Astron. Astrophys. Suppl. Ser. 139, 97-103

HI properties of nearby galaxies from a volume-limited sample

I.D. Karachentsev, D.I. Makarov ¹ and W.K. Huchtmeier²

Send offprint request: W.K. Huchtmeier
e-mail: huchtmeier@mpifr-mpg.de

1 - Special Astrophysical Observatory, Russian Academy of Sciences, N.Arkhyz, KChR, 357147, Russia
2 - Max-Planck-Institut für Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany

Received May 25; accepted July 1, 1999

Abstract:

We consider global HI and optical properties of about three hundred nearby galaxies with V₀ < 500 kms^-1. The majority of them have individual photometric distance estimates. The galaxy sample parameters show some known and some new correlations implying a meaningful dynamic explanation: 1) In the whole range of diameters, 1 - 40 Kpc, the galaxy standard diameter and rotational velocity follows a nearly linear Tully-Fisher relation, ${\rm log}A_{25}\propto(0.99\pm0.06){\rm log}V_{\rm m}.$ 2) The HI mass-to-luminosity ratio and the HI mass-to-"total" mass (inside the standard optical diameter) ratio increase systematically from giant galaxies towards dwarfs, reaching maximum values $5 \;M_{\hbox{$\odot$}}/L_{\hbox{$\odot$}}$ and 3, respectively. 3) For all the Local Volume galaxies their total mass-to-luminosity ratio lies within a range of [0.2-16] $M_{\hbox{$\odot$}}/L_{\hbox{$\odot$}}$ with a median of $3.0 \;M_{\hbox{$\odot$}}/L_{\hbox{$\odot$}}$. The M₂₅/L ratio decreases slightly from giant towards dwarf galaxies. 4) The $M_{\rm HI}/L$ and M₂₅/L ratios for the sample galaxies correlate with their mean optical surface brightness, which may be caused by star formation activity in the galaxies. 5) The $M_{\rm HI}/L$ and M₂₅/L ratios are practically independent of the local mass density of surrounding galaxies within the range of densities of about six orders of magnitude. 6) For the LV galaxies their HI mass and angular momentum follow a nearly linear relation: ${\rm log}M_{\rm HI}\propto(0.99\pm0.04){\rm log}(V_{\rm m}\cdot A_{25})$,expected for rotating gaseous disks being near the threshold of gravitational instability, favourable for active star formation.

Key words: galaxies: global HI parameters -- galaxies