Setting Survey and Alias Epochs

In the previous example, you may have noticed some warnings stating that ATK failed to account for proper motion in our queries to AllWISE. This is true, but the reason is simple: we have not yet set an epoch for our new catalogue alias, and so ATK doesn’t know the magnitude of any necessary corrections. While this wasn’t a problem for the source used in our example due to its small proper motion, this issue is nonetheless worth solving since this will not always be the case.

To highlight this, we return to our high proper motion source from the introduction, Wolf 28 (Van Maanen 2). With no epoch definition, a query to AllWISE (in this case via the command line) returns no data:

ATKquery data allwise --source 2552928187080872832

Running allwise data query
source = 2552928187080872832
pos = None
radius = 3.0

Note: allwise has no epoch definition. Proper motion has therefore not been corrected.
Note: allwise data query unsuccessful or returned no data.

However, we can remedy this. The Epochs module allows us to access and edit all epochs that are used by ATK. Much like the Alias and Config modules, this module is most easily utilised via the command line. In this case, we can use the ATKepoch tool. We can start by showing the current epoch definitions:

ATKepoch show

Current ATKEpochs.ini values:

[default_data_surveys]
gaia = 2016,0
panstarrs = 2012,0
skymapper = 2016,0
galex = 2006,8
rosat = 1991,0
sdss = 2017,0
wise = 2010,5
twomass = 1999,0
erosita = 2022,0

[additional_data_surveys]

[lightcurve_surveys]
atlas = 2021,0
ztf = 2019,0
crts = 2000,0
asassn = 2015,0
gaia = 2016,0
tess = 2020,0

[spectrum_surveys]
sdss = 2017,0

The above shows the current epoch definitions in our instance of ATK. The Default_data_surveys section lists those of the supported surveys in data queries, while lightcurve_surveys and spectrum_surveys list those that are available in lightcurve queries and spectrum queries. As expected, the additional_data_surveys section is empty. To remedy this, we use the set mode of the ATKepoch command:

ATKepoch set additional_data_surveys allwise 2010,5

Returning to our previous query, we now see that data is successfully retrieved!

ATKquery data allwise --source 2552928187080872832

.kind:       data
.subkind:    data
.survey:     allwise
.catalogue:  ii/328/allwise
.source:     2552928187080872832
.pos:        [12.293161429221492, 5.384403492110555]
.identifier: J004910.36+052303.85
.dataname:   J004910.36+052303.85_2552928187080872832_allwise_ATKdata.fits
.trace:      start -> extracted pos from source query, assumed [2016, 0] -> allwise: [2010, 5] -> allwise query performed -> [2000,0] -> end

.data:
    AllWISE:   ['J004910.78+052249.8']
    RAJ2000:   [12.2949231]
    DEJ2000:   [5.3805217]
    W1mag:     [11.40999985]
    e_W1mag:   [0.023]
    W2mag:     [11.35700035]
    e_W2mag:   [0.02]
    W3mag:     [11.38000011]
    e_W3mag:   [0.197]
    W4mag:     [8.88000011]
    e_W4mag:   [nan]
    ...

For reference: finding this detection via the object’s name in Vizier would require a search radius of over 30 arcsec, resulting in the retrieval of three possible detections. Furthermore, this detection is actually listed as the furthest one from the source! To prove that this is in fact an accurately assigned detection, we can use an image with an allwise overlay:

[INSERT AN IMAGE ONCE I SORT OUT CUSTOM OVERLAYS]

Much like the ATKalias command, we can also delete epoch definitions for a specific alias:

ATKepoch del allwise

We can also reset the list of epoch definitions to its default state:

ATKepoch reset

and can open it in the default text editor:

ATKepoch open

Note: Epochs do not need to be set for image surveys when used in image queries, as the proper motion correction in this case makes use of the specific image epoch rather than a single definition. Similarly, epoch definitions are not required for SED and bulkdata queries, as these simply use the definitions of the relevant surveys above.