# GalFIT 使用说明

## 1. 输入文件格式

```
# IMAGE PARAMETERS
A) gal.fits # 输入图像(FITS文件)，只能有一个hdu
B) imgblock.fits # 输出文件名，包含4个hdu，分别为空白、原图像、模型图像和残差
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) both # Display type (regular, curses, both)
P) 0 # Options: 0=normal run; 1,2=make model/imgblock & quit
# INITIAL FITTING PARAMETERS
#
# For object type, the allowed functions are:
# nuker, sersic, expdisk, devauc, king, psf, gaussian, moffat,
# ferrer, and sky.
#
# Hidden parameters will only appear when they’re specified:
# C0 (diskyness/boxyness),
# Fn (n=integer, Azimuthal Fourier Modes).
# R0-R10 (PA rotation, for creating spiral structures).
#
# ------------------------------------------------------------------------------
# par) par value(s) fit toggle(s) # parameter description
# ------------------------------------------------------------------------------
# Object number: 1 -- A TRUE point source
0) psf # Object type
1) 50.00 50.00 1 1 # position x, y
3) 18.000 1 # total magnitude
Z) 0 # Output option (0 = residual, 1 = Don’t subtract)
# Object number: 2
0) sersic # object type
1) 48.5180 51.2800 1 1 # position x, y
3) 20.0890 1 # integrated magnitude
4) 5.1160 1 # R_e (half-light radius) [pix]
5) 4.2490 1 # Sersic index n (de Vaucouleurs n=4)
9) 0.7570 1 # axis ratio (b/a)
10) -60.3690 1 # position angle (PA) [deg: Up=0, Left=90]
F1) 0.0001 0.0000 1 1 # azim. Fourier mode 1, amplitude, & phase angle
F3) 0.0001 0.0000 1 1 # azim. Fourier mode 3, amplitude, & phase angle
Z) 0 # output option (0 = resid., 1 = Don’t subtract)
# Object number: 3
0) expdisk # object type
1) 48.5180 51.2800 1 1 # position x, y
3) 20.0890 1 # integrated magnitude
4) 5.1160 1 # R_s (disk scale-length) [pix]
9) 0.7570 1 # axis ratio (b/a)
10) -60.3690 1 # position angle (PA) [deg: Up=0, Left=90]
C0) -0.05 0 # diskyness(-)/boxyness(+)
Z) 0 # output option (0 = resid., 1 = Don’t subtract)
# Object number: 4
0) nuker # object type
1) 48.5180 51.2800 1 1 # position x, y
3) 20.0890 1 # mu(Rb) [mag/arcsec^2]
4) 5.1160 1 # Rb [pix]
5) 4.2490 1 # alpha
6) 1.1000 1 # beta
7) 0.3000 1 # gamma
9) 0.7570 1 # axis ratio (b/a)
10) -60.3690 1 # position angle (PA) [deg: Up=0, Left=90]
Z) 0 # output option (0 = resid., 1 = Don’t subtract)
# Object number: 5
0) sky # object type
1) 1.3920 1 # sky background at center of fitting region [ADUs]
2) 0.0000 0 # dsky/dx (sky gradient in x)
3) 0.0000 0 # dsky/dy (sky gradient in y)
Z) 0 # output option (0 = resid., 1 = Don’t subtract
```

## 2. 运行方式

```
./galfit 输入文件名
```