Linking neutral gas inflows and outflows to offsets in the star-forming main sequence and mass-metallicity relation
Year: 2026
Type: preprint
Abstract: 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 $\leq$ -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 $\geq$ 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_n$4000) 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.
Source: arXiv (Cornell University)
Authors: Weng, S., Pieri, M., Saintonge, A., Scholte, D., Santos, D. Muñoz, Hu, T., Aguilar, J., Ahlen, S., Beutler, F., Bianchi, D., Brooks, D., Rosell, A. Carnero, Castander, F. J., Claybaugh, T., de la Macorra, A., Dey, B., Doel, P., Fawcett, V. A., Forero-Romero, J. E., Gaztañaga, E., Gontcho, S. Gontcho A, Gutierrez, G., Kremin, A., Landriau, M., Guillou, L. Le, Meisner, A., Miquel, R., Moustakas, J., Nadathur, S., Percival, W. J., Prada, F., Pérez-Ràfols, I., Ravoux, C., Rossi, G., Ruggeri, R., Sanchez, E., Saulder, C., Schlegel, D., Silber, J., Siudek, M., Tarlé, G., Weaver, B. A., Zou, H.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, California Institute of Technology, Ministerio de Ciencia, Innovación y Universidades, Agence Nationale de la Recherche, Chinese Academy of Sciences, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Office of Science, Jet Propulsion Laboratory, Science and Technology Facilities Council, Agencia Estatal de Investigación, Division of Astronomical Sciences, High Energy Physics, Lawrence Berkeley National Laboratory
Awards: G1044631029, G1079818582, G1105844351, G1143651532, G1175115578, G1286236842, G1632040200, G1813527838, G1863003419, G2262748287, G294895050, G300979063, G3083819904, G3452655474, G3470217882, G3480869486, G419881185, G425668148, G42916606, G4501827968, G491712853, G498139845, G5080475149, G5264466959, G5635532810, G593054264, G6652958823, G6876926712, G7084143925, Management and Operations of the National Optical Astronomy Observatory, G7354628648, G7395345766, G759921648, G7805626310, G7863371703, Exploiting two large astrophysical surveys: WEAVE-QSO and J-PAS, G8345352404, G8497050386, G8667377315, G969889393
OpenAlex ID: W7207751531