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No certainty of a Milky Way–Andromeda collision (2025)
Journal Article
Sawala, T., Delhomelle, J., Deason, A. J., Frenk, C. S., Häkkinen, J., Johansson, P. H., Keitaanranta, A., Rawlings, A., & Wright, R. (online). No certainty of a Milky Way–Andromeda collision. Nature Astronomy, https://doi.org/10.1038/s41550-025-02563-1

It is commonly believed that our own Milky Way is on a collision course with the neighbouring Andromeda galaxy. As a result of their merger, predicted in around 5 billion years, the two large spiral galaxies that define the present Local Group would... Read More about No certainty of a Milky Way–Andromeda collision.

The Hubble Space Telescope Survey of M31 Satellite Galaxies. IV. Survey Overview and Lifetime Star Formation Histories (2025)
Journal Article
Savino, A., Weisz, D. R., Dolphin, A. E., Durbin, M. J., Kallivayalil, N., Wetzel, A., Anderson, J., Besla, G., Boylan-Kolchin, M., Brown, T. M., Bullock, J. S., Cole, A. A., Collins, M. L., Cooper, M. C., Deason, A. J., Dotter, A. L., Fardal, M., Ferguson, A. M., Fritz, T. K., Geha, M. C., …Marel, R. P. D. (2025). The Hubble Space Telescope Survey of M31 Satellite Galaxies. IV. Survey Overview and Lifetime Star Formation Histories. Astrophysical Journal, 979(2), Article 205. https://doi.org/10.3847/1538-4357/ada24f

From >1000 orbits of HST imaging, we present deep homogeneous resolved star color-magnitude diagrams that reach the oldest main-sequence turnoff and uniformly measured star formation histories (SFHs) of 36 dwarf galaxies (−6 ≥ M<inf>V</inf> ≥ −17) as... Read More about The Hubble Space Telescope Survey of M31 Satellite Galaxies. IV. Survey Overview and Lifetime Star Formation Histories.

Galactic Archaeology with Gaia (2024)
Journal Article
Deason, A. J., & Belokurov, V. (2024). Galactic Archaeology with Gaia. New Astronomy Reviews, 99, Article 101706. https://doi.org/10.1016/j.newar.2024.101706

The Gaia mission has revolutionized our view of the Milky Way and its satellite citizens. The field of Galactic Archaeology has been piecing together the formation and evolution of the Galaxy for decades, and we have made great strides, with often li... Read More about Galactic Archaeology with Gaia.

Detection of Accretion Shelves Out to the Virial Radius of a Low-mass Galaxy with JWST (2024)
Journal Article
Conroy, C., Johnson, B. D., van Dokkum, P., Deason, A., Tacchella, S., Belli, S., …Emami, R. (2024). Detection of Accretion Shelves Out to the Virial Radius of a Low-mass Galaxy with JWST. The Astrophysical Journal, 968(2), Article 129. https://doi.org/10.3847/1538-4357/ad414a

We report the serendipitous discovery of an extended stellar halo surrounding the low-mass galaxy Ark 227 (M * = 5 × 109 M ⊙; d = 35 Mpc) in deep JWST NIRCam imaging from the Blue Jay Survey. The F200W–F444W color provides robust star–galaxy separati... Read More about Detection of Accretion Shelves Out to the Virial Radius of a Low-mass Galaxy with JWST.

The Hubble Space Telescope Survey of M31 Satellite Galaxies. II. The Star Formation Histories of Ultrafaint Dwarf Galaxies (2023)
Journal Article
Savino, A., Weisz, D. R., Skillman, E. D., Dolphin, A., Cole, A. A., Kallivayalil, N., …van der Marel, R. P. (2023). The Hubble Space Telescope Survey of M31 Satellite Galaxies. II. The Star Formation Histories of Ultrafaint Dwarf Galaxies. Astrophysical Journal, 956(2), Article 86. https://doi.org/10.3847/1538-4357/acf46f

We present the lifetime star formation histories (SFHs) for six ultrafaint dwarf (UFD; M V > − 7.0, 4.9<log10(M*(z=0)/M⊙)<5.5 ) satellite galaxies of M31 based on deep color–magnitude diagrams constructed from Hubble Space Telescope imaging. These ar...

HALO7D. III. Chemical Abundances of Milky Way Halo Stars from Medium-resolution Spectra (2023)
Journal Article
McKinnon, K. A., Cunningham, E. C., Rockosi, C. M., Guhathakurta, P., Escala, I., Kirby, E. N., & Deason, A. J. (2023). HALO7D. III. Chemical Abundances of Milky Way Halo Stars from Medium-resolution Spectra. Astrophysical Journal, 951(1), Article 43. https://doi.org/10.3847/1538-4357/acd33d

The Halo Assembly in Lambda Cold Dark Matter: Observations in 7 Dimensions (HALO7D) survey measures the kinematics and chemical properties of stars in the Milky Way (MW) stellar halo to learn about the formation of our Galaxy. HALO7D consists of Keck... Read More about HALO7D. III. Chemical Abundances of Milky Way Halo Stars from Medium-resolution Spectra.

