VLA-FIRST Search Help

The MAST search pages basically contain three parts. The top of the page lists the input search fields. Entering values (as described below) for one or more of these fields will define the selection criteria for the database search. The middle of the form contains buttons to initiate various actions including:

perform the search using the specified search criteria and output format,
clear the search form and reset values to the original defaults,
reset entries to the set of (default) values used the previous time the search page was drawn, and
display this help page.

The bottom portion of the page deals with formatting the table of found entries that appears after the search is completed. The format options include specifying which columns appear in the output list, the order of the entries, the maximum number of returned entries, the epoch of the output coordinates, and the option to display the actual SQL command used to retrieve the database entries. First time users may want to run the search using the default output options.

After selecting search criteria, output options, and clicking the search button, a second page will appear listing the returned database entries. From this table, clicking on the filenames will submit a request to download the selected FITS file.

Local File Name

The name of a local file containing a table or list of either coordinates or targets names to be uploaded to the server and used to query the database. The file must be an ASCII text file with either one entry per line (i.e., a target name or set of coordinates), or in a table separated with one of the allowed delimiters, with targets or RA and Dec values in the designated columns. Coordinates may be given in several formats including sexigesimal and decimal degrees.

The search script will perform a database search for each target, or set of coordinates, contained in the uploaded list. If a resolver error occurs, the search will abort and the compiled results displayed. If the output is requested in CSV or Excel spreadsheet format, a blank line will be used to distinguish the results of one target search from another. VOTable format incorporates separate RESOURCE tags for each database query.

Use the other form entries to specify field delimiters, RA, DEC, or Target column numbers (when the file contains a table of values), and file contents (target names or coordinates). The browse button allows users to seach local directories to locate files.

Warning: Uploading long lists can take a while to produce results.

File Contents

Specifies whether the local file to be uploaded contains coordinates, target names or Data ID's. By default, coordinates are assumed.

RA/Target/Data ID Column Number

The column number containing either the Right Ascension, target name or Data ID (depending on how file_contents is set). The default is to assume the first column is to be used.

Dec Column Number

The column number containing the Declnation. The default is to assume the second column contains the DEC value. If the file contents is set to Target Name or Data ID, this parameter is ignored.

Column Delimiter

The character used to delimit table entries in the uploaded file. Allowed values include tabs( ), commas(,), vertical bar (|), or semi-colons(;). The default is to assume tabs are the delimiters. If the file contains only a single column, use tabs as the delimiter.

Target Name

The name of the astronomical object you want to search for. Examples of valid names include gam Gem, NGC 1068, JUPITER, and hd 45677.

The Target Name is used in combination with the Resolver Field. If the SIMBAD or NED Resolver options are chosen, then coordinates returned from these services are used to perform the search.

You do NOT have to use the resolver. Choose the "Don't resolve" option to perform string searches on the object name in the database.

When you search on the object name in the database (i.e. without using the name resolver), case will be ignored. The object name will not be wildcarded at the front and back automatically (that's so if you innocently enter IO, you don't match things like ORION). You can however wildcard the object name using * (for example, *IO*). You can also enter a comma-separated list; for example, *JUP*,*SAT* would match object names containing either JUP or SAT. Note that most, if not all, missions store target names in a format that is not always compatible with the NED or SIMBAD name resolvers.

Resolver

The name resolver to use, if you want to resolve a target name into its coordinates. You can also elect not to resolve the object name when doing the search, and search on the object name instead. To do this, choose the "Don't resolve" option.

The two main name resolver services are SIMBAD and NED. NED is the NASA Extragalactic Database at Caltech in Pasadena, California, and SIMBAD is the Set of Identifications, Measurements, and Bibliography for Astronomical Data at the Centre de Données astronomiques in Strasbourg, France (CDS). NED is an extragalactic database, and generally won't resolve object names within the Milky Way galaxy.

