The ALMA Survey of Gas Evolution in PROtoplanetary Disks

ALMA Large Program | Project Code: 2021.1.00128.L | Cycle 8

PI: Ke Zhang (University of Wisconsin-Madison)

https://agepro.das.uchile.cl

Associated image: Credit: AGE-PRO Collaboration, C. Agurto-Gangas / NSF/AUI/NSF NRAO/S. Dagnello.

1. Program Abstract

AGE-PRO (the ALMA Survey of Gas Evolution in PROtoplanetary Disks) is the first ALMA Large Program (103 hours) specifically designed to systematically trace the evolution of gas in protoplanetary disks. Gas is the dominant mass constituent of protoplanetary disks and its structure and evolution profoundly impact every major step of planet formation, including planetesimal formation, accretion of planetary atmospheres, and migration of planets. Yet a basic understanding of how the gas disk evolves and what mechanism drives its global evolution has been lacking.

Through deep molecular line observations of a carefully selected sample of 30 disks around M3–K6 stars in three nearby star-forming regions—Ophiuchus (0.5–1 Myr), Lupus (1–3 Myr), and Upper Scorpius (2–6 Myr)—AGE-PRO provides an unprecedented view into how the gas content in disks evolves over time. By combining observations of CO isotopologues and N₂H⁺ with advanced thermo-chemical modeling, AGE-PRO delivers robust measurements of disk gas mass and size for the full 30-disk sample.

Key findings include: (1) the median gas disk mass decreases with age, from ~6 M_Jup in Ophiuchus to ~0.68 and ~0.44 M_Jupin Lupus and Upper Sco; (2) gas and dust disk masses evolve on different timescales, evidenced by a “swing” in the gas-to-dust mass ratio; and (3) surviving disks retain more gas than expected, with implications for giant planet formation timescales. These findings are compared against key theoretical frameworks of disk evolution, including turbulent viscosity and magneto-hydrodynamical (MHD) disk winds. We find the AGE-PRO results favor the MHD disk wind mechanism over the viscous evolution.

AGE-PRO is a collaboration of more than 20 astronomers across multiple institutions. The results have been published in a coordinated set of 12 scientific publications (AGE-PRO I through XII) in a focus issue of The Astrophysical Journal, and all associated datasets are publicly available.

2. ALMA Large Program Project Codes

AGE-PRO is a single ALMA Large Program approved in Cycle 8. The project details are listed below.

Project Code	Title	PI
2021.1.00128.L	AGE-PRO: The ALMA Survey of Gas Evolution in PROtoplanetary Disks	Ke Zhang (U. Wisconsin-Madison)

Note: AGE-PRO is an ALMA Large Program (Cycle 8) with a total allocation of ~103 hours on the ALMA 12-m Array. Observations cover ALMA Bands 6 and 7.

3. Team Members

AGE-PRO is a collaboration of more than 20 astronomers across multiple institutions worldwide. The following list is compiled from the author lists of AGE-PRO publications. For the complete and up-to-date team list, see: https://agepro.das.uchile.cl/team

Name	Affiliation	Role
Ke Zhang	University of Wisconsin-Madison, USA	PI
Laura M. Perez	Universidad de Chile, Chile	Co-PI
Ilaria Pascucci	University of Arizona, USA	Co-PI
Paola Pinilla	University College London, UK	Co-PI
Lucas A. Cieza	Universidad Diego Portales, Chile	Co-I
John Carpenter	Joint ALMA Observatory (JAO), Chile	Co-I
Giovanni P. Rosotti	University of Milan, Italy	Co-I
Leon Trapman	University of Wisconsin-Madison, USA	Co-I
Benoit Tabone	Universite Paris-Saclay / CNRS / IAS, France	Co-I
Nicolas T. Kurtovic	Max Planck Institute for Extraterrestrial Physics, Germany	Co-I
Miguel Vioque	European Southern Observatory	Co-I
Dingshan Deng	University of Arizona, USA	Co-I
Carolina Agurto-Gangas	Universidad de Chile, Chile	Co-I
Dary A. Ruiz-Rodriguez	NRAO, USA	Co-I
Anibal Sierra	University College London, UK	Co-I
James M. Miley	Universidad de Santiago de Chile, Chile	Co-I
Rossella Anania	University of Milan, Italy	Co-I
Camilo Gonzalez-Ruilova	Universidad Diego Portales, Chile	Co-I
Estephani E. TorresVillanueva	University of Wisconsin-Madison, USA	Co-I
Aleksandra Kuznetsova	University of Connecticut	Co-I
Michiel R. Hogerheijde	Leiden University, Netherlands	Co-I
Kamber Schwarz	Max Planck Institute for Astronomy, Germany	Co-I

