# ESASky Queries (astroquery.esasky)¶

## Getting started¶

This is a python interface for querying the ESASky web service. This supports querying an object as well as querying a region around the target. For region queries, the region dimensions may be specified as a radius. The queries may be further constrained by specifying a choice of catalogs or missions. Documentation on the ESASky web service can be found here.

### Get the available catalog names¶

If you know the names of all the available catalogs you can use list_catalogs():

>>> catalog_list = ESASky.list_catalogs()
>>> print(catalog_list)
['INTEGRAL', 'CHANDRA', 'XMM-EPIC', 'XMM-OM', 'XMM-SLEW', 'Tycho-2',
'Gaia DR1 TGAS', 'Gaia DR1', 'Hipparcos-2', 'HSC', 'Herschel-HPPSC-070',
'Herschel-HPPSC-100', 'Herschel-HPPSC-160', 'Herschel-SPSC-250',
'Herschel-SPSC-350', 'Herschel-SPSC-500', 'Planck-PGCC2',
'Planck-PCCS2E', 'Planck-PCCS2-HFI', 'Planck-PCCS2-LFI', 'Planck-PSZ']


### Get the available maps mission names¶

If you know the names of all the available maps missions you can use list_maps():

>>> maps_list = ESASky.list_maps()
>>> print(maps_list)
['INTEGRAL', 'XMM-EPIC', 'CHANDRA', 'SUZAKU', 'XMM-OM-OPTICAL',
'XMM-OM-UV', 'HST', 'Herschel', 'ISO']


### Query an object¶

There are two query objects methods in this module query_object_catalogs() and query_object_maps(). They both work in almost the same way except that one has catalogs as input and output and the other one has mission names and observations as input and output.

For catalogs, the query returns a maximum of 10000 sources per mission by default. However, this can be modified by the row_limit parameter. You can set the parameter to -1, which will result in the maximum number of sources (currently 100 000). To account for observation errors, this method will search for any sources within 5 arcsec from the object.

For instance to query an object around M51 in the integral catalog:

>>> from astroquery.esasky import ESASky


Note that the catalog may also be specified as a list. So the above query may also be written as:

>>> result = ESASky.query_object_catalogs("M51", ["integral", "XMM-OM"])


To search in all available catalogs you can write "all" instead of a catalog name. The same thing will happen if you don’t write any catalog name.

>>> result = ESASky.query_object_catalogs("M51", "all")


To see the result:

>>> print(result)
TableList with 3 tables:
'0:HSC' with 8 column(s) and 135 row(s)
'1:XMM-EPIC' with 4 column(s) and 2 row(s)
'2:XMM-OM' with 12 column(s) and 3 row(s)


All the results are returned as a astroquery.utils.TableList object. This is a container for Table objects. It is basically an extension to collections.OrderedDict for storing a Table against its name.

To access an individual table from the astroquery.utils.TableList object

>>> interesting_table = result['PLANCK-PCCS2-HFI']
>>> print(interesting_table)
name              ra [1]       dec [1]
----------------------- ------------- -------------
PCCS2 217 G104.83+68.55 202.485459453 47.2001843799


To do some common processing to all the tables in the returned astroquery.utils.TableList object, do just what you would do for a python dictionary:

>>> for table_name in result:
...     table = result[table_name]
...     # table is now an astropy.table.Table object
...     # some code to apply on table


As mentioned earlier, astroquery.esasky.ESASkyClass.query_object_maps() works extremely similar. It will return all maps that contain the chosen object or coordinate. To execute the same command as above you write this:

>>> result = ESASky.query_object_maps("M51", "all")


The parameters are interchangeable in the same way as in query_object_catalogs().

### Query a region¶

The region queries work in a similar way as query_object, except that you must choose a radius as well. There are two query region methods in this module astroquery.esasky.ESASkyClass.query_region_catalogs() and astroquery.esasky.ESASkyClass.query_region_maps(). The row_limit parameter can be set to choose the maximum number of row to be selected. If this parameter is not set, the method will return the first 10000 sources. You can set the parameter to -1, which will result in the maximum number of sources (currently 100 000).

To query a region either the coordinates or the object name around which to query should be specified along with the value for the radius of the region. For instance to query region around M51 in the integral catalog:

>>> from astroquery.esasky import ESASky
>>> import astropy.units as u
>>> result = ESASky.query_region_catalogs("M51", 10 * u.arcmin, "integral")


Note that the catalog may also be specified as a list. So the above query may also be written as:

>>> result = ESASky.query_region_catalogs("M51", 10 * u.arcmin, ["integral", "XMM-OM"])


To search in all available catalogs you can write "all" instead of a catalog name. The same thing will happen if you don’t write any catalog name.

>>> result = ESASky.query_region_catalogs("M51", 10 * u.arcmin, "all")
>>> result = ESASky.query_region_catalogs("M51", 10 * u.arcmin)


In the same manner, the radius can be specified with either a string or any Quantity

>>> result = ESASKY.query_region_catalogs("M51", "10 arcmin")


To see the result:

>>> print(result)
TableList with 4 tables:
'0:XMM-EPIC' with 4 column(s) and 3 row(s)
'1:HSC' with 8 column(s) and 10000 row(s)
'2:XMM-OM' with 12 column(s) and 220 row(s)
'3:PLANCK-PCCS2-HFI' with 8 column(s) and 1 row(s)


As mentioned earlier, query_region_maps() works extremely similar. To execute the same command as above you write this:

>>> result = ESASky.query_region_maps("M51", 10 * u.arcmin, "all")


The parameters are interchangeable in the same way as in query_region_catalogs().

### Get images¶

You can fetch images around the specified target or coordinates. When a target name is used rather than the coordinates, this will be resolved to coordinates using astropy name resolving methods that utilize online services like SESAME. Coordinates may be entered using the suitable object from astropy.coordinates.

The method returns a dict to separate the different missions. All mission except Herschel returns a list of HDUList. For Herschel each item in the list is a dictionary where the used filter is the key and the HDUList is the value.

>>> from astroquery.esasky import ESASky
...                            missions=['Herschel', 'XMM-EPIC'])

...

>>> print(images)
{
'HERSCHEL': [{'70': [HDUList], '160': [HDUList]}, {'70': [HDUList], '160': [HDUList]}, ...],
'XMM-EPIC' : [HDUList], HDUList], HDUList], HDUList], ...]
...
}


Note that the fits files also are stored to disk. By default they are saved to the working directory but the location can be chosen by the download_dir parameter:

>>> images = ESASky.get_images("m51", radius="20 arcmin",
...                            missions=['Herschel', 'XMM-EPIC'],


### Get maps¶

You can also fetch images using astroquery.esasky.ESASkyClass.get_maps(). It works exactly as astroquery.esasky.ESASkyClass.get_images() except that it takes a TableList instead of position, radius and missions.

>>> table_list = ESASky.query_region_maps("m51", radius="20 arcmin",
...                                       missions=['Herschel', 'XMM-EPIC'])


This example is equivalent to:

>>> images = ESASky.get_images("m51", radius="20 arcmin",
...                            missions=['Herschel', 'XMM-EPIC'],

 ESASkyClass() Conf Configuration parameters for astroquery.esasky.