Aims

The WISSHFUL program is an ambitious research program designed to explore the nature and impact of AGN-driven winds on the evolution of SMBH and their host galaxies, particularly during the peak period of galaxy formation and black hole growth known as Cosmic Noon (z = 2-4). In particular, UFOs are thought to play a pivotal role in the co-evolution of SMBHs and their host galaxies by removing or heating cold gas, thereby quenching star formation and halting further SMBH growth. This process may help explain the observed correlation between the mass of SMBHs and their host galaxies.

UFOs are quasi-relativistic, highly ionized winds detected in the X-rays as blue-shifted absorption features of He- and H-like iron. These features are indicative of extreme outflow velocities (v_out ≳ 0.1c). UFOs have been systematically observed in a significant fraction of low-redshift Seyfert galaxies, QSOs, and radio galaxies, but their presence at high redshift remains sparsely documented, especially in the most luminous and massive SMBHs at Cosmic Noon.

To address this gap, the WISSHFUL program utilizes a combination of extensive X-ray observations from the XMM-Newton and NuSTAR telescopes. The XMM WISSHFUL program has been allocated long exposure times ranging from 60 to 220 ks per target, summing up to a total of 2.3 Ms over three observational cycles (the eighth largest program ever awarded by XMM). This will enable the program to provide a homogeneous and statistically significant characterization of UFOs in 15 of the most luminous radio-quiet, non-lensed QSOs selected from the WISSH samples.

NuSTAR observations, totaling 750 ks for the first 7 targets to be observed in 2023-2024, are coordinated with XMM to enhance the study of the coronal properties of these luminous QSOs. The quasi-simultaneous data from XMM and NuSTAR will allow for a detailed analysis of the hot corona properties, such as the electron temperature and optical depth, through measurements of the photon index and high-energy cut-off in the X-ray spectra. This is crucial for understanding the physical conditions of the X-ray-emitting corona in high-redshift QSOs and their relation with the presence of nuclear winds.

The primary aims of these observations include:

1. Systematic Study of UFOs: Detect and characterize UFO features in a large, luminosity-selected sample of high-redshift QSOs, providing insights into the wind's physical properties and energetics.

2. Coronal Properties: Derive the temperature and optical depth of the electron corona, which produces X-rays via inverse Compton scattering. This information will help test theoretical models like the runaway pair-production mechanism that predicts limited temperature ranges for coronal electrons in high-luminosity QSOs.

3. Broadband Spectral Energy Distribution (SED): Obtain precise broadband SEDs of the accretion disk-corona system spanning over four decades in energy. This will aid in building self-consistent photoionization models to fit UFO features and test models of warm corona and thin/slim disk accretion for highly accreting QSOs.

4. AGN Feedback: Investigate the connection between nuclear winds and accretion properties, contributing to the broader understanding of AGN feedback mechanisms that influence galaxy evolution. This investigation will benefit from the integration of existing studies and data on these targets, including multi-wavelength observations and analyses, ensuring a comprehensive understanding of the diverse processes at play. The extensive body of research already available on these targets provides a robust foundation for these new observations and interpretations.