Abstract
We report the discovery of a Multi Unit Spectroscopic Explorer (MUSE) galaxy group at z = 4.32 lensed by the massive galaxy cluster ACT-CL J0102-4915 (aka El Gordo) at z
= 0.87, associated with a 1.2 mm source that is at a 2.07 ± 0.88 kpc
projected distance from one of the group galaxies. Three images of the
whole system appear in the image plane. The 1.2 mm source has been
detected within the Atacama Large Millimetre/submillimetre Array (ALMA)
Lensing Cluster Survey (ALCS). As this ALMA source is undetected at
wavelengths λ < 2 μm, its redshift cannot be
independently determined, however, the three lensing components indicate
that it belongs to the same galaxy group at z = 4.32. The four members of the MUSE galaxy group have low to intermediate stellar masses (~107–1010 M⊙) and star formation rates (SFRs) of 0.4–24 M⊙ yr−1,
resulting in high specific SFRs (sSFRs) for two of them, which suggest
that these galaxies are growing fast (with stellar mass doubling times
of only ~2 × 107 yr). This high incidence of starburst
galaxies is likely a consequence of interactions within the galaxy
group, which is compact and has high velocity dispersion. Based on the
magnification-corrected sub-/millimeter continuum flux density and
estimated stellar mass, we infer that the ALMA source is classified as
an ordinary ultra-luminous infrared galaxy (with associated
dust-obscured SFR ~ 200–300 M⊙ yr−1) and
lies on the star formation main sequence. This reported case of an
ALMA/MUSE group association suggests that some presumably isolated ALMA
sources are in fact signposts of richer star-forming environments at
high redshifts.
Original language | English |
---|---|
Article number | 146 |
Journal | Astrophysical Journal |
Volume | 908 |
Issue number | 2 |
Number of pages | 9 |
ISSN | 0004-637X |
DOIs | |
Publication status | Published - 2021 |