Merge pull request #3175 from cds-astro/simbad-hierarchy

feat: add query_hierarchy

CHANGES.rst

@@ -176,6 +176,9 @@ simbad
 - fixed ``query_objects`` that would not work in combination with the additional field
   ``ident`` [#3149]
 
+- added ``query_hierarchy``: a new method that allows to get the parents, children, or
+  siblings of an object [#3175]
+
 skyview
 ^^^^^^^
 

astroquery/simbad/core.py

@@ -176,6 +176,7 @@ def columns_in_output(self):
         - `query_objects`,
         - `query_region`,
         - `query_catalog`,
+        - `query_hierarchy`,
         - `query_bibobj`,
         - `query_criteria`.
 
@@ -359,6 +360,7 @@ def add_votable_fields(self, *args):
         - `query_objects`,
         - `query_region`,
         - `query_catalog`,
+        - `query_hierarchy`,
         - `query_bibobj`,
         - `query_criteria`.
 
@@ -487,6 +489,7 @@ def reset_votable_fields(self):
         - `query_objects`,
         - `query_region`,
         - `query_catalog`,
+        - `query_hierarchy`,
         - `query_bibobj`,
         - `query_criteria`.
 
@@ -855,6 +858,86 @@ def query_catalog(self, catalog, *, criteria=None, get_query_payload=False,
         return self._query(top, columns, joins, instance_criteria,
                            get_query_payload=get_query_payload)
 
+    def query_hierarchy(self, name, hierarchy, *,
+                        detailed_hierarchy=False,
+                        criteria=None, get_query_payload=False):
+        """Query either the parents or the children of the object.
+
+        Parameters
+        ----------
+        name : str
+            name of the object
+        hierarchy : str
+            Can take the values "parents" to return the parents of the object (ex: a
+            galaxy cluster is a parent of a galaxy), the value "children" to return
+            the children of an object (ex: stars can be children of a globular cluster),
+            or the value "siblings" to return the object that share a parent with the
+            given one (ex: the stars of an open cluster are all siblings).
+        detailed_hierarchy : bool
+            Whether to add the two extra columns 'hierarchy_bibcode' that gives the
+            article in which the hierarchy link is mentioned, and
+            'membership_certainty'. membership_certainty is an integer that reflects the
+            certainty of the hierarchy link according to the authors. Ranges between 0
+            and 100 where 100 means that the authors were certain of the classification.
+            Defaults to False.
+        criteria : str
+            Criteria to be applied to the query. These should be written in the ADQL
+            syntax in a single string. See example.
+        get_query_payload : bool, optional
+            When set to `True` the method returns the HTTP request parameters without
+            querying SIMBAD. The ADQL string is in the 'QUERY' key of the payload.
+            Defaults to `False`.
+
+        Returns
+        -------
+        table : `~astropy.table.Table`
+            Query results table
+
+        Examples
+        --------
+        >>> from astroquery.simbad import Simbad
+        >>> parent = Simbad.query_hierarchy("2MASS J18511048-0615470",
+        ...                                 hierarchy="parents")  # doctest: +REMOTE_DATA
+        >>> parent[["main_id", "ra", "dec"]] # doctest: +REMOTE_DATA
+        <Table length=1>
+         main_id     ra     dec
+                    deg     deg
+          object  float64 float64
+        --------- ------- -------
+        NGC  6705 282.766  -6.272
+        """
+        top, columns, joins, instance_criteria = self._get_query_parameters()
+
+        sub_query = ("(SELECT oidref FROM ident "
+                     f"WHERE id = '{name}') AS name")
+
+        if detailed_hierarchy:
+            columns.append(_Column("h_link", "link_bibcode", "hierarchy_bibcode"))
+            columns.append(_Column("h_link", "membership", "membership_certainty"))
+
+        if hierarchy == "parents":
+            joins += [_Join("h_link", _Column("basic", "oid"), _Column("h_link", "parent"))]
+            instance_criteria.append("h_link.child = name.oidref")
+        elif hierarchy == "children":
+            joins += [_Join("h_link", _Column("basic", "oid"), _Column("h_link", "child"))]
+            instance_criteria.append("h_link.parent = name.oidref")
+        elif hierarchy == "siblings":
+            sub_query = ("(SELECT DISTINCT basic.oid FROM "
+                         f"{sub_query}, basic JOIN h_link ON basic.oid = h_link.parent "
+                         "WHERE h_link.child = name.oidref) AS parents")
+            joins += [_Join("h_link", _Column("basic", "oid"), _Column("h_link", "child"))]
+            instance_criteria.append("h_link.parent = parents.oid")
+        else:
+            raise ValueError("'hierarchy' can only take the values 'parents', "
+                             f"'siblings', or 'children'. Got '{hierarchy}'.")
+
+        if criteria:
+            instance_criteria.append(f"({criteria})")
+
+        return self._query(top, columns, joins, instance_criteria,
+                           from_table=f"{sub_query}, basic", distinct=True,
+                           get_query_payload=get_query_payload)
+
     @deprecated_renamed_argument(["verbose"], new_name=[None],
                                  since=['0.4.8'], relax=True)
     def query_bibobj(self, bibcode, *, criteria=None,
@@ -1369,7 +1452,7 @@ def _get_query_parameters(self):
         """Get the current building blocks of an ADQL query."""
         return tuple(map(copy.deepcopy, (self.ROW_LIMIT, self.columns_in_output, self.joins, self.criteria)))
 
