Proceedings of the Workshop
"The Magellanic Clouds and Other Dwarf Galaxies"
of the Bonn/Bochum-Graduiertenkolleg

The Near-IR Tully-Fisher Relation

for Giant and Dwarf Late-type Galaxies

Daniele Pierini and Richard Tuffs

Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117, Heidelberg, Germany

Received 11th March 1998
Abstract. We present the Near-IR (K'-band, i.e.: λeq = 2.1 µm) Tully-Fisher (TF) relation for 50 giant and dwarf late-type galaxies of the Virgo cluster. We find that LVMax4 for dwarf, faint, slow rotators as well as for giant, bright, fast rotators. The present slope is in agreement with the recent results on the Near-IR Fundamental Plane for disk systems and with the scenario of self-regulation of star formation in disks.

1. Introduction

The origin of the relation between the maximum rotational velocity and the luminosity of giant high surface brightness late-type galaxies (Tully & Fisher 1977) is still debated. Aaronson et al. (1979) gave an ``a posteriori'' justification of the Near-IR TF law (LVMax4), based on the virial theorem and the three following assumptions:
  1. ``all galaxies have the same mass profiles and rotation curves as a function of some dimensionless scale-length'';
  2. ``all galaxies have the same central mass surface density'';
  3. ``all galaxies have the same mean M/L''.
Some of the previous seminal ideas have been restated by Burstein et al. (1997), who claimed that the Tully-Fisher relation is a projection of the so-called κ-space three-dimensional parameter system of the late-type galaxies. However, Silk (1997) has proposed a scenario of self-regulated star formation for disk systems explaining the (B-band) TF relation, without any dynamical assumption. In the present work we extend previous determinations of the Near-IR (NIR) TF relation to dwarf galaxies and discuss the two hypotheses of its origin.

2. Results and Conclusions

K'-band imaging of a complete sample of 84 VCC (Binggeli et al. 1985) member (Binggeli et al. 1993) dwarf and giant galaxies later than S0a, with BT≤16 mag, was obtained by Boselli et al. (1997). From the latter sample we selected 50 objects (24 with 1≤T≤8 and 26 with 9≤T≤11) according to the following criteria:
  1. 35°<i<80°;
  2. no interacting system;
  3. H I linewidths (W, i.e.: full width at 20% level of I/Imax) with σW/W < 1/3 (see Pierini & Tuffs 1998 for H I references).
Near-IR magnitudes (at the isophotal diameter D25) are taken from Boselli et al. (1997) and corrected for Galactic and internal extinction. The equation of the Tully-Fisher relation, obtained through a bivariate least-squares fit algorithm, is: K' = -9.82 (±0.13)·log(V)+30.06 (±0.25), when turbulent and z-motion corrections are not applied (Fig. 1).

We want to emphasize the following results:

  1. the linearity of the NIR TF relation seems to prevail over a range of 8 magnitudes, for galaxies with different phenomenologies, structures, and, perhaps, age and metallicities (see Fig. 1);
  2. the present slope of -9.81±0.13 is fully consistent with the derivations of the Near-IR TF relation for giant spiral galaxies in the literature, e.g: Aaronson et al. (1979) (-9.67±0.24), Kraan-Korteweg et al. (1988) (-9.81), Pierce & Tully (1988) (-9.25±0.43), Peletier & Willner (1993) (-10.2±0.6).

[Click here to see Fig. 1!]

The existence of the LVMax4 law in the Near-IR is confirmed by the distribution of galaxies within the NIR (H-band, i.e.: λ = 1 µm) κ2 - κ3 plane (where κ2 ∝ log(M/L·Ieff3) and κ3 ∝ log(M/L)), shown in Fig. 2 (see Pierini & Tuffs for its derivation). However, the present slope is also consistent with the scenario of Silk (1997). In fact, assuming that LK'VMax4 and LBVMax2.1 (Silk 1997), it follows that ΣB∼0.5 ΣK' (where Σ is for the mean surface brightness within D25), as shown in Fig. 3 for our sample.

[Click here to see Figs. 2 and 3!]

On the basis of the present data, we cannot exclude the possibility that the two building blocks for the physical basis of the Tully-Fisher relation (dynamical equilibrium and self-regulated star formation) are independent.

References


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First version: 02ndAugust,1998
Last update: 30thSeptember,1998

Jochen M. Braun   &   Tom Richtler
 (E-Mail: jbraun|richtler@astro.uni-bonn.de)