S4G PIPELINE4
S4G final sample
LAST UPDATED _2-Oct-2014_19_20
The Spitzer Survey of Stellar Structure in Galaxies (S4G, PI K. Sheth,
NRAO)
is a deep 3.6 and 4.5 micron survey of over 2300 nearby
galaxies (dist< 40Mpc).
For the S4G homepage, see
www.cv.nrao.edu/~ksheth/S4G/Site/S4G_Home.html
The task of Pipeline 4 is to carry 2D multicomponent structural
decompositions for the 3.6 micron S4G images, using Chien Pengs's GALFIT (v3.0).
The decompositions are done with the help of the GALFIDL package,
which is a collection of IDL tools we have developed for visualization and running of GALFIT decompositions.
The pipeline decompositions include semi-automatic 1-component Sersic fits
and 2-component bulge-disk fits, and most importantly, human-supervised final
decompositions, using up to 4 simultaneous components (modeled with
GALFIT's "sersic", "expo", "edgedisk", "ferrer2", and "psf" fitting
functions, used for bulge, disk, nearly edge-on disk, bar, and
unresolved central components, respectively).
Note that the term 'pipeline' is misleading to describe the last type of
decompositions, relying heavily on human interpretation.
The current pages (evolved from the pipeline 4 internal work pages) illustrate the preliminary steps required for starting the
decompositions (masking, clipping, isophotal analysis, sky background
determinations) as well as results of decompositions (model & observation
comparisons, residuals).
The final pipeline products, including tables of decomposition
parameters, is published via IRSA
The decompositions are described in detail in Salo et al. (2014).
The data release includes both the decompositions and all input files
needed for repeating/refining the pipeline 4 decompositions.
The GALFIDL software can be loaded from
here .
This Pipeline 4
main-page contains a list of names of all 2352 galaxies in the
final S4G sample
Blue entry indicates that IRAC1 data exists: the
The morphological types are from Buta et al. (2014) mid-IR classification.
This Pipeline 4
main-page contains a list of names of all 2352 galaxies in the
final S4G sample
Blue entry indicates that IRAC1 data exists: the
entry links to an index page, showing 100 galaxies/page.
The index page displays for each galaxy
a row of icon-sized images (clicking on icon displays the full-size image):
1) Raw IRAC1 image,
2) Clipped mask image (masked regions attenuated by 5 magnitudes)
3) Clipped image
4) Deprojected image (even when the deprojection does not make sense, e.g. ellipticals)
5) IRAF ellipse-profiles
6) Sky background determination
7) One-component Sersic model:residuals
9) Final model: residuals
9) Final model: component-plot
The blue link takes to a decomposition page (20 galaxies/page), 'main' takes back to
the galaxy list page
The decomposition page shows:
1) mask, isophote, sky-determination plots (same as on index page)
2) 1-comp model sky-plane profile, residuals, 1d-plot
2) 2-comp model sky-plane profile, residuals, 1d-plot
3) Final model sky-plane profile, residuals, 1d-plot
4) Final model components
A missing final model indicates that no reliable decomposition could
be done (problems with the image, no convergence, or very complicated
morphology etc.)
The links take to:
previous/next galaxy decomposition (slight delay when the page is switched)
back to galaxy index-page
back to main galaxy list
For a summary tables of the parameters, see
Final models (compact format)
Final models
1-component Sersic models
This page contains links to subsamples od S4G (based on the fit quality)
Have fun & send suggestions to heikki.salo@oulu.fi