-    def _query(self, top, columns, joins, criteria, from_table="basic",
+    def _query(self, top, columns, joins, criteria, from_table="basic", distinct=False,
                get_query_payload=False, **uploads):
         """Generate an ADQL string from the given query parameters and executes the query.
 
@@ -1386,6 +1469,8 @@ def _query(self, top, columns, joins, criteria, from_table="basic",
             with an AND clause.
         from_table : str, optional
             The table after 'FROM' in the ADQL string. Defaults to "basic".
+        distinct : bool, optional
+            Whether to add the DISTINCT instruction to the query.
         get_query_payload : bool, optional
             When set to `True` the method returns the HTTP request parameters without
             querying SIMBAD. The ADQL string is in the 'QUERY' key of the payload.
@@ -1400,6 +1485,7 @@ def _query(self, top, columns, joins, criteria, from_table="basic",
         `~astropy.table.Table`
             The result of the query to SIMBAD.
         """
+        distinct_results = " DISTINCT" if distinct else ""
         top_part = f" TOP {top}" if top != -1 else ""
 
         # columns
@@ -1433,7 +1519,7 @@ def _query(self, top, columns, joins, criteria, from_table="basic",
         else:
             criteria = ""
 
-        query = f"SELECT{top_part}{columns} FROM {from_table}{join}{criteria}"
+        query = f"SELECT{distinct_results}{top_part}{columns} FROM {from_table}{join}{criteria}"
 
         response = self.query_tap(query, get_query_payload=get_query_payload,
                                   maxrec=self.hardlimit,

astroquery/simbad/tests/test_simbad.py

@@ -345,6 +345,37 @@ def test_query_catalog():
     assert adql.endswith(where_clause)
 
