Spitzer/Infrared Array Camera 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 µm in the Spitzer Survey of Stellar Structure in Galaxies (S 4 G). 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.

Two Orders of Magnitude Variation in the Star Formation Efficiency across the Premerger Galaxy NGC 2276

“…While other external (e.g. minor mergers, gas accretion) or internal (asymmetries in the dark matter halo) mechanisms cannot be ruled out as the origin of these features (Laine et al 2014), we propose (as previous authors have done) that the asymmetric Σ(M stellar ) in NGC 2276 is due to tidal forces.…”

Two Orders of Magnitude Variation in the Star Formation Efficiency across the Premerger Galaxy NGC 2276

“…While other external (e.g. minor mergers, gas accretion) or internal (asymmetries in the dark matter halo) mechanisms cannot be ruled out as the origin of these features (Laine et al 2014), we propose (as previous authors have done) that the asymmetric Σ(M stellar ) in NGC 2276 is due to tidal forces.…”

Inferring the 3D Shapes of Extremely Metal-poor Galaxies from Sets of Projected Shapes

“…In this sense, XMPs often have large H I reservoirs with asymmetric morphology (Filho et al 2013). Simulations have also revealed elongated stellar distributions within elongated dark matter halos (Velliscig et al 2015), so that the shape of the stellar distribution is inherited in part from the dark matter halo shape (e.g., Zaritsky et al 2013;Laine et al 2014). The presence of filaments (Vega-Ferrero et al 2017), cosmic accretion (Ravindranath et al 2006), gas clumps, and radiative feedback (Ceverino et al 2014) may also all contribute to an elongated shape, and such factors are all expected for typical XMPs.…”

Here Be SDRAGNs - Spiral Galaxies Hosting Large Double Radio Sources

“…This dichotomy makes dust warps prominent only from certain directions, where backlighting highlights the portions making the largest projected angles with the stellar disks (which, unlike the dust, are seen more nearly integrated along the line of sight). Among edge-on disks, the incidence of stellar warps is substantial, although occurrence fractions reported in various studies range from 12% (Laine et al 2014) to 65% (Reshetnikov et al 2016, de Grijs 1997) with evidence that it grows in denser environments (Reshetnikov et al 2016). Very roughly, associated warped dust disks should be four times less frequent than warped stellar disks in random samples of edgewise spirals, due to these front/back and angle effects.…”

Two Orders of Magnitude Variation in the Star Formation Efficiency across the Premerger Galaxy NGC 2276

“…While other external (e.g. minor mergers, gas accretion) or internal (asymmetries in the dark matter halo) mechanisms cannot be ruled out as the origin of these features (Laine et al 2014), we propose (as previous authors have done) that the asymmetric Σ(M stellar ) in NGC 2276 is due to tidal forces.…”

Inferring the 3D Shapes of Extremely Metal-poor Galaxies from Sets of Projected Shapes

“…In this sense, XMPs often have large H I reservoirs with asymmetric morphology (Filho et al 2013). Simulations have also revealed elongated stellar distributions within elongated dark matter halos (Velliscig et al 2015), so that the shape of the stellar distribution is inherited in part from the dark matter halo shape (e.g., Zaritsky et al 2013;Laine et al 2014). The presence of filaments (Vega-Ferrero et al 2017), cosmic accretion (Ravindranath et al 2006), gas clumps, and radiative feedback (Ceverino et al 2014) may also all contribute to an elongated shape, and such factors are all expected for typical XMPs.…”

Here Be SDRAGNs - Spiral Galaxies Hosting Large Double Radio Sources

“…This dichotomy makes dust warps prominent only from certain directions, where backlighting highlights the portions making the largest projected angles with the stellar disks (which, unlike the dust, are seen more nearly integrated along the line of sight). Among edge-on disks, the incidence of stellar warps is substantial, although occurrence fractions reported in various studies range from 12% (Laine et al 2014) to 65% (Reshetnikov et al 2016, de Grijs 1997) with evidence that it grows in denser environments (Reshetnikov et al 2016). Very roughly, associated warped dust disks should be four times less frequent than warped stellar disks in random samples of edgewise spirals, due to these front/back and angle effects.…”

Two Orders of Magnitude Variation in the Star Formation Efficiency across the Premerger Galaxy NGC 2276

“…While other external (e.g. minor mergers, gas accretion) or internal (asymmetries in the dark matter halo) mechanisms cannot be ruled out as the origin of these features (Laine et al 2014), we propose (as previous authors have done) that the asymmetric Σ(M stellar ) in NGC 2276 is due to tidal forces.…”

Inferring the 3D Shapes of Extremely Metal-poor Galaxies from Sets of Projected Shapes

“…In this sense, XMPs often have large H I reservoirs with asymmetric morphology (Filho et al 2013). Simulations have also revealed elongated stellar distributions within elongated dark matter halos (Velliscig et al 2015), so that the shape of the stellar distribution is inherited in part from the dark matter halo shape (e.g., Zaritsky et al 2013;Laine et al 2014). The presence of filaments (Vega-Ferrero et al 2017), cosmic accretion (Ravindranath et al 2006), gas clumps, and radiative feedback (Ceverino et al 2014) may also all contribute to an elongated shape, and such factors are all expected for typical XMPs.…”

Here Be SDRAGNs - Spiral Galaxies Hosting Large Double Radio Sources

“…This dichotomy makes dust warps prominent only from certain directions, where backlighting highlights the portions making the largest projected angles with the stellar disks (which, unlike the dust, are seen more nearly integrated along the line of sight). Among edge-on disks, the incidence of stellar warps is substantial, although occurrence fractions reported in various studies range from 12% (Laine et al 2014) to 65% (Reshetnikov et al 2016, de Grijs 1997) with evidence that it grows in denser environments (Reshetnikov et al 2016). Very roughly, associated warped dust disks should be four times less frequent than warped stellar disks in random samples of edgewise spirals, due to these front/back and angle effects.…”