Because we occasionally have problems with network connections and web servers, we now store previous queries in our own local database and use these before trying to access other name resolvers using various web services. By default, If no entry is found the entered object names will first be sent to the CDS service known as Sesame which will look for the object name first in SIMBAD, then in NED, and finally VizieR. If the main Sesame server is not working, we automatically check their backup web server. If no coordinates are returned, the program will automatically try the local Hubble Legacy Archive (HLA) web service which also uses SIMBAD and NED, but also saves previously entered target names in a local database so coordinates may be retrieved without a network connection to either NED or SIMBAD. If HLA fails, the program tries NED directly. We also allow users to go directly to HLA or NED by changing the selected name resolver, although the local cache is always checked first.

If any error occurs, the search form will be redrawn with an error message at the top. Otherwise, the returned coordinates will then be used to search the database, along with whatever other query qualifications you have given.

We recommend that you use object name resolution to find observations of specific stationary targets. This is the most reliable way to look up observations, because the observer could have given any object name at all (for example, NGC1976 instead of M42, or PARALLEL-FIELD).

The SIMBAD and NED name resolvers can resolve only fixed objects; they cannot compute the positions of moving objects (planets, comets, etc.). To find moving objects, try selecting the appropriate category option available on most MAST search forms, or as mentioned above, enter an object name that could match what you're looking for, and select "Don't resolve" for the name resolver. Note wild cards are allowed, so for Jupiter you might enter "*JUP*".

Right Ascension, Declination

The Right Ascension and Declination values. If single values are entered, a cone search is performed using the specified search radius (default = 3 arcminutes).

You may also enter ranges of right ascension or declination, using the ".." operator. For example, you can enter 21h 51m .. 21h 52m for the right ascension, and 28 51 .. 29 51 for the declination. Comparators can also be used, i.e. ">", ">=", "<", "<=". For example, "> 85" as a declination value will return all observations with declination larger than 85 degrees. (Note when ranges of coordinates are specified the search radius will be ignored. Also, searches on ranges can be quite time consuming.)

Coordinate values may be specified using a number of formats. Examples of accepted values include:

    Decimal Degrees
       	185.63325 29.8959861111111
 
    Hours, minutes and Seconds
        12 22 31.98      29 53 45.55
        12h22m31.98s     29d53m45.55s
        12:22:31.98     +29:53:45.55
        12h22'31.98"     29d53'45.55"
        12h 22m 31.98s   29d 53m 45.55s
        12h 22' 31.98"   29d 53' 45.55"
        12h 22' 31.98"  -29d 53' 45.55"
        12h22'31".98    -29d53'45".55
        12h22m31s.98    -29o53m45s.55
        12h 22' 31".98  -29d 53' 45".55
     
    Hours/Degrees and Minutes (no seconds)
        12 22     29 53
        12h22m   +29d53m
        12h22m    29d53m
        12:22m    29:53m
        12h22'    29d53'
        12h 22m   29d 53m
        12h 22'   29d 53'
        12h 22'  -29d 53'

    The RA may be given in decimal degrees by indicating
    a D or d after the degrees:
        12d 22m   29d 53m

Spacing is not important, as long as the value is unambiguous. You can delimit the hours/degrees, minutes, and (optional) seconds with letters, colons, spaces, or any character that's not a digit or a decimal point.

Radius

The radius of the search box around the RA and Dec, in floating-point arcminutes (e.g., 5.0). You should be careful about giving too restrictive a search radius since (for some missions) the coordinates of the object were given by the Guest Observer, and may not reflect the precise pointing of the instrument at the time of the observation.

The search routine computes the angular separation between each result dataset and the search center so this really is a circular radius. (Results are generally sorted on the angular separation by default.) Note a range may also be specified so, for example, to search for all observations between 2 and 8 arcminutes from the center of a galaxy, just enter 2 .. 8 for the radius.

