Linking neutral gas inflows and outflows to offsets in the star-forming main sequence and mass-metallicity relation

@misc{weng2026linking,
  title = {{Linking neutral gas inflows and outflows to offsets in the star-forming main sequence and mass-metallicity relation}},
  author = {S Weng and M Pieri and A Saintonge and D Scholte and D. Muñoz Santos and T Hu and J Aguilar and S Ahlen and F Beutler and D Bianchi and D Brooks and A Carnero Rosell and F.J Castander and T Claybaugh and A de la Macorra and B Dey and P Doel and V.A Fawcett and J.E Forero-Romero and E Gaztañaga and S Gontcho A. Gontcho and G Gutierrez and A Kremin and M Landriau and L Le Guillou and A Meisner and R Miquel and J Moustakas and S Nadathur and W.J Percival and F Prada and I Pérez-Ràfols and C Ravoux and G Rossi and R Ruggeri and E Sanchez and C Saulder and D Schlegel and J Silber and M Siudek and G Tarlé and B.A Weaver and H Zou},
  howpublished = {HAL},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.01707},
  eprint = {2609.01707},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05758202v1},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Linking neutral gas inflows and outflows to offsets in the star-forming main sequence and mass-metallicity relation
AU  - S Weng
AU  - M Pieri
AU  - A Saintonge
AU  - D Scholte
AU  - D. Muñoz Santos
AU  - T Hu
AU  - J Aguilar
AU  - S Ahlen
AU  - F Beutler
AU  - D Bianchi
AU  - D Brooks
AU  - A Carnero Rosell
AU  - F.J Castander
AU  - T Claybaugh
AU  - A de la Macorra
AU  - B Dey
AU  - P Doel
AU  - V.A Fawcett
AU  - J.E Forero-Romero
AU  - E Gaztañaga
AU  - S Gontcho A. Gontcho
AU  - G Gutierrez
AU  - A Kremin
AU  - M Landriau
AU  - L Le Guillou
AU  - A Meisner
AU  - R Miquel
AU  - J Moustakas
AU  - S Nadathur
AU  - W.J Percival
AU  - F Prada
AU  - I Pérez-Ràfols
AU  - C Ravoux
AU  - G Rossi
AU  - R Ruggeri
AU  - E Sanchez
AU  - C Saulder
AU  - D Schlegel
AU  - J Silber
AU  - M Siudek
AU  - G Tarlé
AU  - B.A Weaver
AU  - H Zou
PY  - 2026
DA  - 2026/09/01
PB  - HAL
DO  - 10.48550/arxiv.2609.01707
UR  - https://hal.science/hal-05758202v1
AB  - Gas inflows and outflows regulate galaxy growth, but direct observational links between measured gas flows and galaxy scaling relations remain limited. Using ~6,000 star-forming galaxies with down-the-barrel Na I D absorption from DESI DR2, we examine how systems with detected neutral-gas inflows and outflows populate the star-forming main sequence (SFMS) and mass-metallicity relation (MZR). Inflow and outflow hosts are compared with stellar-mass- and redshift-matched controls, and with SFMS and MZR fits derived from galaxies without detected gas flows. Outflow hosts (v_flow ≤ -50 km s^−1) show enhanced sSFRs by 0.25-0.40 dex and elevated central metallicities by 0.04-0.06 dex in the lower-redshift sample. Slow inflow hosts (0 < v_flow < 100 km s^−1) show similarly enhanced sSFRs of 0.20-0.30 dex, but no significant metallicity offset, while fast inflow hosts (v_flow ≥ 100 km s^−1) show weaker SFR enhancement and modestly lower metallicities. Together, these trends support a regulator picture in which neutral gas flows trace different phases of the baryon cycle. Slow inflow hosts lie above the SFMS, consistent with accretion sustaining enhanced star formation without strong central metallicity dilution. This may indicate that inflowing gas is already metal-enriched or has mixed or enriched over extended timescales. By contrast, outflow hosts lie near the upper 1{σ} SFMS envelope, consistent with feedback regulating subsequent growth. Gas-flow hosts also show small but systematic offsets in the narrow 4000 Å break strength (D_n4000) relative to controls matched in redshift, stellar mass and SFR. Our results show that neutral gas flows are associated with population-level offsets from the SFMS and MZR, consistent with a baryon-cycle contribution to scaling-relation scatter.
ER  -