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# IMAGE and GALFIT CONTROL PARAMETERS
A) gal.fits # Input data image (FITS file)
B) imgblock.fits # Output data image block
C) none # Sigma image name (made from data if blank or "none")
D) psf.fits # # Input PSF image and (optional) diffusion kernel
E) 1 # PSF fine sampling factor relative to data
F) none # Bad pixel mask (FITS image or ASCII coord list)
G) none # File with parameter constraints (ASCII file)
H) 1 93 1 93 # Image region to fit (xmin xmax ymin ymax)
I) 100 100 # Size of the convolution box (x y)
J) 26.563 # Magnitude photometric zeropoint
K) 0.038 0.038 # Plate scale (dx dy) [arcsec per pixel]
O) regular # Display type (regular, curses, both)
P) 0 # Options: 0=normal run; 1,2=make model/imgblock & quit
# THE OBJECT LIST BELOW can be however long or short as the complexity
# requires. The user has complete freedom to mix and match the components
# by duplicating each object block.
# INITIAL FITTING PARAMETERS
#
# column 1: Parameter number
# column 2:
# -- Parameter 0: the allowed functions are: sersic, nuker, expdisk
# edgedisk, devauc, king, moffat, gaussian, ferrer, psf, sky
# -- Parameter 1-10: value of the initial parameters
# -- Parameter C0: For diskiness/boxiness
# <0 = disky
# >0 = boxy
# -- Parameter Z: Outputting image options, the options are:
# 0 = normal, i.e. subtract final model from the data to create
# the residual image
# 1 = Leave in the model -- do not subtract from the data
#
# column 3: allow parameter to vary (yes = 1, no = 0)
# column 4: comment
# Sersic function
0) sersic # Object type
1) 300. 350. 1 1 # position x, y [pixel]
3) 20.00 1 # total magnitude
4) 4.30 1 # R_e [Pixels]
5) 5.20 1 # Sersic exponent (deVauc=4, expdisk=1)
9) 0.30 1 # axis ratio (b/a)
10) 10.0 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# Nuker function
0) nuker # Object type
1) 250. 475. 1 1 # position x, y [pixel]
3) 17.2 1 # mu(Rb) [surface brightness mag. at Rb]
4) 20.5 1 # Rb [pixels]
5) 1.2 1 # alpha (sharpness of transition)
6) 0.5 1 # beta (outer powerlaw slope)
7) 0.7 1 # gamma (inner powerlaw slope)
9) 0.72 1 # axis ratio (b/a)
10) -25.2 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# deVaucouleur function
0) devauc # Object type
1) 301.2 351.5 1 1 # position x, y [pixel]
3) 18. 1 # total magnitude
4) 32. 1 # R_e [Pixels]
9) 0.5 1 # axis ratio (b/a)
10) 107. 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# Exponential function
0) expdisk # Object type
1) 405. 365 1 1 # position x, y [pixel]
3) 17.0 1 # total magnitude
4) 20.5 1 # Rs [Pixels]
9) 0.3 1 # axis ratio (b/a)
10) 25 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# Edge-on disk function
0) edgedisk # Object type
1) 405. 365 1 1 # position x, y [pixel]
3) 17.0 1 # central surface brightness [mag/arcsec^2]
4) 10.5 1 # disk scale-height [Pixels]
5) 20.5 1 # disk scale-length [Pixels]
10) 25 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# Moffat function
0) moffat # object type
1) 372.0 450.0 1 1 # position x, y [pixel]
3) 16.5 1 # total magnitude
4) 0.5 1 # FWHM [Pixels]
5) 1.5 1 # powerlaw
9) 0.3 1 # axis ratio (b/a)
10) 25 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# Ferrer function
0) ferrer # Component type
1) 100.0 100.0 0 0 # Position x, y
3) 10.0000 0 # Central surface brghtness [mag/arcsec^2]
4) 50.0000 0 # Outer truncation radius [pix]
5) 4.0000 0 # Alpha (outer truncation sharpness)
6) 2.0000 0 # Beta (central slope)
9) 0.5000 1 # Axis ratio (b/a)
10) 50.0000 1 # Position angle (PA) [deg: Up=0, Left=90]
Z) 0 # Skip this model in output image? (yes=1, no=0)
# Gaussian function
0) gaussian # object type
1) 402.3 345.9 1 1 # position x, y [pixel]
3) 18.5 1 # total magnitude
4) 0.5 0 # FWHM [pixels]
9) 0.3 1 # axis ratio (b/a)
10) 25 1 # position angle (PA) [Degrees: Up=0, Left=90]
Z) 0 # leave in [1] or subtract [0] this comp from data?
