Hα kinematics of S4G spiral galaxies – II. Data description and non-circular motions

Abstract

We present a kinematical study of 29 spiral galaxies included in the Spitzer Survey of Stellar Structure in Galaxies, using Hα Fabry-Perot data obtained with the Galaxy Hα Fabry-Perot System instrument at the William Herschel Telescope in La Palma, complemented with images in the R band and in Hα. The primary goal is to study the evolution and properties of the main structural components of galaxies through the kinematical analysis of the FP data, complemented with studies of morphology, star formation and mass distribution. In this paper we describe how the FP data have been obtained, processed and analysed. We present the resulting moment maps, rotation curves, velocity model maps and residual maps. Images are available in FITS format through the NASA/IPAC Extragalactic Database and the Centre de Données Stellaires. With these data products we study the non-circular motions, in particular those found along the bars and spiral arms. The data indicate that the amplitude of the non-circular motions created by the bar does not correlate with the bar strength indicators. The amplitude of those non-circular motions in the spiral arms does not correlate with either arm class or star formation rate along the spiral arms. This implies that the presence and the magnitude of the streaming motions in the arms is a local phenomenon.

The Lyman alpha reference sample

“…The observed shearing amplitude v shear = 150 km s −1 is consistent with this gradient being caused by rotation (e.g. Epinat et al 2008aEpinat et al , 2010Erroz-Ferrer et al 2015). Unfortunately the beam of our GBT single-dish H  observations is likely contaminated by other sources.…”

“…Such high intrinsic dispersions are in contrast to H  velocity dispersions of ∼10−50 km s −1 typically found in local spirals (e.g. Epinat et al 2008aEpinat et al ,b, 2010Erroz-Ferrer et al 2015). In high-z, star-forming galaxies intrinsic dispersions 50 km s −1 appear to be the norm (e.g.…”

“…We measure v shear ≈ 140 km s −1 , a value that is in the domain of typical maximum velocities of inclination corrected Hα rotation curves of spiral galaxies (e.g. Epinat et al 2008aEpinat et al , 2010Erroz-Ferrer et al 2015). With v FWHM 300 km s −1 highest velocity dispersions are observed in the western part.…”

Tracing the Spiral Structure of the Outer Milky Way with Dense Atomic Hydrogen Gas

“…First, some spiral arm segments could have been shifted and/or deformed by non-circular motions. Spiral arms with strength similar to those in the Milky way are known to excite non-circular streaming motions of order 10-20 km s −1 (e.g., Fresneau et al 2005;Kim & Kim 2014;Erroz-Ferrer et al 2015), which can shift their locations in real space by a few kpc during the mapping. It is difficult to locate such shifts or deformations in Figure 2 without prior information.…”

The MUSE Hubble Ultra Deep Field Survey

“…As a result, the ionised gas velocity dispersion in the disk component of high-redshift galaxies is about 5 to 10 times larger than in the local Universe (≥ 60 km s −1 , as compared to ≈ 10 -20 km s −1 ; e.g. Epinat et al 2010;Erroz-Ferrer et al 2015) and the origin of the gas velocity dispersion is still under debate. A constant evolution (decrease) of the ionised gas velocity dispersion is observed from z ≈ 2 to z ≈ 1 and seems to follow the gas fraction of galaxies (Wisnioski et al 2015), as expected from disk stability theory (Toomre 1964).…”