The Nançay H i Zone of Avoidance survey of 2MASS bright galaxies

Abstract

To complement the 2MASS Redshift Survey (2MRS) and the 2MASS Tully-Fisher survey (2MTF) a search for 21cm HI line emission of 2MASS bright galaxy candidates has been pursued along the dust-obscured plane of the Milky Way with the 100m Nancay Radio Telescope. For our sample selection we adopted an isophotal extinction-corrected K-band magnitude limit of $K_s^o = 11.25$mag, corresponding to the first 2MRS data release and 2MTF, for which the 2MASX completeness level remains fairly constant deep into the Zone of Avoidance (ZoA). About one thousand galaxies without prior redshift measurement accessible from Nancay (Dec > -40\deg) were observed to an rms noise level of ~3 mJy for the velocity range -250 to 10'600 km/s. This resulted in 220 clear and 12 marginal detections of the target sample. Only few detections have redshifts above 8000 km/s due to recurring radio frequency interference (RFI). A further 29 detections and 6 marginals have their origin in non-target galaxies in the telescope beam. The newly detected galaxies are on average considerably more \HI-rich (mostly $10^9 - 10^{10}$M$_\odot$) compared to systematic (blind) HI surveys. The HI detections reveal various new filaments crossing the mostly uncharted northern ZoA (e.g. at $\ell \sim 90\deg, 130\deg, 160\deg$), whilst consolidating galaxy agglomerations in Monoceros and Puppis ($\ell \sim 220\deg, 240\deg$). Considerably new insight has been gained about the extent of the Perseus-Pisces Supercluster through the confirmation of a ridge ($\ell \sim 160\deg$) encompassing the 3C129 cluster that links Perseus-Pisces to Lynx, and the continuation of the second Perseus-Pisces arm ($\ell \sim 90\deg$) across the ZoA.