The Astrophysical Journal (Jan 2023)
DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of Our Nearest Neighbor
- Arjun Dey,
- Joan R. Najita,
- Sergey E. Koposov,
- J. Josephy-Zack,
- Gabriel Maxemin,
- Eric F. Bell,
- C. Poppett,
- E. Patel,
- L. Beraldo e Silva,
- A. Raichoor,
- D. Schlegel,
- D. Lang,
- A. Meisner,
- Adam D. Myers,
- J. Aguilar,
- S. Ahlen,
- C. Allende Prieto,
- D. Brooks,
- A. P. Cooper,
- K. S. Dawson,
- A. de la Macorra,
- P. Doel,
- A. Font-Ribera,
- Juan García-Bellido,
- S. Gontcho A Gontcho,
- J. Guy,
- K. Honscheid,
- R. Kehoe,
- T. Kisner,
- A. Kremin,
- M. Landriau,
- L. Le Guillou,
- Michael E. Levi,
- T. S. Li,
- Paul Martini,
- R. Miquel,
- J. Moustakas,
- Jundan Nie,
- N. Palanque-Delabrouille,
- F. Prada,
- E. F. Schlafly,
- Ray M. Sharples,
- Gregory Tarlé,
- Yuan-Sen Ting,
- L. Tyas,
- M. Valluri,
- Risa H. Wechsler,
- H. Zou
Affiliations
- Arjun Dey
- ORCiD
- NSF’s NOIRLab, 950 N. Cherry Avenue, Tucson, AZ 85719, USA ; [email protected]
- Joan R. Najita
- ORCiD
- NSF’s NOIRLab, 950 N. Cherry Avenue, Tucson, AZ 85719, USA ; [email protected]
- Sergey E. Koposov
- ORCiD
- Institute for Astronomy, University of Edinburgh , Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK; Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge, CB3 0HA, UK; Kavli Institute for Cosmology, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UK
- J. Josephy-Zack
- Harvard College , Cambridge, MA 02138, USA
- Gabriel Maxemin
- Harvard College , Cambridge, MA 02138, USA
- Eric F. Bell
- ORCiD
- Department of Astronomy, University of Michigan , Ann Arbor, MI 48109, USA
- C. Poppett
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA; Space Sciences Laboratory, University of California , Berkeley, 7 Gauss Way, Berkeley, CA 94720, USA; University of California , Berkeley, 110 Sproul Hall #5800, Berkeley, CA 94720, USA
- E. Patel
- ORCiD
- Astronomy Dept., University of California at Berkeley , Berkeley, CA 94720, USA
- L. Beraldo e Silva
- ORCiD
- Department of Astronomy, University of Michigan , Ann Arbor, MI 48109, USA
- A. Raichoor
- ORCiD
- Lawrence Berkeley National Laboratory , Berkeley, CA 94720, USA
- D. Schlegel
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- D. Lang
- Perimeter Institute for Theoretical Physics , 31 Caroline Street N, Waterloo, ON N25 2YL, Canada; Department of Physics and Astronomy, University of Waterloo , Waterloo, ON N2L 3G1, Canada
- A. Meisner
- ORCiD
- NSF’s NOIRLab, 950 N. Cherry Avenue, Tucson, AZ 85719, USA ; [email protected]
- Adam D. Myers
- Department of Physics & Astronomy, University of Wyoming , 1000 E. University, Dept. 3905, Laramie, WY 82071, USA
- J. Aguilar
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- S. Ahlen
- ORCiD
- Physics Dept., Boston University , 590 Commonwealth Avenue, Boston, MA 02215, USA
- C. Allende Prieto
- ORCiD
- Instituto de Astrofísica de Canarias , C/ Vía Láctea, s/n, E-38205 San Cristóbal de La Laguna, Santa Cruz de Tenerife, Spain
- D. Brooks
- ORCiD
- Department of Physics & Astronomy, University College London , Gower Street, London, WC1E 6BT, UK
- A. P. Cooper
- ORCiD
- Institute of Astronomy and Department of Physics, National Tsing Hua University , 101 Kuang-Fu Road Sec. 2, Hsinchu 30013, Taiwan; Center for Informatics and Computation in Astronomy, NTHU, 101 Kuang-Fu Road Sec. 2, Hsinchu 30013, Taiwan; Physics Division, National Center for Theoretical Sciences , Taipei 10617, Taiwan
- K. S. Dawson
- ORCiD
- Department of Physics and Astronomy, The University of Utah , 115 South 1400 East, Salt Lake City, UT 84112, USA
- A. de la Macorra
- Instituto de Física, Universidad Nacional Autónoma de México , Cd. de México C.P. 04510, México
- P. Doel
- Department of Physics & Astronomy, University College London , Gower Street, London, WC1E 6BT, UK
- A. Font-Ribera
- ORCiD
- Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, E-08193 Bellaterra Barcelona, Spain
