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MAST/AGN Cross Correlation Help

This page explains how to use the MAST/AGN cross-correlator. For information on how the AGN catalog was constructed, see the page describing the contents of the AGN catalog.

You can use this page to cross-correlate subsets of our AGN catalog with the HST, IUE, and EUVE archives. To use the form, simply indicate the classes, redshift range, visual magnitude range, and/or 6cm flux range that define the subset of the AGN 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 AGN catalog that meets your qualifications, and will begin polling the selected mission databases to see which missions have observed the AGN. 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.)

Object Class
The classification of the AGN. For information on how the AGN were classified, see the section The Classification in the page describing the contents of the AGN catalog.

You may select one or more of these classifications. If you select more than one, then the cut will find AGN that fall into any one of the selected classes. (Each AGN has only one class associated with it.)

Redshift
The redshift of the AGN, expressed as z. You can enter a range of floating point numbers here in any of the following ways: 
Qualification  Meaning
-------------- ---------------------------------------
    > 4        z greater than 4
    < 2        z less than 2
 2.5 .. 3.5    z between 2.5 and 3.5
    2.0        z of exactly 2

Visual Magnitude
The visual magnitude (V) of the AGN. For information on how the visual magnitude was derived, see the page describing the contents of the AGN catalog.

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

6cm Flux
The radio flux at 6cm, in mJy. For information on how the 6cm flux was derived, see the page describing the contents of the AGN catalog.

This field can accept a range of floating point numbers: 

Qualification  Meaning
-------------- ---------------------------------------
   > 18        flux greater than 18 mJy
   < 22        flux less than 22 mJy
 18.5 .. 22.5  flux between 18.5 mJy and 22.5 mJy
   18.0        flux of exactly 18 mJy

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.