Astronomy and Astrophysics, volume 596A, 25-25 (2016/12-1)
Influence of galaxy stellar mass and observed wavelength on disc breaks in S4G, NIRS0S, and SDSS data.
LAINE J., LAURIKAINEN E. and SALO H.
Abstract (from CDS):
Context. Breaks in the surface brightness profiles in the outer regions of galactic discs are thought to have formed by various internal (e.g. bar resonances) and external (e.g. galaxy merging) processes. By studying the disc breaks we aim to better understand what processes are responsible for the evolution of the outer discs of galaxies, and galaxies in general.
Aims. We use a large well-defined sample to study how common the disc breaks are, and whether their properties depend on galaxy mass. By using both optical and infrared data we study whether the observed wavelength affects the break features as a function of galaxy mass and Hubble type.
Methods. We studied the properties of galaxy discs using radial surface brightness profiles of 753 galaxies, obtained from the 3.6µm images of the Spitzer Survey of Stellar Structure in Galaxies (S4G), and the Ks-band data from the Near InfraRed S0-Sa galaxy Survey (NIRS0S), covering a wide range of galaxy morphologies (-2≲T≲9) and stellar masses (8.5≲log10(M*/M☉)≲11). In addition, optical Sloan Digital Sky Survey (SDSS) or Liverpool telescope data was used for 480 of these galaxies.
Results. We find that in low-mass galaxies the single exponential profiles (Type I) are most common, and that their fraction decreases with increasing galaxy stellar mass. The fraction of down-bending (Type II) profiles increases with stellar mass, possibly due to more common occurrence of bar resonance structures. The up-bending (Type III) profiles are also more common in massive galaxies. The observed wavelength affects the scalelength of the disc of every profile type. Especially the scalelength of the inner disc (hi) of Type II profiles increases from infrared to u-band on average by a factor of ∼2.2. Consistent with the previous studies, but with a higher statistical significance, we find that Type II outer disc scalelengths (ho) in late-type and low mass galaxies (T>4, log10(M*/M☉)≲10.5) are shorter in bluer wavelengths, possibly due to stellar radial migration populating the outer discs with older stars. In Type III profiles ho are larger in the u-band, hinting to the presence of young stellar population in the outer disc. While the observed wavelength affects the disc parameters, it does not significantly affect the profile type classification in our sample. Our results indicate that the observed wavelength is a significant factor when determining the profile types in very low mass dwarf galaxies, for which more Type II profiles have been previously found using optical data.
© ESO, 2016
galaxies: evolution - galaxies: structure - galaxies: statistics
VizieR on-line data:
<Available at CDS (J/A+A/596/A25): table1.dat table3.dat>
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