Letters of Intent for 2015

LoI 2015-206
Focus Meeting: New Light on First Light


6 August 2015 to 6 August 2015


to be held during the next General Assembly of the IAU, in Honolulu, HI USA Aug. 3-14, United States


Rachel Osten (osten@stsci.edu)

Coordinating division:

Division J Galaxies and Cosmology

Chair of SOC:

Massimo Stiavelli (STScI)

Chair of LOC:




How do we find the first objects in the universe?

Was the reionization of the universe a single event or was it extended?

What sets the parameters of reionization?



A study of the first stars and their end products (supernovae and mini-quasars) is important for understanding the conditions present in the early universe. These objects make up the first galaxies and star clusters. Advances with current instrumentation at a variety of wavelengths are pushing the redshift frontier to critical times when reionization may have been occurring. The reionization of the universe is a major transition state of the primary components of the universe at that point. The process by which this occurred and the sources involved are important for a deeper understanding of the early universe. A multi-wavelength approach is necessary to identifying and studying the first stars, supernovae, quasars and galaxies, and will involve a collaborative effort between ground-based near-infrared and radio telescopes, and space-based near- and mid-infrared telescopes and high energy telescopes.

What is the best strategy to use? How will we be certain that these objects do represent the first generation of stars? What do these objects tell us about the conditions present in the early universe?

To paraphrase John Donne, “no telescope is an island.” Many of the scientific questions which motivate the current and future set of large ground- and space-based telescopes have threads in common. The universe does not know artificial splits of wavelength or observing technique -- these are imposed by humans. This focus meeting is designed to address some of the large-scale questions related to the early universe and demonstrate how observations can be used to make progress in answering those questions.

The proposed focus meeting will be one day in length, and focus on topics listed above. The date given is notional, and can be changed to any day within the schedule of the General Assembly.

The topics listed above are timely, as recent developments have shown progress in addressing them [ALMA constraints on redshifts, high redshift galaxies seen in the Hubble Ultra-Deep Field, high redshift GRBs seen by Swift]. They also illustrate the complementarity inherent in science done at different wavelengths. The aim is to think synergistically about how the purported first light objects can be discovered, characterized, and interpreted. The general assembly is an excellent venue for bringing together these diverse communities. This proposal originates from representatives of several current and future large astronomical facilities .

The 2015 time frame is propitious, as it is midway through the decade and offers the opportunity for reflection on progress towards answering these overarching questions. The time frame is also forward-looking, as preparations begin for the next sequence of advanced telescopes. A broad discussion is necessary to include the contributions of different types of observations towards addressing these topics. The General Assembly offers a venue for astronomers from different countries and scientific communities to come together, and so is appropriate for the meeting being proposed. In addition to the attendees to the General Assembly, we would also like to broaden participation through web interaction with astronomers at other institutions.

IAU General Assembly
Honolulu, 3-14 August 2015

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