J/A+A/625/A36 Breaks in surf. brightness prof. of galaxy disks (Watkins+, 2019)
Varied origins of up-bending breaks in galaxy disks.
Watkins A.E., Laine J., Comeron S., Janz J., Salo H.
<Astron. Astrophys. 625, A36 (2019)>
=2019A&A...625A..36W 2019A&A...625A..36W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; Morphology
Keywords: galaxies: evolution - galaxies: photometry - galaxies: spiral -
galaxies: structure
Abstract:
Using a sample of 175 low-inclination galaxies from the S4G, we
investigate the origins of up-bending (Type III) breaks in the
3.6µm surface brightness profiles of disk galaxies.
We reanalyzed a sample of previously identified Type III disk
break-hosting galaxies using a new, unbiased break-finding algorithm,
which uncovered many new, sometimes subtle disk breaks across the
whole sample. We classified each break by its likely origin through
close examination of the galaxy images across wavelengths, and compare
samples of galaxies separated by their outermost identified break
types in terms of their stellar populations and local environments.
We find that more than half of the confirmed Type III breaks in our
sample can be attributed to morphological asymmetry in the host
galaxies. As these breaks are mostly an artifact of the azimuthal
averaging process, their status as physical breaks is questionable.
Such galaxies occupy some of the highest density environments in our
sample, implying that much of this asymmetry is the result of tidal
disturbance. We also find that Type III breaks related to extended
spiral arms or star formation often host down-bending (Type II) breaks
at larger radius which were previously unidentified. Such galaxies
reside in the lowest density environments in our sample, in line with
previous studies that found a lack of Type II breaks in clusters.
Galaxies occupying the highest density environments most often show
Type III breaks associated with outer spheroidal components.
We find that Type III breaks in the outer disks of galaxies arise most
often through environmental influence: either tidal disturbance
(resulting in disk asymmetry) or heating through, for example, galaxy
harrassment (leading to spheroidal components). Galaxies hosting the
latter break types also show bimodal distributions in central g-r
color and morphological type, with more than half of such galaxies
classified as Sa or earlier; this suggests these galaxies may be
evolving into early-type galaxies. By contrast, we find that Type III
breaks related to apparently secular features (e.g., spiral arms) may
not truly define their hosts' outer disks, as often in such galaxies
additional significant breaks can be found at larger radius. Given
this variety in Type III break origins, we recommend in future break
studies making a more detailed distinction between break subtypes when
seeking out, for example, correlations between disk breaks and
environment, to avoid mixing unlike physical phenomena.
Description:
Table 4 contains the break classifications, inner and outer radius
boundaries of the break-finding algorithm, and all disk break
parameters, including break radii and linear fits to the profiles in
between breaks.
tablea1.dat to tablea3.dat contain the detailed surface brightness,
local slope, position angle, ellipticity, and Fourier mode amplitude
radial profiles for every galaxy in the sample, as well as detailed
justifications for the chosen break classifications, including
morphological types from Buta et al. (2015, Cat. J/ApJS/217/32).