 
+@pytest.mark.usefixtures("_mock_simbad_class")
+def test_query_hierarchy():
+    simbad_instance = simbad.Simbad()
+    detailed = ('h_link."link_bibcode" AS "hierarchy_bibcode", h_link."membership"'
+                ' AS "membership_certainty"')
+    # the three possible cases
+    adql = simbad_instance.query_hierarchy("test", hierarchy="parents",
+                                           detailed_hierarchy=True,
+                                           get_query_payload=True)["QUERY"]
+    assert "h_link.child = name.oidref" in adql
+    assert detailed in adql
+    adql = simbad_instance.query_hierarchy("test", hierarchy="children",
+                                           criteria="test=test",
+                                           get_query_payload=True)["QUERY"]
+    assert "h_link.parent = name.oidref" in adql
+    assert "test=test" in adql
+    assert detailed not in adql
+    adql = simbad_instance.query_hierarchy("test", hierarchy="siblings",
+                                           get_query_payload=True)["QUERY"]
+    assert "h_link.parent = parents.oid" in adql
+    # if the keyword does not correspond
+    with pytest.raises(ValueError, match="'hierarchy' can only take the values "
+                       "'parents', 'siblings', or 'children'. Got 'test'."):
+        simbad_instance.query_hierarchy("object", hierarchy="test",
+                                        get_query_payload=True)
+    # if the people were used to the old votable_fields
+    with pytest.raises(ValueError, match="The hierarchy information is no longer an "
+                       "additional field. *"):
+        simbad_instance.add_votable_fields("membership")
+
+
 @pytest.mark.parametrize(('coordinates', 'radius', 'where'),
                          [(ICRS_COORDS, 2*u.arcmin,
                            r"WHERE CONTAINS\(POINT\('ICRS', basic\.ra, basic\.dec\), "

astroquery/simbad/tests/test_simbad_remote.py

@@ -55,6 +55,17 @@ def test_query_catalog(self):
         result = self.simbad.query_catalog('M')
         assert len(result) == 110
 
+    def test_query_hierarchy(self):
+        self.simbad.ROW_LIMIT = -1
+        obj = "NGC 4038"
+        parents = self.simbad.query_hierarchy(obj, hierarchy="parents")
+        assert len(parents) == 4
+        children = self.simbad.query_hierarchy(obj, hierarchy="children")
+        assert len(children) >= 45  # as of 2025, but more could be added
+        siblings = self.simbad.query_hierarchy(obj, hierarchy="siblings",
+                                               criteria="otype='G..'")
+        assert len(siblings) >= 29
+
     def test_query_region(self):
         self.simbad.ROW_LIMIT = 10
         result = self.simbad.query_region(ICRS_COORDS_M42, radius="1d")

astroquery/simbad/utils.py

@@ -37,6 +37,9 @@ def _catch_deprecated_fields_with_arguments(votable_field):
     if votable_field.startswith("bibcodelist("):
         raise ValueError("Selecting a range of years for bibcode is removed. You can still use "
                          "bibcodelist without parenthesis and get the full list of bibliographic references.")
+    if votable_field in ["membership", "link_bibcode"]:
+        raise ValueError("The hierarchy information is no longer an additional field. "
+                         "It has been replaced by the 'query_hierarchy' method.")
 
 # ----------------------------
 # Support wildcard argument

docs/simbad/simbad.rst

@@ -155,6 +155,96 @@ associated with an object.
             NAME North Star
                   WEB  2438
 
