Clarification of each line_prop calculation and results

[Bovornpratch]

Hi,

I am doing some fitting for several SDSS spectra and would like to understand the output results better.
I have performed some tests on the code and have read the code itself but I would like some clarification on how the FWHM is calculated in the results file, the FWHM returned from the function line_prop, and line_prop_from_name

For context, I am fitting MgII lines with 1 narrow and 1 broad line as a baseline. As you can see, the MgII is fitted with 2 broad components instead. When I called line_prop_from_name('MgII_br', 'broad') I found that the results are inconsistent with the results MgII_whole_br_fwhm. however, I noticed that line_prop_from_name('MgII_nl', 'broad') also returns a non-zero value.
I tested the code assuming different numbers lines to fit in MgII (eg, only broad, only gaussian, etc).

I check the code and would like the following points.

1. My understanding now is that the FWHM of whole_br listed in the results file and stored under fur_result is calculated from the model emission line constructed from all broad line components in the best fit and calculated numerically following Peterson+04. Is this correct?
2. Internally, initially assumed narrow emission lines can be switched to broad emission lines if the line widths exceed a threshold (ln_sigma_br). Correct?
3. If the line with an assumed narrow line width (eg. MgII_nl) is switched into a broad line, it is added to the composite broad line into the final result file correct?
4. line_prop (and by extension line_prop_from_name) checks the best fit emission line width correct? eg. I noticed that line_prop_from_name('MgII_nl', 'broad') returns the result of the best fit suggesting it is broad.

Thanks for the work you guys have done btw! Sorry if the questions are a bit convoluted.

[legolason]

Hi,
The MgII fitted by two broad components is caused by hitting the boundary(0.0017, ~ 1200 km/s ) in the initial setting. You can change 0.0017. to 0.0016, since 0.0017 is slightly larger than 1200 km/s. You can use the CALFWHM function to do the conversion.
Point 1, yes! Point 2, yes, if your setting is 0.0017 for narrow components. When it hit the boundary, the PLOT function will plot it in red color. Point 3, change 0.0017, and you will not meet this problem again. Point 4 Line_prop function is designed to calculate the line properties including the line width for black hole mass estimation. You only need to feed the right Gaussian parameters ([scale, line center, width]), then you can calculate any single Gaussian profile or two/three combined Gaussian profiles.

Hope it helps~