Images of the galaxies and the profiles are also included for
reference.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 147 175 Disk break parameters
tablea1.dat 64 15005 Radial profiles 1
tablea2.dat 45 43050 Radial profiles 2
tablea3.dat 706 175 Detailed break justifications
images/* . 350 Individual images
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See also:
J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Galaxies (Sheth+ 2010)
J/A+A/569/A91 : Optical imaging for S4G (Knapen+, 2014)
J/ApJS/217/32 : S4G galaxy morphologies in the CVRHS system (Buta+, 2015)
J/A+A/582/A86 : Catalogue of features in the S4G (Herrera-Endoqui+, 2015)
J/A+A/596/A25 : Disc breaks across masses and wavelengths (Laine+, 2016)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Galaxy Galaxy Name
12- 25 A14 --- Btype Break classification (G1)
27- 32 F6.2 arcsec Rin Inner radius boundary
34- 38 F5.1 arcsec Rout Outer radius boundary
40- 46 F7.2 arcsec Rbr1 ?=-999 First break radius
48- 54 F7.2 arcsec Rbr2 ?=-999 Second break radius
56- 62 F7.2 arcsec Rbr3 ?=-999 Third break radius
64- 70 F7.2 arcsec muRbr1 ?=-999 Surface brightness at first break
radius
72- 78 F7.2 mag/arcsec2 muRbr2 ?=-999 Surface brightness at second break
radius
80- 86 F7.2 mag/arcsec2 muRbr3 ?=-999 Surface brightness at second break
radius
88- 93 F6.2 arcsec h1 Scale length of first disk segment (1)
95-101 F7.2 arcsec h2 ?=-0 Scale length of second disk segment (1)
103-109 F7.2 arcsec h3 ?=-0 Scale length of third disk segment (1)
111-117 F7.2 arcsec h4 ?=-0 Scale length of fourth disk segment (1)
119-123 F5.2 mag/arcsec2 mu01 Central surface brightness of first disk
segment (1)
125-131 F7.2 mag/arcsec2 mu02 ?=-999 Central surface brightness of second
disk segment (1)
133-139 F7.2 mag/arcsec2 mu03 ?=-999 Central surface brightness of third
disk segment (1)
141-147 F7.2 mag/arcsec2 mu04 ?=-999 Central surface brightness of fourth
disk segment (1)
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Note (1): The first segment includes the disk between Rin and Rbr1.
If a second break exists, the second segment is between Rbr1 and Rbr2;
otherwise it is between Rbr1 and Rout, and likewise for additional breaks.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Galaxy Galaxy name
12- 17 F6.2 arcsec Rad Radius along major axis
19- 25 F7.2 mag/arcsec2 mu36 ?=-999 Mean surface brightness at
radius Rad
27- 36 F10.2 arcsec Loch ?=-999 Local slope in surface brightness
at radius Rad
38- 46 F9.2 arcsec Smoothloch ?=-999 Median-smoothed version of
Loch (1)
48- 55 F8.3 --- A1 m=1 Fourier mode amplitude at radius Rad
57- 64 F8.3 --- A2 m=2 Fourier mode amplitude at radius Rad
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Note (1): This is local slope measured using the four adjacent points on
the surface brightness profile, parametrized as a local disk scale length.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Galaxy Galaxy name
12- 17 F6.2 arcsec Rad Radius along major axis
19- 24 F6.2 deg PA [0/360] Position angle of isophote major axis
26- 32 F7.2 deg dPA ?=-999 Position angle of deprojected image
isophote major axis
34- 37 F4.2 --- Ell Ellipticity of isophote major axis
39- 45 F7.2 --- dEll ?=-999 Ellipticity of deprojected image
isophote major axis
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Fname1 Name of image file showing radial profiles of
galaxy, in subdirectory images
23- 43 A21 --- Fname2 Name of image file showing galaxy images,
in subdirectory images
45- 54 A10 --- Galaxy Galaxy name
56- 87 A32 --- MClass Detailed morphological classification of
galaxy (1)
89-120 A32 --- Btype Break classification
122-153 A32 --- L16Btype Break classification from Laine et al.
(2016, Cat. J/A+A/596/A25) (G1)
155-706 A552 --- Notes Detailed notes justifying Btype
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Note (1): Complete explanation of these classifications can be found
in Buta et al. (2015, Cat. J/ApJS/217/32).
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Global notes:
Note (G1): The classifications of profiles are as follows:
0 = not an exponential disk
I = single exponential disk
II = down-bending break, no associated feature identifiable
IId = down-bending break associated with disklike features
(e.g. spiral arms)
IIa = down-bending break associated with asymmetric features
(e.g. tidal streams)
III = up-bending break, no associated feature identifiable
IIId = up-bending break associated with disklike features
(e.g. spiral arms)
IIIa = up-bending break associated with asymmetric features
(e.g. tidal streams)
IIIs = up-bending break associated with outer spheroidal component
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Acknowledgements:
A.E. Watkins, aaron.watkins(at)oulu.fi
(End) Aaron Watkins [Univ. Oulu], Patricia Vannier [CDS] 03-Apr-2019