What is potentially confusing here is that, from the main search page, you could conceivably stumble into having (1) nothing overlaid; (2) only the central source overlaid, so it looks like nothing is overlaid; (3) so many sources overlaid that you can't see the image. From the layers pop-up, you can control which of these loaded catalogs are shown on the selected image (and in which colors, and what symbol shape); see the visualization section.
Contents of page/chapter:
+Initially Searching on Catalogs - Catalogs from the Search Page
+Catalogs from IRSA -- Overlaying catalogs from IRSA
+Catalogs from disk -- Overlaying your own catalogs
+Catalogs from VO -- Overlaying catalogs obtained via the VO
+Catalog from NED -- Overlaying catalog from NED
+Columns and filters -- Interacting with catalogs
+Example of catalog plots #1: Catalog pulled after searching
+Example of catalog plots #2: Catalogs pulled during initial search
If you search on catalogs from the search results page, then Finder Chart will overlay these catalogs on your images as additional layers. These catalogs behave in the same way as the catalogs described in the rest of this section.
However, if you search on catalogs from the main search page, Finder Chart overlays the catalogs on your images right away, and it does so in a way that is quite powerful, but may be initially confusing. In order to understand what it is doing, you need to use the visualization tools, so there is more information (including an example) in the Visualization section. Critical to understanding what it is doing (and how you can change it) is the concept of the "selected image" -- different things are overlaid on different images (and image sets), and your choices change depending on which image you have selected. If you choose to search the catalogs just over a small radius, and/or further constrain it to just find the closest source (one-to-one match) to your target, the overlays of the catalogs will (presumably) all be over the same, single source, and it will be much less clear that the catalogs are overlaid at all, much less that the catalogs are different on each set of images. But, it is behaving in the same way.
In the upper left of the window, you specify the catalog you want to
search. In order to help it give you a specific list of choices, you
need to first tell it the project (default: WISE) and category
(default: AllWISE Database). After you have selected these items,
right below those choices, you then pick the specific catalog
(default: AllWISE Source Catalog). To change catalogs, first select
the "project" under which they are housed at IRSA, such as 2MASS,
IRAS, WISE, MSX, etc. The options under the "category" and the
specific clickable catalog change according to the project you have
selected. A short description is provided for each of the catalogs,
with links for more information (including definitions of the
sometimes cryptic column names); an example of this link for more
information is here:
In the upper right is the search target and search region. By default, it pre-fills your search target to match your most recently searched target. To change the target, simply enter the new coordinates in the search box, with all the same options as searching Finder Chart in general. Next, choose your search shape ("Search Method") from the pulldown; the options below the search method change accordingly (and sometimes the target vanishes, when it is not relevant):
Power user tip: By default, it may show you fewer columns than are available in the full catalog. By selecting "long form", you can access the full range of available columns. In some cases, there are literally hundreds of columns that you can access!
Click on "Search" to initiate the search. It will load the catalog into a tab of its own on the bottom left of the screen (in the catalogs window pane) and make a plot (see below) on the bottom right. The catalog objects will also be overlaid on the images you have loaded. The image and the plot and the catalog panes are interlinked -- clicking on a row in the table shows it on the image and plot; clicking on a source in the plot shows it in the image and table; clicking a source on the image shows it in the plot and table.
To close the catalog search window without searching on a catalog, click on "cancel" in the lower left.
NOTE THAT the search may take a long time to return, especially if you have asked for a large catalog, and you may think that nothing has happened, but be patient.
It may give you the option to put the catalog search in the background monitor (from which you can load it into a tab), or return a tab directly. If you do ask it to put it in the background monitor, the monitor will dynamically update to reflect its status, and will let you know when the catalog is ready to download or display. You may ask it to email you when it is ready. A popup appears asking if you want to load the catalog. Either click on the popup or explicitly open the background monitor and click on the catalog name to load it into a tab of its own.
Use large search radii with caution! Be sure you have a sense of how many sources you are likely to retrieve. Searches that retrieve more rows will take longer. Searches that retrieve thousands or tens of thousands of rows will take quite a while.
