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Working with Catalogs in the OPT and Using the Source Catalog Tool (SCT)

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Observation Preparation Tool (OPT)

1. Orientation and Working with Catalogs in the OPT

Log in to the OPT web application and, assuming that there is no message in the Important message banner that makes you decide to abandon the OPT for the moment, look for the navigation strip at the top. If Sources is not in bold face, but in normal font and underlined, click it with your mouse button to navigate to the SCT (Figure 2.1). To exit the tool properly, use the Exit link in the upper right corner or log out with FILE - EXIT; do not kill the browser window/tab!

A short introduction to the layout of this tool's page has been given in the introduction (Chapter 1). There is an icon menu at the top and a source search tool below it in the left hand side column. At least one VLA catalog must be visible in the bottom part in the left hand side column, which is the catalog browser (Figure 2.1). For orientation and to get a feel for the tool(s), it is instructive to walk through this VLA catalog first. The search tool will also be described. After this orientation it should be almost intuitive to create your own personal source catalog(s) which you will use in your project's SB scans. Note that a source catalog for each of your successful proposals may be pre-filled; it is important that you check the pre-filled information for correctness.

Figure 2.1: Web browser screen shot of the SCT page showing the first few sources in the DEC=-10 group, which is part of the Dec Groups in the read-only VLA catalog of sources.


Example of a Source Catalog: the VLA Calibrator Catalog

The VLA catalog (Figure 2.1) is the VLA calibrator list, described in the VLA calibrator manual. These sources are suggested to be good calibrators for specific frequencies and array configurations, but not necessarily for all frequencies in all configurations. Browsing this source catalog is instructive to become familiar with catalogs in the OPT web application and with the information available for sources. The source search tool is an extra feature in the SCT only.

Note that the VLA source catalog is in red italics, which means that this catalog is read-only.  A plus-icon (xpnd) in front of the open book icon (Open Book) indicates that a catalog includes source groups. A catalog does not need to contain groups, but at some point it may be more convenient to create them. If you click the plus-icon or VLA (or, in general, the name of the catalog) these groups will appear in the catalog tree and the plus-icon will change to a minus-icon (clps).

If you click on the catalog name, here VLA, you will also see the contents of the highlighted VLA catalog in the main SCT window, the big field to the right hand side of the catalog column (Figure 2.1). This table list combines the contents of all groups and possible entries in the catalog that do not belong to a group (though in this case there are no such free-agent entries). The pre-defined groups in the VLA catalog are RA Groups, Dec Groups, and VLA Flux Cal. The RA Groups and Dec Groups also have subgroups (Figure 2.1), but these subgroups are a special case implementation in the VLA catalog only; groups cannot be nested.  When a group name is highlighted (or selected) using the mouse button, the right-hand side window with the contents will only show (filter) the sources which were grouped in this sub-catalog. For example, selecting the VLA Flux Cal group will now only list the standard flux density calibrator sources. Similarly, the DEC +10 subgroup will show the VLA sources with Declinations between +10 and +20.

Clicking VLA differs from clicking the plus-icon in that it will expose the total content of the catalog in the main (editing) window, with 25 sources per page, starting with source J0001+1914 (clicking the plus-icon only exposes the names of the groups in the left hand side column). At the top of the table, you will notice that the top line is a small page navigation menu. A similar page navigation menu can be found at the bottom. This VLA catalog contains more entries that fit on the page (25), and in this case is distributed over many pages. Below is a list of the menu icon buttons and what they mean:

Arrow First first page of the catalog (or group)
Arrow FR 10 pages backward in the catalog (or group), or as many as possible if less than 10 exist
Arrow Previous previous page in the catalog (or group)
1, 2, .. individual page numbers in the catalog (or group), with the current page highlighted
click to select another page from this small list (up to ten page numbers) if desired
Arrow Next next page in the catalog (or group)
Arrow FF 10 pages forward in the catalog (or group), or as many as possible if less than 10 remain
Arrow Last last page of the catalog (or group).