+Query to get all parents (or children, or siblings) of an object
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Let's find the galaxies composing the galaxy pair ``Mrk 116``:
+
+.. doctest-remote-data::
+
+    >>> from astroquery.simbad import Simbad
+    >>> galaxies = Simbad.query_hierarchy("Mrk 116",
+    ...                                   hierarchy="children", criteria="otype='G..'")
+    >>> galaxies[["main_id", "ra", "dec"]]
+    <Table length=2>
+     main_id         ra            dec
+                    deg            deg
+      object      float64        float64
+    --------- --------------- --------------
+    Mrk  116A 143.50821525019 55.24105273196
+    Mrk  116B      143.509956      55.239762
+
+Alternatively, if we know one member of a group, we can find the others by asking for
+``siblings``:
+
+.. doctest-remote-data::
+
+    >>> from astroquery.simbad import Simbad
+    >>> galaxies = Simbad.query_hierarchy("Mrk 116A",
+    ...                                   hierarchy="siblings", criteria="otype='G..'")
+    >>> galaxies[["main_id", "ra", "dec"]]
+    <Table length=2>
+     main_id         ra            dec
+                    deg            deg
+      object      float64        float64
+    --------- --------------- --------------
+    Mrk  116A 143.50821525019 55.24105273196
+    Mrk  116B      143.509956      55.239762
+
+Note that if we had not added the criteria on the object type, we would also get
+some stars that are part of these galaxies in the result.
+
+And the other way around, let's find which cluster of stars contains
+``2MASS J18511048-0615470``:
+
+.. doctest-remote-data::
+
+    >>> from astroquery.simbad import Simbad
+    >>> cluster = Simbad.query_hierarchy("2MASS J18511048-0615470", hierarchy="parents")
+    >>> cluster[["main_id", "ra", "dec"]]
+    <Table length=1>
+     main_id     ra     dec
+                deg     deg
+      object  float64 float64
+    --------- ------- -------
+    NGC  6705 282.766  -6.272
+
+If needed, we can get a more detailed report with the two extra columns:
+ - ``hierarchy_bibcode`` : the paper in which the hierarchy is established,
+ - ``membership_certainty``: if present in the paper, a certainty index (100 meaning
+   100% sure).
+
+.. doctest-remote-data::
+
+    >>> from astroquery.simbad import Simbad
+    >>> cluster = Simbad.query_hierarchy("2MASS J18511048-0615470", 
+    ...                                  hierarchy="parents",
+    ...                                  detailed_hierarchy=True)
+    >>> cluster[["main_id", "ra", "dec", "hierarchy_bibcode", "membership_certainty"]]
+    <Table length=13>
+     main_id     ra     dec    hierarchy_bibcode  membership_certainty
+                deg     deg                             percent
+      object  float64 float64        object              int16
+    --------- ------- ------- ------------------- --------------------
+    NGC  6705 282.766  -6.272 2014A&A...563A..44M                  100
+    NGC  6705 282.766  -6.272 2015A&A...573A..55T                  100
+    NGC  6705 282.766  -6.272 2016A&A...591A..37J                  100
+    NGC  6705 282.766  -6.272 2018A&A...618A..93C                  100
+    NGC  6705 282.766  -6.272 2020A&A...633A..99C                  100
+    NGC  6705 282.766  -6.272 2020A&A...640A...1C                  100
+    NGC  6705 282.766  -6.272 2020A&A...643A..71G                  100
+    NGC  6705 282.766  -6.272 2020ApJ...903...55P                  100
+    NGC  6705 282.766  -6.272 2020MNRAS.496.4701J                  100
+    NGC  6705 282.766  -6.272 2021A&A...647A..19T                  100
+    NGC  6705 282.766  -6.272 2021A&A...651A..84M                  100
+    NGC  6705 282.766  -6.272 2021MNRAS.503.3279S                   99
+    NGC  6705 282.766  -6.272 2022MNRAS.509.1664J                  100
+
+Here, we see that the Simbad team found 13 papers mentioning the fact that 
+``2MASS J18511048-0615470`` is a member of ``NGC  6705`` and that the authors of these
+articles gave high confidence indices for this membership (``membership_certainty`` is
+close to 100 for all bibcodes).
+
 
 Query a region
 ^^^^^^^^^^^^^^
@@ -421,6 +511,7 @@ Some query methods outputs can be customized. This is the case for:
 - `~astroquery.simbad.SimbadClass.query_objects`
 - `~astroquery.simbad.SimbadClass.query_region`
 - `~astroquery.simbad.SimbadClass.query_catalog`
+- `~astroquery.simbad.SimbadClass.query_hierarchy`
 - `~astroquery.simbad.SimbadClass.query_bibobj`
 
 For these methods, the default columns in the output are:
@@ -523,6 +614,7 @@ Most query methods take a ``criteria`` argument. They are listed here:
 - `~astroquery.simbad.SimbadClass.query_objects`
 - `~astroquery.simbad.SimbadClass.query_region`
 - `~astroquery.simbad.SimbadClass.query_catalog`
+- `~astroquery.simbad.SimbadClass.query_hierarchy`
 - `~astroquery.simbad.SimbadClass.query_bibobj`
 - `~astroquery.simbad.SimbadClass.query_bibcode`
 - `~astroquery.simbad.SimbadClass.query_objectids`