J/MNRAS/478/5689 S4G galaxies disk/bar decomposition (Lewis+, 2018)
Non-parametric decompositions of disc galaxies in S4G using DISKFIT.
Lewis C., Spekkens K.
<Mon. Not. R. Astron. Soc., 478, 5689-5701 (2018)>
=2018MNRAS.478.5689L 2018MNRAS.478.5689L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; Morphology ; Models
Keywords: galaxies: bulges - galaxies: photometry - galaxies: spiral -
galaxies: structure
Abstract:
We present photometric models of 532 disc galaxies in 3.6um images
from the Spitzer Survey of Stellar Structure in Galaxies (S4G)
using the non-parametric DISKFIT algorithm. We first test DISKFIT's
performance on 400 synthetic S4G-like galaxy images. DISKFIT is
unreliable in the bulge region, but accurately disentangles
exponential discs from Ferrers bars farther out as long as their
position angles differ by more than 5°. We then proceed to model
the S4G galaxies, successfully fitting 489 of them using an
automated approach for initializing DISKFIT, optimizing the model and
deriving uncertainties using a bootstrap-resampling technique. The
resulting component geometries and surface brightness profiles are
compared to those derived by Salo et al. using the parametric model
GALFIT. We find generally good agreement between the models, but
discrepancies between best-fitting values for individual systems are
often significant: the choice of algorithm clearly impacts the
inferred disc and bar structure. In particular, we find that DISKFIT
typically assigns more light to the bar and less light to the disc
relative to the Ferrers and exponential profiles derived using GALFIT
in the bar region. Given DISKFIT's reliability at disentangling these
components in our synthetic images, we conclude that the surface
brightness distributions of barred S4G galaxies are not
well-represented by these functional forms. The results presented here
underscore the importance of validating photometric decomposition
algorithms before applying them to real data and the utility of
DISKFIT's non-parametric approach at measuring the structure of discs
and bars in nearby galaxies.
Description:
We present non-parametric photometric models of over 500 disc galaxies
from S4G using DISKFIT. We use a suite of simulated galaxies
embedded in S4G-like images to validate DISKFIT's performance on our
570-galaxy S4G subsample and find that diskfit non-parametrically
recovers the geometry and surface brightness distributions of
exponential discs and Ferrers bars as long as their position angles
differ by more than 5°.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 109 570 Galaxies in S4G subsample
prof/* . 616 Individual surface brightness profiles
from DiskFit fit
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See also:
J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Galaxies (S4G)
(Sheth+, 2010)
J/ApJ/772/135 : 3.6um surface brightness from S4G (Zaritsky+, 2013)
J/A+A/562/A121 : ARRAKIS: Atlas of Resonance Rings as Known In S4G
(Comeron+ 2014)
J/A+A/569/A91 : Optical imaging for S4G (Knapen+, 2014)
J/MNRAS/441/1992 : Galaxies with disc breaks in S4G and NIRS0S (Laine+, 2014)
J/MNRAS/444/3015 : Morphologies of S4G galaxies (Laine+, 2014)
J/A+A/582/A86 : Catalogue of features in the S4G (Herrera-Endoqui+, 2015)
J/ApJS/217/32 : S4G galaxy morphologies in the CVRHS system (Buta+, 2015)
J/ApJS/219/4 : S4G pipeline 4: multi-component decompositions (Salo+, 2015)
J/A+A/587/A160 : 3.6um S4G Galactic bars characterization
(Diaz-Garcia+, 2016)
J/A+A/596/A25 : Disc breaks across masses and wavelengths (Laine+, 2016)
J/A+A/596/A84 : S4G disk galaxies stellar mass distribution
(Diaz-Garcia+, 2016)
J/ApJS/234/18 : GALEX/S4G surface brightness profiles. I. (Bouquin+, 2018)
J/A+A/631/A94 : Avg pitch angles + spiral amplitudes in S4G
(Diaz-Garcia+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Galaxy name
12- 16 A5 --- Model Model used in DiskFit (1)
18 A1 --- l_PAD [~] Limit flag on PA
19- 25 F7.2 deg PAD ?=- Disk position angle
27- 31 F5.2 deg e_PAD ? Disk PA error
33 A1 --- l_EllD [~] Limit flag on EllD
34- 37 F4.2 --- EllD ?=- Disk Ellipticity
39- 42 F4.2 --- e_EllD ? Disk Ellipticity error
44 A1 --- l_PAB [~] Limit flag on PAB
45- 49 F5.1 deg PAB ?=- Bar position angle
51- 54 F4.1 deg e_PAB ? Bar PA error
56 A1 --- l_EllB [~] Limit flag on EllB
57- 60 F4.2 --- EllB ?=- Bar Ellipticity
62- 65 F4.2 --- e_EllB ? Bar Ellipticity error
67 A1 --- l_GLD [~] Limit flag on GLD
68- 70 I3 % GLD ?=- Percent of galaxy light in Disk
72- 73 I2 % e_GLD ? Percent of galaxy light in Disk error
75 A1 --- l_GLB [~] Limit flag on GLB
76- 80 F5.2 % GLB ?=- Percent of galaxy light in Bar
82- 86 F5.2 % e_GLB ? Percent of galaxy light in Bar error
88- 92 A5 --- Flag Flags (2)
94 A1 --- Prof [*] see surface brightness profiles
96-109 A14 --- FileName Name of the file with surface brightness
profiles in subdirectory prof
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Note (1): Model as follows:
d = Disk
bd = Disk+Bulge
dbar = Disc+Bar
bdbar = Disk+Bulge+Bar
Note (2): Flags as follows:
a = Excluded because |PAdisk-PAbar| <5 deg
b = Nucleus in GALFIT fit, not in DiskFit fit
c = Two Disks in GALFIT fit, one in DiskFit fit
d = Disk only model in DiskFit fit
e = Lower radial resolution needed to complete fit
f = DiskFit fit failed when using GALFIT parameters as input
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Byte-by-byte Description of file: prof/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
5- 10 F6.2 pix r Radius from centre in pixels
(1pix=0.75arcsec)
12- 20 F9.2 --- npts Effective number of points contributing
to fit at r
27- 32 F6.2 mag/arcsec+2 Idisk Disk surface brightness at r
35- 44 F10.2 mag/arcsec+2 e_Idisk Uncertainty in disk surface brightness
at r
51- 56 F6.2 mag/arcsec+2 Ibar Bar surface brightness at r
64- 68 F5.2 mag/arcsec+2 e_Ibar Uncertainty in bar surface brightness
at r
76- 80 F5.2 mag/arcsec+2 Ibulge Bulge surface brightness at r
85- 92 F8.2 mag/arcsec+2 e_Ibulge Uncertainty in bulge surface brightness
at r
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Jan-2022