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Spectral Line Selection Tool

The ALMA Spectral Line Selection Tool contains the rest frequencies of millions of spectral line transitionsthat are contained within NRAO's Splatalogue . A subset of the Splatalogue is packaged with theObserving Tool, which should be sufficient to select some of the mostcommonly targeted transitions. If network connectivity is available,access to the complete catalogue becomes possible using the onlinesearch functionality. The tool is launched from within a Science Goalusing either the Select Lines to Observe... or the Select Lines to Overlay... buttons. Within an SB it is launched via the Line Catalogue button.

When the transition selector dialogue is launched, the offlinespectral line catalogue is displayed and every transition in theoffline catalogue is available for selection. Specific transitions canbe located by using the controls in the left-hand panel to set yoursearch criteria. Transitions are matched by species or transitiontitle by typing into the Filter/Species input box, and matched byfrequency and ALMA instrument band by dragging the range sliders orusing the frequency input boxes. Note that the frequency slider refersto sky frequencies. Filtering is also done on sideband availability,maximum upper-state energy of the transition and on collections ofpopular molecules.

The Filter/Species filter operates on substrings, so an input of CO will match all species containing CO regardless of where the COmolecule is found (ie., CO, (17)OCO, and c-H2COCH2 are all positivematches). The instrument band sliders, frequency sliders and frequencyinput boxes are all linked, so that adjusting the target instrumentband also alters the matched frequency range, and vice versa.

Below the Filter/Species field is a checkbox ( Include description in search ), which when checked includes the transitiondescription in the search. With this option enabled, a search can bemade by transition name rather than formula, e.g. 'water', 'carbonmonosulfide', 'cyanobutadiyne', etc. Matching descriptions canoccasionally obscure desired matches (e.g. searching for 'CO' alsomatches hundreds of reCOmbination lines), in which case it can bedisabled. The same matching rules described above apply todescriptions too.

The spectral line selector accepts wildcards, which are entered withthe '*' symbol. For example, searching for 'CO' matches transitionswhose originating species begins with CO, e.g. 'CO v=0 1-0'. Entering'*CO ' matches transitions with CO at the end of the species, such as'CCCO' and '(CH3)2CO'. Multiple wildcards can be used; for example,searching for '*CO*' matches molecules with CO anywhere in theirmolecular formula, such as 't-DCOOH'.

Note that online searches do not handle wildcards, and the Search Online button will be disabled whenever a wildcard is entered. Oncethe additional lines have been retrieved from the network, wildcardsearches can be performed on the newly-expanded catalogue as normal.Also, network searches are not as advanced as searches of the OTcatalogue. Network searches can only match transitions by species andfrequency, not description or quantum numbers. For example, searchingfor 'CO' in band 3 will give a result; searching for 'carbon monoxide'or 'CO 1-0' will not.

Figure 5.5: The ALMA Spectral Line Selection Tool.
\resizebox{12cm}{!}{\includegraphics{images/LineSelectionTool.eps}}

The table with transitions show the rest frequency as well as the skyfrequency which is calculated using the source velocity when theselector dialog is launched. Clicking on the column headingsTransition, Frequency, and Catalog will cause a sort of the tableentries so that they are ordered by the entries in that column. And,after the first such click on any column heading, an up/down arrowheaddoes appear and the sort can be made to be ascending or descending.

If your desired line cannot be found in the offline catalogue, it mayexist in the more extensive online catalogue. The online catalogue canbe queried by clicking the Search Online button; the query willrequest transitions originating from the species given in theFilter/Species box whose frequency is contained within the frequencylimits. The results of the query will be added to the list ofselectable transitions, and will persist as part of the offlinedatabase for your observing tool session so that repeat searches neednot be submitted.

Having located your target transition in the available transitionstable, select the transition and return to the observing tool bydouble-clicking the appropriate row. Multipletransitions can be selected in somecontexts, for example when adding lines to the Spectral Visual Editoror selecting multiple spectral elements. In this case, the list ofselected transitions is compiled by double-clicking a chosen row or byselecting rows from the available transitions and clicking the Add to Selected Transitions button. Likewise, transitions can beremoved from the selected table with a double-click or by selectingrows and clicking Remove from Selected Transitions .



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Next: Sideband Filter Up: Tools Previous: Sensitivity Calculator   Contents   Index
The ALMA OT Team, 2011 May 20