Contents of page/chapter:
+Catalogs from IRSA -- Overlaying catalogs from IRSA
+Catalogs from disk -- Overlaying your own catalogs
+Catalogs from VO -- Overlaying catalogs obtained via the VO
+Columns and filters -- Interacting with catalogs
+Examples of catalog plots
Catalogs -- Overview
Once you have conducted a search and have some displayed images, you
can perform a catalog search, which will (among other things) overplot
those catalog sources on all the images shown. Catalogs are available
via a blue tab that appears at the top of the page only after you have
performed at least one search -- in essence, you need to have
something on which to overlay the catalog before it will let you
By default, it assumes you want to perform a catalog search that covers the same region as your recent search, and pre-fills the form with that region -- but you can choose to change those search criteria. You can choose from any of a number of catalogs. You can also upload your own catalogs.
The catalog will be overlaid on the images in the details pane, such as data coverage and any data shown. The highlighted source will change depending on which source is selected in the catalog tab in the results pane.
If you searched on the SEIP Source List from the main position search page, that catalog is overlaid on the images as part of the search results. You can turn a catalog overlay off temporarily via the "layers" icon.
By default, it pre-fills your search region to match what you have been doing with your current object. If you would like to change the region of the search for the catalog search, change the coordinates of the polygon it shows by default, or (easier), change the search method to "cone" and click on "modify target" and enter the new information. You can customize the search for options beyond a cone search (e.g., an elliptical search). The default cone radius is 500 arcsec. Caution: 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. Note that these limits are catalog-dependent.
You then need to 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, on the right,
you can 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 on the
right 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:
You can also set restrictions on specific columns by clicking on "Set Column Restrictions" on the left hand side, under the "category" selection pull-down menu. A new window will open up with the available column names in the corresponding catalog, and you can choose what to display, and filter what is returned (for example, only return objects with values in column y that are greater than x). If you add more than one restriction, they are combined logically using an "AND" operators; be careful, because you can thus restrict data such that none of the catalog meets your criteria.
Power user tip: By default, this interface may show you fewer columns than are available in the full catalog. By clicking on "Set Column Restrictions" and selecting "long form" from the pulldown at the top of the pop-up window ("Please select long or short form display"), 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 as part of the search results pane. The objects will also be overlaid on any images you have loaded; you can also make an x-y plot from the results. (For more on the x-y plots, see below.) All of these representations are interlinked -- clicking on a row in the table shows it on the image and in the plot, and clicking on an object in the image shows it in the table and in the plot, and clicking on an object in the plot shows it in the table and on the image.
(You can obtain a full-screen view of your catalog -- click on the expand icon in the upper right of the window pane when your mouse is in the window: . )
To close the catalog search window without searching on a catalog, click on "Close" in the upper 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 and eventually it will either spin off to the background monitor (from which you can load it into a tab), or return a tab directly.
Searches that take longer than a few seconds get spun off to the background monitor. If it does spin off to the background monitor, it will dynamically update to reflect its status, and will let you know when the catalog is ready to download or display. 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 understand how many sources you are likely to retrieve. Searches that retrieve more rows will take longer. Searches that retrieve millions 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 left of the catalogs screen, "Load Catalog", to load your own catalog.
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.
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 left, "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. Type your desired keywords into the keywords box and click on "Search Registry". All of the URLs it finds for your keywords within the VO registry service are shown in the box. Locate the one you want to use, and click on "Use" on the far left of the corresponding row. The "Cone Search URL" is populated properly for that catalog. 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. Here are the links to VO registries that we are using, just in case you want to do more flexible searches of the registry. The URL you enter into the box in Finder Chart, though, must be a Cone Search base URL (not containing RA and Dec parameters, which are inserted into the URL by Finder Chart 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).
Columns and filters
After you have loaded a catalog, it appears as an additional tab in
the search results pane (on the left); all the catalogs you choose to
load are in their own tab within the search results pane, one tab per
catalog. The objects will also be overlaid on any images you have
loaded, you can also make a x-y plot (for more on the x-y plots, see
below). All of these representations are
interlinked -- clicking on a row in the table shows it on the image
and in the plot, and clicking on an object in the image shows it in
the table and in the plot, and clicking on an object in the plot shows
it in the table and on the image.
To see more of the columns (and see more of the options described shortly below), grab the divider(s) between the window panes and slide it to widen the catalog pane until you can see the icon that looks like this: .
The table is shown exactly as it appears in the 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 (available via the catalog searching popup window shown above, or by navigating through the IRSA website.)
The tab (and table) name itself is the name of the catalog file as stored on the system at IRSA; it may be a little cryptic, but the first few words should make it clear whether it is WISE, 2MASS, etc. To remove the tab, click on the blue "X".