If you find the default of 25 lines per table page too few, you can change to a larger number of lines per page (50, 100 or 200) at the top of the page.  Every table column with the font turning orange when the mouse hovers over it can be sorted by using a click of the mouse button.  All pages in the catalog are used in the sorting which means that catalog entries may have moved from one page to another after a sort. When a column is sorted, it will show a small orange arrow next to the header name, pointing up if the column is sorted in ascending order (going to larger values when going down in the table) and pointing down when the sorting is in descending order. A sorted table can be re-sorted in the opposite direction by clicking the column again (note that the header of a sorted column, the one with the arrow, might not change to the orange color anymore).

As a small exercise, use the navigation tools at the top or bottom to confirm that (with 25 sources per page) the catalog has 75 pages. Using the table header sort, confirm that the source with the most southern Declination is J1118-4634.  For any source, hovering over details or aliases pops up additional information on the sources if available: flux densities at different frequency bands, closure phase properties and aliases for the source in non-sortable columns (see the key to the VLA calibrator manual). The angular view near a calibrator on the sky can be displayed in a new browser tab by clicking the Sky Map icon (bullseye). Above the table on top of the page, it is shown that the coordinates in the table are in the Equatorial coordinate system. If another coordinate system is selected in the drop-down menu, e.g., Galactic, the positions are recalculated from the positions entered originally, which is indicated by a small red asterisk next to the coordinates.

Each row in the table represents one source with a name and some descriptive information. A row starts with a tick-box and an edit icon (Edit Source). The tick-boxes can be used to select one or more entries in the catalog for copy/paste as described in a later section. A shortcut to select all, or to deselect all catalog entries on the current page can be found above the table. Selecting and copy/paste (see below) has to be redone for every page. The Edit Source edit icon is used to access the details of the source entry in the catalog, i.e., the specifics of the source of interest. Here it will be a VLA calibrator source; later this might be the specifics of your scientific target source, and the information contained may be slightly different from entries in a personal source catalog created by an observer or by the automatic PST to OPT pre-filler.

Select a random source (not J1118-4634) and expose the source details (click on the editing icon Edit Source in front of the name of the source of which you want to view the properties). The source properties in the main editing window are divided over three tabs, shown on top, labeled with the source's name, Images, and Notes. Most of the useful information is in the first tab, labeled with the source's name: the source name, its position, its velocity (if applicable) and its brightness (if applicable). The Images tab holds the Elevation curve for this source and the LST times for different elevation limits, which is useful for calculating LST ranges for which this source can be observed above a certain elevation. The Azimuth curve is also shown. Another useful piece of information is in the Notes tab. Press the blue circle with the white triangle/arrow (Expand Arrow) to show the VLA calibrator manual entry for this source (and press it again to hide this information). This and some extra information in a different form is given in the same tab under User Defined Values.

Navigate back to the VLA catalog either by clicking VLA in the catalog column tree, or by clicking Return to VLA (or, e.g., DEC +10, depending on how you got there) at the top of the page. Please allow the web application to finish its operation and do not use the browser Back button.

Other read-only catalogs may contain or use slightly different source properties and auxiliary information. In particular, the source names are those of the original catalogs; not necessarily according to the J2000 IAU convention as for the VLA catalog.


Searching for Sources

Select the VLA source catalog in the catalog tree at the left hand side and view the main editing window to the right. Source names follow J2000 IAU naming convention (i.e., truncated 10-character Jhhmm+ddmm) and aliases can be found by hovering over aliases or by viewing the source properties (through the editing icon \includegraphics[height=3mm]{psimg/source.png.ps}). To find source 3C279 may take a while, even if you know this source is J1256-0547 (note the capital "J") in the IAU convention. Entering 3C279 (note the capital "C") in the source search tool in the upper part of the left hand side column will search the selected source catalog for the source name in that catalog. If the "Search Aliases As Well" tick-box is not ticked, the search will only be matching for the name entered in the catalog (for VLA these are IAU names, but in your personal catalog you could have named your source 3C279 or "Skippy", etc); it then will only find this source in the VLA source catalog if J1256-0547 is entered. Therefore the aliases tick-box is by default ticked, but because searching is done on partial strings you may want to remove the option if you otherwise expect many matches (e.g., if you are looking for your source matching on the string "C" and don't want all 3C-sources to appear).

