The BaLROG project - I. Quantifying the influence of bars on the kinematics of nearby galaxies

TL;DR

This study characterizes how bars influence the kinematic properties of nearby galaxies using high-resolution IFU spectroscopy, revealing correlations between bar strength and various kinematic features, and developing new measurement methods.

Contribution

It introduces a new kinematic-based method to measure bar strength and compares it with classical torque analysis, supported by N-body simulations, enhancing understanding of bar-driven galaxy evolution.

Findings

Bar strengths from ionised gas are ~2.5 times larger than stellar kinematics.

Stronger bars correlate with enhanced inner kinematic features.

Stellar angular momentum dips at ~0.2 bar lengths, indicating bar influence.

Abstract

We present the BaLROG (Bars in Low Redshift Optical Galaxies) sample of 16 morphologically distinct barred spirals to characterise observationally the influence of bars on nearby galaxies. Each galaxy is a mosaic of several pointings observed with the IFU spectrograph SAURON leading to a tenfold sharper spatial resolution (~100 pc) compared to ongoing IFU surveys. In this paper we focus on the kinematic properties. We calculate the bar strength Qb from classical torque analysis using 3.6 {\mu}m Spitzer (S4G) images, but also develop a new method based solely on the kinematics. A correlation between the two measurements is found and backed up by N-body simulations, verifying the measurement of Qb . We find that bar strengths from ionised gas kinematics are ~2.5 larger than those measured from stellar kinematics and that stronger bars have enhanced influence on inner kinematic features. We detect that stellar angular momentum "dips" at 0.2$\pm$0.1 bar lengths and half of our sample exhibits an anti-correlation of h3 - stellar velocity (v/{\sigma}) in these central parts. An increased flattening of the stellar {\sigma} gradient with increasing bar strength supports the notion of bar-induced orbit mixing. These measurements set important constraints on the spatial scales, namely an increasing influence in the central regions (0.1-0.5 bar lengths), revealed by kinematic signatures due to bar-driven secular evolution in present day galaxies.