By clicking on the blue "Catalogs" tab, you are by default dropped into the interface for searching for catalogs at IRSA. However, you can pick another tab from the top, "Load Catalog", to load your own catalog, either from disk or from the IRSA Workspace.
Your catalog needs to be in IPAC table format, which is a varietal of plain text. IRSA has a table reformatting and validation service which may be helpful, or you can download just about any catalog you find through IRSA, and copy that format.
Your table file MUST have RA and Dec values, and unless it is specified, it assumes J2000.
You can add a "SYMBOL" parameter to change the shape (X, SQUARE, CROSS, EMP_CROSS, DIAMOND, DOT) of catalog marks, e.g.:
\SYMBOL = X
You can add a "DEFAULT_COLOR" parameter to assign a CSS color name or a HEX value to catalog marks, e.g., either of these two:
\DEFAULT_COLOR = lightcyan \DEFAULT_COLOR = #00FF00You can find the CSS color code or the CSS color HEX values online.
Your catalog is then shown (and interacted with) in the same way as the other catalogs described here.
By clicking on the blue "Catalogs" tab, you are by default dropped into the interface for searching for catalogs at IRSA. However, you can pick another tab from the top, "VO Catalog", to search for and load catalogs from the VO.
As for the IRSA catalog search, the tool pre-fills the target position with the coordinates of the target with which you have been working. In this case, you are limited to a cone search, so the next option is the cone search radius. As usual, pick your units from the pulldown first, and then enter a number; if you enter a number and then select from the pulldown, it will convert your number from the old units to the new units. There are both upper and lower limits to your search radius; it will tell you if you request something too big or too small.
If you know your VO URL already, you can jump down to the Cone Search URL box and type or paste your URL into the box and hit search.
More commonly, however, users do not know a priori which URL to use. Click on "Find Astronomical Data Resources" to be droped into a VO search. Find the URL corresponding to the catalog you want, copy it, and go back and paste it in the URL box. The URL should not have the RA and Dec in it; the tool will add your RA and Dec as listed to the URL in the right syntax. Click on "Search" to initiate the search.
The search results are then shown (and interacted with) in the same way as the other catalogs described here.
Load the tool. Search on IC1396. Go to the catalogs tab. Choose "VO Catalog." It wants the root URL for a cone search. I click on "Find Astronomical Data Resources", which takes me here. Search on IPHAS. Get this page. Look for the complete catalog release (not just one associated with one specific study). The name of the catalog goes here. Hit the [+] to expand it. There is one URL listed there, under "available endpoints for the standard interface." Copy that URL and paste it into the search form. The IRSA tool will append your coordinates and radius and return you a table.
Note that searching the VO means that you are using resources not specifically housed at IRSA, so servers may be down, or timeouts set, or limits on numbers of returned sources, etc., that are beyond our control. In most cases the solution is to specify as precise a search as possible. The URL you enter into the box in Finder Chart must be a Cone Search base URL (not containing RA and Dec parameters, which are inserted into the URL by the tool in response to the search parameters you give it).
The master list of registries is here. You can also search the registries directly via that link (as opposed to via the IRSA tools).
By clicking on the blue "Catalogs" tab, you are by default dropped into the interface for searching for catalogs at IRSA. However, you can pick another tab from the right, "NED", to search for and load a catalog from NED.
As for the other catalog searches, the tool pre-fills the target position with the coordinates of the target with which you have been working. In this case, you are limited to a cone search, so the next option is the cone search radius. As usual, pick your units from the pulldown first, and then enter a number; if you enter a number and then select from the pulldown, it will convert your number from the old units to the new units. There are both upper and lower limits to your search radius; it will tell you if you request something too big or too small.
The search results are then shown (and interacted with) in the same way as the other catalogs described here.
The table is shown exactly as it appears in the corresponding database
(or as it appeared on your disk), with all columns as defined for that
catalog. To understand what each column is, please see the
documentation associated with that catalog. (For IRSA catalogs, this
documentation is available via the catalog searching popup window, see
figure below, or by navigating through the IRSA website.)
The tab (and table) name itself indicates whether it is WISE, 2MASS, etc. To remove the tab, click on the "X" on the tab.
