The Photometric Reference Catalog is a catalog which contains magnitudes in common bands, coordinates and names for standard stars. The Photometric Reference Catalog and the standard extinction curve are two calibration files that are provided by the system. Both calibration files are directly accessible for the user from the awe-prompt.
The Photometric Reference Catalog present in the Astro-WISE system is the result of an
ongoing project. This section describes
the contents of the most recent version of this Photometric Reference Catalog wich has the filename cal569E_v11.cat. The catalog file can be found in the
The catalog is in FITS table format and its columns are described in Table . Whenever a magnitude or its associated error has value 0.0 it means that no value has been determined.
The Photometric Reference Catalog can be retrieved from the database to the local directory as follows:
The Photometric Reference Catalog has six methods for querying/accessing its content.
The first four of these are simple methods without parameters. These are the
following:
In order to retrieve the magnitudes for all the stars in the standard star
catalog for one particular photometric band (mag_id), type:
Besides this dedicated method, the Photometric Reference Catalog also has an allround
query method that can be used to retrieve any information that is needed. This
method and its signature are:
As was mentioned in §, the Photometric Reference Catalog contains stars from various contributary catalogs.
To allow the user (and the system) to see/use/select the stars of only one or a select few of the contributaries, the standard
star catalog is outfitted with a filter on the origin column. In the current version of the Photometric Reference Catalog this attribute
can have one of the following values: Landolt, SDSS5 and Stetson for Landolt, SDSS DR5 and Stetson
catalogs, respectively, and AW2S for the Preliminary Catalog.
To select/see/use only stars from the Photometric Reference Catalog that originate from the 'Landolt' catalog use:
To de-activate the filter so that the full view on the catalog is restored:
It is obvious that the setting of the filter affects the return values of the
query methods described in §.
The OmegaCAM system distinguishes two types of bands: key bands, and
user bands. This distinction has its origin in the OmegaCAM calibration
plan, and has implications for the inner workings of the photometric pipeline.
The key bands are the Sloan ugri
To process data that have been observed in a user band, a transformation
table is needed. This table contains information about which key bands to use
in the transformation, and a set of transformation coefficients. Such a table
should be present in the database for every filter that belongs to a user band.
The contents of such a table could be so simple as providing a substitute key
band for a given user band (e.g. for a Gunn r
The Johnson-Cousins bands and the Sloan z
The Photometric Reference Catalog described above is the default Photometric Reference Catalog
automatically used by AWE. This standard catalog has the reserved name cal569E_v*.cat, with the version number at the asterisk. This naming
convention should never be used for your own catalog! In the event that
you need to use standard stars which are not provided by the default standard
catalog you can create your own catalog and ingest it in AWE.
A Photometric Reference Catalog requires a specific format.
One can create this format from an input ascii format using the refcat_generator.py code available in https://gitlab.astro-wise.org/omegacen/catalog/tree/master/toolscatalog/tools
Once created, you can ingest it into the system doing the following:
To be written.
To retrieve the standard extinction curve from the database, do the
following:
Before the photometric pipeline can be used, the system should be initialized
by putting a standard extinction curve into the system. Note : this should
only have to be done once by the maintainer of the system. After
initialization, every user of the system has access to the standard
extincintion curve. To put a standard extinction curve into the system, do the
following:
References
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992AJ....104..340L&db_key=AST&data_type=HTML&format=&high=43c2adf22401012Landolt, A.U. 1992, AJ, 104(1), 340
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005AJ....130..873J&db_key=ASTJester, S., et al. 2005, AJ, 130, 873
http://www.astro-wise.org/Public/blankenberge_verdoes.ps.gzVerdoes Kleijn et al. 2006
https://gitlab.astro-wise.org/omegacen/catalogcatalog project. This catalog contains stars from four sources: the Landolt catalog, the Stetson catalog, the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) catalog and the Preliminary Catalog for the OmegaCAM Secondary Standards Programme which is based on our own observations. For all four sources stellar magnitudes are given in both the Johnson-Cousins UBVRI
Field
1#1
2#2
Landolt
Stetson
SDSS DR5
PC
(deg)
(deg)
SA51
112.663
+
0
0
214
0
SA57
197.171
+
0
0
952
0
SA68
4.146
+
0
0
1302
0
SA92
13.946
+
41
213
1094
6475
SA93
28.783
+
4
0
1128
0
SA94
44.033
+
7
0
1099
0
SA95
58.500
+
45
426
1093
0
SA98
103.021
-
46
1116
0
23840
SA100
133.529
+
6
1
3343
0
SA101
149.112
-
35
117
1776
5591
SA102
163.779
+
5
66
1517
0
SA103
178.779
+
2
0
1507
0
SA104
190.4875
-
34
76
1576
5701
SA105
204.533
+
4
0
2172
0
SA106
220.533
+
2
15
2864
0
SA107
234.8250
-
28
728
3889
12006
SA108
248.033
+
6
3
6148
0
SA110
280.6000
+
39
589
0
38562
SA112
310.529
+
7
73
12087
0
SA113
325.3750
+
42
483
4046
13947
SA114
340.529
+
9
5
1957
0
SA115
355.779
+
10
0
1170
0
column name
description
SeqNr
sequence number
origin
origin of stellar magnitude:
Landolt: Landolt catalog, Stetson: Stetson catalog,
SDSS5: SDSS DR5,
AW2S: Preliminary Catalog for OmegaCAM Secondary Standards
Name
Name of star
Ra/Ra_err
Right Ascension / its error (deg)
Dec/Dec_err
Declination / its error (deg)
Epoch
epoch of coordinates: all J2000
Flag
flag, (not used currently)
JohnsonU/JohnsonU_err
Johnson U / its error (mag)
JohnsonB/JohnsonB_err
Johnson B / its error (mag)
JohnsonV/JohnsonV_err
Johnson V / its error (mag)
CousinsR/CousinsR_err
Cousins R / its error (mag)
CousinsI/CousinsI_err
Cousins I / its error (mag)
SloanU/SloanU_err
Sloan u / its error (mag)
SloanG/SloanG_err
Sloan g / its error (mag)
SloanR/SloanR_err
Sloan r / its error (mag)
SloanI/SloanI_err
Sloan i / its error (mag)
SloanZ/SloanZ_err
Sloan z / its error (mag)
1.1.1.2 Retrieving the Photometric Reference Catalog
awe> from astro.main.PhotRefCatalog import PhotRefCatalog
awe> refcat = PhotRefCatalog.get()
awe> refcat.retrieve()
which will automatically give the most recent Photometric Reference Catalog in the
system. Note the retrieve operation in the last line; this is
important. The contents of the catalog thus retrieved to the local directory can then be queried using
the methods described in §.
