PHAT. XIX. The Ancient Star Formation History of the M31 Disk
Open accessAbstract
We map the star formation history across M31 by fitting stellar evolution models to color–magnitude diagrams of each 83″ × 83″ (0.3 × 1.4 kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost portion. We find that most of the star formation occurred prior to ∼8 Gyr ago, followed by a relatively quiescent period until ∼4 Gyr ago, a subsequent star formation episode about 2 Gyr ago, and a return to relative quiescence. There appears to be little, if any, structure visible for populations with ages older than 2 Gyr, suggesting significant mixing since that epoch. Finally, assuming a Kroupa initial mass function from 0.1 to 100 M ⊙ , we find that the total amount of star formation over the past 14 Gyr in the area over which we have fit models is 5 × 10 10 M ⊙ . Fitting the radial distribution of this star formation and assuming azimuthal symmetry, (1.5 ± 0.2) × 10 11 M ⊙ of stars has formed in the M31 disk as a whole, (9 ± 2) × 10 10 M ⊙ of which has likely survived to the present after accounting for evolutionary effects. This mass is about one-fifth of the total dynamical mass of M31.
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The measured SFR in the log-age 8.7-8.6 bin agrees with the ancient SFH of Williams et al. (2017) over the same interval.
“The measured SFR in the log-age 8.7-8.6 bin agrees with the ancient SFH of Williams et al. (2017) over the same interval, providing an important consistency check at the boundary between the two analyses.”
From The Panchromatic Hubble Andromeda Southern Treasury (PHAST). II. The Spatially Resolved Recent Star Formation History in M31 (2026) · cites this paper as Williams et al. (2017)
The SFH results for PHAST regions with density lower than 1.5 stars per arcsecond squared, extending back to 1.2 Gyr, are in striking agreement with the ancient SFH seen in PHAT.
“These results are in striking agreement with the ancient SFH seen in PHAT (Williams et al. 2017).”
From The Panchromatic Hubble Andromeda Southern Treasury (PHAST). II. The Spatially Resolved Recent Star Formation History in M31 (2026) · cites this paper as Williams et al. 2017
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Lewis, A. R., Dolphin, A. E., Dalcanton, J. J., Weisz, D. R., Williams, B. F., Bell, E. F., Seth, A. C., Simones, J. E., Skillman, E. D., Choi, Y., et al. (2015) · The Astrophysical Journal · doi:10.1088/0004-637x/805/2/183 · Cited by 132 · see citing works
Self-citationClues about the star formation history of the M31 disc from WFPC2 photometry
Williams, B. F. (2002) · Monthly Notices of the Royal Astronomical Society · doi:10.1046/j.1365-8711.2002.05088.x · Cited by 44 · see citing works
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On the duration of the embedded phase of star formation
Kim, J., Chevance, M., Kruijssen, J. M. D., Schruba, A., Sandstrom, K., Barnes, A. T., Bigiel, F., Blanc, G. A., Cao, Y., Dale, D. A., et al. (2021) · Monthly Notices of the Royal Astronomical Society · doi:10.1093/mnras/stab878 · Cited by 95 · see citing works
Lazzarini, M., Williams, B. F., Durbin, M. J., Dalcanton, J. J., Smercina, A., Bell, E. F., Choi, Y., Dolphin, A., Gilbert, K., Guhathakurta, P., et al. (2022) · The Astrophysical Journal · doi:10.3847/1538-4357/ac7568 · Cited by 28 · see citing works
Self-citationDark matter fraction derived from the m31 rotation curve
Hammer, F., Yang, Y. B., Amram, P., Chemin, L., Mamon, G. A., Wang, J. L., Akib, I., Jiao, Y. J., & Wang, H. F. (2025) · Astronomy & Astrophysics · doi:10.1051/0004-6361/202452753 · Cited by 6 · see citing works
Wainer, T. M., Williams, B. F., Chen, Z., Lazzarini, M., Dalcanton, J. J., Bell, E. F., Goold, K., Dolphin, A., Durbin, M. J., Dubón, S. L. F., et al. (2026) · The Astrophysical Journal · doi:10.3847/1538-4357/ae6db9
“The ancient SFH derived from the PHAT survey shows that M31 experienced a strong enhancement in star formation ∼ 2 Gyr ago, during which the global SFR reached upwards of 6M ⊙ , yr − 1 , followed by a gradual decrease toward quiescence (Williams et al. 2015, 2017).”
InfluentialSelf-citation
- Authors
- Williams, B. F., Dolphin, A. E., Dalcanton, J. J., Weisz, D. R., Bell, E. F., Lewis, A. R., Rosenfield, P., Choi, Y., Skillman, E., & Monachesi, A.
- Affiliations
- University of Washington (US)
- RTX (United States) (US)
- University of Michigan (US)
- Harvard University (US)
- University of Arizona (US)
- University of Minnesota (US)
- University of La Serena (CL)
- Corresponding author
- Dolphin, Andrew E.
- Weisz, Daniel R.
- Bell, Eric F.
- Lewis, Alexia R.
- Rosenfield, Philip
- Skillman, Evan
- Monachesi, Antonela
- ORCID
- Venue
- The Astrophysical Journal
- Publisher
- American Astronomical Society
- Published
- 2017-09-10
- Volume
- 846
- Issue
- 2
- Pages
- 145
- ISSN
- 0004-637X (ISSN-L)
- 1538-4357
- OpenAlex
- W2755451496
- Cited by
- 107
- References
- 2
- Citations by year
- 2026: 3 · 2025: 13 · 2024: 13 · 2023: 16 · 2022: 11 · 2021: 12 · 2020: 11 · 2019: 18 · 2018: 8 · 2017: 2
- FWCI
- 5.83
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astrophysical Journal (publishedVersion)
- UA Campus Repository (The University of Arizona) (acceptedVersion)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
- Keywords
- M31, star formation history, disk galaxies, stellar populations, stellar evolution models, color-magnitude diagram, initial mass function, Kroupa IMF, chemical mixing, stellar mass, dynamical mass
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