Immediately below the tab name, there are several symbols:
which we now describe.
The first thing to notice is that only the first 50 rows of the retrieved catalog are displayed in the table. In the example here, there are 1358 sources that were retrieved as part of the search. The left/right black arrows plus the page number allow you to navigate among these 'pages' of 50 sources each. Note that the entire set of results (not just the 50 rows you are currently viewing) can be sorted by clicking on any column's name.
By default, the catalogs you retrieve via this search are NOT overplotted on the images. To overplot the catalog (the entire catalog, not just the first 50 shown on the first page of the catalog tab), select the image on which you want the sources to appear, then go to the layers icon and turn on the catalog overlay.
Going from left to right along the top of the catalog tab, the next icon represents a filter: Filters are a very powerful way of exploring the catalog data. Click on this icon in order to start the process of adding filters. A text entry box appears above each of the current catalog columns, with a small version of the filter icon corresponding to that row on the far left. You can type operators and values in these boxes -- hit return or tab after typing or click in another box to implement the filter. For fields with a limited set of choices, instead of a text entry box, a filter icon will appear; click on it to select from the available choices. As an example, to show only those sources with declination above a certain value (say, 31 degrees), type "> 31" in the box above the "dec" column. Or, if you have retrieved a WISE catalog and would like to only view the objects with a W1 (3.4 micron) profile-fitted magnitude less than 6 magnitudes, above the 'w1mpro' column, type "< 6" in the form.
After you impose a filter, then the number of rows in the catalog is restricted according to the rules you have specified, and the "filters" icon on the top right of the catalog pane has changed to remind you that there has been a filter applied, in this case just one filter: . To clear the filters, click on the cancel filters icon (which also appears after you impose filters): .
Note that the filters are logically "AND"ed together -- it will impose this AND that AND this other restriction. You can relatively easily restrict things such that no data are left; if that is the case, you will get "There are no data to display." You can then cancel all the filters at once via the cancel filters icon (), or remove them individually by hand by editing the filter boxes at the top of each column, just as you did to impose the filters.
The available logical operators are :
You can also interactively impose filters from plots from the catalog - see the next section.
The next icon is -- clicking on this changes the table display into a text display. The icon then changes to -- click this again to return to the default table view.
The next icon is which is "Save" -- this is how you may save the catalog to your own local disk. If you have filtered the catalog down, it will save the filtered catalog (though as of this writing, the total number of rows retrieved in the table header will still be the original number). It will save it as an IPAC table file, which is basically ASCII text with headers explaining the type of data in each column, separated by vertical bars. By default, the file is called "GatorQuery.tbl" because, under the hood, the software is talking to the IRSA General Catalog Query Engine, powered by Gator.
The next to last option on the top of the catalog tab is this: . From here, you can change:
Note also that if you resize columns, and then go and add new columns, the original columns are resized back to their defaults after the new columns are added.
Finally, when your mouse is in the catalog window pane, you see this as the last option on the top of the catalog tab: . Clicking on this expands the catalog window pane to take up the entire browser window. To return to the prior view, click on "Close" in the upper left.
To obtain a full-screen view of your plot, click on the expand icon in the upper right of the window pane when your mouse is in the window: . To return to the prior view, click the "Close" arrow in the upper left.
The plotting tool, by default, starts with RA and Dec plotted. Note that it does so properly -- that is, RA increases to the left (following astronomical convention). To change what is plotted, click on the gears icon in the upper right of the plot window: . Configuration options then appear on the right of the plot, as shown:
Across the top of this window, the buttons are "Apply", "Clear", and "Reset". To close this window without doing anything, click on the gears again.
Below those buttons, if you have few enough points in the plot, you have several options for the plot style:
Optionally, if you have few enough points in your plot, you can specify the column containing the errors in whatever column you have selected. To do this, click on the error pulldown and select either symmetric or asymmetric errors and enter the column or the scalar you want to use for the error bar in that direction.
By default, it uses the column name as the axis label, but you may want to change this. Some database columns can be cryptic. You can also specify the units for the axis label.