Equinox

The equinox of the RA and Dec you have entered, either B1950 or J2000. (Note: currently only J2000 is allowed as input.) This only applies to the input coordinates. The coordinates displayed in the search results will depend on the mission database and the selected output columns. (Note: all MAST missions include J2000 coordinates as default output columns.)

If you enter a target name and use either the SIMBAD or NED name resolver, the equinox will be set to J2000.

Program ID

The VLA Program ID.

Observer Columns

The observer designation given by the VLA-FIRST team.

Image Class

Image class for the image. Choices are COADD and FCPRT.

Output equinox

Just what you'd think: the equinox of the coordinates displayed in the output.

User Option

You may now search on any column in the mission database. Select the field you wish to search on and type in the qualification. You may find the valid range of values by clicking on the field name. NOTE only fields which are not already included on the search form should be selected. Specifying search criteria for a field that is listed in BOTH the form and in the User Option field, may cause either the query to fail or return unexpected results.

Output Columns

This form element allows one to choose the columns to be displayed and their order, for the search results. A set of columns that are commonly requested has been chosen as a default.

You remove output columns by highlighting the column to be removed and then clicking on the remove button to the right of the output columns list.

You may determine the order of columns by highlighting a column and then clicking on the up or down buttons to the right of the list of chosen output columns.

You may also add a column to the list. Select the desired column from the pull down menu beneath the list of chosen output columns, then click the add button. The column will be added to the bottom of the output column list.

Note the output column form element has its own reset button to restore the list of output columns to the values initially displayed when the page was drawn. The reset button at the top of the form is used to reset the other form elements. Clicking the "clear form" button however can be used to restore the original default values.

Sort output by:

Choose how you want the output rows sorted (by default). You can select up to three fields to sort on. The rows will be sorted in the order of the first sort field; if two rows have the same sort field, they will be sorted in order of the second sort field, and so on.

For each field, you can select that the rows be sorted in reverse order on that field by selecting the reverse checkbox. For example, you can sort the rows with the most recent observations first by selecting Observation Date for the first sort field and selecting the reverse checkbox next to it.

Note that the latest search scripts also allow users to sort results based on any of the displayed fields, simply by clicking on the column names at the top of the search results table. Clicking a second time will sort results in descending order. This sorting feature however does require javascript to be turned on.

Display Coordinates

Specifies whether coordinates are output in decimal or sexigesimal format. Decimal coordinates will have 5 significant figures to the right of the decimal pont. Sexigesimal format is used by default.

Maximum Records

This value specifies the maximum number of rows returned in a single query. For the standard mission search forms, the current default is 1,001, but values from 1 to 15,001 are allowed. For the file upload forms in which multiple targets, data ID's, or coordinates can be specified, the default is set to 20 rows per file entry, with allowed values ranging from 1 to 500.

Note when displayed as HTML, the latest search scripts will display 50 records per page. Links to the additional pages are shown on the results page. This paging feature however does require javascript to be turned on.

When queries are submitted as a web service, the default number of rows returned is 2,000, but any value is allowed when max_rows is specified as a query parameter. (See the MAST Web services page for more information.)

Records per page

This parameter controls the number of records displayed per web page. By default, 50 rows or records are displayed per HTML page. Therefore if 200 records are returned, links to 4 pages will be displayed at the top and bottom of the results table. Selecting 100 would display 100 records and links to 2 pages. The paging feature however uses javascript, so if javascript is turned off, paging won't work and only the rows shown on the first page can be displayed. This is one reason why increasing the default value may be helpful. The current limit is 500 rows per page. Note this value is ignored when output formats other than HTML are selected.

Show SQL Query

Select this checkbox if you want to see the SQL query that the IUE Search engine constructs from your query qualifications. The query will be shown at the end of the search results.

SQL (Standard Query Language, pronounced either "ess cue ell" or "sequel") is a language used used by most relational database systems for retrieving information from database tables. The sarch script takes your search specifications and converts them to an SQL query to run on our database. Viewing the generated query is often useful for debugging, and may also be useful for SQL-literate users who want to see what logic was used in the query. (In fact, this may be useful for most people, since SQL is pretty easy to understand.)

