Since ARC2D and ARCSDI have much in common with LONGSLIT as regards line selection, we will only describe this part once, noting the differences when they occur.
% longslit (IMage) Name of image for input [1052-5VIG] - 1052-5VIG[2040,171] HH 1-2 HALPHA/[N II] =========< A r c _ O p t s >========= New : Set up line identifications from scratch Repeat : Use existing line identifications Clone : Use line identifications from another file Fit option [REPEAT] - NEW
The options here are:
NEW mode is needed to set up line identifications.
(MAXLines) Maximum number of lines to allow room for  -
This only affects the size of the arrays to be used, so you are not committed to 10 lines! You cannot, however, later have more than the number set here.
(MAXGauss) Maximum number of Gaussians to allow room for  -
Similarly this only sets the maximum allowed number of components in a fit. Note that this is the only ``hard'' limit to the number of components to be fitted when guesses are made for multiple component fits. A look at the data should allow a sensible value to be selected, five is a reasonable value (data rarely needs more components than this).
(YStart) analysis lower limit  - (YEnd) analysis upper limit  -
A one-dimensional spectrum is extracted from the two-dimensional spectrum, and used for line selection. For LONGSLIT it is probably best to include all the data as here (the example data has 171 cross-sections), but for ARC2D and ARCSDI a central portion should be chosen (e.g. cross-sections 70-80 for a total of 171 cross-sections). At this stage the actual lines are located by marking to either side with a cursor. Be sure to include some base to either side, so that the optimisation routines can determine the base level precisely.
Locate Line : 1 2nd tram line Locate Line : 2 2nd tram line Locate Line : 3
A list of cursor options can be obtained by hitting the ``?' key (hitting any key will then return to displaying the spectrum). Note that the options change depending upon whether the display is zoomed, and also upon whether any lines are identified (see below). If the key ``Y'' is pressed, this causes the program to set a new maximum Y value for the display based on the current cursor position. This is used to select weak lines, where the default display is such that they are small on the display, due to the presence nearby of much stronger line(s). The remaining lines are located.
Alternatively we could have used an automatic line-finding algorithm, by hitting key A. This option is available only while no lines have been found, or those found have only been located using this option (in which case the previously identified lines are discarded if the option is selected). This uses a routine adapted from SPICA, the predecessor to FIGARO. The automatic line finding algorithm checks for a minimum acceptable height for a line and for the values of the data dropping off to either side. It then finds the centroids and checks that the possible lines are above a minimum width. A check is also made for the line's being sufficiently above the noise, and for not being a side-peak to another line.
The lines have now been located, LONGSLIT and ARC2D now need to know the identifications of these lines. Line lists are provided and users may create their owns lists. Alternatively the ``ID'' option in the ``Identification Menu'' can be used, in which a wavelength and name are used as given. Since ARCSDI only aims to straighten the lines, you would leave ARCSDI here.
=========< L i n e L i s t M e n u >========= Emission : Emission lines Absorption : Absorption lines Neon : Neon arc Cuar : Copper-argon arc Helium : Helium arc Iron : Iron arc SKy : Sky lines STored : User supplied list in file Ok : All tables read in Line List Menu - e Emission line list. Current version August 1990 78 lines read from EMISSION
The user can create his/her own file for use here. No responsibility is accepted for the wavelengths of the lines in the lists supplied. The format is as below, and the files can be created using an editor. The header consists of a number (as many as you want) of lines with an asterix in the first column, the only thing that is done with these is that they are written to the terminal (without the asterix). Blank lines are ignored, and all remaining lines are taken as data lines. The data lines have the wavelength (read free-format) followed by the (optional) name, the array for the names is character*10 line_name(number of line slots). These files can be placed in the default directory (the program will search there first, so they can have the same names as those supplied). The first few lines of the emission line list supplied are given here:
* Emission line list. * Current version August 1990 3726.1600 [OII] 3728.9100 [OII] 4101.0000 HDELTA 4276.8300 [FeII] 4287.4000 [FeII] 4319.6200 [FeII]
It is possible to specify the FIGARO .ARC files, as alternatives, but if there is a file included with Twodspec with the same name, excluding the extension, then the extension must be given (note that most of these do not include line names, so these will be left blank). When you have read in all the required line lists, you reply ``ok'' to the above menu.
