In its first billion years, the Universe underwent two rapid transitions. First, it transitioned from an ionized state to a nearly completely neutral state, an era that has been extensively and productively probed with the cosmic microwave background for multiple decades. The second transition was from the nearly completely neutral state back to a nearly fully ionized state. This second transition, involved the formation of the first stars, the first black holes, and the assembly of the first galaxies. Known as Cosmic Dawn and the Epoch of Reinoization, it is only now beginning to be revealed. A combination of ground- and space-based telescopes is beginning to detect and study youthful galaxies near the end of the Epoch of Reionization. A small number of gamma-ray bursts from early generations of stars have also been detected. These observations constitute only the first steps, however. The JWST will identify galaxies much earlier in the Epoch of Reionization, and various space-based missions offer the potential of probing even deeper into the Cosmic Dawn, potentially to the era of the formation of the first stars.
The New Worlds, New Horizons Decadal Survey identified "Cosmic Dawn" as one of the three science objectives for this decade, and it will likely continue to be a research focus well into the next decade. In order to realize the potential of probing as deeply into the Cosmic Dawn epoch, new space-based missions will be needed to provide imaging and spectroscopic capabilities, likely across the electromagnetic spectrum and even including multi-messenger approaches. Studies of the first black holes, either with X-ray telescopes or gravitational wave detectors, offer the possibility for synergies with the Physics of the Cosmos Program.
This Cosmic Dawn Science Interest Group [SIG #3] will work with the COPAG to collect community input and define long-term Cosmic Origins science objectives toward Cosmic Dawn that can be addressed by space-based observations. A primary goal for the SIG will be to identify a compelling suite of science cases to provide programmatic focal points that would justify and energize the community to support investment in next generation missions or facilities. The SIG will also be expected to suggest potential technologies for further development, with the expectation that the SIG will work with the community to update the existing community-based roadmap for technology development for missions of different scales. The SIG will facilitate communication that will merge the needs and desires of the science community with the achievements and plans of the technology community. The SIG activities are expected to occur over an extended period of time, with results reported at periodic intervals (quarterly or semi-annually) to the COPAG Executive Committee and the Astrophysics Subcommittee. The SIG is open to any interested members of the community, and we welcome any and all input.