The 3D kinematics of stellar substructures in the periphery of the Large Magellanic Cloud (2023)
Journal Article
Navarrete, C., Aguado, D. S., Belokurov, V., Erkal, D., Deason, A., Cullinane, L., & Carballo-Bello, J. (2023). The 3D kinematics of stellar substructures in the periphery of the Large Magellanic Cloud. Monthly Notices of the Royal Astronomical Society, 523(3), 4720-4738. https://doi.org/10.1093/mnras/stad1698

We report the 3D kinematics of 27 Mira-like stars in the northern, eastern, and southern periphery of the Large Magellanic Cloud (LMC), based on Gaia proper motions and a dedicated spectroscopic follow-up. Low-resolution spectra were obtained for mor... Read More about The 3D kinematics of stellar substructures in the periphery of the Large Magellanic Cloud.

The progenitor galaxies of stellar haloes as ‘failed’ Milky Ways (2023)
Journal Article
Bose, S., & Deason, A. J. (2023). The progenitor galaxies of stellar haloes as ‘failed’ Milky Ways. Monthly Notices of the Royal Astronomical Society, 522(4), 5013-5021. https://doi.org/10.1093/mnras/stad1123

The stellar halo of the Milky Way records the history of its interactions with dwarf galaxies, whose subsequent destruction results in the formation of an extended stellar component. Recent works have suggested that galaxies with masses comparable to... Read More about The progenitor galaxies of stellar haloes as ‘failed’ Milky Ways.

Overview of the DESI Milky Way Survey (2023)
Journal Article
Cooper, A. P., Koposov, S. E., Allende Prieto, C., Manser, C. J., Kizhuprakkat, N., Myers, A. D., Dey, A., Gänsicke, B. T., Li, T. S., Rockosi, C., Valluri, M., Najita, J., Deason, A., Raichoor, A., Wang, M.-Y., Ting, Y.-S., Kim, B., Carrillo, A., Wang, W., Beraldo e Silva, L., …Zou, H. (2023). Overview of the DESI Milky Way Survey. Astrophysical Journal, 947(1), Article 37. https://doi.org/10.3847/1538-4357/acb3c0

We describe the Milky Way Survey (MWS) that will be undertaken with the Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4 m telescope at the Kitt Peak National Observatory. Over the next 5 yr DESI MWS will observe approximately seven millio... Read More about Overview of the DESI Milky Way Survey.

Constraining the shape of dark matter haloes with globular clusters and diffuse stellar light in the E-MOSAICS simulations (2023)
Journal Article
Reina-Campos, M., Trujillo-Gomez, S., Pfeffer, J. L., Sills, A., Deason, A. J., Crain, R. A., & Diederik Kruijssen, J. M. (2023). Constraining the shape of dark matter haloes with globular clusters and diffuse stellar light in the E-MOSAICS simulations. Monthly Notices of the Royal Astronomical Society, 521(4), 6368–6382. https://doi.org/10.1093/mnras/stad920

We explore how diffuse stellar light and globular clusters (GCs) can be used to trace the matter distribution of their host halo using an observational methodology. For this, we use 117 simulated dark matter (DM) haloes from the
periodic volume of... Read More about Constraining the shape of dark matter haloes with globular clusters and diffuse stellar light in the E-MOSAICS simulations.

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation (2023)
Journal Article
Jin, S., Trager, S. C., Dalton, G. B., Aguerri, J. A. L., Drew, J. E., Falcón-Barroso, J., Gänsicke, B. T., Hill, V., Iovino, A., Pieri, M. M., Poggianti, B. M., Smith, D. J. B., Vallenari, A., Abrams, D. C., Aguado, D. S., Antoja, T., Aragón-Salamanca, A., Ascasibar, Y., Babusiaux, C., Balcells, M., …Zurita, C. (2024). The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation. Monthly Notices of the Royal Astronomical Society, 530(3), 2688-2730. https://doi.org/10.1093/mnras/stad557

Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function (2023)
Journal Article
Deason, A. J., Koposov, S. E., Fattahi, A., & Grand, R. J. (2023). Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function. Monthly Notices of the Royal Astronomical Society, 520(4), 6091-6103. https://doi.org/10.1093/mnras/stad535

Accreted stellar populations are comprised of the remnants of destroyed galaxies, and often dominate the ‘stellar haloes’ of galaxies such as the Milky Way (MW). This ensemble of external contributors is a key indicator of the past assembly history o... Read More about Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function.

On the edge: the relation between stellar and dark matter haloes of Milky Way-mass galaxies (2023)
Journal Article
Genina, A., Deason, A., & Frenk, C. (2023). On the edge: the relation between stellar and dark matter haloes of Milky Way-mass galaxies. Monthly Notices of the Royal Astronomical Society, 520(3), 3767-3787. https://doi.org/10.1093/mnras/stad397

We investigate the build-up of the accreted stellar and dark matter haloes of Milky Way-like galaxies in APOSTLE suite of cosmological hydrodynamics simulations. We show that the stellar halo is made up primarily of stars stripped from a small number... Read More about On the edge: the relation between stellar and dark matter haloes of Milky Way-mass galaxies.