Because the search is performed on a partial string, searching for "-" (a minus sign) in the VLA catalog, for example, will return a 16 page table with all VLA calibrators with negative Declination (J2000), plus some extra sources with a minus sign in the name if you left the "Search Aliases" checked. A search on 1331+ will return 3C286 (as J1331+3030). Searches should not be case sensitive, but sometimes weird returns happen if lower cases are supplied; use upper case (J, B, C) for the standard VLA calibrators and their aliases. Two wild-cards are allowed: "?" and "*"; they have the usual meaning of a single arbitrary character and any number of arbitrary characters, respectively. However, they are only useful between two other characters in the search string, as the search on string is automatically performed as a search on *string* (an empty search string returns the whole catalog).

A source may also be obtained using the External Search if it is unknown to any of the existing catalogs. This search will be performed on the names, including aliases, in the SIMBAD database, using the same search and character rules.


Advanced Search

The Advanced Search (Figure 2.2) is used to search in an existing, selected catalog for other criteria than source name or alias. A common example is to search for a nearby calibrator at a position of your source of interest. This Advanced Search will bring up a dialog box in the main editing window containing various search parameter options. In that window, select the catalog(s) in which the search should be performed, and select the table(s) with the required parameters by checking the upper left tick-box of the relevant tables. Above the search parameter tables, you can select "All" or "None" catalogs and subsequently toggle individual catalogs. Table options and editing fields become active only when you select to use it. More than one catalog and more than one parameter table may be selected; the search interprets additional parameters as an AND condition. To perform the search, click the "Search" button below the parameter fields. Be patient, as searching can take a while; please do not continue clicking with the mouse button until the search operation has finished.

Figure 2.2: Web browser screen shot of the Advanced Search options with an example of a cone search in combination with a minimum flux density. After you have selected your parameters, click the "Search" button for results.

  •  A Cone Search searches a radius, entered in degrees, around a position (J2000) or around the position of a source selected from any of the source catalogs by using the Select Source button (which brings up a dialog box to select a source from one of your catalogs). The resulting table should be sorted in increasing distance from the position; the table can be resorted if desired (by clicking table headers that turn orange). Positions are interpreted as decimal degrees if not supplied as, e.g., 1h 37m [41.3s] for R.A. and [+]33d 9' [35"] for Dec.; not supplied as a group of three numbers separated by a space or a colon, or otherwise not recognized as a sexagesimal entry. To activate the interpretation in the fields entered, click with the mouse button somewhere outside the boxes to validate the input. Always check the coordinates after entering each position or after pressing the Search button; it will replace your values with the interpretation of the validation procedure. You should check these values; the validation procedure will always be able to convert your entered values with these rules, but you are the only one to know whether the validation conversion is sensible!
  • Activating the Calibrator Code search allows a search for sources with a closure phase structure code (P, S, W, X) equal or better than the code selected for a certain observing band and VLA array configuration. This Calibrator Code is not to be confused with the the AIPS calibrator code (A, B, C, T) indicating a positional accuracy. Consult the VLA calibrator manual for more information on the definition of these codes and positional accuracy.
  • A Flux Density search searches for flux densities above the given limit in the selected observing band. This is of course only useful when flux densities are included in the catalog(s) selected.
  • The Name search is the same search action with the same string rules as for the string entered in the top search tool in the left hand side column, with the difference that here more than one catalog can be searched, and that other constraints can be included.
  • The Right Ascension and Declination searches are performed on a J2000 coordinate range, with the equal to or larger than (>=), or equal to or smaller than (<=) operators on the given limits. It uses the same rules on entering positions as for the Cone Search. When both limits are given, the search returns the sources between the limits (i.e., you will see proper results for a search on sources with R.A. between 23 and 01 hours).

Figure 2.3: Web browser screen shot of results of the Advanced Search. Hovering with the mouse over details or aliases displays the source information (if available).


Search Results

Note that the sources matching the search parameters are listed below the Search Results header at the bottom. The results of a search are displayed read-only in the familiar SCT table format in a Search Results tree structure with the possibility to sort on different columns (Figure 2.3). Previous searches may be saved in the left hand column tree for convenience -- navigating to a previous search is done by simply selecting that search.  Sources presented in the Search Results can be selected, and added to a personal source catalog using copy/paste, etc. Search results are cleared when you log out from the SCT or the OPT web application.

