nuclei at High Redshift: Prospects of the Line Emission Mapper Probe Mission

The Line Emission Mapper (LEM) is an X-ray Probe-class Mission concept which combines 1-2 eV spectral resolution in the soft X-ray band (0.2 to 2 keV) with an area of ~2600 cm2 at 1 keV, and a spatial resolution of 10″ (half-power diameter) over a large 30′ by 30′ field of view. The mission directly addresses the Astro2020 Decadal Report’s Priority Area of Unveiling the Drivers of Galaxy Growth and will support multiple major science themes of AGN research while enabling discoveries for the broad astrophysical community. LEM’s particular strength for high-redshift AGN is the combination of its extremely high spectral resolution and low detector background, which is well suited for detecting the (virtually ubiquitous) Fe Kα line from AGN that are redshifted into the LEM band. There is also the unique possibility of spectrally decoupling X-ray emission features of AGN photoionization and shock heating from starbursts/stellar sources, allowing us to separate even a high redshift AGN from its host galaxy. For deep survey areas, we expect LEM to detect Fe Kα lines from several tens of AGN (both unobscured and obscured) per square degree. By measuring the Fe Kα line fluxes and equivalent widths, as well as the line-of-sight absorption intrinsic to the AGNs, we can assess AGN type and evolution as a function of redshift at z>2.5. Another key science area will be the study of AGN in galaxy mergers, which can be spatially separated at distances of 30″, but also, critically, spectrally separated even in the case of unresolved point sources (which is not possible with CCD-type detectors) because of the unprecedented imaging spectroscopy capabilities of LEM. This poster highlights AGN science in these and other areas.

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