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, there are 1358 sources that were retrieved as part of the search. The 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 alphabetically by clicking on any column's name. (Note also that in the plotting and overlay features described below, all the sources in the catalog are plotted on the images you have, not just the 50 shown in the first page.)
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, and they work the same way as they did on the Spitzer search results. 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 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 catalog with brightness measurements less than 6 magnitudes, find the corresponding column and type "< 6" in the form on the top of the column.
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 :
The next icon is which is "Save" -- this is how you may save the whole catalog (NOTE: the WHOLE TABLE, not just the rows shown) to your own local disk. 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: . Clicking on this icon brings up options for the table, e.g., how many rows are displayed per page, and which columns are shown. By default, all columns are shown. The default page size is 50 rows. Note that expanding the page size to numbers much greater than 50 may result in a substantial performance degradation (e.g., your browser will appear to freeze or not appear to be doing anything while it manages and renders the large table).
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.
You can also interactively impose filters from plots you make from the catalog - see the next section for discussion.
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 strictly mathematically correctly -- that is, RA increases to the right (the reverse of astronomical convention). To change what is plotted, click on the gears icon in the upper left of the plot window pane: . Configuration options then appear to the left of the plot. You can choose a single column to plot against another column -- if you have loaded a WISE catalog, you could plot w1snr vs. w1mpro. You can start typing a column name into the X and Y boxes, and it will help provide you viable options from the column headings. Alternatively, you can click on the "Cols" link to bring up a pop-up window with all the columns for that catalog listed. NOTE THAT you must type in the column name exactly matching the column headings as displayed. By default, it echoes the x and y labels and units from the original table, but you can change this by clicking on the triangles below each entry box (e.g., make the label "SNR in WISE-1" rather than the more cryptic column header "w1snr").
You can also do simple mathematical manipulations. For example, you
can plot w1mpro vs. w1mpro-w4mpro. However, note that as of this
version, the axes are from min to max in the strict mathematical
definition of the term, so in this example, the fainter W1 objects are
at the top of the plot. As a workaround for this, plot -w1mpro vs.
w1mpro-w4mpro to get the axes aligned in the way you are expecting
such that brighter objects are at the top of the plot.
Note that the SEIP Source List has brightnesses measured in flux densities, so that you can plot flux densities.. or use the mathematical manipulations to convert them to magnitudes using the zero point of your choice.
Note that the plot symbols are shades of grey corresponding to how many points are represented at that location in the plot. The lightest shade of grey (and smallest points) represent one point in the plot at that location, and the darkest shades of grey (and the largest points) represent many more points in the plot at that location. Put your mouse over any of the points to find out more about what is represented at that location.
You can add or remove the gridlines via the "Grid" checkbox. If you have zoomed in enough such that there are just black boxes -- one object per point -- you can change the plot style such that the points are connected or unconnected.
You can also restrict what data are plotted in any of several different ways. You can set limits based on the "more options" (click on the triangle next to "more options") on the lower left of the plotting window pane, 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 you have selected, select the objects in the catalog, filter the catalog to leave only those objects, or expand the plot to take up the whole browser screen. If you click on the zoom icon, then the plot axes change to encompass just the sources you have selected. 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. 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.) For more on filters, see the filter section.
If you move your mouse over any of the points, you will get a pop-up telling you the values corresponding to the point under your cursor. If you click on any of the points, the object(s) corresponding to that point will be highlighted in the overlays in the images shown, and highlighted in the catalog table. This works the other way too - click on a row in the catalog, or an object in the images, and the object will be highlighted in the plot or the catalog or the image.
If you have a very large catalog or many points in a particular location of the plot, the tool will rebin the points in the plot such that displaying the plot is faster. The plot symbols are shades of grey corresponding to how many points are represented at that location in the plot. Put your mouse over any of the points to find out more about what is represented at that location. It will tell you how many catalog rows correspond to that point, and clicking on it will highlight all of the corresponding rows in the table view and the image overlays. In order to have the tool plot one point per row, you need to zoom in or otherwise restrict 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 a small point.
Want to save a plot to file? At this time, the best way to do that is a screen snapshot. On a Mac, this is accomplished via holding down command, then shift, then 4, then let go and your mouse cursor changes. Hit the space bar to select the window over which your mouse is hovering. Your mouse cursor changes again, and hit the mouse button. A snapshot is then saved to your Desktop, tagged with the date and time.
Once you have made an x-y plot, the plot is then effectively treated as another 'image' in the stack of images you have loaded into the program. In the Visualization section, it describes various tools, including blinking images, and removing images from the blink sequence. If, after you make a plot, you want to blink some of the FITS images, you will need to remove the plot from the image sequence, as described in the Visualization section.
In a star-forming region defined for this example, we are trying to find young stars. We will search in the SEIP source list. Stars without circumstellar dust should be at a variety of brightnesses, but all have infrared colors near 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 investigate its spectral energy distribution (SED).