Revealing hidden structures in the Zone of Avoidance – a blind MeerKAT H i Survey of the Vela Supercluster

Abstract

Abstract We conducted the MeerKAT Vela Supercluster survey, named Vela−$\rm {H}\, \scriptstyle \mathrm{I}$, to bridge the gap between the Vela SARAO MeerKAT Galactic Plane Survey (Vela−SMGPS, −2○ ≤ b ≤ 1○), and optical and near-infrared spectroscopic observations of the Vela Supercluster (hereafter Vela−OPT/NIR) at |b| ≳ 7○. Covering coordinates from 263○ ≤ ℓ ≤ 284○ and 1○ ≤ b ≤ 6.2○ above, and −6.7○ ≤ b ≤ −2○ below the Galactic Plane (GP), we sampled 667 fields spread across an area of ${\sim } \rm 242 ~deg^2$. With a beam size of ∼38″ × 31″, Vela−$\rm {H}\, \scriptstyle \mathrm{I}$ achieved a sensitivity of $\langle \rm rms \rangle = 0.74$ $\rm mJy\, beam^{-1}$ at 44.3 $\rm km\, s^{-1}$ velocity resolution over ∼67 hours of observations. We cataloged 719 galaxies, with only 211 (29%) previously documented in the literature, primarily through the HIZOA, 2MASX, and WISE databases. Among these known galaxies, only 66 had optical spectroscopic redshift information. We found marginal differences of less than one channel resolution for all galaxies in common between HIZOA and Vela−SMGPS, and a mean difference of 70 ± 15 $\rm km\, s^{-1}$ between optical and $\rm {H}\, \scriptstyle \mathrm{I}$ velocities. Combining data from Vela−SMGPS, Vela−$\rm {H}\, \scriptstyle \mathrm{I}$, and Vela−OPT/NIR confirmed the connection of the Hydra/Antlia filament across the GP and revealed a previously unknown diagonal wall at a heliocentric velocity range of 6500 − 8000 $\rm km\, s^{-1}$. Vela−$\rm {H}\, \scriptstyle \mathrm{I}$ reinforces the connection between the first wall at 18500 − 20000 $\rm km\, s^{-1}$ and the inner ZOA. The second wall seems to traverse the GP at 270○ ≤ ℓ ≤ 279○, where it appears that both walls intersect, jointly covering the velocity range 18500 − 21500 $\rm km\, s^{-1}$.