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Peer-reviewedCC BY 4.0The Astrophysical Journal

The KAGG Survey: KCWI Analysis of Gas around Galaxies at z ≈ 3–5

  • Grecco A. Oyarzún1,2
  • Marc Rafelski2,3
  • J. Xavier Prochaska4,5,6
  • Nissim Kanekar7
  • M. Neeleman8
  • M. E. Wisz9,4
  • Michele Fumagalli10,11
  • Regina A. Jorgenson9,12
12 affiliations
  1. 1The University of Oklahoma
  2. 2Johns Hopkins University
  3. 3Space Telescope Science Institute
  4. 4University of California
  5. 5Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)
  6. 6Division of Science
  7. 7Pune University
  8. 8National Radio Astronomy Observatory
  9. 9Maria Mitchell Observatory
  10. 10Università degli Studi di Milano-Bicocca
  11. 11INAF—Osservatorio Astronomico di Trieste
  12. 12Department of Physics & Astronomy
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Abstract

We present the KCWI Analysis of Gas around Galaxies (KAGG) survey of Ly α emission around damped Ly α absorbers (DLAs) at z ≈ 3–5 with the Keck Cosmic Web Imager (KCWI) integral-field spectrograph. The KAGG survey is characterized by the sample of 36 DLAs spanning a wide metallicity range, the wide search area for associated Ly α emission (impact parameter b ≲ 120 kpc), and the high emission sensitivity, reaching Ly α luminosities ≤10 ⁴² erg s ⁻¹ . We identify seven DLA Ly α emitters that are likely DLA galaxy candidates due to the good match between the Ly α emission and DLA redshifts. Based on a composite sample of 11 DLA Ly α emitters from KAGG and MUSE Analysis of Gas around Galaxies (MAGG), we find that the impact parameters of DLA Ly α emitters decrease with DLA metallicity, from b > 50 kpc at [M/H] ≈ −2 to b < 50 kpc at [M/H] ≈ −1. Including Ly α emitters at larger velocity offsets and at larger impact parameters from the DLAs, we construct samples of 35 “group” Ly α emitters and 17 “large-scale” Ly α emitters. We find that their impact parameters and incidence rates also depend on DLA metallicity. Based on simulations of our survey and comparisons with models of galaxy formation, we conclude that higher DLA metallicities are associated with higher halo masses. The low Ly α emission detection rate at low impact parameters suggests that most DLA galaxies either have low stellar masses ( M ≲ 10 ⁸ M ⊙ ) or have their Ly α emission suppressed due to H i resonant scattering and/or dust absorption.

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Cite

BibTeXRIS
BibTeX
@article{oyarzun2026kagg,
  title = {{The KAGG Survey: KCWI Analysis of Gas around Galaxies at z ≈ 3–5}},
  author = {Grecco A. Oyarzún and Marc Rafelski and J. Xavier Prochaska and Nissim Kanekar and M. Neeleman and M. E. Wisz and Michele Fumagalli and Regina A. Jorgenson},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/aea982},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea982},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - The KAGG Survey: KCWI Analysis of Gas around Galaxies at z ≈ 3–5
AU  - Grecco A. Oyarzún
AU  - Marc Rafelski
AU  - J. Xavier Prochaska
AU  - Nissim Kanekar
AU  - M. Neeleman
AU  - M. E. Wisz
AU  - Michele Fumagalli
AU  - Regina A. Jorgenson
PY  - 2026
DA  - 2026/10/27
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea982
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea982
AB  - We present the KCWI Analysis of Gas around Galaxies (KAGG) survey of Ly α emission around damped Ly α absorbers (DLAs) at z ≈ 3–5 with the Keck Cosmic Web Imager (KCWI) integral-field spectrograph. The KAGG survey is characterized by the sample of 36 DLAs spanning a wide metallicity range, the wide search area for associated Ly α emission (impact parameter b ≲ 120 kpc), and the high emission sensitivity, reaching Ly α luminosities ≤10 ⁴² erg s ⁻¹ . We identify seven DLA Ly α emitters that are likely DLA galaxy candidates due to the good match between the Ly α emission and DLA redshifts. Based on a composite sample of 11 DLA Ly α emitters from KAGG and MUSE Analysis of Gas around Galaxies (MAGG), we find that the impact parameters of DLA Ly α emitters decrease with DLA metallicity, from b > 50 kpc at [M/H] ≈ −2 to b < 50 kpc at [M/H] ≈ −1. Including Ly α emitters at larger velocity offsets and at larger impact parameters from the DLAs, we construct samples of 35 “group” Ly α emitters and 17 “large-scale” Ly α emitters. We find that their impact parameters and incidence rates also depend on DLA metallicity. Based on simulations of our survey and comparisons with models of galaxy formation, we conclude that higher DLA metallicities are associated with higher halo masses. The low Ly α emission detection rate at low impact parameters suggests that most DLA galaxies either have low stellar masses ( M ≲ 10 ⁸ M ⊙ ) or have their Ly α emission suppressed due to H i resonant scattering and/or dust absorption.
SN  - 1538-4357
SN  - 0004-637X
ER  -