Supplementing the 2MRS survey: The 2MZoA catalogue

TL;DR

The paper expands the 2MZoA project to include extinction-corrected galaxies down to $K^{\rm o}_{\rm s} \le 11\fm75$, providing a nearly all-sky, homogeneous redshift survey that complements 2MRS to form e2MRS. It adopts GNILC Planck extinction maps with a correction factor $f=0.86$, introduces a diameter-dependent extinction extension, and presents two main subsamples (ZoA and EBV) plus a supplementary extended set to improve completion in highly extincted regions. The resulting catalogue contains 10 493 objects, including 6899 galaxies (6757 ZoA, 142 EBV), with ~75% redshift completeness; extensive metadata and velocity data from literature are provided. This work improves the census of local large-scale structures and flow fields across the ZoA, enabling more robust studies of cosmic flows, extinction, and mass distribution. The extended dataset, while offering greater completeness in obscured regions, underscores the ongoing need for infrared and HI follow-up to secure redshifts and photometry, with planned future work leveraging deeper NIR imaging and next-generation facilities. All data are publicly available through CDS, enabling wide reuse for cosmography and large-scale structure analyses.

Abstract

We present a homogeneous 2MASX galaxy catalogue at low Galactic latitudes (|b| <= 10.0 deg, called Zone of Avoidance, ZoA) which is complete to a Galactic extinction-corrected magnitude of Ko <= 11.75 mag. Also included are galaxies at higher latitudes in areas of high foreground extinctions (E(B-V) > 0.95). This catalogue supersedes the previously presented bright 2MZoA catalogue which was only complete to Ko < 11.25 mag. It fully complements the 2MASS Redshift Survey (2MRS) galaxy catalogue, which has the same magnitude limit but excludes high extinction regions. The combination of the two catalogues, the extended 2MRS or e2MRS, is is a uniquely whole sky redshift survey and forms a sound basis for studies of large-scale structures, flow fields and extinction across the ZoA. The here presented catalogue comprises 6899 galaxies with 6757 galaxies at low latitudes and 142 galaxies in highly obscured high-latitude areas. The completion rate in redshifts is almost 75%. The catalogue is complete up to star density levels of at least log N_*/deg^2 < 4.3, but the completion rate of the fainter part is affected by foreground extinction at all levels. This can be rectified by using a diameter-dependent extinction correction, adding 1083 highly obscured but apparently faint galaxies (with Ko > 11.75 mag and Ko,d <= 11.75 mag) to the sample. This extended sample shows good completion rates with extinction up to at least AK < 1.3 mag. Omission of such a diameter-dependent extinction correction may lead to a biased flow field even at intermediate extinction values as found in the 2MRS survey. As in our previous investigations, we do not find a dependence of the correction factor f=0.86 to the extinction maps on Galactic longitudes or latitudes, but note a possible influence by cosmic variance.

Figures (14)

• Figure 1: 2MASS extinction-corrected colour--colour plot, $(H-K_{\rm s})^{\rm o}$ versus $(J-K_{\rm s})^{\rm o}$ . A reddening vector, representing the mean of the sample shown, is indicated by a red arrow in the bottom right corner. The reddening path for objects within the intrinsic colour range of galaxies is indicated with two parallel dashed lines.
• Figure 2: WISE extinction-corrected colour--colour plot, $(W1-W2)^o$ versus $(W2-W3)^o$, for the full sample. A reddening vector, representing the mean of the sample shown, is indicated by a red arrow in the top right corner. Open circles mark active galaxies as labelled.
• Figure 3: Histograms of objects in the ZOA sample as a function of Galactic latitude for all objects (blue) and for galaxies only (red). The black line represents the average 2MASX galaxy count outside the ZoA. Panel (a): for all Galactic longitudes; panel (b) for the semi-circle towards the anti-centre region; panel (c) for the semi-circle towards the bulge.
• Figure 4: Histograms of the number density of all ZOA sample objects (blue) and galaxies only (red) as a function of stellar density (top panel) and Galactic extinction $A_{\rm K}$ (bottom panel; only regions with $\log N_*/{\rm deg}^2 \le 4.5$ were used). The error bars indicate Poissonian errors per bin. The black dotted lines represent the average 2MASX bright galaxy number density outside of the ZoA.
• Figure 5: Normalised histograms of 2MASX colours $(J-K_{\rm s})^{\rm o}$ (left) and $(H-K_{\rm s})^{\rm o}$ (right). Green histograms are the full sample and the magenta histograms show colours corrected for stellar densities. the yellow-filled histograms represent the average high Galactic latitude sample.