The AMIGA sample of isolated galaxies

XIII. The HI content of an almost “nurture free” sample^⋆

¹ Instituto de Astrofísica de Andalucía (CSIC), Apdo. 3004, 18008 Granada, Spain
e-mail: mjones@iaa.es
² National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
³ The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, 181-0015 Tokyo, Japan
⁴ Max-Planck-Institut fuer Radioastronomie, Postfach 2024, 53010 Bonn, Germany
⁵ Departamento de Física Teórica y del Cosmos, Universidad de Granada, 18071 Granada, Spain
⁶ Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071 Granada, Spain
⁷ Joint ALMA Observatory – ESO, Av. Alonso de Córdova, 3104 Santiago, Chile
⁸ Institute for Astronomy, University of Edinburgh, EH9 3 HJ Edinburgh, UK
⁹ SAMSI, 19 T.W. Alexander Drive, PO Box 110207, Research Triangle Park, NC 27709, USA
¹⁰ Department of Statistical Sciences, Duke University, PO Box 90251, Durham, NC 27708, USA

Received: 26 June 2017
Accepted: 7 October 2017

Abstract

Context. We present the largest catalogue of HI single dish observations of isolated galaxies to date, as part of the multi-wavelength compilation being performed by the AMIGA project (Analysis of the interstellar Medium in Isolated GAlaxies). Despite numerous studies of the HI content of galaxies, no revision focused on the HI scaling relations of the most isolated L_∗ galaxies has been made since Haynes & Giovanelli (1984, AJ, 89, 758).

Aims. The AMIGA sample has been demonstrated to be almost “nurture free”, therefore, by creating scaling relations for the HI content of these galaxies we will define a metric of HI normalcy in the absence of interactions.

Methods. The catalogue comprises of our own HI observations with Arecibo, Effelsberg, Nançay and GBT, and spectra collected from the literature. In total we have measurements or constraints on the HI masses of 844 galaxies from the Catalogue of Isolated Galaxies (CIG). The multi-wavelength AMIGA dataset includes a revision of the B-band luminosities (L_B), optical diameters (D₂₅), morphologies, and isolation. Due to the large size of the catalogue, these revisions permit cuts to be made to ensure isolation and a high level of completeness, which was not previously possible. With this refined dataset we fit HI scaling relations based on luminosity, optical diameter and morphology. Our regression model incorporates all the data, including upper limits, and accounts for uncertainties in both variables, as well as distance uncertainties.

Results. The scaling relation of HI mass with D₂₅ is in good agreement with that of Haynes & Giovanelli (1984), but our relation with L_B is considerably steeper. This disagreement is attributed to the large uncertainties in the luminosities, which introduce a bias when fitting with ordinary least squares regression (as was done in previous works), and the different morphology distributions of the samples. We find that the main effect of morphology on the D₂₅-relation is to increase the intercept towards later types, while for the L_B-relation it is to flatten the slope. These trends were not evident in previous works due to the small number of detected early-type galaxies. Applying our relations to HI detected galaxies in the Virgo cluster we find that although the typical HI-deficiency is only ~0.3 dex, the tail of the distribution extends over an order of magnitude beyond that of the AMIGA sample. These results are in general agreement with previous studies of HI-deficiency in the Virgo cluster.

Conclusions. The HI scaling relations of the AMIGA sample define an up-to-date metric of the HI content of almost “nurture free” galaxies. These relations allow the expected HI mass, in the absence of interactions, of an individual galaxy to be predicted to within 0.25 dex (for typical measurement uncertainties). These relations are thus suitable for use as statistical measures of the impact of interactions on the neutral gas content of galaxies.