2. Creating a Personal Source Catalog


Personal (re)source catalogs can be created, modified, and removed using the menu strip and icon menu at the top of the tools page. It is convenient to collect (re)sources for a specific project in a separate catalog, especially for convenience during schedule block creation and also, e.g., when sharing with co-I's.

Usually NRAO has already been able to retrieve your sources from what you specified in your proposal. If this is the case you will find these in a source catalog, labeled with the project name in the left hand side column. You should follow the exercise above and examples below to get a feel for what is in your source catalog. You will want to check the entries in your source catalog, especially the accuracy of positions of your target sources, and the examples will help you check and/or modify the content.

Copy/Paste from Existing Catalogs

Regardless of how you create (or how NRAO fills) your source catalog entries, make sure they are correct before you continue with using them in the OPT. The OPT does not use global source properties; when you have modified a source you must use the OPT to reassign the new source separately to every scan that needs it. For this a Bulk Scan Edit has been implemented in the OPT (described later). Check your catalogs before making scans!

Options from the icon menu and menu strip

The icon menu is the line of little icons at the top of the (re)source catalogs in the left hand side column. They have the same functionality as the options from the menu strip (below), although not every menu strip option is represented as they are not used as often. Only basic cut/copy/paste and reordering can be done with this icon menu. Note that the actions selected from the icon menu apply only to editing in the left hand side column. Only valid actions will have an active icon in the menu, i.e., pasting an item may only be performed after copying or cutting the item first -- until then the paste-icon will appear grayed-out. Hovering over an item with your mouse will display a pop-up tool-tip help to remind you of the action attached to the icon, but we also show them for reference below:

Cut Cut (or delete) selected tree item
Page Copy Copy selected tree item
Page Paste Paste selected tree item
Arrow Up Move the selected catalog up in the tree
Arrow Down Move the selected catalog down in the tree

The same icon menu can be found in the RCT; for the OPT we will present additional icons for more options related to ordering scans in the OPT. Remember that these icons act only on the left hand side column items.

The menu strip in the dark blue banner at the top of the page is used for creating new catalogs: FILE - CREATE NEW - CATALOG. It is not advisable to copy the VLA catalog personal catalog in a new personal catalog and add new target sources, but it is useful to copy VLA sources into a new or existing personal catalog. The menu strip options under FILE and EDIT are grayed out with a line through them if that particular option is not valid for the current selection (highlighted item in the catalog tree in the left hand side column). If the action you want to perform shows up as an invalid option (e.g., EDIT - CUT - GROUP to delete your group of sources) this usually means that you are not at the right place in the tree (e.g., not in the group, but in the upper level catalog). The names of the actions are quite self-explanatory, so we only list them for reference in the table; the ones in square brackets only appear when relevant, in particular when a source in a group is selected. A similar list of menu strip options is available in the RCT and OPT, but with options specific to the tools. The menu strip options may act on both items in the left hand side column as well as items in the main editing window.



Adding Sources to Your Personal Catalog

There are three ways to add sources to a personal catalog, each described below. A fourth one is that the OPT gets filled with information from the PST once the TAC has approved observing time for your project. If you find a catalog imported directly from the PST, please carefully check the target source positions before you start using them in the OPT as you may have not entered them in the PST as you want them to appear in the SCT/OPT.

Importing Source Lists, Including Sources Entered in the PST

If you or a co-investigator uploaded a source list with your proposal in the PST, and this source list has not been transferred from the PST (or you prefer to delete that one), you should be able to get a head-start by uploading the same source list to the OPT. Use FILE - IMPORT... to communicate with a dialog box. Choose PST as input format and name your source catalog after it has been uploaded by selecting the New Catalog and navigating to the Properties tab. As a reminder, the PST format is/can be found in the relevant section of the PST manual (or in the complete description) in case you decide to make such a file at this stage. You may want to check the details of some sources to verify that the information has ended up correctly in the source property definitions. Verifying it now may save you more trouble later on when creating SBs.

