Detecting the halo heating from AGN feedback with ALMA
  The Sunyaev-Zel'dovich (SZ) effect can potentially be used to investigate the
heating of the circumgalactic medium and subsequent suppression of cold gas
accretion onto the host galaxy caused by quasar feedback. We use a deep ALMA
observation of HE0515-4414 in band 4, the most luminous quasar known at the
peak of cosmic star formation (z=1.7), to search for the SZ signal tracing the
heating of the galaxy's halo. ALMA's sensitivity to a broad range of spatial
scales enables us to disentangle emitting compact sources from the negative,
extended SZ signal. We obtain a marginal S-Z detection (~3.3$\sigma$) on scales
of about 300 kpc (30-40 arcsec), at the 0.2 mJy level, 0.5 mJy after applying a
correction factor for primary beam attenuation and flux that is resolved out by
the array. We show that our result is consistent with a simulated ALMA
observation of a similar quasar in the FABLE cosmological simulations. We
emphasise that detecting an SZ signal is more easily achieved in the visibility
plane than in the (inferred) images. We also confirm a marginal detection
(3.2$\sigma$) of a potential SZ dip on smaller scales (<100 kpc) already
claimed by other authors, possibly highlighting the complex structure of the
halo heating. Finally, we use SZ maps from the FABLE cosmological simulations,
convolved with ALMA simulations, to illustrate that band 3 observations are
much more effective in detecting the SZ signal with higher significance, and
discuss the optimal observing strategy.
