4.7 Article

MusE GAs FLOw and Wind (MEGAFLOW) VIII. Discovery of a Mg II emission halo probed by a quasar sightline

Journal

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 507, Issue 3, Pages 4294-4315

Publisher

OXFORD UNIV PRESS
DOI: 10.1093/mnras/stab2165

Keywords

galaxies: evolution; galaxies: haloes; intergalactic medium; quasars: absorption lines; quasars: individual: SDSSJ0937+0656

Funding

  1. European Southern Observatory under ESO programmes [095.A-0365(A), 096.A-0609(A), 0100.A-0089, 0101.A-0287(A)]
  2. ANR FOGHAR [ANR-13-BS05-0010]
  3. ANR 3DGasFlows [ANR-17-CE31-0017]
  4. OCEVU Labex [ANR-11-LABX-0060]
  5. Dutch Research Council (NWO) [639.043.409]
  6. SNF [PP00P2_176808]
  7. ERC [ERC-757258-TRIPLE]
  8. Swiss National Science Foundation [PP00P2_163824, PP00P2_190092]
  9. European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme [864361]
  10. Fundacao para a Ciencia e a Tecnologia (FCT) [UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020]
  11. Investigador FCT [IF/01654/2014/CP1215/CT0003]
  12. National Science Foundation [ACI-1440620]
  13. Swiss National Science Foundation (SNF) [PP00P2_190092, PP00P2_176808] Funding Source: Swiss National Science Foundation (SNF)

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The study reports the first detection of extended Mg II emission from a galaxy's halo probed by a quasar sightline, along with observations of Mg II absorption, and compares the kinematics of both emission and absorption. The research suggests that shocks may be a more viable source to power the extended Mg II emission.
Using deep (11.2 h) VLT/MUSE data from the MEGAFLOW survey, we report the first detection of extended Mg II emission from a galaxy's halo that is probed by a quasar sightline. The Mg II lambda lambda 2796, 2803 emission around the z = 0.702 galaxy (log(M-*/M-circle dot) = 10.0(-0.11)(+0.15)) is detected out to approximate to 25 kpc from the central galaxy and covers 1.0 x 10(3) kpc(2) above a surface brightness of 14 x 10(-19) erg s(-1) cm(-2) arcse(-2) (2 sigma; integrated over 1200 km s(-1) = 19 angstrom and averaged over 1.5 arcsec(2)). The Mg II emission around this highly inclined galaxy (i similar or equal to 75 deg) is strongest along the galaxy's projected minor axis, consistent with the Mg II gas having been ejected from the galaxy into a bi-conical structure. The quasar sightline, which is aligned with the galaxy's minor axis, shows strong Mg II absorption (EW0 lambda 2796 = 1.8 angstrom) at an impact parameter of 39 kpc from the galaxy. Comparing the kinematics of both the emission and the absorption - probed with VLT/UVES - to the expectation from a simple toy model of a bi-conical outflow, we find good consistency when assuming a relatively slow outflow (v(out) = 130 km s(-1)). We investigate potential origins of the extended Mg II emission using simple toy models. With continuum scattering models we encounter serious difficulties in explaining the luminosity of the Mg II halo and in reconciling density estimates from emission and absorption. Instead, we find that shocks might be a more viable source to power the extended Mg II (and non-resonant [O II] emission.

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