Copying Sources from Existing Catalogs

It is likely that your anticipated calibrator sources (which may not have been included in the proposal cover sheets) are already defined in, e.g., the VLA calibrator source catalog. You can search for calibrator sources using the search tool described earlier in this chapter. In the catalog (or group) or in the search results you can select one or more sources you desire to add to your personal catalog by ticking the check-box(es) in front of the source name and editing icon using the top menu strip EDIT - COPY - SOURCES, etc. Then select the destination catalog or group and simply paste the copied sources: EDIT - PASTE - SOURCES, etc. You must repeat this action for each catalog or search results table page. Again verify that the source information in your personal source catalog is correct, e.g., by adding additional digits to a source position, prior to assigning source information to scans in the OPT. An example sequence would be as follows:

  • Make sure you have navigated to the SCT.
  • From the top menu strip, select FILE - CREATE NEW -  CATALOG; you can skip this step (and the next step) if the catalog you want to use already exists and is writable (i.e., the catalog name is not in slanted red font), e.g., the catalog automatically
    generated with your project ID.
  • Your new catalog with the default name [New Catalog] appears in the main editing window, in the Properties tab. Change the name of the catalog to something useful to remind you of its purpose.
  • Optionally add the names of coauthors that you want to share the catalog with and who may edit the sources in the catalog.
  • At this stage you can opt to group your sources. This is not necessary, but convenient if you are going to have many sources. If you want to group sources in this catalog, select FILE - CREATE NEW - GROUP, and name your group under the Properties tab.
  • Click to navigate back to the first tab: Sources.
  • Select the VLA source catalog and perform your source search as described previously; use Advanced Search or External Search if necessary.
  • In the source table to the right, in main editing window, check the source(s) you want. If you don't know which source to select, study the details of each before selecting one. If there are more sources than fit on a page you can change the number of sources per page from 25 to 50 or 100, or use multiple actions to select all your sources in subsequent steps.
  • From the top menu strip, select EDIT - COPY - SOURCES.
  • Select your newly named source catalog (or group within it).
  • From the top menu strip, select EDIT - PASTE - SOURCES. If there are groups in the catalog, you will have the option to add them to a group as well. The sources now show up on the right hand side.
  • This can also be achieved by copy/paste of entire groups and/or entire catalogs using the top menu strip options or the menu icons at the top of the (left hand side) source catalog column. Use the fly-over tool-tip help to identify the proper icon for each action.
  • Maybe you want to check the source properties using the Show/Edit icon for each catalog entry. You can also reorganize your sources by adding groups (FILE - CREATE NEW - GROUP) and move your sources around using the column icon menu, or using EDIT in the top menu strip. Unwanted sources can be deleted using Cut.
  • If you are unhappy with the name of the catalog or group you can always rename it by highlighting it and then clicking on the
    Properties tab.

Note that sources do not have to belong to a group. If you have specified groups, sources that do not belong to that group will not show up if you select that group. When there are sources in groups and sources not belonging to a group in the same catalog, you can only see and select a source without a group when you select the entire catalog.

Entering Source Information from Scratch

If you do not use the PST upload file and your source does not appear in any of the existing catalogs, you would create a new source in a source catalog (or group) after selecting (or creating) the catalog or group you want to place the source in: (FILE - CREATE NEW - CATALOG/GROUP,) FILE - CREATE NEW - SOURCE. You will be presented with a blank source page consisting of three tabs (or pages) labeled New Source, Images, and Notes. Name your source something convenient to search for at a later point, and fill in the necessary details (see below). You may also care to fill in the origin of your data for your own reference (e.g., PST file name, SIMBAD data base, scooped draft paper, etc.).


Source Positions

There are five different types of positions you can enter: a Simple Position, a Distant source with Proper Motion, a Solar System Body with Table of Polynomials, Solar System Body with Internal Ephemeris, and Solar System Body with Uploaded Ephemeris (Solar Observation is obsolete; use either internal or uploaded ephemeris).

