The resolved star-formation efficiency of early-type galaxies
ABSTRACT Understanding how and why star formation varies between galaxies is fundamental to our comprehension of galaxy evolution. In particular, the star-formation efficiency (SFE; star-formation rate or SFR per unit cold gas mass) has been shown to vary substantially both across and within galaxies. Early-type galaxies (ETGs) constitute an extreme case, as about a quarter have detectable molecular gas reservoirs but little to no detectable star formation. In this work, we present a spatially resolved view of the SFE in 10 ETGs, combining state-of-the-art Atacama Large Millimeter/submillimeter Array (ALMA) and Multi Unit Spectroscopic Explorer (MUSE) observations. Optical spectroscopic line diagnostics are used to identify the ionized emission regions dominated by star formation, and reject regions where the ionization arises primarily from other sources. We identify very few regions where the ionization is consistent with pure star formation. Using ${\rm H}\alpha$ as our SFR tracer, we find that previous integrated measurements of the star-formation rate based on UV and 22 $\mu$m emission are systematically higher than the SFR measured from ${\rm H}\alpha$. However, for the small number of regions where ionization is primarily associated with star formation, the SFEs are around 0.4 dex higher than those measured in star-forming galaxies at a similar spatial resolution (with depletion times ranging from $10^8$ to $10^{10}$ yr). Whilst the SFE of ETGs is overall low, we find that the SFEs of individual regions within ETGs can be similar to, or higher than, similar sized regions within star-forming galaxies.
Authors
- Jindra Gensior (ORCID: https://orcid.org/0000-0001-6119-9883)
- Francesco Belfiore (ORCID: https://orcid.org/0000-0002-2545-5752)
- Ryan Chown (ORCID: https://orcid.org/0000-0001-8241-7704)
- Martin Bureau (ORCID: https://orcid.org/0000-0003-4980-1012)
- Toshiki Saito (ORCID: https://orcid.org/0000-0002-2501-9328)
- Ilaria Ruffa (ORCID: https://orcid.org/0000-0002-4578-1205)
- Woorak Choi (ORCID: https://orcid.org/0000-0001-5033-7208)
- Jacob S Elford (ORCID: https://orcid.org/0000-0002-6139-2226)
- Ashley T. Barnes (ORCID: https://orcid.org/0000-0003-0410-4504)
- Frank Bigiel (ORCID: https://orcid.org/0000-0003-0166-9745)
- P. Sánchez–Blázquez (ORCID: https://orcid.org/0000-0003-0651-0098)
- Thomas G. Williams (ORCID: https://orcid.org/0000-0002-0012-2142)
- Brent A Groves (ORCID: https://orcid.org/0000-0002-9768-0246)
- Simon C. O. Glover (ORCID: https://orcid.org/0000-0001-6708-1317)
- Eva Schinnerer (ORCID: https://orcid.org/0000-0002-3933-7677)
- Timothy A. Davis (ORCID: https://orcid.org/0000-0003-4932-9379)
- Ralf S. Klessen (ORCID: https://orcid.org/0000-0002-0560-3172)
- Fu-Heng Liang (ORCID: https://orcid.org/0000-0003-2496-1247)
- Hsi-An Pan (ORCID: https://orcid.org/0000-0002-1370-6964)
- Daniel A. Dale (ORCID: https://orcid.org/0000-0002-5782-9093)
- M. Sarzi (ORCID: https://orcid.org/0000-0003-2227-4902)
- Dario Colombo
Institutions
- Tamkang University (TW)
- Universidad Complutense de Madrid (ES)
- University of Wyoming (US)
- Shizuoka University (JP)
- European Southern Observatory (DE)
- University of Bonn (DE)
- Harvard University (US)
- The University of Western Australia (AU)
- Heidelberg University (DE)
- Armagh Observatory & Planetarium (GB)
- Arcetri Astrophysical Observatory (IT)
- Harvard University Press (US)
- University of Oxford (GB)
- Royal Observatory (GB)
- Max Planck Institute for Astronomy (DE)
- Center for Astrophysics Harvard & Smithsonian (US)
- International Centre for Radio Astronomy Research (AU)
- The Ohio State University (US)
- Cardiff University (GB)
- Universidad Diego Portales (CL)
- McMaster University (CA)
- University of Edinburgh (GB)
Publication Details
- Journal
- Monthly Notices of the Royal Astronomical Society
- Published
- 2025-03-26
- DOI
- https://doi.org/10.1093/mnras/staf498
- Citations
- 1
- Primary Topic
- Astronomy and Astrophysical Research
- Type
- article
- Field-Weighted Citation Impact
- 1.19
Funders
- Science and Technology Facilities Council