J/ApJS/219/4 S4G pipeline 4: multi-component decompositions (Salo+, 2015)
The Spitzer Survey of Stellar Structure in Galaxies (S4G):
multi-component decomposition strategies and data release.
Salo H., Laurikainen E., Laine J., Comeron S., Gadotti D.A., Buta R.,
Sheth K., Zaritsky D., Ho L., Knapen J., Athanassoula E., Bosma A.,
Laine S., Cisternas M., Kim T., Munoz-Mateos J.C., Regan M., Hinz J.L.,
Gil de Paz A., Menendez-Delmestre K., Mizusawa T., Erroz-Ferrer S.,
Meidt S.E., Querejeta M.
<Astrophys. J. Suppl. Ser., 219, 4 (2015)>
=2015ApJS..219....4S 2015ApJS..219....4S
ADC_Keywords: Galaxies, IR ; Morphology ; Surveys
Keywords: galaxies: fundamental parameters; galaxies: kinematics and dynamics;
galaxies: spiral; galaxies: structure
Abstract:
The Spitzer Survey of Stellar Structure in Galaxies (S4G) is a deep
3.6 and 4.5µm imaging survey of 2352 nearby (<40Mpc) galaxies. We
describe the S4G data analysis pipeline 4, which is dedicated to
two-dimensional structural surface brightness decompositions of
3.6µm images, using GALFIT3.0. Besides automatic 1-component Sersic
fits, and 2-component Sersic bulge + exponential disk fits, we present
human-supervised multi-component decompositions, which include, when
judged appropriate, a central point source, bulge, disk, and bar
components. Comparison of the fitted parameters indicates that
multi-component models are needed to obtain reliable estimates for the
bulge Sersic index and bulge-to-total light ratio (B/T), confirming
earlier results. Here, we describe the preparations of input data done
for decompositions, give examples of our decomposition strategy, and
describe the data products released via IRSA and via our web page
(www.oulu.fi/astronomy/S4G_PIPELINE4/MAIN). These products include all
the input data and decomposition files in electronic form, making it
easy to extend the decompositions to suit specific science purposes.
We also provide our IDL-based visualization tools (GALFIDL) developed
for displaying/running GALFIT-decompositions, as well as our mask
editing procedure (MASK_EDIT) used in data preparation. A detailed
analysis of the bulge, disk, and bar parameters derived from
multi-component decompositions will be published separately.
Description:
The Spitzer Survey of Stellar Structure in Galaxies (S4G, Sheth et al.
2010, J/PASP/122/1397) is a survey of 2352 galaxies observed in the
mid-infrared (mid-IR) at 3.6 and 4.5um, wavelengths that are largely
unaffected by internal extinction.
The data have been processed through Pipeline 1 (Munoz-Mateos et al.
2015ApJS..219....3M 2015ApJS..219....3M; MM15) which makes mosaics of the observed
individual frames, Pipeline 2 (MM15) which makes masks of the
foreground stars and image defects, and Pipeline 3 (MM15) which
measures the basic photometric parameters like the galaxy magnitudes
and concentration indices. In Pipeline 4 (P4), described in this
study, we decompose the two-dimensional flux distributions of the
images into several structural components using GALFIT (Peng et al.
2010AJ....139.2097P 2010AJ....139.2097P).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 2352 Pipeline 4 parameters: galaxy center, outer
orientation, and sky background
table6.dat 58 2352 Parameters of 1-component Sersic fits
table7.dat 227 4629 *Parameters of final multicomponent decompositions
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Note on table7.dat: All decompositions assume a fixed common center for all
components and elliptical isophotal shape, constant over radius.
One line per component for each galaxy.
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See also:
J/ApJS/217/32 : S4G galaxy morphologies in the CVRHS system (Buta+, 2015)
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/ApJ/772/135 : 3.6um surface brightness from S4G (Zaritsky+, 2013)
J/ApJ/771/59 : Surface brightness of S4G face-on gal. (Munoz-Mateos+, 2013)
J/ApJS/196/11 : Bulge+disk decompositions of SDSS galaxies (Simard+, 2011)
J/MNRAS/418/1452 : NIR Atlas of S0-Sa galaxies (NIRS0S) (Laurikainen+, 2011)
J/AJ/142/145 : Outer disks of S0-Sb galaxies II. (Gutierrez+, 2011)
J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Gal. (Sheth+, 2010)
J/ApJS/190/147 : Mid-IR galaxy morphology from S4G (Buta+, 2010)
J/MNRAS/405/1089 : Photometric scaling for L/S0 galaxies (Laurikainen+ 2010)
J/ApJ/716/942 : Bulges of nearby galaxies with Spitzer (Fisher+, 2010)
J/ApJS/182/216 : Surface photometry of Virgo ellipticals (Kormendy+, 2009)
J/MNRAS/393/1531 : BUDDA structural properties of galaxies (Gadotti+, 2009)
J/ApJS/143/73 : Morphology of spiral galaxies (Eskridge+, 2002)
http://www.oulu.fi/astronomy/S4G_PIPELINE4/MAIN/ : S4G PIPELINE4 home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Galaxy name (IDE)
12- 18 F7.2 pix xc ? X pixel of galaxy center
20- 26 F7.2 pix yc ? Y pixel of galaxy center
28- 32 F5.1 deg PA [0.2/180]? Outer isophote position angle
34- 37 F4.1 deg e_PA [0/63]? Standard deviation in PA
39- 43 F5.3 --- Ell [0.008/1]? Outer isophote ellipticity
45- 49 F5.3 --- e_Ell [0/0.3]? Standard deviation in Ell
51- 54 I4 arcsec Rmin [1/1125]? Lower range of outer isophote
56- 59 I4 arcsec Rmax [6/1425]? Upper range of outer isophote
61- 62 A2 --- Flag [ok uz] Uncertainty flag (1)
64- 70 F7.4 MJy/sr Sky [-0.06/0.3]? Estimated sky level
72- 77 F6.4 MJy/sr s_Sky [0.0004/0.04]? Global variation of sky level
79- 84 F6.4 MJy/sr RMS [0.001/0.04]? Local variation of sky level
86- 91 F6.4 MJy/sr sigma [0/0.03]? Estimated extra instrumental noise
component (2)
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Note (1): Indicates whether the inclination can be reliably estimated from
the ellipticity of the outer isophotes:
ok = reliable;
u = uncertain;
z = nearly edge-on galaxy.