By default the first tab-page uses Simple Position below the source name and aliases. Select a coordinate system (Equatorial, Galactic or Ecliptic) and equinox in which you specify the coordinates and, if you care, also supply a distance (if known). For anything else than the Simple Position use the drop-down menu. The new selection will redraw the position table accordingly with all variables defaulted. You can select a predefined Solar System body name, upload an ephemeris table, or you can specify the position and some motion terms valid for some time range. Motion terms are entered as polynomials in time [display]\rm position\ at\ Reference\ Time\ in\ Equinox + value(1) \times time + value(2) \times time^2 + value(3) \times time^3,  etc [/display] Press the [+] for each extra motion term, enter the value and choose the order of the polynomial in time. The motion term units and uncertainty will help recalculating the position (and error) at the time of observations, though this is currently not yet fully tested. Leave the motion terms at zero if the source is considered not to move in the specified time interval. If you need another position and/or different motion terms for another time interval, simply add another position to the previous one. Delete old or obsolete positions using the tick-box in the upper left of a position table and REMOVE SELECTED POSITIONS. More information, in particular about generating ephemeris files, is given in the Observing Guide under Moving Objects.


Adding Information

In addition to specifying a position, some extra reference information may be specified for this catalog entry. These items however are not necessary for the observation and are provided for your own reference.

Source Velocities

In the next table, under Source Positions, Source Velocities can be entered using the Add button (Figure 2.4). Enter the value and select a rest frame and rest frame convention. Just like a position you can add more than one velocity, but valid for another frequency range. Removing old or obsolete velocities is also a very similar procedure: tick the unwanted velocity and use REMOVE SELECTED.

Note however, that source velocity information is not used anywhere in the OPT or in the observations, nor is it transferred with the data. Source velocity information entered here is purely a user supplied comment, just like brightness and image links below or distance above. The proper place to enter a source velocity is in the resource of the scan, where Doppler corrections are calculated for the time of observing. How to do this is explained in the "Creating your Resource" section.

Figure 2.4: Adding a source velocity.

Source Brightness

Similar to specifying a source velocity, with ADD you can specify a source flux density and distribution. You are asked which type of brightness distribution you want to add to your source properties. For unresolved (point-like) sources you would probably choose type Point, and fill out the Flux Density at some Frequency Range. A slightly resolved source perhaps would be better described by a Gaussian model with a Major Axis and Minor Axis Diameter at some Position Angle. Planets also use the Limb Darkening property of the Disk models. You can specify more than one brightness model for a source, or provide a FITS image or clean-components model file. The actual parameters differ for each flux distribution model. A source brightness model is simply removed with ticking a check box and REMOVE SELECTED.

Images tab

This tab displays the Visibility Chart consisting of the elevation and azimuth of the source as function of LST together with a table of rise and set LST (at 8° elevation) and some other elevation/azimuth and LST properties for your reference. Below are Image Links. It allows you to keep a catalog of image URL links, e.g., to the images in the VLA archive; use ADD or REMOVE SELECTED as many times as desired.

Notes tab

This tab-page is where you can collect all other information you wish to attach to this source. For example, for a target source you can remind yourself of the nearby calibrators you have found to be useful at some frequency, a reference to a paper mentioning an alternate position or a source property, or anything else you want to note. Click the blue expand button or New Note to add information to the Notes field. You can add links to papers or any other URLs for that matter. User defined values can be added at the bottom, e.g., the UV-range you determined to be proper for a point source calibration model, or whatever you deem useful.


Final check

After all this data entering, make sure you check your catalogs for correctness. It is important that your source positions are correct before creating scans in the OPT and before storing to disk or sharing your catalogs with your collaborators.

3. Setting Up Pointing Scans and Tipping Scans

Pointing scans are typically done at X band (8 GHz) on strong (> 0.3 Jy/beam) continuum sources near your target source, i.e., within about 20 degrees. Most likely you will find such a source in the VLA calibrator catalog. Note that for longer tracks, the optimum pointing source is at roughly the same Declination and about 10 degrees earlier in LST (40/cos(Dec) minutes in RA), but the source itself (if bright enough in X band) is also a relatively safe bet. You may want to add the pointing source to your personal source catalog if it is not in there already. If you plan on doing secondary reference pointing scans (see the next chapter) and your intended pointing source is not strong enough at the observing frequency you wish to use for the secondary reference pointing scan, you may need to add another pointing source that is strong enough at this frequency, or perhaps even revisit your first choice. More details can be found in the Observing Guide.

Tipping scans on the other hand are typically done independently of your sources. The only interest is the observing frequency and the direction, in Azimuth, of the main distribution of your sources so that the opacity is measured in the global direction of your targets and the slew time between sources and tips is minimal. Tipping scans currently are set up in the OPT only; no extra sources are needed.