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Cited by 132Galaxies: Formation, Evolution, PhenomenaStellar, planetary, and galactic studiesAstrophysics and Star Formation Studies

THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. XI. THE SPATIALLY RESOLVED RECENT STAR FORMATION HISTORY OF M31

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Lewis, Alexia R., Dolphin, Andrew E., Dalcanton, Julianne J., Weisz, Daniel R., Williams, Benjamin F., Bell, Eric F., Seth, Anil C., Simones, Jacob E. +10 more·2015·The Astrophysical Journal
DOI 10.1088/0004-637x/805/2/183
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Abstract

We measure the recent star formation history (SFH) across M31 using optical images taken with the Hubble Space Telescope as part of the Panchromatic Hubble Andromeda Treasury (PHAT). We fit the color–magnitude diagrams in ∼9000 regions that are ∼100 pc × 100 pc in projected size, covering a 0.5 square degree area (∼380 kpc 2 , deprojected) in the NE quadrant of M31. We show that the SFHs vary significantly on these small spatial scales but that there are also coherent galaxy-wide fluctuations in the SFH back to ∼500 Myr, most notably in M31's 10 kpc star-forming ring. We find that the 10 kpc ring is at least 400 Myr old, showing ongoing star formation (SF) over the past ∼500 Myr. This indicates the presence of molecular gas in the ring over at least 2 dynamical times at this radius. We also find that the ring's position is constant throughout this time, and is stationary at the level of 1 km s −1 , although there is evidence for broadening of the ring due to the diffusion of stars into the disk. Based on existing models of M31's ring features, the lack of evolution in the ring's position makes a purely collisional ring origin highly unlikely. Besides the well-known 10 kpc ring, we observe two other ring-like features. There is an outer ring structure at 15 kpc with concentrated SF starting ∼80 Myr ago. The inner ring structure at 5 kpc has a much lower star formation rate (SFR) and therefore lower contrast against the underlying stellar disk. It was most clearly defined ∼200 Myr ago, but is much more diffuse today. We find that the global SFR has been fairly constant over the last ∼500 Myr, though it does show a small increase at 50 Myr that is 1.3 times the average SFR over the past 100 Myr. During the last ∼500 Myr, ∼60% of all SF has occurred in the 10 kpc ring. Finally, we find that in the past 100 Myr, the average SFR over the PHAT survey area is 0.28 ± 0.03 with an average deprojected intensity of , which yields a total SFR of ∼0.7 when extrapolated to the entire area of M31's disk. This SFR is consistent with measurements from broadband estimates.

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  • Much of M31's recent star formation is concentrated in the 10 kpc ring, which stands out particularly strongly in the north as a coherent, nearly continuous structure traced by active star-forming regions.

    “First, much of M31's recent star formation is concentrated in the”

    From The Panchromatic Hubble Andromeda Southern Treasury (PHAST). II. The Spatially Resolved Recent Star Formation History in M31 (2026) · cites this paper as Lewis et al. 2015

    Section 5.4.1 reports that about 60% of star formation in the surveyed area over the last 400 Myr occurred in the 10 kpc ring. Section 4.1 describes coherent, continuous star-forming structures, and Section 5.4.1 identifies high-SFR associations along the ring’s northeast portion. But the study covers the northeast quadrant, so it does not establish that the ring stands out more strongly in the north than elsewhere in M31. (LLM, conf=0.82)

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  • Their decision to match the PHAST SFH calculation to that used previously by Lewis et al. (2015) for PHAT has produced seamless maps despite different observing strategies and depths of the two surveys.

    “Finally, we note that our decision to match the PHAST SFHcalculation to that used previously by Lewis et al. (2015) for PHAT has produced seamless maps despite different observing strategies and depths of the two surveys.”

    From The Panchromatic Hubble Andromeda Southern Treasury (PHAST). II. The Spatially Resolved Recent Star Formation History in M31 (2026) · cites this paper as Lewis et al. (2015)

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  1. [107]107. Williams, B. F., Dalcanton, J. J., Dolphin, A. E., et al. 2015, (arXiv:1504.02120) · arXiv

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Authors
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., Fouesneau, M., Guhathakurta, P., Johnson, L. C., Kalirai, J. S., Leroy, A. K., Monachesi, A., Rix, H.-W., & Schruba, A.
Affiliations
  • University of Washington (US)
  • RTX (United States) (US)
  • University of Michigan (US)
  • University of Utah (US)
  • University of Minnesota (US)
  • Max Planck Institute for Astronomy (DE)
  • University of California, Santa Cruz (US)
  • Space Telescope Science Institute (US)
  • National Radio Astronomy Observatory (US)
  • Max Planck Institute for Astrophysics (DE)
  • Max Planck Institute for Extraterrestrial Physics (DE)
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2015-06-02
Volume
805
Issue
2
Pages
183
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1088/0004-637x/805/2/183
OpenAlex
W1843140030
Cited by
132
References
101
Citations by year
2026: 7 · 2025: 16 · 2024: 14 · 2023: 9 · 2022: 9 · 2021: 8 · 2020: 11 · 2019: 13 · 2018: 14 · 2017: 13 · 2016: 11 · 2015: 7
FWCI
8.54
Type
journal article
Language
en
Open access
Licence
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • Max Planck Institute for Plasma Physics (submittedVersion)
  • Max Planck Digital Library (submittedVersion)
  • MPG.PuRe (Max Planck Society) (submittedVersion)
  • arXiv (Cornell University)
Funders
National Aeronautics and Space Administration (NAS 526555, 526555)
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-forming ring, color-magnitude diagram, spatially resolved star formation, molecular gas, star formation rate, ring origin, spiral disk galaxies, star formation rate surface density

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