Make Rows Distinct

Select this checkbox if you want to have a set of distinct rows displayed. This is useful if you would like to see a distinct list of objects with certain criteria e.g. all the objects within an IUE or FUSE object class. In this case, one would limit all but the "Target Name" (or RA and Dec); this is done with the "Remove" button in the Output Columns window. This action permits a selection only on unique targets names (or coordinates) that have been observed by the satellite for the object class given. (Hint: be sure to keep the "Maximum Records" number large enough for the length of your anticipated list!) Also note that columns such as RA, Dec and Magnitude were frequently defined by the observer and often have different values for the same target name. If columns such as these are chosen as output columns, there will often be more than one row listed per object name.

Output Format

You may choose any of the following formats for displaying/storing search results. If you are using a browser (e.g., Firefox, etc) to submit a query from a MAST web form, the formats labelled "File: ..." offer a way to download results directly to your local computer. Choose any of the other format options if you want to display the results in the browser, or if you are submitting the request from a program (see MAST web services).

HTML_Table (default) - results returned as a standard HTML table including various links for retrieving data, displaying previews, literature references, plotting spectra, etc.
File: Excel_Spreadsheet - results are stored as an Excel spreadsheet file. (Note: assumes users computer/browser provides support for Excel-format files). The default file name when downloaded is "mission"_search.xls where "mission" is the mission name (e.g., fuse_search.xls).
VOTable - an XML format adopted by the Virtual Observatory (VO) project and displayed in the user's browser. Note coordinates in VOTable format are always in decimal degrees rather than sexigesimal format. For searches returning results from more than one mission and/or target, multiple "resource" tags are created. Searches with a radius of 0 will return a VOTable file listing the output fields for that particular mission/catalog. (For more information on the XML file format, see VOTable documentation.)
Comma-separated values - a simple ASCII array containing column headings followed by rows of comma-separated values. In file upload mode, a blank line is inserted between the search results to separate multiple target queries.
Space-separated values - a simple ASCII array containing column headings followed by rows of space-separated values. In file upload mode, a blank line is inserted between the search results to separate multiple target queries. Note users may want to select coordinates in decimal rather than sexigesimal format to maintain the correspondence between column headings and entries although some column headings may contain blanks as well. (Semi-colons or commas are probably safer delimiters.)
Semi-colon separated values - a simple ASCII array containing column headings followed by rows of semi-colon separated values. In file upload mode, a blank line is inserted between the search results to separate multiple target queries.
File: comma-separated values - a simple ASCII text file containing column headings followed by rows of comma-separated values. In file upload mode, a blank line is inserted between the search results to separate multiple target queries. Rather than being displayed in the browser, the results are directly downloaded to the users computer using the file name "mission"_search.txt where "mission" is the mission name (e.g., hst_search.txt). Depending on the browser settings, the user may be prompted for a file location before the file is downloaded.
File: Space-separated values - a simple ASCII text file containing column headings followed by rows of space-separated values. In file upload mode, a blank line is inserted between the search results to separate multiple target queries. Rather than being displayed in the browser, the results are directly downloaded to the users computer using the file name "mission"_search.txt where "mission" is the mission name (e.g., hst_search.txt). Depending on the browser settings, the user may be prompted for a file location before the file is downloaded.
File: Semicolon-separated values - a simple ASCII text file containing column headings followed by rows of semicolon-separated values. In file upload mode, a blank line is inserted between the search results to separate multiple target queries. Rather than being displayed in the browser, the results are directly downloaded to the users computer using the file name "mission"_search.txt where "mission" is the mission name (e.g., hst_search.txt). Depending on the browser settings, the user may be prompted for a file location before the file is downloaded.

Note: If no entries are found for an entry a "no entries found" message is written in the selected format and the program continues. In all cases, error conditions will cause the database search to abort.