The Califa and Hipass velocity function for all morphological galaxy types

TL;DR

This paper presents the first comprehensive velocity function for all galaxy types across a broad velocity range, combining data from HI surveys and integral field spectroscopy, and compares it with cosmological simulations.

Contribution

It introduces a unified, observational velocity function for all galaxy types from 60 to 320 km/s, integrating data from HIPASS and CALIFA surveys, filling a gap in galaxy population statistics.

Findings

The observed velocity function differs significantly from dark matter-only simulation predictions.

Hydrodynamic simulations better match the observed velocity function but still show discrepancies.

The combined velocity function provides a more complete picture of galaxy kinematics across types.

Abstract

The velocity function is a fundamental observable statistic of the galaxy population, similarly impor- tant as the luminosity function, but much more difficult to measure. In this work we present the first directly measured circular velocity function that is representative between 60 < v_circ < 320 km/s for galaxies of all morphological types at a given rotation velocity. For the low mass galaxy population (60 < v_circ < 170 km/s), we use the HIPASS velocity function. For the massive galaxy population (170 < v_circ < 320 km/s), we use stellar circular velocities from the Calar Alto Legacy Integral Field Area Survey (CALIFA). In earlier work we obtained the measurements of circular velocity at the 80% light radius for 226 galaxies and demonstrated that the CALIFA sample can produce volume- corrected galaxy distribution functions. The CALIFA velocity function includes homogeneous velocity measurements of both late and early-type rotation-supported galaxies and has the crucial advantage of not missing gas-poor massive ellipticals that HI surveys are blind to. We show that both velocity functions can be combined in a seamless manner, as their ranges of validity overlap. The resulting observed velocity function is compared to velocity functions derived from cosmological simulations of the z = 0 galaxy population. We find that dark matter-only simulations show a strong mismatch with the observed VF. Hydrodynamic simulations fare better, but still do not fully reproduce observations.