The remnants of galaxy formation from a panoramic survey of the region around M31
Alan W. Mcconnachie
(1)
,
Michael J. Irwin
(2)
,
Rodrigo A. Ibata
(3)
,
John Dubinski
(4)
,
Lawrence M. Widrow
(5)
,
Nicolas F. Martin
(6)
,
Patrick Côté
(1)
,
Aaron L. Dotter
(7)
,
Julio F. Navarro
(7)
,
Annette M. N. Ferguson
(8)
,
Thomas H. Puzia
(1)
,
Geraint F. Lewis
(9)
,
Arif Babul
(7)
,
Pauline Barmby
(10)
,
Olivier Bienaymé
(3)
,
Scott C. Chapman
(2)
,
Robert Cockcroft
(11)
,
Michelle L. M. Collins
(2)
,
Mark A. Fardal
(12)
,
William E. Harris
(11)
,
Avon Huxor
(13)
,
A. Dougal Mackey
(8)
,
Jorge Peñarrubia
(2)
,
R. Michael Rich
(14)
,
Harvey B. Richer
(15)
,
Arnaud Siebert
(3)
,
Nial R. Tanvir
(16)
,
David Valls-Gabaud
(17, 18)
,
Kimberly A. Venn
(7)
1
NRC -
National Research Council of Canada
2 IoA - Institute of Astronomy, University of Cambridge
3 OAS - Observatoire astronomique de Strasbourg
4 Department of Astronomy and Astrophysics, University of Toronto
5 Department of Physics, Engineering Physics and Astronomy, Queen's University
6 MPIA - Max-Planck-Institut für Astronomie
7 Department of Physics and Astronomy, University of Victoria
8 Edin. - University of Edinburgh
9 SIfA - Sydney Institute for Astronomy
10 UWO - University of Western Ontario
11 Department of Physics and Astronomy, McMaster University
12 Department of Astronomy, University of Massachusetts
13 H. H. Wills Physics Laboratory [Bristol]
14 Department of Physics and Astronomy, University of California
15 UBC - University of British Columbia [Canada]
16 University of Leicester
17 GEPI - Galaxies, Etoiles, Physique, Instrumentation
18 Physique des Galaxies et Cosmologie
2 IoA - Institute of Astronomy, University of Cambridge
3 OAS - Observatoire astronomique de Strasbourg
4 Department of Astronomy and Astrophysics, University of Toronto
5 Department of Physics, Engineering Physics and Astronomy, Queen's University
6 MPIA - Max-Planck-Institut für Astronomie
7 Department of Physics and Astronomy, University of Victoria
8 Edin. - University of Edinburgh
9 SIfA - Sydney Institute for Astronomy
10 UWO - University of Western Ontario
11 Department of Physics and Astronomy, McMaster University
12 Department of Astronomy, University of Massachusetts
13 H. H. Wills Physics Laboratory [Bristol]
14 Department of Physics and Astronomy, University of California
15 UBC - University of British Columbia [Canada]
16 University of Leicester
17 GEPI - Galaxies, Etoiles, Physique, Instrumentation
18 Physique des Galaxies et Cosmologie
Résumé
In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars surrounding the galaxy, at distances that reach 10-100 times the radius of the central disk. The number, luminosity and morphology of the relics of this process provide significant clues to galaxy formation history, but obtaining a comprehensive survey of these components is difficult because of their intrinsic faintness and vast extent. Here we report a panoramic survey of the Andromeda galaxy (M31). We detect stars and coherent structures that are almost certainly remnants of dwarf galaxies destroyed by the tidal field of M31. An improved census of their surviving counterparts implies that three-quarters of M31's satellites brighter than Mv = -6 await discovery. The brightest companion, Triangulum (M33), is surrounded by a stellar structure that provides persuasive evidence for a recent encounter with M31. This panorama of galaxy structure directly confirms the basic tenets of the hierarchical galaxy formation model and reveals the shared history of M31 and M33 in the unceasing build-up of galaxies.