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Hi!
I am trying to calculate radial velocities using FXCOR. I am testing with two fits files. I do not get velocity values; except I get all the velocities as INDEF. Could you please help me figure out what's wrong?
Thanks in advance!
-Prabhani

This is how my rv.log looks like:

Description of Fit to CCF Peak and Cross-Correlation
NOAO/IRAF V2.16 ****** Thu 01:37:50 12-Jul-2018

Obj = ` aperture_19.fits[19]' star = `'
Temp = ` temp.0182.fits[19]' star = `'
Deltav = INDEF Km/sec Tempvel = INDEF Km/sec

Fit Parameters:
Function = `gaussian' Width = INDEF
Height = 0. Minwidth = 3.
Peak = no Maxwidth = 21.
Weights = YES Background = 0.
Wincenter = INDEF Window = INDEF

Number of points fit = 21
Number of iterations = 4
Number of coeffs fit = 1 - 3
Chi Squared of fit = 9.238E-5
Fit Coefficients:
c[1] = 0.2691 +/- 0.4598 # Amplitude
c[2] = -0.1959 +/- 15.799 # Center
c[3] = 35.7311 +/- 261.15 # Sigma^2
c[4] = 0.0000 (fixed) # Background

Mean Residual = 0.0057840
Sigma of Residuals = 0.0166981
Maximum of cross-correlation is in bin = -1.
Variance of cross-correlation = 0.009574991
HJD of observation = INDEF MJD = INDEF
Object sample used in correlation = `*'
Template sample used in correlation = `*'
Tonry&Davis R value = 19.87068

Velocity Results:
Shift of peak = -0.1959 pixels
Correlation height = 0.269
FWHM of peak = INDEF Km/sec (=14.07606 pixels)

Velocity computed from shift = INDEF Km/sec
Observed velocity = INDEF Km/sec
Heliocentric velocity = INDEF +/- INDEF Km/sec

It's hard to tell what's going wrong without seeing the image header or a plot of the correlation peak fit. INDEF values typically mean there is some information missing from the header (e.g. dispersion keywords, date of observation) or the peak fit did not converge properly. normally, missing keywords would be listed as errors in the log file, but zero values or values that couldn't be parsed might not.

Please post the image header, my suspicion is that there is some error with the dispersion keywords (e.g. a missing DC-FLAG, W0 or WPC, etc).

Thank you for the quick reply!

This is the headers of the object (aperture_19.pro):

SIMPLE = T / Fits standard
BITPIX = -32 / Bits per pixel
NAXIS = 1 / Number of axes
NAXIS1 = 4334 / Axis length
EXTEND = T / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE = '2018-07-06T03:27:36' / Date FITS file was generated
IRAF-TLM= '2018-07-06T03:27:36' / Time of last modification
CTYPE1 = 'LINEAR ' /
CRVAL1 = 3900 /
CRPIX1 = 1 /
CDELT1 = 1.20000 /
CD_1 = 1.20000 /
CD_2 = 1 /
WAT0_001= 'system=equispec' /
WAT1_001= 'wtype=linear label=wavelength units=angstroms' /
APNUM1 = '19 19 ' /
WCSDIM = 1
CD1_1 = 1.2
LTM1_1 = 1.

And, this is the header of the template (temp.0182.fits):

SIMPLE = T / Fits standard
BITPIX = -32 / Bits per pixel
NAXIS = 1 / Number of axes
NAXIS1 = 4334 / Axis length
EXTEND = T / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE = '2018-07-12T04:37:19' / Date FITS file was generated
IRAF-TLM= '2018-07-12T04:37:19' / Time of last modification
CTYPE1 = 'LINEAR ' /
CRVAL1 = 3900 /
CRPIX1 = 1 /
CDELT1 = 1.20000 /
CD_1 = 1.20000 /
CD_2 = 1 /
WAT0_001= 'system=equispec' /
WAT1_001= 'wtype=linear label=wavelength units=angstroms' /
APNUM1 = '182 182 ' /
WCSDIM = 1
CD1_1 = 1.2
LTM1_1 = 1.
--------------------------------------------
I used scopy to create these 1D spectra. I am not sure if I made a mistake when I run scopy.
--> scopy m33-iraf.fits[0] temp aperture='19' format='onedspec'

The header of the initial file (m33-iraf.fits) was:

