Antitruncation of Disks in Early-Type Barred Galaxies

By P. Erwin, J. Beckman, M. Pohlen. 2005

181 citations recorded by the source corpus.

The disks of spiral galaxies are commonly thought to be truncated: the radial surface brightness profile steepens sharply beyond a certain radius (3-5 inner disk scale lengths). Here we present the radial brightness profiles of a number of barred S0-Sb galaxies with the opposite behavior: their outer profiles are distinctly shallower in slope than the main disk profile. We term these "antitruncations"; they are found in at least 25% of a larger sample of barred S0-Sb galaxies. There are two distinct types of antitruncations. About one-third show a fairly gradual transition and outer isophotes that are progressively rounder than the main disk isophotes, suggestive of a disk embedded within a more spheroidal outer zone—either the outer extent of the bulge or a separate stellar halo. But the majority of the profiles have rather sharp surface brightness transitions to the shallower, outer exponential profile and, crucially, outer isophotes that are not significantly rounder than the main disk; in the Sab-Sb galaxies, the outer isophotes include visible spiral arms. This suggests that the outer light is still part of the disk. A subset of these profiles are in galaxies with asymmetric outer isophotes (lopsided or one-armed spirals), suggesting that interactions may be responsible for at least some of the disklike antitruncations.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Evolution of galactic discs: multiple patterns, radial migration, and disc outskirts (2012, background): “…into galaxies at a range of inclinations have actually found that galactic discs do not end at the truncation, but rather exhibit a change in the exponential scale-length of the light distribu ion (e.g. Pohlen et al., 2002; Erwin et al., 2005; Pohlen and Trujillo, 2006; Hunter and Elmegreen, 2006).”
Beyond Inside-Out Growth: Formation and Evolution of Disk Outskirts (2007, result): “This has been confirmed by an abundance of recent data (e.g., Pohlen et al. 2000, 2002; Bland-Hawthorn et al. 2005; Erwin et al. 2005; Pohlen & Trujillo 2006, hereafter PT06).”
THE OUTER DISKS OF EARLY-TYPE GALAXIES. I. SURFACE-BRIGHTNESS PROFILES OF BARRED GALAXIES (2007, methodology): “As shown in Erwin et al. (2005) and Figure 9, this is a clear case of an outer spheroid dominating the light at large radii; at smaller radii, the profile is Type II.o-OLR(?).”
How Large Are the Bars in Barred Galaxies (2005, background): “There are additional galaxies where the surface brightness profile at large radii is shallower than that of disc immediately outside the bar; these are the “Type III” or “anti-truncation” profiles discussed in Erwin et al. (2005).”
The structure of galactic disks - Studying late-type spiral galaxies using SDSS (2006, background): “The galaxies with a break followed by an upbending (shallower outer) profile are calledType III according to Erwin et al. (2005a) who find two sub-classes.”
A Search for Extended Ultraviolet Disk (XUV-Disk) Galaxies in the Local Universe (2007, background): “…not purely exponential with a sharp outer truncation as once thought (e.g. van der Kruit & Searle 1981, Florido et al. 2001), but rather best represented as a complex broken exponential (Pohlen & Trujillo 2006, Erwin et al. 2005, Pohlen et al. 2002) – sometimes even flattening in the outer disk.”
The Secular Evolution of Disk Structural Parameters (2005, background): “In that case, depending on the frequency of the perturbation, anti-truncations (Erwin et al. 2005) may also be possible in a unified picture.”