CE31 - Physique subatomique et astrophysique

3D Mapping of the Distant Universe with Lyman Break Galaxies – HZ-3D-MAP

Submission summary

The HZ-3D-MAP project aims at addressing fundamental questions of cosmology through new observables, made accessible thanks to modern imaging and spectroscopic all-sky surveys. This research will shed new light on the following key questions. What is the origin of the primordial expansion of the Universe called inflation? What are the properties of the cosmic web over time? What is the multi-scale distribution of the gas in the intergalactic medium and around galaxies?

Our project is designed to map a large volume of the Universe with a sufficient density of Lyman Break Galaxies (LBG), with redshifts in the 2.1<z<3.5 range. This large sample will be used to work on three main projects: <br />1) We will measure the extremely-large-scale density fluctuations required to explore primordial inflation through the search for a non-Gaussian imprint. We will measure the LBG clustering in the angular power spectrum.
2) We will map the distant universe using the hydrogen absorption in the Ly-alpha forest detected in the spectrum of the LBGs down to 2Mpc scales. This 3D tomography will allow us to provide catalogs of voids and proto-clusters.
3) The study of LBG and quasar Ly-alpha forest close pairs will shed light on the relationship between gas and galaxies at high redshift, a key ingredient to complete our understanding of galaxy formation and to study the so-called circum-galactic medium (CGM).

We will select the LBGs using the photometric catalogs of the CFHT Large Area U-band Deep Survey (CLAUDS, 20 sq. deg.), the Deep Euclid U band Survey (DEUS, 10 sq. deg.) and the shallower but very wide (9,000 sq. deg.) u-band component of the Canada-France Imaging Survey (CFIS). CLAUDS is now complete and CFIS has already observed over 70% of its footprint. We are part of the DESI survey, conducted on the Mayall 4-meter telescope at Kitt Peak, Arizona. This survey will provide the redshifts of the LBGs and, via their spectra, of the hydrogen absorption in the Ly-$\alpha$ forest. DESI can simultaneously observe 5000 objects over 8 sq. deg., from the UV to the NIR, with a mean spectral resolution R~4000. It is ideally suited for the goals of this proposal. The DESI main survey began in May 2021 for a duration of five years.

During the first year of HZ-3D-MAP, the very deep CLAUDS catalog will allow us to finalize the LBG selection and, combined with DESI, to measure the first 3D maps. Then, CFIS, which provides a much wider footprint in overlap with the sky coverage of DESI, will be utilized over the whole HZ-3D-MAP footprint. We are planning three complementary surveys:

1) A wide photometric survey of 9,000 sq. deg. for the measurement of LBG clustering with the angular correlation function. We are aiming a target density of (500 per sq. deg) LBGs to r<23.8 selected with CFIS photometric catalog.
2) A deep spectroscopic survey of 100 sq. deg with DESI for tomography of the intergalactic medium using the Ly-alpha forest of LBGs. We will observe a dense sample of LBGs of (500 per sq. deg) to $r<23.8$. To achieve a signal-to-noise ratio of the order of 2 per 1-Mpc pixel, we will use a DESI exposure time of about 5 hours.
3) A sparse spectroscopic survey over the DESI footprint overlapping CFIS footprint. For the CGM studies, we expect ~5 close pairs of (LBG-QSO) targets with a small angular separation (<20-30'').

We will structure our effort around three complementary activities, each driven by a science topic (very-large-scale clustering, 3D tomography and interplay between galaxies and gas at high-z). The ANR funding will mainly bring to the project the resources required to recruit three post-docs, to travel mostly to US and to organize a conference on the mapping of the distant Universe.

Project coordination

Christophe YECHE (Commissariat à l'énergie atomique et aux énergies alternatives)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


IAP Institut d'astrophysique de Paris
DPhP Commissariat à l'énergie atomique et aux énergies alternatives
AIM Commissariat à l'énergie atomique et aux énergies alternatives
LAM Centre national de la recherche scientifique

Help of the ANR 547,819 euros
Beginning and duration of the scientific project: - 48 Months

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