en
Scientific article
English

Metal-enriched galactic outflows shape the mass–metallicity relationship

Published inMonthly Notices of the Royal Astronomical Society, vol. 481, no. 2, p. 1690-1706
Publication date2018
Abstract

The gas-phase metallicity of low-mass galaxies increases with increasing stellar mass (M*) and is nearly constant for high-mass galaxies. Theory suggests that this tight mass–metallicity relationship is shaped by galactic outflows removing metal-enriched gas from galaxies. Here, we observationally model the outflow metallicities of the warm outflowing phase from a sample of seven local star-forming galaxies with stellar masses between 107and 1011 M⊙. We estimate the outflow metallicities using four weak rest-frame ultraviolet absorption lines, the observed stellar continua, and photoionization models. The outflow metallicity is flat with M*, with a median metallicity of 1.0 ± 0.6 Z⊙. The observed outflows are metal-enriched: low and high-mass galaxies have outflow metallicities 10–50 and 2.6 times larger than their interstellar medium (ISM) metallicities, respectively. The observed outflows are mainly composed of entrained ISM gas with at most 22 per cent of the metals directly coming from recent supernovae enrichment. The metal outflow rate shallowly increases with M*, as M0.2±0.1∗ because the mass outflow rate shallow increases with M*. Finally, we normalize the metal outflow rate by the rate at which star formation retains metals to calculate the metal-loading factor. The metal-loading factor inversely scales with M*. The normalization and scaling of the metal-loading factor agree with analytic expressions that reproduce observed mass-metallicity relations. Galactic outflows fundamentally shape the observed mass–metallicity relationship.

Keywords
  • ISM
  • Jets and outflows
  • Galaxies
  • Evolution
  • Formation
  • Ultraviolet
Citation (ISO format)
CHISHOLM, John Peter, TREMONTI, C, LEITHERER, C. Metal-enriched galactic outflows shape the mass–metallicity relationship. In: Monthly Notices of the Royal Astronomical Society, 2018, vol. 481, n° 2, p. 1690–1706. doi: 10.1093/mnras/sty2380
Main files (1)
Article (Published version)
accessLevelRestricted
Identifiers
ISSN of the journal0035-8711
283views
0downloads

Technical informations

Creation06/27/2019 8:27:00 AM
First validation06/27/2019 8:27:00 AM
Update time03/15/2023 5:45:00 PM
Status update03/15/2023 5:44:59 PM
Last indexation01/17/2024 5:48:48 AM
All rights reserved by Archive ouverte UNIGE and the University of GenevaunigeBlack