Two growing modes and the morphology-quiescence relation in isolated galaxies
Abstract
Quiescence in galaxies correlates strongly with the central density/morphology of the stellar distribution. We investigate two possible explanations for this morphology-quiescence relation: (1) the central density results from a dissipative core-building event (`compaction') that feeds an active galactic nucleus (AGN) that quenches the galaxy and (2) the central density results from inside-out growth by galaxy-wide star formation that is quenched by processes unrelated to the central density. We aim to distinguish these two scenarios using the MaNGA survey to determine profiles of stellar age, specific star formation rate (sSFR), and gas-phase metallicity (O/H) as a function of stellar mass surface density within 1 kpc (Σ∗,1 kpc) and total stellar mass (M∗). We find that gradients in age, sSFR, and O/H depend on the galaxy's position on the Σ∗,1 kpc-M∗ diagram, suggesting at least two evolutionary pathways. The first pathway consists of galaxies with low Σ∗,1 kpc for their M∗, whose centres are old, metal-rich, and suppressed in sSFR compared to their outskirts, consistent with the inside-out growth scenario. The second pathway, consistent with a compaction-like core-building scenario, consists of galaxies with higher Σ∗, 1 kpc for their M∗, whose centres are younger, enhanced in sSFR, and metal-deficient compared to their outskirts. Moreover, the WISE-selected AGN fraction peaks in the same area of the Σ∗,1 kpc-M∗ diagram as the core-building pathway. The sSFR profiles of the quiescent population suggest that galaxies on the compaction-like path quench uniformly, while those on the inside-out growing path quench their centres first. Our results imply that both pathways contribute to the morphology-quiescence relation.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2019
- DOI:
- 10.1093/mnras/stz1377
- arXiv:
- arXiv:1810.12298
- Bibcode:
- 2019MNRAS.487.1927W
- Keywords:
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- galaxies: evolution;
- galaxies: general;
- galaxies: stellar content;
- galaxies: structure;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 15 pages, 10 figures, 2 appendices, MNRAS accepted