EMSAO Example 4: Removing a Cosmic Ray

Galaxy Spectrum with Cosmic Ray This spectrum contains emission lines and a large cosmic ray hit which diverts emsao from the correct redshift. emsao was run using these parameters.

First Pass Yields the Wrong Redshift When the program is first run on the spectrum, it finds only one line, an indication that it might have the wrong redshift.

rv> emsao
List of input spectra (1994.0305.0359.09306p0546.fits): 
IRAF rvsao.emsao 2.0b mink@xena  01-Oct-1997 13:52

File: 1994.0305.0359.09306p0546.fits[1]
Object: 09306p0546  RA: 09:30:36.00 Dec: 05:46:00.0 1950.0
Observed  6-Mar-1994 05:15:21.50 = JD 2449417.7190 :   0.00
Combined vel = 15894.94 +-   35.05 km/sec, z= 0.0530 
Correlation vel = 11176.94 +-   80.16 km/sec, z= 0.0373 R=    3.2 
Emission vel = 15894.94 +-   31.68 km/sec, z= 0.0530 for 1/1 lines

Line  Rest lam  Obs. lam    Pixel     z         vel    dvel    eqw    wt
 OII   3727.30   3924.92   140.73  0.0530  15894.94   31.68 18406.9  1.000  

Zoom in on the Cosmic Ray The cursor was positioned on each side of the cosmic ray and the z command was typed.

z again to zoom from  3832.90 angstroms
zooming from  3832.90 to  3960.53 angstroms

Delete the Cosmic Ray The cursor was positioned at the very edge of the cosmic ray and the d command was typed.

d again to delete data from pixel 133.0000000
filling from pixel 133.0000000 to pixel 147.0000000

Unzoom the Spectrum The spectrum, now without the cosmic ray, was unzoomed using the u command, and the emission line information reappears.

Second Pass Yields the Correct Redshift After the f command was typed, the program identified the brightest emission line as H-alpha and found a velocity which fit several emission lines.

File: 1994.0305.0359.09306p0546.fits[1]
Object: 09306p0546  RA: 09:30:36.00 Dec: 05:46:00.0 1950.0
Observed  6-Mar-1994 05:15:21.50 = JD 2449417.7190 :   0.00
Combined vel = 11201.65 +-   49.02 km/sec, z= 0.0374 
Correlation vel = 11176.94 +-   80.16 km/sec, z= 0.0373 R=    3.2 
Emission vel = 11214.31 +-   57.39 km/sec, z= 0.0374 for 5/8 lines

Line  Rest lam  Obs. lam    Pixel     z         vel    dvel    eqw    wt
  Hb   4861.33   5043.39   903.12  0.0375  11227.51   36.72   7.17  0.085  
OIII   4958.91   5142.34   970.57  0.0370  11089.10  102.88   5.43  0.011  
OIII   5006.84   5193.77  1005.63  0.0373  11192.80   19.99  12.12  0.287  
  N1   6548.06   6806.92     0.00  0.0000      0.00    0.00   0.00  0.000 X1
  Ha   6562.82   6831.30     0.00  0.0000      0.00    0.00   0.00  0.000 X1
  N2   6583.57   6792.42     0.00  0.0000      0.00    0.00   0.00  0.000 X1
  S1   6716.44   6967.96  2214.99  0.0374  11226.81   14.87   8.96  0.519  
  S2   6730.81   6982.58  2224.95  0.0374  11213.58   34.17   7.08  0.098  
rv>