4. List of Publications

The AGE-PRO results were published in a Focus Issue of The Astrophysical Journal (Volume 989, Number 1, June 13, 2025). The full focus issue is available at: https://iopscience.iop.org/collections/apj-250623-01-Focus-on-AGE-PRO

For updates, see: https://agepro.das.uchile.cl/publications

4.1. AGE-PRO Focus Issue Papers

#	Title	Lead Author	Reference	DOI
I	Program Overview and Summary of First Results	K. Zhang et al.	2025 ApJ 989 1	10.3847/1538-4357/addebe
II	Dust and Gas Disk Properties in the Ophiuchus Star-forming Region	D. A. Ruiz-Rodriguez et al.	2025 ApJ 989 2	10.3847/1538-4357/add2ec
III	Dust and Gas Disk Properties in the Lupus Star-forming Region	D. Deng et al.	2025 ApJ 989 3	10.3847/1538-4357/add43a
IV	Dust and Gas Disk Properties in the Upper Scorpius Star-forming Region	C. Agurto-Gangas et al.	2025 ApJ 989 4	10.3847/1538-4357/adc7ab
V	Protoplanetary Gas Disk Masses	L. Trapman et al.	2025 ApJ 989 5	10.3847/1538-4357/adcd6e
VI	Comparison of Dust Evolution Models to AGE-PRO Observations	N. T. Kurtovic et al.	2025 ApJ 989 6	10.3847/1538-4357/add1d0
VII	Testing Accretion Mechanisms from Disk Population Synthesis	B. Tabone et al.	2025 ApJ 989 7	10.3847/1538-4357/adc7b1
VIII	The Impact of External Photoevaporation on Disk Masses and Radii in Upper Scorpius	R. Anania et al.	2025 ApJ 989 8	10.3847/1538-4357/adb587
—	Hints of Planet Formation Signatures in a Large-cavity Disk Studied in the AGE-PRO ALMA Large Program	A. Sierra et al.	2024 ApJ 974 102	10.3847/1538-4357/ad6e73
X	Dust Substructures, Disk Geometries, and Dust-disk Radii	M. Vioque et al.	2025 ApJ 989 9	10.3847/1538-4357/adc7b0
XI	Beam-corrected Gas Disk Sizes from Fitting ¹²CO Moment Zero Maps	L. Trapman et al.	2025 ApJ 989 10	10.3847/1538-4357/adc7af
XII	Extreme Millimeter Variability Detected in a Class II Disk	J. M. Miley et al.	2025 ApJ 989 11	10.3847/1538-4357/add25c

Note: All papers are open access. More papers in prep

5. Main Deliveries

• Calibrated ALMA datasets from Bands 6 and 7 for all 30 disks, available via the AGE-PRO website.
• Value-added data products: images, moment maps, radial profiles, visibility data, and derived physical quantities (disk masses, sizes, gas-to-dust ratios).
• Thermochemical model grids used to derive gas disk masses from CO isotopologue and N₂H⁺ observations (DALI models).
• Dust evolution model grids (DustPy + RADMC-3D) comparing observed trends to theoretical predictions.
• Population synthesis models for turbulence-driven and MHD wind-driven disk evolution scenarios.
• 12 peer-reviewed publications in a coordinated Focus Issue of The Astrophysical Journal.
• Code and analysis tools made available through Zenodo (e.g., https://zenodo.org/records/15360478 for Paper XI code).