L I N E I D E N T I F I C A T I O N ------------------------------------- Identify line number 1
The line with some of the surrounding spectrum is displayed so the user can, it is hoped, recognise the line! If the displayed width is not satisfactory, it can be changed using the WIDTH option of the menu shown below. A default response is given which is the value of the X array at the peak in intensity within the line boundaries. If, however, you already have two or more lines identified, the default will be interpolated or extrapolated from these (again using the positions of the maximum intensities within the line boundaries). It is possible to leave lines unidentified, although at present the only way to get back to the menu is by identifying at least one more line--you can edit the line list, but you then don't have the advantage of the interpolation to help guessing (the fitting of the dispersion relationship in ARC2D can be used to help line identification). You can keep looping around the line list, identifying the lines in any order.
=========< I d e n t i f i c a t i o n M e n u >========= [number] : Line wavelength Width [number] : Redraw with different width Next : Go to next line Display : Start/stop displaying tables of wavelengths Id [wavelength] [name] : Give line ID/wavelength (just taken as given) Quit : Exit leaving lines unidentified Identification Menu [ 6548.4] - 6548.1001 [NII]6548 ok? [YES] Identify line number 2 =========< I d e n t i f i c a t i o n M e n u >========= [number] : Line wavelength Width [number] : Redraw with different width Next : Go to next line Display : Start/stop displaying tables of wavelengths Id [wavelength] [name] : Give line ID/wavelength (just taken as given) Quit : Exit leaving lines unidentified Identification Menu [ 6563.1] - 6562.8169 HALPHA ok? [YES]
If you enter just a wavelength the nearest line in the lists will be located, and you will be asked if this is what you want (as shown).
=========< I d e n t i f i c a t i o n M e n u >========= [number] : Line wavelength Width [number] : Redraw with different width Next : Go to next line Display : Start/stop displaying tables of wavelengths Id [wavelength] [name] : Give line ID/wavelength (just taken as given) Quit : Exit leaving lines unidentified Identification Menu [ 6730.5752] - 6730.8501 [SII]6731 ok? [YES] C U R R E N T L I N E L I S T _________________________________ line No identification wavelength 1 [NII]6548 6548.1001 2 HALPHA 6562.8169 3 [NII]6584 6583.6001 4 [SII]6717 6716.4702 5 [SII]6731 6730.8501 Edit line list? [NO]
Errors can be corrected using this edit option. The user now reaches the Main Menu:
Current value of iteration is 1 =========< M a i n m e n u >========= ADd : Add more lines It : Change iteration TEmplates : Input data for template based fits AUto : Fixed window & fits type menu (use DEFINE to setup models) Manual : Interactive setup of window & fits Define : Define fits for AUTO EDit : Edit/look at results structures TOls : Apply tolerances Output : Create output plots, etc. SKy : Sky subtraction and data vignetting corrections SYnthetic : Generate synthetic spectra from input data and/or fits EXit : Leave program Main menu [MANUAL] -
Once you have located and identified lines in one file, this information may be CLONED to another file. A powerful feature of ARC2D and LONGSLIT is the ability to CLONE a set of line locations from another file, rather than, or in addition to (but preceding), the normal line selection. For this, the two arcs are plotted one above the other and, from three points marked by the user on each arc, the locations of the lines are interpolated for the new arc. The wavelengths and identifications are then also copied over. This means that if two spectra of the same wavelength range are to be used, without co-adding, then the whole process of line identification can be circumvented. If the spectra are very similar, then the information can be copied straight over, even in batch mode. The parts of the images to be extracted for the plots are prompted for.
FIGARO A general data reduction system