IRAC Near-Infrared Features in the Outer Parts of S4G Galaxies

Abstract

We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R_25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy/sr per pixel at 3.6 microns in the Spitzer Survey of Stellar Structure in Galaxies (S4G). We also tabulate companion galaxies. We find asymmetries in the outer isophotes in 22+/-1 per cent of the sample. The asymmetry fraction does not correlate with galaxy classification as an interacting galaxy or merger remnant, or with the presence of companions. We also compare the detected features to similar features in galaxies taken from cosmological zoom re-simulations. The simulated images have a higher fraction (33 per cent) of outer disc asymmetries, which may be due to selection effects and an uncertain star formation threshold in the models. The asymmetries may have either an internal (e.g., lopsidedness due to dark halo asymmetry) or external origin.

26 pages, 16 embedded + 100 online-only figures, accepted for publication in MNRAS

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• Stellar masses, sizes, and radial profiles for 465 nearby early-type galaxies: an extension to the Spitzer Survey of Stellar Structure in Galaxies (S${}^4$G)
• Two Orders of Magnitude Variation in the Star Formation Efficiency Across the Pre-Merger Galaxy NGC 2276
• Globular Cluster Populations: First Results from S${}^4$G Early-Type Galaxies
• The AMIGA sample of isolated galaxies. XIV. Disc breaks and interactions through ultra-deep optical imaging
• Radial velocities in the outermost disk toward the anticenter
• The Complete Spitzer Survey of Stellar Structure in Galaxies (CS${}^4$G)
• Semi-analytical near-Earth objects propagation: the orbit history of (35107) 1991 VH and (175706) 1996 FG3
• Kinematic Lensing Inference II: Cluster Lensing with $\mathcal{O}$(1) Galaxies