Chandra Announcement: Announcement of the Call for Chandra Legacy Program Proposals

[Tara Gokas]

Announcement of the Call for Chandra Legacy Program Proposals 

In November 2023 the CXC issued the Chandra Legacy Program (CLP) call for white papers to identify science challenges for which the capabilities of Chandra are absolutely required. These science programs were to be designed to address fundamental questions about our current understanding of the components and evolution of the Universe. A committee of seven (non-CXC) members of the astrophysics community reviewed the twenty-two white papers that were submitted. After the CLP Review Committee completed its evaluation of the white papers, recommendations for major science initiatives were presented to the CXC Director. These recommendations have been used to form the themes of this Call for Legacy Proposals. 

Chandra Legacy Program Major Initiatives 

The CLP major initiatives identified through the white paper call are: 

Initiative I: Probing the Physics of Baryon Cycles and Feedback using Deep Observations of Nearby Galaxies

Deep X-ray observations of nearby galaxies offer unique opportunities to detect and characterize the spatial distribution of elusive hot X-ray-emitting gas in and around galaxies. Chandra’s superb angular resolution is essential for resolving X-ray binary populations and mapping the internal structures of the X-ray emitting circumgalactic medium (CGM) in and around galaxies. We seek an ambitious and compelling science proposal that can be uniquely enabled by high-resolution X-ray maps of a well-chosen sample of relatively nearby galaxies coupled with high resolution multi-wavelength coverage, within a CLP exposure time of ~3 Ms. Previous Chandra exposures should be considered when constructing a proposed observing program. A successful proposal must articulate the legacy values of the Chandra observations, its complementarity and synergy with multiwavelength observations, and why the proposed science is not possible as part of the General Observer (GO) program.

Probing the cycling of baryons in galaxies is critical to building a complete picture of galaxy assembly and growth. However, even at low redshift, key unknowns persist that Chandra can address via observations of the hot gas phase. Examples might include:

1. providing an X-ray view of stellar population evolution;

2. measuring how stellar evolution and AGN feedback circulate energy and metals;

3. determining the structure of the multiphase ISM/CGM;

4. establishing the influence of mergers of galaxies and of their super massive black holes (SMBHs). 

The proposed Chandra legacy observations and resulting data products should leverage existing and/or proposed high spatial-resolution multi-wavelength coverage of nearby galaxies to provide a fundamental and enduring anchor point for understanding the evolution of the baryon cycle over cosmic time.

Initiative II: Deep Observation of a Galaxy Cluster to Understand Key Physical Processes

Deep X-ray observations of galaxy clusters offer a unique opportunity to study the physics of galaxy formation, plasma physics, and cosmology. Chandra’s superb angular resolution is essential for providing detailed physical insights into the roles of AGN feedback in clusters, the microphysics of astrophysical plasma and the nature of dark matter using merging clusters, and the cosmological growth of structures in cluster outskirts. We seek an ambitious and compelling science proposal that can be uniquely enabled by a deep (~3 Msec) Chandra observation of an appropriately selected galaxy cluster. A successful proposal must articulate how the proposed observations and data products will open up new discovery space or significantly advance the state-of-the-art astrophysical constraints. 

Potential science objectives for this theme include understanding the heating mechanisms of AGN feedback and cooling-heating balance in cluster cores, which might be achieved by: 

1. determining the equation-of-state of the intra-cluster medium (ICM);

2. distinguishing among physical mechanisms for heating of the ICM;

3. measuring the electron mean free path; 

4. testing the precipitation model in a multiphase cool core.

Important Deadlines

Call for CLP Proposals February 20, 2024

Chandra Cycle 26 Proposals Due March 14, 2024

CLP Letters of Intent Due       March 28, 2024 

CLP Proposals Due                April 15, 2024 

CLP Review Results Announced May 15, 2024

Additional important details can be found in the full Call for CLP Proposals.