- Juan García-Bellido
- ORCiD
- Instituto de Física Teórica (IFT) UAM/CSIC, Universidad Autónoma de Madrid , Cantoblanco, E-28049, Madrid, Spain
- S. Gontcho A Gontcho
- ORCiD
- Lawrence Berkeley National Laboratory , One Cyclotron Road, Berkeley, CA 94720, USA
- J. Guy
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- K. Honscheid
- Center for Cosmology and AstroParticle Physics, The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA; Department of Physics, The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA
- R. Kehoe
- ORCiD
- Department of Physics, Southern Methodist University , 3215 Daniel Avenue, Dallas, TX 75275, USA
- T. Kisner
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- A. Kremin
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- M. Landriau
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- L. Le Guillou
- ORCiD
- Sorbonne Université , CNRS/IN2P3, Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), F-75005 Paris, France
- Michael E. Levi
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- T. S. Li
- ORCiD
- Department of Astronomy & Astrophysics, University of Toronto , Toronto, ON M5S 3H4, Canada
- Paul Martini
- ORCiD
- Center for Cosmology and AstroParticle Physics, The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA; Department of Astronomy, The Ohio State University , 4055 McPherson Laboratory, 140 W 18th Avenue, Columbus, OH 43210, USA
- R. Miquel
- ORCiD
- Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, E-08193 Bellaterra Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats , Passeig de Lluís Companys, 23, E-08010 Barcelona, Spain
- J. Moustakas
- ORCiD
- Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211, USA
- Jundan Nie
- ORCiD
- National Astronomical Observatories, Chinese Academy of Sciences , A20 Datun Road, Chaoyang District, Beijing, 100012, People’s Republic of China
- N. Palanque-Delabrouille
- ORCiD
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA; IRFU, CEA, Université Paris-Saclay , F-91191 Gif-sur-Yvette, France
- F. Prada
- Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, E-18080 Granada, Spain
- E. F. Schlafly
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore MD 21218, USA
- Ray M. Sharples
- ORCiD
- Centre for Advanced Instrumentation, Department of Physics, Durham University , South Road, Durham DH1 3LE, UK
- Gregory Tarlé
- ORCiD
- Department of Physics, University of Michigan , Ann Arbor, MI 48109, USA
- Yuan-Sen Ting
- ORCiD
- Research School of Astronomy & Astrophysics, Australian National University , Cotter Road, Weston, ACT 2611, Australia; School of Computing, Australian National University , Acton ACT 2601, Australia
- L. Tyas
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720, USA
- M. Valluri
- ORCiD
- Department of Astronomy, University of Michigan , Ann Arbor, MI 48109, USA
- Risa H. Wechsler
- ORCiD
- Kavli Institute for Particle Astrophysics and Cosmology, Stanford University , 452 Lomita Mall, Stanford, CA 94305, USA; Physics Department, Stanford University , Stanford, CA 93405, USA; SLAC National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, CA 94025, USA
- H. Zou
- ORCiD
- National Astronomical Observatories, Chinese Academy of Sciences , A20 Datun Road, Chaoyang District, Beijing, 100012, People’s Republic of China
- DOI
- https://doi.org/10.3847/1538-4357/aca5f8
- Journal volume & issue
-
Vol. 944,
no. 1
p. 1
Abstract
We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the 11,416 sources studied in 3.75 hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars ([Fe/H] > − 0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be ${\mathrm{log}}_{10}\,{M}_{\mathrm{NFW}}(\lt 125\,\mathrm{kpc})/{M}_{\odot }={11.80}_{-0.10}^{+0.12}$ . The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies.
Keywords
- Andromeda Galaxy
- Galaxy mergers
- Galaxy evolution
- Galaxy dynamics
- Stellar kinematics
- Redshift surveys