# The Empirical King Profile
0) king # Object type
1) 49.9925 49.9705 1 1 # position x, y
3) 14.9805 1 # mu(0)
4) 10.1328 1 # Rc
5) 51.0968 1 # Rt
6) 2.0485 1 # alpha
9) 0.9918 1 # axis ratio (b/a)
10) 20.7684 1 # position angle (PA)
Z) 0 # Skip this model in output image? (yes=1, no=0)
# PSF fit.
0) psf # object type
1) 402.3 345.9 1 1 # position x, y [pixel]
3) 18.5 1 # total magnitude
Z) 0 # Skip this model in output image? (yes=1, no=0)
# sky
0) sky
1) 0.77 0 # sky background [ADU counts]
2) 0.000 0 # dsky/dx (sky gradient in x)
3) 0.000 0 # dsky/dy (sky gradient in y)
Z) 0 # Skip this model in output image? (yes=1, no=0)
# The parameters C0, B1, B2, F1, F2, etc. listed below are hidden
# from the user unless he/she explicitly requests them. These can
# be tagged on to the end of any previous components except, of
# course, the PSF and the sky -- although galfit won't bar you from doing
# so, and will just ignore them. Note that a Fourier or Bending mode
# amplitude of exactly 0 will cause GALFIT to crash because the
# derivative image GALFIT computes internally will be entirely 0. If a
# Fourier or Bending amplitude is set to 0 initially GALFIT will reset it
# to a value of 0.01. To prevent GALFIT from doing so, one can set it to any
# other value.
# Bending modes
B1) 0.07 1 # Bending mode 1 (shear)
B2) 0.01 1 # Bending mode 2 (banana shape)
B3) 0.03 1 # Bending mode 3 (S-shape)
# Azimuthal fourier modes
F1) 0.07 30.1 1 1 # Az. Fourier mode 1, amplitude and phase angle
F2) 0.01 10.5 1 1 # Az. Fourier mode 2, amplitude and phase angle
F6) 0.03 10.5 1 1 # Az. Fourier mode 6, amplitude and phase angle
F10) 0.08 20.5 1 1 # Az. Fourier mode 10, amplitude and phase angle
F20) 0.01 23.5 1 1 # Az. Fourier mode 20, amplitude and phase angle
# Traditional Diskyness/Boxyness parameter c
C0) 0.1 0 # traditional diskyness(-)/boxyness(+)
