Simbad module evolutions¶
Translating query_criteria into criteria¶
The method query_criteria is now deprecated in the SIMBAD module. It is replaced by
a criteria argument in the following methods:
This new argument expects a criteria formatted as a WHERE clause in an ADQL string,
it consists of:
logical operators
AND,OR,NOT,comparison operators
=,!=(or its alternative notation<>),<,>,<=,>=,range comparison
BETWEEN(ex: range of spectral typessp_type BETWEEN 'F3' AND 'F5'),membership check
IN(ex: either active galaxy nucleus, or active galaxy nucleus candidateotype IN ('AGN', 'AG?')),case-sensitive string comparison:
LIKE,null value check
IS NULL,IS NOT NULL.
This list is extracted from the section 2.2.3 of the ADQL specification.
Here, for example, we add a criteria on the desired type of objects to a region query in 2° around M11:
>>> from astroquery.simbad import Simbad
>>> Simbad(ROW_LIMIT=20).query_region("M11", "2d",
... criteria="otype = 'Star..'")[["main_id", "ra", "dec"]]
<Table length=20>
main_id ra dec
deg deg
object float64 float64
---------------------------- ------------------ ------------------
ATO J283.9680-04.7022 283.9680584302754 -4.702210643396667
2MASS J18553904-0441576 283.912704 -4.699355
2MASS J18434437-0532364 280.934909910062 -5.543481872277222
IRAS 18410-0535 280.93514361343995 -5.534989946319999
Gaia DR3 4255168174887091584 281.9199370352171 -4.607529439915277
... ... ...
Gaia DR3 4255168415418002432 281.8446179288175 -4.647683641737222
OGLE GD-RRLYR-8997 281.93337499999996 -4.824888888888889
2MASS J18471362-0444391 281.80677257235084 -4.744217391975
IRAS 18449-0454 281.89339967202 -4.85617020367
* bet Sct 281.79364256535 -4.74787304458
Gaia DR2 4255222566334653952 282.4900966404579 -4.434419082480556
We only retrieve objects which main type (otype) is a star (Star)
or its descendants (..) – see section on Object types –.
If you already have a string that was a valid criteria in query_criteria,
there is a helper method to translate a criteria from query_criteria into a string
that will work as criteria in the other query methods cited above:
>>> from astroquery.simbad.utils import CriteriaTranslator
>>> CriteriaTranslator.parse("region(box, ICRS, 0 +0, 3d 1d) & otype='SNR'")
"CONTAINS(POINT('ICRS', ra, dec), BOX('ICRS', 0.0, 0.0, 3.0, 1.0)) = 1 AND otypes.otype = 'SNR'"
This string can now be incorporated in any of the query methods that accept a criteria argument.
See a more elaborated example:
>>> from astroquery.simbad import Simbad
>>> from astroquery.simbad.utils import CriteriaTranslator
>>> # not a galaxy, and not a globular cluster
>>> old_criteria = "maintype != 'Galaxy..' & maintype != 'Cl*..'"
>>> simbad = Simbad()
>>> # we add the main type and all the types that have historically been attributed to the object
>>> simbad.add_votable_fields("otype", "alltypes")
>>> result = simbad.query_catalog("M", criteria=CriteriaTranslator.parse(old_criteria))
>>> result.sort("catalog_id")
>>> result[["main_id", "catalog_id", "otype", "otypes"]]
<Table length=11>
main_id catalog_id otype otypes
object object object object
--------- ---------- ------ ----------------------------------------
M 1 M 1 SNR HII|IR|Psr|Rad|SNR|X|gam
M 24 M 24 As* As*|Cl*|GNe
M 27 M 27 PN *|G|HS?|IR|PN|UV|WD*|WD?|X|blu
M 40 M 40 ? ?
M 42 M 42 HII C?*|Cl*|HII|OpC|Rad|X
M 43 M 43 HII HII|IR|Rad
M 57 M 57 PN *|HS?|IR|PN|Rad|WD*|WD?|blu
NGC 6994 M 73 err Cl*|err
M 76 M 76 PN *|IR|PN|Rad|WD*
M 78 M 78 RNe C?*|Cl*|ISM|RNe
M 97 M 97 PN *|HS?|IR|NIR|Opt|PN|Rad|UV|WD*|WD?|X|blu
And we indeed get objects from the Messier catalog (as query_catalog is
meant to return), but with the additional criteria that these objects should be neither galaxies
nor clusters of stars.
Object types¶
The example above highlights the subtlety of assigning a type for every object. The SIMBAD database
evolves with the literature and the otype value reflects the most precise type that was
identified through a literature review at the moment at which the query is done.
All the former otype assignations are also stored in the otypes column. These can be either less
precise or false. See in the previous example M27 that is now classified as PN (Planetary Nebula)
and was in the past thought to be a G (Galaxy).
The definitions of object types can be found either in SIMBAD’s
documentation on object types
or with TAP queries. For example, to see the definition of PN, one can do:
>>> from astroquery.simbad import Simbad
>>> result = Simbad.query_tap("SELECT * FROM otypedef WHERE otype = 'PN'")
>>> result[["otype", "label", "description", "is_candidate", "path"]]
<Table length=1>
otype label description is_candidate path
object object object int16 object
------ ------------ ---------------- ------------ ------------
PN PlanetaryNeb Planetary Nebula 0 * > Ev* > PN
Where otypedef is the table of SIMBAD containing the definitions of object types.