6. Links to Other Resources

Resource	URL
AGE-PRO Project Website	https://agepro.das.uchile.cl
AGE-PRO Data Page	https://agepro.das.uchile.cl/data_page
AGE-PRO Theory / Models	https://agepro.das.uchile.cl/scripts_page
AGE-PRO Targets	https://agepro.das.uchile.cl/regions
AGE-PRO Publications	https://agepro.das.uchile.cl/publications
AGE-PRO Press Releases	https://agepro.das.uchile.cl/press
ALMA Archive (Project)	https://almascience.eso.org/alma-data/lp (search: AGE-PRO / 2021.1.00128.L)
ALMA LP Deliverables Page	https://almascience.eso.org/alma-data/lp/age-pro
ALMA Observatory Press Release	https://www.almaobservatory.org/en/press-releases/alma-reveals-lives-of-planet-forming-disks/
NRAO Press Release	https://public.nrao.edu/news/alma-planet-forming-disks/
IOP Focus Issue Page	https://iopscience.iop.org/collections/apj-250623-01-Focus-on-AGE-PRO

7. Main Science Drivers (Optional)

The overarching science question motivating AGE-PRO is: How does the gas content of protoplanetary disks evolve over time, and what physical mechanism drives this global evolution?

This question is fundamental because:

• Disk gas mass determines the type of planets that form: The available gas reservoir dictates whether a planet ends up as a gas giant, icy giant, or mini-Neptune.
• Gas drives planet migration: The direction and speed of planetary migration depend on the gas mass distribution.
• Gas-to-dust ratio regulates dust dynamics: The gas density and gas-to-dust mass ratio regulate the dynamical behavior of dust grains and larger solid bodies.
• Accretion mechanism is unknown: Two leading models—turbulent viscosity and MHD disk winds—predict different evolutionary pathways and can be distinguished by measuring gas mass and size evolution.
• Gas disk lifetime sets the giant planet formation clock: Most disks last 3–10 Myr. Understanding when the gas dissipates constrains the timescale for giant planet formation.

8. Observing Strategy (Optional)

AGE-PRO employs a carefully designed observing strategy to achieve its science goals:

8.1. Sample Selection

• 30 disks around M3–K6 stars (similar spectral type range to control for stellar mass effects).
• Three star-forming regions spanning the disk lifetime: Ophiuchus (10 disks, 0.5–1 Myr, embedded/Class I phase), Lupus (10 disks, 1–3 Myr, middle age), and Upper Scorpius (10 disks, 2–6 Myr, late stage).

8.2. Spectral Setup

• ALMA Band 6 (~1.3 mm): Dust continuum at 234 GHz + CO isotopologues (¹²CO, ¹³CO, C¹⁸O J=2–1). For Ophiuchus, also C¹⁷O. Serendipitous coverage of H₂CO, DCN, DCO⁺, N₂D⁺, CH₃CN, and other molecules.
• ALMA Band 7 (~1 mm): Dust continuum at 285 GHz + N₂H⁺ J=3–2 (critical for constraining the CO abundance and improving gas mass estimates by 5–10x).

8.3. Angular Resolution and Configurations

• Each target was observed with a combination of compact and extended antenna configurations to recover both large-scale and small-scale structure.
• Angular resolution ~0.3″ (Band 6), corresponding to ~45 au at the distance of these regions.

8.4. Key Methodology

• Gas masses derived using large grids of DALI thermochemical models, simultaneously fitting CO isotopologue and N₂H⁺ fluxes via MCMC (see Paper V).
• Gas disk sizes measured from ¹²CO moment-zero maps using beam-corrected fitting methods (see Paper XI).
• Dust disk properties derived via visibility fitting of 1.3 mm continuum (see Paper X).
• Results compared to dust evolution models (DustPy, Paper VI) and disk population synthesis models for turbulent viscosity and MHD wind-driven accretion (Paper VII).