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Project AMIGA: The Circumgalactic Medium of Andromeda

Lehner, Nicolas and Berek, Samantha C. and Howk, J. Christopher and Wakker, Bart P. and Tumlinson, Jason and Jenkins, Edward B. and Prochaska, J. Xavier and Augustin, Ramona and Ji, Suoqing and Faucher-Giguère, Claude-André and Hafen, Zachary and Peeples, Molly S. and Barger, Kat A. and Berg, Michelle A. and Bordoloi, Rongmon and Brown, Thomas M. and Fox, Andrew J. and Gilbert, Karoline M. and Guhathakurta, Puragra and Kalirai, Jason S. and Lockman, Felix J. and O’Meara, John M. and Pisano, D. J. and Ribaudo, Joseph and Werk, Jessica K. (2020) Project AMIGA: The Circumgalactic Medium of Andromeda. Astrophysical Journal, 900 (1). Art. No. 9. ISSN 1538-4357.

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Project AMIGA (Absorption Maps In the Gas of Andromeda) is a survey of the circumgalactic medium (CGM) of Andromeda (M31, R_(vir) ≃ 300 kpc) along 43 QSO sightlines at impact parameters 25 ≤ R ≤ 569 kpc (25 at R ≾ R_(vir)). We use ultraviolet absorption measurements of Si II, Si III, Si IV, C II, and C IV from the Hubble Space Telescope/Cosmic Origins Spectrograph and O VI from the Far Ultraviolet Spectroscopic Explorer to provide an unparalleled look at how the physical conditions and metals are distributed in the CGM of M31. We find that Si III and O VI have a covering factor near unity for R ≾ 1.2 R_(vir) and ≾1.9 R_(vir), respectively, demonstrating that M31 has a very extended ~10⁴–10^(5.5) K ionized CGM. The metal and baryon masses of the 10⁴–10^(5.5) K CGM gas within R_(vir) are ≳ 10⁸ and ≳ 4 × 10¹⁰ (Z/0.3 Z⊙)⁻¹ M⊙, respectively. There is not much azimuthal variation in the column densities or kinematics, but there is with R. The CGM gas at R ≾ 0.5 R_(vir) is more dynamic and has more complicated, multiphase structures than at larger radii, perhaps a result of more direct impact of galactic feedback in the inner regions of the CGM. Several absorbers are projected spatially and kinematically close to M31 dwarf satellites, but we show that those are unlikely to give rise to the observed absorption. Cosmological zoom simulations of ~L* galaxies have O VI extending well beyond R_(vir) as observed for M31 but do not reproduce well the radial column density profiles of the lower ions. However, some similar trends are also observed, such as the lower ions showing a larger dispersion in column density and stronger dependence on R than higher ions. Based on our findings, it is likely that the Milky Way has a ~10⁴–10^(5.5) K CGM as extended as for M31 and their CGM (especially the warm–hot gas probed by O VI) are overlapping.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lehner, Nicolas0000-0001-9158-0829
Howk, J. Christopher0000-0002-2591-3792
Wakker, Bart P.0000-0002-0507-7096
Tumlinson, Jason0000-0002-7982-412X
Jenkins, Edward B.0000-0003-1892-4423
Prochaska, J. Xavier0000-0002-7738-6875
Augustin, Ramona0000-0001-7472-3824
Ji, Suoqing0000-0001-9658-0588
Faucher-Giguère, Claude-André0000-0002-4900-6628
Hafen, Zachary0000-0001-7326-1736
Peeples, Molly S.0000-0003-1455-8788
Barger, Kat A.0000-0001-5817-0932
Berg, Michelle A.0000-0002-8518-6638
Bordoloi, Rongmon0000-0002-3120-7173
Brown, Thomas M.0000-0002-1793-9968
Fox, Andrew J.0000-0003-0724-4115
Gilbert, Karoline M.0000-0003-0394-8377
Guhathakurta, Puragra0000-0001-8867-4234
Kalirai, Jason S.0000-0001-9690-4159
Lockman, Felix J.0000-0002-6050-2008
O’Meara, John M.0000-0002-7893-1054
Ribaudo, Joseph0000-0003-3381-9795
Werk, Jessica K.0000-0002-0355-0134
Additional Information:© 2020 The American Astronomical Society. Received 2020 February 17; revised 2020 June 26; accepted 2020 June 30; published 2020 August 27. We thank David Nidever for sharing his original fits of the MS H i emission and Ben Oppenheimer for sharing the EAGLE simulations shown in Figure 19. Support for this research was provided by NASA through grant HST-GO-14268 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. C.-A.F.-G. and Z.H. were also supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522; by NASA through grants NNX15AB22G and 17-ATP17-0067; by STScI through grants HST-GO-14681.011 and HST-AR-14293.001-A; and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer, which was operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985. Facilities: HST(COS); HST(STIS); FUSE. Software: Astropy (Astropy Collaboration et al. 2018), emcee (Foreman-Mackey et al. 2013), Matplotlib (Hunter 2007), PyIGM (Prochaska et al. 2017a), yt (Turk et al. 2011), Trident (Hummels et al. 2017).
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:Circumgalactic medium ; Andromeda Galaxy ; Local Group; Quasar absorption line spectroscopy
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Circumgalactic medium (1879); Andromeda Galaxy (39); Local Group (929); Quasar absorption line spectroscopy (1317)
Record Number:CaltechAUTHORS:20200831-075649321
Persistent URL:
Official Citation:Nicolas Lehner et al 2020 ApJ 900 9
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105158
Deposited By: Tony Diaz
Deposited On:08 Sep 2020 19:05
Last Modified:08 Sep 2020 19:05

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