The First Blind Survey of Intervening NaI Absorbers: Incidence and Cosmic Evolution with DESI
Abstract
We present the first blind statistical survey of intervening NaI absorbers over the last ≃3~Gyr using quasar spectra from the Dark Energy Spectroscopic Instrument Data Release~1. We identify 3636 NaI D doublets at 0.01≲ zabs≲0.27 along 214,035 quasar sightlines. We quantify the survey selection function through end-to-end injection--recovery tests and estimate the residual contamination from visual inspection. The completeness reaches 50% at a rest-equivalent width of the NaI λ5891 line, W5891≃0.95 Angstrom, and the catalog-weighted purity is ≃77%. For the fiducial sample with 0.95<W5891<3.5 Angstrom, we measure the equivalent-width distribution (f(Wr)), absorber incidence (dN/dX), and cosmic NaI mass density (ΩNa I). From z≃0.25 to z≃0.03, dN/dX rises by a factor of ≃3.4 in both rest-equivalent-width subsamples, split at the median W5891=1.41 Angstrom, while ΩNa I increases by a similar factor. This corresponds to a smooth increase in the product of the comoving number density of NaI-absorbing hosts (ncom) and the cross-section of the NaI-bearing gas (σeff) with cosmic time. The similar evolution of ΩNa I and dN/dX indicates little change in the mean measured NaI column density per absorber. We also find preliminary evidence that NaI absorbers are associated with foreground galaxies at relatively small projected separations and that their quasar sightlines are redder than matched controls. These results support a picture in which NaI traces dense neutral gas in and around galaxies. Dedicated galaxy surveys and CGM/ISM simulations can test the inferred incidence and cross-section, while spectral stacking can probe the associated gas and dust.
Related
- ALMA Chemical Evolution (ACE) survey: The gas fundamental metallicity relation at cosmic noon
- Cosmic Evolution Survey: LOFAR 144 MHz imaging of the COSMOS field
- ALMA Chemical Evolution (ACE) survey: an overview -- extending dust and gas inference to low metallicities at cosmic noon
- ALMA Chemical Evolution (ACE) Survey: Molecular gas properties of low-mass, low-metallicity galaxies at cosmic noon
- ALMA Chemical Evolution (ACE) survey: the dust content of subsolar metallicity galaxies at cosmic noon
BibTeX
@misc{anand2026first,
title = {{The First Blind Survey of Intervening NaI Absorbers: Incidence and Cosmic Evolution with DESI}},
author = {Abhijeet Anand and Sowgat Muzahid},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.26794},
eprint = {2609.26794},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.26794},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The First Blind Survey of Intervening NaI Absorbers: Incidence and Cosmic Evolution with DESI
AU - Abhijeet Anand
AU - Sowgat Muzahid
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.26794
UR - https://arxiv.org/abs/2609.26794
AB - We present the first blind statistical survey of intervening NaI absorbers over the last ≃3~Gyr using quasar spectra from the Dark Energy Spectroscopic Instrument Data Release~1. We identify 3636 NaI D doublets at 0.01≲ z_abs≲0.27 along 214,035 quasar sightlines. We quantify the survey selection function through end-to-end injection--recovery tests and estimate the residual contamination from visual inspection. The completeness reaches 50% at a rest-equivalent width of the NaI λ5891 line, W_5891≃0.95 Angstrom, and the catalog-weighted purity is ≃77%. For the fiducial sample with 0.95<W_5891<3.5 Angstrom, we measure the equivalent-width distribution (f(W_r)), absorber incidence (dN/dX), and cosmic NaI mass density (Ω_Na I). From z≃0.25 to z≃0.03, dN/dX rises by a factor of ≃3.4 in both rest-equivalent-width subsamples, split at the median W_5891=1.41 Angstrom, while Ω_Na I increases by a similar factor. This corresponds to a smooth increase in the product of the comoving number density of NaI-absorbing hosts (n_com) and the cross-section of the NaI-bearing gas (σ_eff) with cosmic time. The similar evolution of Ω_Na I and dN/dX indicates little change in the mean measured NaI column density per absorber. We also find preliminary evidence that NaI absorbers are associated with foreground galaxies at relatively small projected separations and that their quasar sightlines are redder than matched controls. These results support a picture in which NaI traces dense neutral gas in and around galaxies. Dedicated galaxy surveys and CGM/ISM simulations can test the inferred incidence and cross-section, while spectral stacking can probe the associated gas and dust.
ER -