# PA rotation is used most often to create spiral galaxies, although
# it can be used to fit isophotal rotations too. Note that the parameters
# R9 (inclination to line of sight) and R10 (sky position angle) differ
# very subtly (but importantly) from the classical axis ratio (q, parameter
# 9) and position angle (PA, 10), so you need to understand the
# distinction well. R9 and R10 should be set to 0 if one is modeling early
# type galaxies, because otherwise they are completely degenerate with
# the classical q and PA. R9 and R10 are used to project a spiral galaxy
# disk, assumed to be round viewed face on (i.e. inclination of 0 degrees,
# R9=0), to other orientations and flattening. The disk orientation, R10
# is 0 when pointing up and increases counter-clockwise, just like usual.
# When viewed face on, the thickness of the spiral arm is controlled by
# classical parameter 9, i.e. the axis ratio. When R9 and R10 are zero,
# everything is what you are used to with the old GALFIT. If R9 and R10 are
# not 0, then the classical parameters 9 and 10 (q, PA) will be a bit
# un-intuitive, but perfectly internally consistent with the scheme just
# described. For spiral galaxies, when and both R9 and R10 are 0, the
# classical position angle corresponds to the PA of the galaxy bar. This all
# sounds pretty confusing because you're just reading. But once you start
# playing with it it'll become more clear what I'm talking about.
# To have GALFIT generate some example galaxies, set P=1.
#
# Note that you can couple an arbitrary number of Fourier components with
# coordinate rotation. If you do so, you can create very complex,
# multi-armed, spiral structures, and arms that have different
# thicknesses.
R0) powerlaw # PA rotation function (power, log, none)
R1) 30. 1 # bar radius [pixels]
R2) 100. 1 # 96% asymptotic radius (i.e. at 96% of tanh rotation)
R3) 275. 1 # cumul. coord. rotation out to asymp. radius [degrees]
R4) 0.5 1 # asymptotic spiral arm powerlaw
R9) 0.5 1 # inclination to L.o.S. (controls projected axis ratio)
R10) 30. 1 # sky position angle
# The other coordinate rotation function is the log function.
R0) log # PA rotation func. (tanh, sqrt, log, linear, none)
R1) 30. 1 # bar radius [pixels]
R2) 100. 1 # 96% asymptotic radius (i.e. at 96% of tanh rotation)
R3) -59.9192 1 # cumul. coord. rotation out to asymp. radius [degrees]
R4) 10. 1 # Logarithmic winding scale radius [pixels]
R9) -56.2757 1 # Inclination to L.o.S. [degrees]
R10) 157.9937 1 # Sky position angle
# Create a truncation by multiplying a profile function with a
# hyperbolic tangent transition. The break radius, r_break, is defined
# as the radius which has 99% the flux of an original function, whereas
# the softening radius, r_soft, is where the function has only 1% of the
# flux of the original. Under normal circumstances, r_break < r_soft.
# On the other hand, r_break > r_soft is also possible. This happens,
# for instance, if one wants to generate a ring model with a hyperbolic
# tangent truncation in the inner region.
#
# When multiple profiles are linked, mathematically they are linked by:
# f_net(r) = Sum{f_inner(r)} * (1-s(r)) + Sum{f_outer(r)} * s(r).
# The transition radii are shared by the inner & outer functions in the
# sense that r_break is where inner profiles reaches 99% of their normal
# flux; it is also the radius where the outer functions reaches 1% of their
# own normal flux, and vice versa. When this happens, be careful that the
# sense of the break vs. asymptotic radius are in the correct sense, or
# else things can get very confusing very quickly. So as to minimize
# confusion when linking, consistently use r_break < r_soft.
#
# When linking two profiles, the flux parameter for the inner component
# is the surface brightness at the original (untruncated) effective
# radius "Re" for the Sersic profile instead of the total flux, or central
# surface brightness for all other profiles (gaussian, moffat, etc.).
# The outer component flux normalization is the surface brightness
# at the **break** radius.
#
# Note that the Fourier and bending modes can operate on the truncation
# parameters independently of the light component that the truncation
# parameters are modifying.
#
#
# v--- r_break ---v
#
# ____ ___
# / \
# ___/ \___
#
# ^---- r_soft ----^
#
# There are 4 kinds of truncation modes, designated by, "radial", "radial-b",
# for Type 1, versus "radial2", and "radial2-b" for Type 2.
#
# The difference between Type 1 and Type 2 is in the definition of
# parameters T3 and T4. For Type 1, T3 is "Break radius", and T4 is
# the "Softening length", i.e. (R_break) and (Delta R). For Type 2, T3 is
# still the "Break radius", but T4 is the "Softening radius", i.e.
# inner and outer break radius.
#
# As for Type "b" versus Type "a" (i.e. non-b), the difference is that
# "Type a" is intended for spiral structures, i.e. the truncation shape
# (axis ratio and PA) are tilted and rotated by the same angles as the
# spiral arms. Whereas for "Type b" truncations, the shape parameters
# refer to how they appear in projection, i.e. in the plane of the sky.
# For non-spiral models, there's no difference between "Type a" and
# "Type b".
# Truncated Sersic function
0) sersic # Object type
1) 300. 350. 1 1 # position x, y [pixel]
3) 20.00 1 # total magnitude
4) 4.30 1 # R_e [Pixels]
5) 5.20 1 # Sersic exponent (deVauc=4, expdisk=1)
9) 0.30 1 # axis ratio (b/a)
10) 10.0 1 # position angle (PA) [Degrees: Up=0, Left=90]
Ti) 5 # Inner truncation by component 5
To) 2 # Outer truncation by component 2
Z) 0 # leave in [1] or subtract [0] this comp from data?
# Object number: 5
T0) radial # truncation
T1) 200. 150. 1 1 # Centroid of truncation function (optional)
T4) 4.4179 1 # Break radius (99% normal flux) [pixels]
T5) 9.1777 1 # Softening length (1% normal flux) [pixels]
T9) 0.7 1 # Axis ratio (optional)
T10) -32. 1 # Position angle (optional)
F1) 0.1 30 1 # Fourier mode1 (now modifying truncation)