One of the most powerful features of Marvin 2.0 is ability to query the newly created DRP and DAP databases. You can do this in two ways:
The best part is that both interfaces use the same underlying query structure, so your input search will be the same. Here we will run a few queries with Marvin-tools to learn the basics of how to construct a query and also test drive some of the more advanced features that are unique to the Marvin-tools version of querying.
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# Python 2/3 compatibility
from __future__ import print_function, division, absolute_import
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from marvin import config
config.mode = 'remote'
config.setRelease('MPL-4')
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from marvin.tools.query import Query
Let's search for galaxies with M$_\star$ > 3 $\times$ 10$^{11}$ M$_\odot$.
To specify our search parameter, M$_\star$, we must know the database table and name of the parameter. In this case, MaNGA uses the NASA-Sloan Atlas (NSA) for target selection so we will use the Sersic profile determination for stellar mass, which is the sersic_mass parameter of the nsa table, so our search parameter will be nsa.sersic_mass. You can also use nsa.sersic_logmass
Generically, the search parameter will take the form table.parameter.
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myquery1 = 'nsa.sersic_mass > 3e11'
# or
myquery1 = 'nsa.sersic_logmass > 11.47'
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q1 = Query(searchfilter=myquery1)
r1 = q1.run()
Running the query produces a Results object (r1):
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# show results
r1.results
We will learn how to use the features of our Results object a little bit later, but first let's revise our search to see how more complex search queries work.
Let's add to our search to find only galaxies with a redshift less than 0.1.
Redshift is the z parameter and is also in the nsa table, so its full search parameter designation is nsa.z.
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myquery2 = 'nsa.sersic_mass > 3e11 AND nsa.z < 0.1'
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q2 = Query(searchfilter=myquery2)
r2 = q2.run()
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r2.results
We were hoping for a few more than 3 galaxies, so let's try to increase our search by broadening the criteria to also include galaxies with 127 fiber IFUs and a b/a ratio of at least 0.95.
To find 127 fiber IFUs, we'll use the name parameter of the ifu table, which means the full search parameter is ifu.name. However, ifu.name returns the IFU design name, such as 12701, so we need to to set the value to 127*.
The b/a ratio is in nsa table as the ba90 parameter.
We're also going to join this to or previous query with an OR operator and use parentheses to group our individual search statements into a compound search statement.
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myquery3 = '(nsa.sersic_mass > 3e11 AND nsa.z < 0.1) OR (ifu.name=127* AND nsa.ba90 >= 0.95)'
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q3 = Query(searchfilter=myquery3)
r3 = q3.run()
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r3.results
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# Enter your search here
You should get 8 results:
[NamedTuple(mangaid='1-22438', plate=7992, name='1901', z=0.016383046284318),
NamedTuple(mangaid='1-113520', plate=7815, name='1901', z=0.0167652331292629),
NamedTuple(mangaid='1-113698', plate=8618, name='1901', z=0.0167444702237844),
NamedTuple(mangaid='1-134004', plate=8486, name='1901', z=0.0185601413249969),
NamedTuple(mangaid='1-155903', plate=8439, name='1901', z=0.0163660924881697),
NamedTuple(mangaid='1-167079', plate=8459, name='1901', z=0.0157109703868628),
NamedTuple(mangaid='1-209729', plate=8549, name='1901', z=0.0195561610162258),
NamedTuple(mangaid='1-277339', plate=8254, name='1901', z=0.0192211158573627)]
Now you might want to go out and try all of the interesting queries that you've been saving up, but you don't know what the parameters are called or what database table they are in.
You can find all of the availabale parameters by:
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# You might have to do an svn update to get this to work (otherwise try the next cell)
q = Query()
q.get_available_params()
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# try this if the previous cell didn't return a list of parameters
from marvin.api.api import Interaction
from pprint import pprint
url = config.urlmap['api']['getparams']['url']
ii = Interaction(route=url)
mykeys = ii.getData()
pprint(mykeys)
Go ahead and try to create some new searches on your own from the parameter list. Please feel free to also try out the some of the same search on the Marvin-web Search page.
Often you want to run a query and see the value of parameters that you didn't explicitly search on. For instance, you want to find galaxies above a redshift of 0.1 and would like to know their RA and DECs.
In Marvin-tools, this is as easy as specifying the returnparams option with either a string (for a single bonus parameter) or a list of strings (for multiple bonus parameters).
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myquery5 = 'nsa.z > 0.1'
bonusparams5 = ['cube.ra', 'cube.dec']
# bonusparams5 = 'cube.ra' # This works too
q5 = Query(searchfilter=myquery5, returnparams=bonusparams5)
r5 = q5.run()
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r5.results
Next time, we'll take a closer look at the Results class and its built in MaNGA convenience functions.
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