HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey -- III. Unveiling the obscured part of the Vela Supercluster

Abstract

We conducted a search for HI emission of the gas-rich galaxies in the Vela region ($260^{\circ }\le \ell \le 290^{\circ },-2^{\circ }\le b\le 1^{\circ }$) to explore the Vela Supercluster (VSCL) at $V_{\mathrm{hel}}\sim 18000$ km s${}^{-1}$, largely obscured by Galactic dust. Within the mostly RFI-free band ($250<V_{\mathrm{hel}}<25000$ km s${}^{-1}$) of MeerKAT, the analysis focuses on $157$ hexagonally distributed pointings extracted from the SARAO MeerKAT Galactic Plane Survey located in the Vela region (Vela$-$SMGPS). These were combined into 10 contiguous mosaics, covering a $\sim 90$ deg${}^2$ area. Among the $843$ HI detected sources, 39 were previously discovered in the Parkes HIZOA survey ($V_{\mathrm{hel}}<12000$ km s${}^{-1}$; rms $\sim 6$ mJy beam${}^{-1}$). With the improved rms level of the Vela$-$SMGPS, i.e., $0.29-0.56$ mJy beam${}^{-1}$, our study unveils nearly 12 times more detections (471 candidates) in that same velocity range. We furthermore could identify $187$ galaxy candidates with an HI mass limit reaching $\log (M_{\mathrm{HI}}/{\mathrm{M}}_{\odot })=9.44$ in the VSCL velocity range $V_{\mathrm{hel}}\sim 19500\pm 3500$ km s${}^{-1}$. We find indications of two wall-like overdensities that confirm the original suspicion that these walls intersect at low latitudes around longitudes of $\ell \sim 272^{\circ }-278^{\circ }$. We also find a strong signature most likely associated with the Hydra/Antlia extension and evidence of a previously unknown narrow filament at $V_{\mathrm{hel}}\sim 12000$ km s${}^{-1}$. This paper demonstrates the efficiency of systematic HI surveys with the SKA precursor MeerKAT, even in the most obscured part of the Zone of Avoidance (ZOA).

Accepted for publication in MNRAS, this version contains the full catalogue of detections