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Generall the two axis of a spectrum displayed by splot are wavlength and flux.The y axis are like 1.15e-18,1.25e-18...

Forgive my English.After reading the help page of splot,I am very confused.The unit of y axis is ergs/cm2/sec/hz or ergs/cm2/sec/A?
If I want to calculate the intensity of an emission line,I should integrate from angstroms to angstroms or from Hz to Hz?


https://iraf.net/irafhelp.php?val=splot&help=Help+Page
The integrated fluxes for all the methods are in the same units as the intensities and the integration is done in the same units as the plotted scale. It is the user's responsibility to keep track of the flux units. As a caution, if the data is in flux per unit frequency, say ergs/cm2/sec/hz, and the dispersion in Angstroms then the integrated flux will not be in the usual units but will be A-ergs/cm2/sec/hz. For flux in wavelength units, ergs/cm2/sec/A and the dispersion scale in Angstroms the integrated flux will be correct; i.e. ergs/cm2/sec.

SPLOT has the 'l' and 'n' keystrokes to convert between f-lambda and f-nu scaling, however you have to know what units the data are already in to begin with. I fyou used a task like CALIBRATE to create the spectra then the EX-FLAG and CA-FLAG keywords will be present to indicate the extinction and calibration steps applied (see the CALIBRATE, STANDARD and SENSFUNC tasks for additional details). Simply knowing the values are ~10e-18 doesn't help identify the current units.

The spectra I mentioned above are already the products of iraf tasks standard,sensfunc and calibrate .
However,both EX-FLAG and CA-FLAG values are zero.
That means calibrate did not work?

Seems counterintuitive but a zero value for EX-FLAG and CA-FLAG means the extinction and flux calibration (respectively) were done, I think it is a missing keyword that says it wasn't applied. The BUNIT keyword should also be present that will tell you the units.

I checked several spectra got from different telescopes and did not find bunit.
Generally,there are four data extensions for a spectrum. There should be a hidden unit somewhere.

Did you set the 'flux' parameter to the CALIBRATE task?

yes

calibrate input=@imagelist3//btfc_tran.0001 output=@imagelist3//flux extinct+ flux+ \
extinction="./extinct.dat" observa="lick" sensiti="sens" fnu- airmass=1.15