Misc,
Constraining galaxy overdensities around three z~6.5 quasars with ALMA and MUSE
(2022)cite arxiv:2201.09720Comment: Accepted for publication in The Astrophysical Journal.
Abstract
We quantify galaxy overdensities around three high-redshift quasars with
known CII 158um companions: PJ231-20 (z=6.59), PJ308-21 (z=6.24) and
J0305-3150 (z=6.61). Recent SCUBA2 imaging revealed the presence of 17
submillimeter galaxies (SMG) with sky separations $0.7'< < 2.4'$ from
these three quasars. We present ALMA Band 6 follow-up observations of these
SCUBA2-selected SMGs to confirm their nature and redshift. We also search for
continuum-undetected CII emitters in the ALMA pointings and make use of
archival MUSE observations to search for Lyman-$\alpha$ Emitters (LAE)
associated with the quasars. While most of the SCUBA2-selected sources are
detected with ALMA in the continuum, no CII line emission could be detected,
indicating that they are not at the quasar redshifts. Based on the
serendipitous detection of CO 7-6 and CI emission lines, we find that four
SMGs in the field of PJ231-20 are at z~2.4, which is coincident with the
redshift of a Mg II absorber in the quasar rest-frame UV spectrum. We report
the discovery of 2 LAEs within <0.6 cMpc of PJ231-20 at the same redshift,
indicating a LAE overdensity around this quasar. Taken together, these
observations provide new constraints on the large-scale excess of
Lyman-$\alpha$- and CII-emitting galaxies around z>6 quasars and suggest that
only wide-field observations, such as MUSE, ALMA or JWST mosaics, can reveal a
comprehensive picture of large-scale structure around quasars in the first
billion years of the Universe.
