WISDOM project – XXIII. Star formation efficiencies of eight early-type galaxies and bulges observed with SITELLE and ALMA

ABSTRACT Early-type galaxies (ETGs) are known to harbour dense spheroids of stars with scarce star formation (SF). Approximately a quarter of these galaxies have rich molecular gas reservoirs yet do not form stars efficiently. These gas-rich ETGs have properties similar to those of bulges at the centres of spiral galaxies. We use spatially resolved observations (${\sim} 100$ pc resolution) of warm ionized-gas emission lines (H $\beta$, [O iii], [N ii], H $\alpha$, and [S ii]) from the imaging Fourier transform spectrograph SITELLE at the Canada–France–Hawaii Telescope and cold molecular gas [12CO(2–1) or 12CO(3–2)] from the Atacama Large Millimeter/submillimeter Array to study the SF properties of eight ETGs and bulges. We use the ionized-gas emission lines to classify the ionization mechanisms and demonstrate a complete absence of regions dominated by SF ionization in these ETGs and bulges, despite abundant cold molecular gas. The ionization classifications also show that our ETGs and bulges are dominated by old stellar populations. We use the molecular gas surface densities and H $\alpha$-derived SF rates (in spiral galaxies outside of the bulges) or upper limits (in ETGs and bulges) to constrain the depletion times (inverse of the SF efficiencies), suggesting again suppressed SF in our ETGs and bulges. Finally, we use the molecular gas velocity fields to measure the gas kinematics, and show that bulge dynamics, particularly the strong shear due to the deep and steep gravitational potential wells, is an important SF regulation mechanism for at least half of our sample galaxies.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-04-26
DOI
https://doi.org/10.1093/mnras/staf675
Citations
1
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
1.19

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article

WISDOM project – XXIII. Star formation efficiencies of eight early-type galaxies and bulges observed with SITELLE and ALMA

Jindra Gensior, Laurie Rousseau-Nepton, Martin Bureau, Ilaria Ruffa et al.
1 citations
Monthly Notices of the Royal Astronomical Society
Astronomy and Astrophysical Research
1.19
article

WISDOM project – XXIII. Star formation efficiencies of eight early-type galaxies and bulges observed with SITELLE and ALMA

Jindra Gensior, Laurie Rousseau-Nepton, Martin Bureau, Ilaria Ruffa, Woorak Choi, Jacob S Elford, Hope Boyce, Thomas G. Williams, Hengyue Zhang, Michele Cappellari, Timothy A. Davis, Fu-Heng Liang, Daryl Haggard, Thomas Martin, Anan Lu, Laurent Drissen, Carter Rhea, Sara Babic, Benjamin Cheung, Carmelle Robert, M. Sarzi
article en
1 citations

Abstract

ABSTRACT Early-type galaxies (ETGs) are known to harbour dense spheroids of stars with scarce star formation (SF). Approximately a quarter of these galaxies have rich molecular gas reservoirs yet do not form stars efficiently. These gas-rich ETGs have properties similar to those of bulges at the centres of spiral galaxies. We use spatially resolved observations (${\sim} 100$ pc resolution) of warm ionized-gas emission lines (H $\beta$, [O iii], [N ii], H $\alpha$, and [S ii]) from the imaging Fourier transform spectrograph SITELLE at the Canada–France–Hawaii Telescope and cold molecular gas [12CO(2–1) or 12CO(3–2)] from the Atacama Large Millimeter/submillimeter Array to study the SF properties of eight ETGs and bulges. We use the ionized-gas emission lines to classify the ionization mechanisms and demonstrate a complete absence of regions dominated by SF ionization in these ETGs and bulges, despite abundant cold molecular gas. The ionization classifications also show that our ETGs and bulges are dominated by old stellar populations. We use the molecular gas surface densities and H $\alpha$-derived SF rates (in spiral galaxies outside of the bulges) or upper limits (in ETGs and bulges) to constrain the depletion times (inverse of the SF efficiencies), suggesting again suppressed SF in our ETGs and bulges. Finally, we use the molecular gas velocity fields to measure the gas kinematics, and show that bulge dynamics, particularly the strong shear due to the deep and steep gravitational potential wells, is an important SF regulation mechanism for at least half of our sample galaxies.

Monthly Notices of the Royal Astronomical SocietyVol. 540(1)
Space Science Institute (US), European Southern Observatory (DE), University of Toronto (CA), Yonsei University (KR), ZHAW Zurich University of Applied Sciences (CH), University of Zurich (CH), Armagh Observatory & Planetarium (GB), Arcetri Astrophysical Observatory (IT), University of Oxford (GB), Royal Observatory (GB), Canadian Institute for Theoretical Astrophysics (CA), Université Laval (CA), McGill University (CA), Université de Montréal (CA), Cardiff University (GB), McMaster University (CA), University of Edinburgh (GB)
Royal Astronomical Society, University of Oxford
Openalex Percentile: Top 22%
Astronomy and Astrophysical Research
1.19
DOIOpen Access PDFOpenAlex
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