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MAST/Abell Clusters Cross Correlation Help

This page explains how to use the MAST/Abell Clusters cross-correlator.

You can use this page to cross-correlate subsets of the Abell Clusters catalog with the currently archived MAST missions. To use the form, simply indicate the redshift range, visual magnitude range (see below), richness class(es), and/or a range of galactic coordinates that define the subset of the clusters that you're interested in, and which missions you want to cross correlate this subset with. You can optionally specify a search radius for each mission different from the default given in the page.

The MAST cross-correlator will then extract the subset of the Abell Clusters catalog that meets your qualifications, and will begin polling the selected mission databases to see which missions have observed the clusters. The results will be presented in a simple tabular form, with links to the MAST search pages for individual missions:

  • The name of the catalog or mission will be linked to that mission's search form, with the RA and Dec for the catalog target as defaults.
  • The target name will be linked to a preview image or spectrum, if one is available.
  • The name of the exposure (the Dataset Name for HST data, the Entry ID for IUE data, etc) will be linked to a page of information about that specific observation. (This is still under development for non-HST data.)
A note about the search radius: Abell clusters can be large, so a search radius on the order of the instrument aperture may be too small. We have therefore defined radii for all of the clusters for which we have a valid redshift. The search radius will be the cluster radius (in arcminutes) plus the aperture radius for the instrument. (Clusters for which a radius has not been defined- because a redshift was not available- will be searched on the aperture radius alone.)

Richness Class
The richness class of the cluster.

You may select one or more richness class. If you select more than one, then the cross-correlator will find clusters that fall into any one of the selected classes.

Redshift
The redshift of the cluster, expressed as z. You can enter a range of floating point numbers here in any of the following ways: 
Qualification  Meaning
-------------- ---------------------------------------
    > .75      z greater than .75
    < .3       z less than .3
 .3 .. .75     z between .3 and .75
    .3         z of exactly .3

Mag 10
The visual magnitude (V) of the 10th-brightest galaxy in the cluster. This field can accept a range of floating point numbers: 
Qualification  Meaning
-------------- ---------------------------------------
   > 18        V greater (dimmer) than 18
   < 22        V less (brighter) than 22
 18.5 .. 22.5  V between 18.5 and 22.5
   18.0        V of exactly 18

Galactic Longitude Range
Galactic longitude range (lii). Use this field to restrict the catalog to a range of galactic longitudes.

This field can accept a range of floating point numbers: 

Qualification  Meaning
-------------- ---------------------------------------
   > 270       lii greater than 270 degrees
   < 30        lii less than 30 degrees
 160 .. 200    lii between 160 and 200 degrees
 < 30, > 270   lii between 270 and 30 degrees (including 0 degrees)
If you enter a single floating-point number, the cross-correlator will try to match that number exactly, so this probably isn't a useful way to qualify this field.

Galactic Latitude Range
Galactic latitude range (bii). Use this field to restrict the catalog to a range of galactic latitudes.

This field can accept a range of floating point numbers: 

Qualification  Meaning
-------------- ---------------------------------------
   > 60        bii greater than 60 degrees
   < -60       bii less than -60 degrees
 -30 .. 30     bii between -30 and +30 degrees
< -60, > 60    bii less than -60 or greater than +60 degrees
If you enter a single floating-point number, the cross-correlator will try to match that number exactly, so this probably isn't a useful way to qualify this field.

Missions
Select one or more missions with which to cross-correlate the selected catalog. (For HST, each instrument is treated as a separate mission.) You can use the Show catalog entries that match any/all of the selected missions selector (see below) to control whether any or all missions have to match a catalog entry in order for that catalog entry's results to be displayed.

Radius (arcmin)
The radius in arcminutes on which to cross-correlate the mission with the object catalog catalog. Each mission has its own independent radius. For each mission, a default radius has been chosen that is more or less appropriate for that mission.

Show catalog entries that match any/all of the selected missions
When you select multiple missions, you can use this selector to control how an catalog row's results will be displayed: Set it to any to show results if the catalog entry cross-correlates with at least one of the selected missions, or set it to all to show only those catalog entries that cross-correlate with every selected mission. For example, you might set this selector to all if you are looking for catalog entries that have been observed with both HST and IUE, or to any to find catalog entries observed with either HST or IUE.

Display n rows per mission
Use this selector to determine how many rows from each mission will be displayed. When ALL is selected, every row found for the mission will be displayed. Optionally, you may use this selector to reduce the number of rows from each mission reported, reducing the length of the results page. The total number of rows for each mission will always be reported.