================================================================================ # 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)