1.1.1.3 Query methods
The following query methods have a more elaborate interface. One thing that
should be mentioned is that every single star in the catalog has an index for
cross-referencing purposes. The methods below all return dictionaries which use
these indices as keys.
which returns the number of
sources in he catalog.
which returns a list of the
photometric bands supported by the catalog.
which returns information of
the data content of a source. The information is stored in a dictionary with
the attribute names of the source as keys and their types as values. To just
get the attribute names, do: refcat.get_source_attributes().keys().
which dumps the catalog for overplotting
in skycat.
awe> refcat.get_dict_of_magnitudes(mag_id)
which will return a dictionary with the indices of the sources as keys, and as
values 2-tuples containing the magnitude and its uncertainty. The mag_id
is a string that should match one of the entries in the list generated by the
get_list_of_bands method. If one wants to retrieve the magnitudes for
only a subset of stars, it is possible to provide the method call with an
additional list of indices:
awe> refcat.get_dict_of_magnitudes(mag_id, index_list = [1, 2, 13500])
which will only give the magnitudes for the stars 1, 2 and 13500 in the list.
awe> refcat.get_source_data(column_list, index_list = index_list)
which will return a dictionary with the indices of the sources as keys, and as
values lists of the requested data items in the same order as specified in the
input column_list. The input column_list is the list of data
items to be retrieved, and the optional index_list is used to get data
from a subset of stars only. The entries in column_list should match
the keys of the dictionary that is generated by the get_source_attributes method. These entries are strings.
1.1.1.4 Examples of use
Retrieve the V magnitudes of all the stars in the catalog:
awe> mag_dict = refcat.get_dict_of_magnitudes('JohnsonV')
Retrieve the g'
awe> inds = range(10, 500)
awe> mag_dict = refcat.get_dict_of_magnitudes('SloanG', index_list = inds)
Retrieve the Ra-Dec-Epoch information from all the stars:
awe> info_dict = refcat.get_source_data(['ra', 'dec', 'epoch'])
Retrieve the name (star_id) of the stars 1 and 2:
awe> info_dict = refcat.get_source_data(['star_id'], index_list = [1, 2])
Retrieve the names of the catalogs from which the sources originate (origin):
awe> info_dict = refcat.get_source_data(['origin'])
1.1.1.5 Using a subset of the catalog for photometric calibration
awe> refcat.origin_filter.activate('Landolt')
To select/see/use only stars from both the 'Landolt' and 'Stetson' sub-catalogs use:
awe> refcat.origin_filter.activate('Landolt', 'Stetson')
To select/see/use only stars from the 'Stetson', 'SDSS5' and 'AW2S' sub-catalogs use:
awe> refcat.origin_filter.activate('Stetson', 'SDSS5', 'AW2S')
Note, that the order in which the origin identifiers appear is not important.
awe> refcat.origin_filter.deactivate()
To check whether the filter is actually switched on:
awe> refcat.origin_filter.is_active()
which will return either True or False. By default, the filter is
disabled.
1.1.1.6 Standard and non-standard photometric bands for OmegaCAM
1.1.1.7 Using your own catalog with standard stars
Typing at the operating system command line
linux> awe refcat_generator.py
will generate the help documentation.
awe> from astro.main.PhotRefCatalog import PhotRefCatalog
awe> refcat = PhotRefCatalog(pathname = 'myowncatalog.cat')
awe> refcat.store()
awe> refcat.commit()
Note the extra store command that will put the file on the fileserver.
1.1.2 The standard extinction curve
1.1.2.1 Its present contents
1.1.2.2 Retrieving the standard extinction curve
awe> from astro.main.PhotExtinctionCurve import PhotExtinctionCurve
awe> extcurve = PhotExtinctionCurve.get()
after which it can be used immediately. For example :
awe> extcurve.get_extinction(4861.0)
0.13652400000000001
with 4861.0 the wavelength in Å, and the answer in mag/am. This method
is the only query method defined on the extinction curve.
1.1.2.3 Ingesting the standard extinction curve
awe> from astro.main.PhotExtinctionCurve import PhotExtinctionCurve
awe> extcurve = PhotExtinctionCurve(pathname = 'cal564E.dat')
awe> extcurve.commit()
The standard extinction curve file can be found in a separate catalog project. The file cal564E.dat represents the
La Palma extinction curve in units of mag/am.