The label can also be used in a query if you want your code to be easier to read.
>>> from astroquery.simbad import Simbad
>>> Simbad.query_tap("SELECT top 5 main_id, otype FROM basic WHERE otype = 'PlanetaryNeb'")
<Table length=5>
main_id otype
object object
---------- ------
IC 4634 PN
PN H 2-40 PN
PN PC 12 PN
NGC 6543 PN
NGC 7027 PN
The path column in otypedef is a representation of the hierarchy of objects.
Here PN (Planetary Nebula) derives from Ev* (Evolved Star) which itself derives
from * (Star). This is the classification of objects in place in SIMBAD since 2020.
If you don’t find an object type you used to look for in SIMBAD, you might be interested
in this table of correspondence
between old and new labels for object types.
An interesting feature brought by the hierarchy of objects is the .. notation. For example,
Ev*.. means any object type that derives from evolved star.
>>> from astroquery.simbad import Simbad
>>> Simbad.query_tap("SELECT top 5 main_id, otype "
... "FROM basic WHERE otype = 'Ev*..'")
<Table length=5>
main_id otype
object object
---------------------- ------
IRAS 07506-0345 pA*
D33 J013331.3+302946.9 cC*
D33 J013253.5+303810.2 Ce*
[SC83] G4 Ce*
SSTGC 444055 LP*
This return objects which types are indeed among the 17 types deriving from Ev*
(Evolved Star). For example, pA* is a post-AGB Star.
Optical Filters¶
Historically, there were only three optical filters in SIMBAD, U, B, and V.
This is why one could add these columns to SIMBAD’s output with ubv. This is not
the case anymore.
There are two different ways to add fluxes to the result of a SIMBAD query. If you only need a quick access to the value of the flux without extra information, you can add the votable field corresponding to a specific optical filter. The list of filter names can be printed with
>>> from astroquery.simbad import Simbad
>>> options = Simbad.list_votable_fields()
>>> options[options["type"] == "filter name"]
<Table length=17>
name description type
object object object
------ ----------------- -----------
U Magnitude U filter name
B Magnitude B filter name
V Magnitude V filter name
R Magnitude R filter name
I Magnitude I filter name
J Magnitude J filter name
H Magnitude H filter name
K Magnitude K filter name
u Magnitude SDSS u filter name
g Magnitude SDSS g filter name
r Magnitude SDSS r filter name
i Magnitude SDSS i filter name
z Magnitude SDSS z filter name
G Magnitude Gaia G filter name
F150W JWST NIRCam F150W filter name
F200W JWST NIRCam F200W filter name
F444W JWST NIRCan F444W filter name
There are currently 17 filters in SIMBAD, but more are added as new data is ingested.
Note
This is the only case-sensitive votable field, due to the fact that the filters U
and u (for example) are distinct.
A query for fluxes would then look like:
>>> from astroquery.simbad import Simbad
>>> simbad = Simbad()
>>> simbad.add_votable_fields("U", "V", "B")
>>> simbad.query_object("NGC 5678")[["main_id", "U", "V", "B"]]
<Table length=1>
main_id U V B
object float64 float64 float64
--------- ------- ------- ------------------
NGC 5678 -- -- 12.100000381469727
However, this quick access does not allow to retrieve the flux error or the bibcode of the
article from which the information is extracted. To do so, prefer the flux votable field:
>>> from astroquery.simbad import Simbad
>>> simbad = Simbad()
>>> simbad.add_votable_fields("flux")
>>> result = simbad.query_object("BD-16 5701")
>>> result[["main_id", "flux", "flux_err", "filter", "bibcode"]]
<Table length=6>
main_id flux flux_err filter bibcode
object float32 float32 object object
----------- --------- -------- ------ -------------------
BD-16 5701 10.322191 0.002762 G 2020yCat.1350....0G
BD-16 5701 10.6 0.06 V 2000A&A...355L..27H
BD-16 5701 9.205 0.023 J 2003yCat.2246....0C
BD-16 5701 8.879 0.042 H 2003yCat.2246....0C
BD-16 5701 8.777 0.02 K 2003yCat.2246....0C
BD-16 5701 11.15 0.07 B 2000A&A...355L..27H
This gives more details than the quick view. Each line corresponds to a unique filter.
The bibcode column corresponds to the article in which the flux information was found.
We could also add a criteria to restrict the filters in the output:
>>> from astroquery.simbad import Simbad
>>> simbad = Simbad()
>>> simbad.add_votable_fields("flux")
>>> result = simbad.query_object("BD-16 5701", criteria="filter IN ('U', 'B', 'G')")
>>> result[["main_id", "flux", "flux_err", "filter", "bibcode"]]
<Table length=2>
main_id flux flux_err filter bibcode
object float32 float32 object object
----------- --------- -------- ------ -------------------
BD-16 5701 11.15 0.07 B 2000A&A...355L..27H
BD-16 5701 10.322191 0.002762 G 2020yCat.1350....0G
There was no match for U, but the information is there for B and G.