Discovery of a Damped Ly α Absorber Originating in a Spectacular Interacting Dwarf Galaxy Pair at z = 0.026

Erin Boettcher*, Neeraj Gupta, Hsiao Wen Chen, Mandy C. Chen, Gyula I.G. Józsa, Gwen C. Rudie, Sebastiano Cantalupo, Sean D. Johnson, S. A. Balashev, Françoise Combes, Kathy L. Cooksey, Claude André Faucher-Giguère, Jens Kristian Krogager, Sebastian Lopez, Emmanuel Momjian, Pasquier Noterdaeme, Patrick Petitjean, Marc Rafelski, Raghunathan Srianand, Gregory L. WalthFakhri S. Zahedy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We present the discovery of neutral gas detected in both damped Lyα absorption (DLA) and H i 21 cm emission outside of the stellar body of a galaxy, the first such detection in the literature. A joint analysis between the Cosmic Ultraviolet Baryon Survey and the MeerKAT Absorption Line Survey reveals an H i bridge connecting two interacting dwarf galaxies (log (M star/M ⊙) = 8.5 ± 0.2) that host a z = 0.026 DLA with log[N(H i)/cm-2] = 20.60 ± 0.05 toward the QSO J2339-5523 (z QSO = 1.35). At impact parameters of d = 6 and 33 kpc, the dwarf galaxies have no companions more luminous than ≈0.05L ∗ within at least "v = ±300 km s-1 and d ≈ 350 kpc. The H i 21 cm emission is spatially coincident with the DLA at the 2σ-3σ level per spectral channel over several adjacent beams. However, H i 21 cm absorption is not detected against the radio-bright QSO; if the background UV and radio sources are spatially aligned, the gas is either warm or clumpy (with a spin temperature to covering factor ratio T s /f c > 1880 K). Observations with VLT-MUSE demonstrate that the α-element abundance of the ionized interstellar medium (ISM) is consistent with the DLA (≈10% solar), suggesting that the neutral gas envelope is perturbed ISM gas. This study showcases the impact of dwarf-dwarf interactions on the physical and chemical state of neutral gas outside of star-forming regions. In the SKA era, joint UV and H i 21 cm analyses will be critical for connecting the cosmic neutral gas content to galaxy environments.

Original languageEnglish (US)
Article numberL33
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Feb 1 2022

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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