Catalogue of the morphological features in theSpitzerSurvey of Stellar Structure in Galaxies (S⁴G)

Abstract

Context. A catalogue of the features for the complete Spitzer Survey of Stellar Structure in Galaxies (S 4 G), including 2352 nearby galaxies, is presented. The measurements are made using 3.6 µm images, largely tracing the old stellar population; at this wavelength the effects of dust are also minimal. The measured features are the sizes, ellipticities, and orientations of bars, rings, ringlenses, and lenses. Measured in a similar manner are also barlenses (lens-like structures embedded in the bars), which are not lenses in the usual sense, being rather the more face-on counterparts of the boxy/peanut structures in the edge-on view. In addition, pitch angles of spiral arm segments are measured for those galaxies where they can be reliably traced. More than one pitch angle may appear for a single galaxy. All measurements are made in a human-supervised manner so that attention is paid to each galaxy. Aims. We create a catalogue of morphological features in the complete S 4 G. Methods. We used isophotal analysis, unsharp masking, and fitting ellipses to measured structures. Results. We find that the sizes of the inner rings and lenses normalized to barlength correlate with the galaxy mass: the normalized sizes increase toward the less massive galaxies; it has been suggested that this is related to the larger dark matter content in the bar region in these systems. Bars in the low mass galaxies are also less concentrated, likely to be connected to the mass cut-off in the appearance of the nuclear rings and lenses. We also show observational evidence that barlenses indeed form part of the bar, and that a large fraction of the inner lenses in the non-barred galaxies could be former barlenses in which the thin outer bar component has dissolved.

Stellar populations across galaxy bars in the MUSE TIMER project

“…Two clear breaks are noticeable in all four profiles of this galaxy. The inner break coincides with the position of a nuclear lens component (Herrera-Endoqui et al 2015). Afterwards follows a transition zone leading to a second break.…”

“…First, the stellar kinematics are measured by fitting a linear combination of stellar template 2 Using 3.6 µm images from Spitzer, bar lengths were measured visually, while orientation and ellipticity were determined interactively by visually marking the object and fitting ellipses to the marked points. See Herrera-Endoqui et al (2015) for more detail. spectra from the Indo-US template library (Valdes et al 2004) convolved with a Gaussian line-of-sight velocity kernel to the Voronoi-binned spectra in the cube.…”

“…stellar_pop_paper_arxiv (2) morphological type by Buta et al (2015); (3) inclination of the galaxy; (4) distance to the galaxy; (5) total stellar mass; (6) total H i mass; (7) bar maximum gravitational torque from Díaz-García et al (2016). Column (8)-(10) are taken from Herrera-Endoqui et al (2015) with the exception of NGC 4371, which was found to be inaccurate and taken from Gadotti et al (2015) instead: (8) bar length; (9) position angle of the bar; (10) ellipticity of the bar. code s t e c k m a p (STEllar Content and Kinematics via Maximum A Posteriori; Ocvirk et al 2006b,a) with the E-MILES library and assuming a Kroupa (2001) initial mass function (IMF).…”

What determines the sizes of bars in spiral galaxies?

“…(The Parent Spiral Sample is equivalent to "Sample 2m" in Paper I, except that the latter included galaxies with log (M /M ) > 11.) The identification of galaxies as barred or unbarred is based on the classifications and measurements of Buta et al (2015) and Herrera-Endoqui et al (2015); see Section 2.1.1.…”

“…Bar sizes for S 4 G barred galaxies (as identified by Buta et al 2015) were measured by Herrera-Endoqui et al (2015). These include multiple different measures of bar size; I use their "visual" semi-major axes avis, since these are available for all the barred galaxies, while other measurements are missing for some galaxies based on factors such as low S/N or strong star-formation in the images.…”