Finally, you can choose whether to add grid lines, or reverse the axis (as seen in the screen shot above, ra is reversed so that larger numbers are on the left). "Top" places the x-axis numbers on the top of the plot (by default, they are on the bottom). "Log" changes the axis from linear (default) to log.
The options then repeat for the y-axis.
Finally, you can set the plot boundaries and the aspect ratio of the plot.
Click on the gears again to hide the plot options pop-up.
You can also do simple mathematical manipulations.
For example, if you have loaded a WISE catalog, you can plot w1mpro
vs. w1mpro-w4mpro, even including the errors. Here is the
configuration, including getting the axes aligned in the way you are
expecting such that brighter objects are at the top of the plot.
And here is the resultant plot, complete with error bars:
Click on any point to see the values under the cursor and have that source highlighted in the table and on the images.
If you have many sources, it will bin them up ("decimate" them), and the plot will be shades of grey corresponding to how many points are represented at that location in the plot. The lightest shade of grey represent one point in the plot at that location, and the darkest shades of grey represent many more points in the plot at that location. If you click on one of the points, it will tell you how many catalog rows correspond to that point, e.g., The reason it does this is to more fairly represent the point density -- and to make the plotting faster. In these cases, though, it will not give you the option to overplot errors.
You can change the bin size and shading. If you have a decimated plot, you have a "binning options" arrow near the bottom of the plot options pop-up. You can choose whether the binning is set automatically (leave boxes blank), or by you (populate the boxes). You can also choose if the grey shading is set linearly or logarithmically. NOTE THAT you can't change the bin size in just one direction; if you enter a number for the "Number of x-bins" box, you must also enter a number for the "Number of y-bins" box.
In order to have the tool plot one point per catalog row, you need to zoom in or otherwise restrict (see below) the data such that there are 'few enough' points represented in the plot. If there is just one point in the plot that needs to be rebinned, all of the points will be small blue individual points.
You can also restrict what data are plotted in any of several different ways. You can set limits from the plot options pop-up, or you can use a rubber band zoom, as follows. Click and drag in a sub-region of the plot. The icons in the upper right of the plot change corresponding to what you can do, in this case to these: . They are, from left to right: zoom in on the region of the plot you have selected, select the objects in the catalog, and filter the catalog to leave only those objects. If you click on the zoom icon, then the plot axes change to encompass just the sources you have selected (and the icons in the upper right change, leaving this -- if you click this, you go back to the original view). If you click on the select icon, then the plot symbols corresponding to your selection change shape and color, the corresponding objects overplotted on the image in the image window pane change color, and (if you change back to the table view of the catalog), the rows (corresponding to those sources) in the catalog are highlighted. (Also, the icons in the upper right of the plot change, leaving this -- if you click this, you deselect the sources and go back to the original view) If you click on the filter icon, then the catalog view is filtered down, restricted to just those sources you have selected, and the filter notes in the upper left of the plot window (and in the table view of the catalog) change to remind you that you have a filter applied. Only those sources that pass the filter are shown overlaid on the image(s). (This is the behavior of 'filter', as opposed to 'select'; the former restricts what is shown, the latter just highlights the objects.) You can also pull up an interactive filter on the catalog itself from the plot view -- click on the filter icon near the setting icon on the left. For more on filters, see the filter section.
Want to save a plot to file? Click on the diskette icon and save the plot.
For this example, we are trying to find young stars in a star-forming region. We will search in the WISE AllWISE catalog. Stars without circumstellar dust should be at a variety of W1 brightnesses, but all have [W1]-[W4]~0. Background galaxies should be faint and red. Stars with circumstellar dust (e.g., young stars) should be bright and red. Here, we will make a plot, identify a bright and red object in the plot, and find where it is in the WISE images.
This example provides an opportunity to explore images and catalogs (including 1-to-1 matching, which can be powerful but may be confusing). This example does not walk through every source in detail, but sources can be found in this list where proper motions are high (such that 1-to-1 matching doesn't work well), and/or coordinates are bad, and/or the sources are not point sources, and where the WISE measurements have to be pulled out of the reject catalog.