Note (2): During the Spitzer warm mission (See Sect 2.2.5).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Galaxy name (IDE)
12- 24 A13 --- Comm Comment (3)
26- 30 F5.2 mag Tmag [6.1/17]? Total magnitude
32- 36 F5.3 --- q [0.07/1]? Axial ratio
38- 43 F6.2 deg PA1 [0/180]? Elliptical isophote position angle
45- 50 F6.3 --- n [0.3/19]? Sersic index
52- 58 F7.2 arcsec Re [5/7631]? Effective radius
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Note (3): Indicates cases where "No fit" was made, fit failed to converge
("Fit fails"), or its parameters are not reliable ("Fit uncertain").
No measurement was possible for PGC052336 due to a superposed bright star.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/2352] Running sequence number
6- 15 A10 --- Name Galaxy name
17- 24 A8 --- Mod Type of final decomposition model (1)
26- 31 A6 --- --- [NCOMP=]
32 I1 --- Nc [1/4] Number of components in the model (1-4)
34- 41 A8 --- --- [quality=]
42 I1 --- Q [3/5] Quality flag, 5=most reliable (2)
44- 50 A7 --- C Phsical interpretation of the component (1)
52- 59 A8 --- Fn The GALFIT function used for the component
(sersic, edgedisk, expdisk, ferrer2 or psf)
61- 65 F5.3 --- f1 [0.006/1]? "sersic" fraction of the total
model flux
67- 72 F6.3 mag mag1 [7/19.4]? "sersic" total 3.6um AB magnitude
74- 78 F5.3 --- q1 [0.1/1]? "sersic" axis ratio (3)
80- 86 F7.3 deg PA1 [0.08/180]? "sersic" position angle (3)
88- 94 F7.3 arcsec Re [0.004/430]? "sersic" effective radius (Re)
96-101 F6.3 --- n [0.01/20]? "sersic" parameter n
103-107 F5.3 --- f2 [0.02/1]? "edgedisk" fraction of the total
model flux
109-114 F6.3 mag/arcsec2 mu02 [11.8/24.6]? "edgedisk" central surface
face-on brightness (µ0)
116-122 F7.3 deg PA2 [-90/90]? "edgedisk" PA
124-130 F7.3 arcsec hr2 [1/153]? "edgedisk" exponential scale
length (hr)
132-137 F6.3 arcsec hz2 [0.003/39]? "edgedisk" z-scale hz
139-143 F5.3 --- f3 [0.02/1]? "expdisk" fraction of the total
model flux
145-150 F6.3 mag mag3 [6.5/18.1]? "expdisk" total 3.6um AB magnitude
152-156 F5.3 --- q3 [0.1/1]? "expdisk" axis ratio (3)
158-164 F7.3 deg PA3 [-90/90]? "expdisk" position angle (3)
166-172 F7.3 arcsec hr3 [0.7/332]? "expdisk" exponential scale
length (hr)
174-179 F6.3 mag/arcsec2 mu03 [16.4/25.3]? "expdisk" central surface
face-on brightness (µ0)
181-185 F5.3 --- f4 [0.003/0.6]? "ferrer2" fraction of the total
model flux
187-192 F6.3 mag/arcsec2 mu04 [16/24.8]? "ferrer2" central surface sky
brightness (µ0)
194-198 F5.3 --- q4 [0.01/1]? "ferrer2" axis ratio (3)
200-206 F7.3 deg PA4 [-90/90]? "ferrer2" position angle (3)
208-214 F7.3 arcsec Rbar [3.7/232.5]? "ferrer2" outer truncation
radius of the bar (Rbar)
216-220 F5.3 --- f5 [0.001/0.4]? "psf" fraction of the
total model flux
222-227 F6.3 mag mag5 [11.5/21.1]? "psf" total 3.6um AB magnitude
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Note (1): Coded to all output file names together with underscore prefix
(B=bulge, D=disk, Z=edge-on disk, N=nucleus, Bar/Halo; see section 3)
Note (2): If no final decomposition was made (quality=1 or 2),
then for this galaxy we set an empty type (-) and Nc=0.
Note (3): If there is an (outer) disk, its q and PA parameters
are kept fixed to those in Table 1.
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History:
* 01-Jul-2015: Published electronic version
* 14-Oct-2015: First insertion into VizieR (tables 1,6,7 -
from electronic version of the journal)
* 28-Oct-2015: Table 7 corrected to provide one line per component
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 02-Sep-2015