Energy wrinkles and phase-space folds of the last major merger (2022)
Journal Article
Belokurov, V., Vasiliev, E., Deason, A. J., Koposov, S. E., Fattahi, A., Dillamore, A. M., Davies, E. Y., & Grand, R. J. (2023). Energy wrinkles and phase-space folds of the last major merger. Monthly Notices of the Royal Astronomical Society, 518(4), 6200-6215. https://doi.org/10.1093/mnras/stac3436

Relying on the dramatic increase in the number of stars with full 6D phase-space information provided by the Gaia Data Release 3, we resolve the distribution of the stellar halo around the Sun to uncover signatures of incomplete phase-mixing. We show... Read More about Energy wrinkles and phase-space folds of the last major merger.

The Hubble Space Telescope Survey of M31 Satellite Galaxies. I. RR Lyrae–based Distances and Refined 3D Geometric Structure (2022)
Journal Article
Savino, A., Weisz, D. R., Skillman, E. D., Dolphin, A., Kallivayalil, N., Wetzel, A., Anderson, J., Besla, G., Boylan-Kolchin, M., Bullock, J. S., Cole, A. A., Collins, M. L. M., Cooper, M. C., Deason, A. J., Dotter, A. L., Fardal, M., Ferguson, A. M. N., Fritz, T. K., Geha, M. C., Gilbert, K. M., …van der Marel, R. P. (2022). The Hubble Space Telescope Survey of M31 Satellite Galaxies. I. RR Lyrae–based Distances and Refined 3D Geometric Structure. Astrophysical Journal, 938(2), Article 101. https://doi.org/10.3847/1538-4357/ac91cb

We measure homogeneous distances to M31 and 38 associated stellar systems (−16.8 ≤ MV ≤ −6.0), using time-series observations of RR Lyrae stars taken as part of the Hubble Space Telescope Treasury Survey of M31 Satellites. From >700 orbits of new/arc... Read More about The Hubble Space Telescope Survey of M31 Satellite Galaxies. I. RR Lyrae–based Distances and Refined 3D Geometric Structure.

Observing EAGLE galaxies with JWST: predictions for Milky Way progenitors and their building blocks (2022)
Journal Article
Evans, T. A., Fattahi, A., Deason, A. J., & Frenk, C. S. (2022). Observing EAGLE galaxies with JWST: predictions for Milky Way progenitors and their building blocks. Monthly Notices of the Royal Astronomical Society, 516(3), 3861-3877. https://doi.org/10.1093/mnras/stac2410

We present predictions, derived from the EAGLE ΛCDM cosmological hydrodynamical simulations, for the abundance and properties of galaxies expected to be detected at high redshift by the James Webb Space Telescope (JWST). We consider the galaxy popula... Read More about Observing EAGLE galaxies with JWST: predictions for Milky Way progenitors and their building blocks.

Structural Parameters and Possible Association of the Ultra-faint Dwarfs Pegasus III and Pisces II from Deep Hubble Space Telescope Photometry (2022)
Journal Article
Richstein, H., Patel, E., Kallivayalil, N., Simon, J. D., Zivick, P., Tollerud, E., Fritz, T., Warfield, J. T., Besla, G., van der Marel, R. P., Wetzel, A., Choi, Y., Deason, A., Geha, M., Guhathakurta, P., Jeon, M., Kirby, E. N., Libralato, M., Sacchi, E., & Sohn, S. T. (2022). Structural Parameters and Possible Association of the Ultra-faint Dwarfs Pegasus III and Pisces II from Deep Hubble Space Telescope Photometry. Astrophysical Journal, 933(2), Article 217. https://doi.org/10.3847/1538-4357/ac7226

We present deep Hubble Space Telescope (HST) photometry of the ultra-faint dwarf (UFD) galaxies Pegasus III (Peg III) and Pisces II (Psc II), two of the most distant satellites in the halo of the Milky Way (MW). We measure the structure of both galax... Read More about Structural Parameters and Possible Association of the Ultra-faint Dwarfs Pegasus III and Pisces II from Deep Hubble Space Telescope Photometry.

The chemo-dynamical groups of Galactic globular clusters (2022)
Journal Article
Callingham, T. M., Cautun, M., Deason, A. J., Frenk, C. S., Grand, R. J., & Marinacci, F. (2022). The chemo-dynamical groups of Galactic globular clusters. Monthly Notices of the Royal Astronomical Society, 513(3), 4107-4129. https://doi.org/10.1093/mnras/stac1145

We introduce a multicomponent chemo-dynamical method for splitting the Galactic population of globular clusters (GCs) into three distinct constituents: bulge, disc, and stellar halo. The latter is further decomposed into the individual large accretio... Read More about The chemo-dynamical groups of Galactic globular clusters.