NIBLES: an H I census of stellar mass selected SDSS galaxies^⋆

I. The Nançay H I survey

¹ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
e-mail: wim.vandriel@obspm.fr
² Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU USR 704, Université d’Orléans OSUC, route de Souesmes, 18330 Nançay, France
³ University of Massachusetts, Astronomy Program, 536 LGRC, Amherst, MA 01003, USA
⁴ Institut d’Astrophysique de Paris, UMR 7095, CNRS Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁵ Arecibo Observatory, National Astronomy and Ionosphere Center, Arecibo, PR 00612, USA
⁶ Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa
⁷ Université de Bordeaux, Observatoire Aquitain des Sciences de l’Univers, BP 89, 33271 Floirac Cedex, France
⁸ CNRS, Laboratoire d’Astrophysique de Bordeaux, UMR 5804, BP 89, 33271 Floirac Cedex, France
⁹ Southern African Large Telescope Foundation, PO Box 9, Observatory 7935, Cape Town, South Africa
¹⁰ Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, 43992 Onsala, Sweden
¹¹ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AV Groningen, The Netherlands
¹² ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands

Received: 27 December 2015
Accepted: 1 July 2016

Abstract

To investigate galaxy properties as a function of their total stellar mass, we obtained 21 cm H i line observations at the 100-m class Nançay Radio Telescope of 2839 galaxies from the Sloan Digital Sky Survey (SDSS) in the Local Volume (900 < cz < 12 000 km s^-1), dubbed the Nançay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) sample. They were selected evenly over their entire range of absolute SDSS z-band magnitudes (M_z ~ −13.5 to −24 mag), which were used as a proxy for their stellar masses. In this paper, a first, global presentation of the observations and basic results is given; their further analysis will be presented in other papers in this series. The galaxies were originally selected based on their properties, as listed in SDSS DR5. Comparing this photometry to their total H i masses, we noted that, for a few percent, the SDSS magnitudes appeared severely misunderestimated, as confirmed by our re-measurements for selected objects. Although using the later DR9 results eliminated this problem in most cases, 384 still required manual photometric source selection. Usable H i spectra were obtained for 2600 of the galaxies, of which 1733 (67%) were clearly detected and 174 (7%) marginally. The spectra for 241 other observed galaxies could not be used for further analysis owing to problems with either the H i or the SDSS data. We reached the target number of about 150 sources per half-magnitude bin over the M_z range −16.5 to −23 mag. Down to −21 mag the overall detection rate is rather constant at the ~75% level but it starts to decline steadily towards the 30% level at −23 mag. Making regression fits by comparing total H i and stellar masses for our sample, including our conservatively estimated H i upper limits for non-detections, we find the relationship log(M_{H I}/M_⋆) = −0.59 log(M_⋆) + 5.05, which lies significantly below the relationship found in the M_{H I}/M_⋆ – M_⋆ plane when only using H i detections.