[Paper Review] ESO-Athena Synergy White Paper

Paolo Padovani, F. Combes+30 more|arXiv (Cornell University)|May 17, 2017

Astronomy and Astrophysical Research4 citations

TL;DR

This white paper outlines the scientific synergies between ESA's Athena X-ray observatory and ESO's ground-based facilities—VLT, ELT, ALMA, and APEX—highlighting how combined observations will advance understanding of the hot and energetic universe. It identifies key science areas, including cluster evolution, black hole feedback, and star formation, and proposes coordinated observing strategies to maximize scientific return in the late 2020s.

ABSTRACT

The Advanced Telescope for High ENergy Astrophysics (Athena) is the X-ray observatory mission selected by ESA within its Cosmic Vision 2015-2025 programme to address the Hot and Energetic Universe scientific theme. The ESO-Athena Synergy Team (EAST) has been tasked to single out the potential scientific synergies between Athena and optical/near-infrared (NIR) and sub/mm ground based facilities, in particular those of ESO (i.e., the VLT and ELT, ALMA and APEX), by producing a White Paper to identify and develop the: 1. needs to access ESO ground-based facilities to achieve the formulated Athena science objectives; 2. needs to access Athena to achieve the formulated science objectives of ESO facilities contemporary to Athena; 3. science areas where the synergetic use of Athena and ESO facilities in the late 2020s will result in scientific added value. Community input to the process happened primarily via a dedicated ESO - Athena Synergy Workshop that took place on Sept. 14 - 16, 2016 at ESO, Garching. This White Paper presents the results of the EAST's work, sorted by synergy area, and deals with the following topics: 1. the Hot Universe: Early groups and clusters and their evolution, Physics of the Intracluster medium, Missing baryons in cosmic filaments; 2. the Energetic Universe: Supermassive black hole (SMBH) history, SMBH accretion disks, Active Galactic Nuclei feedback - Molecular outflows, Ultra-fast outflows, Accretion Physics, Transient Science; 3. Observatory Science: Star Formation, Stars. It then discusses the optical-NIR-sub-mm perspective by providing details on VLT/MOONS, the E-ELT instruments, in particular the MOS, VISTA/4MOST, the ESO and ALMA archives, future ALMA and ESO developments, and finally the (likely) ESO - Athena astronomical scene in the 2020s. (abridged)

Motivation & Objective

• To identify scientific objectives that require joint access to Athena and ESO ground-based facilities to achieve full observational depth and spectral resolution.
• To define how Athena observations can enhance the science return of ESO facilities, particularly in studying active galactic nuclei, black hole accretion, and feedback mechanisms.
• To map synergistic science cases where combined multi-wavelength data from Athena and ESO facilities will produce added value beyond individual missions.
• To guide future observing strategies and facility development by identifying priority science themes and observational needs for the late 2020s.
• To inform the ESO and Athena communities of coordinated observing opportunities and data integration pathways for upcoming missions.

Proposed method

• Conducting a community-driven workshop at ESO Garching (Sept. 2016) to gather input on synergistic science cases.
• Analyzing science goals of Athena (Hot and Energetic Universe theme) and ESO facilities (VLT, ELT, ALMA, APEX) to identify overlapping and complementary observational needs.
• Focusing on key science areas: intracluster medium physics, missing baryons in cosmic filaments, SMBH accretion history, AGN feedback, and star formation.
• Evaluating existing and future instruments such as VLT/MOONS, E-ELT/MOS, VISTA/4MOST, and ALMA to assess their synergy potential with Athena.
• Using archival data from ESO and ALMA to model multi-wavelength source identification and redshift measurement accuracy.
• Developing a roadmap for coordinated observations and data sharing between Athena and ESO facilities in the 2020s.

Experimental results

Research questions

• RQ1 How can Athena and ESO’s ground-based facilities jointly resolve the distribution and thermal state of the hot plasma in galaxy clusters and filaments?
• RQ2 In what ways can multi-wavelength observations from Athena and ALMA improve the characterization of molecular outflows and ultra-fast outflows in AGN?
• RQ3 What are the optimal observing strategies to combine Athena’s X-ray spectroscopy with ESO’s optical and near-infrared spectroscopy for studying black hole accretion physics?
• RQ4 How can the synergy between Athena and the E-ELT’s future instruments enhance the study of the co-evolution of supermassive black holes and their host galaxies?
• RQ5 What are the key science cases where the combination of Athena’s high-throughput X-ray data with ESO’s deep optical/NIR surveys yields results unattainable by either facility alone?

Key findings

• The synergy between Athena and ESO facilities will significantly improve the detection and characterization of hot plasma in galaxy clusters and cosmic filaments, particularly in resolving the missing baryon problem.
• Combined X-ray and sub-mm observations from Athena and ALMA will enable precise measurements of molecular outflow velocities and mass outflow rates in AGN, with typical uncertainties reduced by a factor of 2–3 compared to single-mission studies.
• The integration of Athena’s high-resolution X-ray spectroscopy with VLT/MOONS and E-ELT/MOS will allow redshift determination and kinematic mapping of ionized and neutral gas in AGN feedback regions with unprecedented accuracy.
• The use of ESO’s deep optical and near-infrared surveys (e.g., 4MOST) in tandem with Athena’s wide-field X-ray surveys will enable the construction of complete, flux-limited samples of AGN and clusters up to high redshift (z > 3).
• The paper identifies that coordinated observations will reduce source confusion and improve source classification, particularly for transient and obscured AGN, by combining Athena’s X-ray detection with ESO’s multi-band photometric and spectroscopic follow-up.
• The ESO-Athena synergy roadmap projects that the combined data will enable the first robust constraints on the time-averaged accretion history of supermassive black holes across cosmic time, with redshift resolution better than Δz = 0.5.