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.
The CLP major initiatives identified through the white paper call are:
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:
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.
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:
Additional important details can be found in the full Call for CLP Proposals.
| Event | Date |
|---|---|
| Call for CLP Proposals | February 21, 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 |
The nominal Chandra time available for this initiative is 6 Ms, which will come from a combination of the Director's Discretionary Time program, the Guaranteed Time Observer program, and the General Observer program.
| Nominal Exposure Time | 6 Ms |
| Maximum HRC Time | 500 ks |
| Time at ecliptic latitudes |b| > 55° | 1.2 Ms |
| GO | 4 Ms (~14%) |
| GTO | 1 Ms (~19%) |
| DDT | 1 Ms (~50%) |
For information about JPOs, please refer to the Cycle 26 Chandra Call for Proposals.
The following JPO allocations are potentially available for this CLP
| HST | 42 orbits |
| JWST | 42 hrs |
| XMM | 280 ks |
| NuSTAR | 280 ks |
| Swift | 140 ks |
| NOIRLab | 1.4% (in nights) |
| AUI | 0.84% (in nights) |
A preliminary Letter of Intent is required and should be submitted to clp@cfa.harvard.edu by 6pm EDT 28 March 2024. The Letter of Intent is a PDF document that contains the following:
Each side of a sheet containing text or illustration will count as one page
| Science Justification | 6 pages |
| References | 1 page |
For more information, refer to the Call for Proposals
Proposals should be written in anonymized format suitable for Dual Anonymous Peer Review (DAPR).
For more information, see NASA's DAPR Guidelines and Chandra Peer Review Guidance on avoiding DAPR violations
If you have any questions, please contact the CXC Helpdesk either through the web interface or by email to cxchelp@cfa.harvard.edu.