SIMPLE = T / Fits standard
BITPIX = -32 / Bits per pixel
NAXIS = 2 / Number of axes
NAXIS1 = 4334 / Axis length
NAXIS2 = 300 / Axis length
EXTEND = T / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE = '2018-07-13T16:17:09' / Date FITS file was generated
IRAF-TLM= '2018-07-13T16:17:25' / Time of last modification
CTYPE1 = 'LINEAR ' /
CRVAL1 = 3900 /
CRPIX1 = 1 /
CDELT1 = 1.20000 /
CDELT2 = 1 /
CD_1 = 1.20000 /
CD_2 = 1 /
WAT0_001= 'system=equispec' /
WAT1_001= 'wtype=linear label=wavelength units=angstroms' /
WAT2_001= 'wtype=linear' /
APNUM1 = '0 0 ' /
APNUM2 = '1 1 ' /
APNUM3 = '2 2 ' /
APNUM4 = '3 3 ' /
APNUM5 = '4 4 ' /
APNUM6 = '5 5 ' /
APNUM7 = '6 6 ' /
APNUM8 = '7 7 ' /
APNUM9 = '8 8 ' /
APNUM10 = '9 9 ' /
APNUM11 = '10 10 ' /
APNUM12 = '11 11 ' /
APNUM13 = '12 12 ' /
APNUM14 = '13 13 ' /
APNUM15 = '14 14 ' /
APNUM16 = '15 15 ' /
:
:
APNUM300= '299 299 ' /

-Prabhani

The spectra appear to be missing the W0, WPC and DC-FLAG keywords that tells IRAF how to interpret the WCS. For both your object and templates you should have DC-FLAG=0, and W0=, and WPC=. You can do this with command such as

cl\$this->_split2($m[0]) hedit DC-FLAG 0 add+ # add the DC-FLAG keyword
cl\$this->_split2($m[0]) type cmds # create a 'cmds' file to add W0/WPC keywords
w0 = crval1
wpc = cdelt1
cl\$this->_split2($m[0]) asthedit cmds # add W0/WPC using asthedit task

Thanks a lot!!

It started working somewhat. I get these Comments on the log file when I'm referring the same aperture as the temp file (I am using a 1-D spec extracted from the spectrum), but otherwise, I still get the same INDEF (velocities and uncertainties) and no comments.

Velocity Results:
Shift of peak = 327.9466 pixels
Correlation height = 0.317
FWHM of peak = 1237.362 Km/sec (=21.1082 pixels)

Velocity computed from shift = 19853.9844 Km/sec
Observed velocity = INDEF Km/sec
Heliocentric velocity = INDEF +/- 56.275 Km/sec

Comments:
WARNING: Using template velocity of 0 km/s.
ERROR: Error getting 'DATE-OBS' from temp image header.
ERROR: Error getting 'RA' from temp image header.
ERROR: Error getting 'DEC' from temp image header.
ERROR: Missing EPOCH keyword.
ERROR: Missing exposure time keyword.

I am trying to find the values and see if it works. I would like to have if you've got any suggestions!

And, I have one more question if you don't mind:
My inputs and outputs are as bellow. I am not sure if this is correct (extracting an aperture from a 1-D spectrum??).

E.g.:
Input file names and apertures on the parameter editor:
Objects m33-iraf.fits[0]
templates temp.0142.fits
(apertures) "19"

Output (extracted from the log file):
Obj = ` m33-iraf.fits[0][19]' star = `'
Temp = ` temp.0142.fits[19]' star = `'

Could you please help me with this?

Thank you for your time!

Best,
Prabhani

Hey guys,

Just wanted to follow up on this, as I have the same INDEF velocity issue, and no suggestions I have encountered worked for me.

My template files are generated via rspectext from text files, with the first column containing wavelength values 3000, 3001, 3002, ..., 10000, and the second containing the flux values. Afterwards I add a set of headers. My headers currently look like this:



No matter what I try to cross-correlate this *.fits file with, I get an INDEF velocity, but not always an INDEF velocity error. For example, if I cross-correlate this template with itself, I get:



My observation spectra are SDSS spectra in the IRAF format, and they work fine when cross-correlated with each other:



But, again, cross-correlating them with templates always leads to INDEF:



What could be causing this?

Thanks a lot!