Splatalogue Queries (astroquery.splatalogue)

Getting Started

This module provides an interface to the Splatalogue web service It returns tables of spectral lines with features that you can specify by the same means generally available on the Splatalogue website.

Searching for Lines

In the Splatalogue web interface, you select “species” of interest using the left side menu seen in the query interface You can access the line list:

>>> from astroquery.splatalogue import Splatalogue
>>> line_ids = Splatalogue.get_species_ids()

This will return the complete Splatalogue chemical species list, including all isotopologues, etc. To search within this list for a particular species, you can use regular expressions:

>>> CO_containing_species = Splatalogue.get_species_ids('CO')
>>> len(CO_containing_species)
91
>>> just_CO = Splatalogue.get_species_ids(' CO ') # note the spaces
>>> len(just_CO)
4
>>> just_CO  # includes different vibrationally excited states
{u'02812 CO v = 0 - Carbon Monoxide': u'204',
 u'02813 CO v = 1 - Carbon Monoxide': u'990',
 u'02814 CO v = 2 - Carbon Monoxide': u'991',
 u'02815 CO v = 3 - Carbon Monoxide': u'1343'}
>>> carbon_monoxide = Splatalogue.get_species_ids('Carbon Monoxide')
>>> len(carbon_monoxide) # includes isotopologues
13
>>> carbon_monoxide
>>>
{u'02812 CO v = 0 - Carbon Monoxide': u'204',
 u'02813 CO v = 1 - Carbon Monoxide': u'990',
 u'02814 CO v = 2 - Carbon Monoxide': u'991',
 u'02815 CO v = 3 - Carbon Monoxide': u'1343',
 u'02816 CO+ - Carbon Monoxide Ion': u'709',
 u'02910 13CO v = 0 - Carbon Monoxide': u'4',
 u'02911 13CO v = 1 - Carbon Monoxide': u'992',
 u'02912 13CO v = 2 - Carbon Monoxide': u'993',
 u'02913 C17O - Carbon Monoxide': u'226',
 u'03004 14CO - Carbon Monoxide': u'778',
 u'03005 C18O - Carbon Monoxide': u'245',
 u'03006 13C17O - Carbon Monoxide': u'264',
 u'03101 13C18O - Carbon Monoxide': u'14'}
>>> atomic_weight_88 = Splatalogue.get_species_ids('^088')
>>> atomic_weight_88
{u'08801 SiC5 - ': u'265',
 u'08802 CH3C6H - Methyltriacetylene': u'388',
 u'08803 C6O - Hexacarbon monoxide': u'585'}

The returned items are dictionaries, but they are also searchable.

>>> carbon_monoxide.find(' 13')  # note leading space
{u'02910 13CO v = 0 - Carbon Monoxide': u'4',
 u'02911 13CO v = 1 - Carbon Monoxide': u'992',
 u'02912 13CO v = 2 - Carbon Monoxide': u'993',
 u'03006 13C17O - Carbon Monoxide': u'264',
 u'03101 13C18O - Carbon Monoxide': u'14'}

Querying Splatalogue: Getting Line Information

Unlike most astroquery tools, the Splatalogue tool closely resembles the online interface. In principle, we can make a higher level wrapper, but it is not obvious what other parameters one might want to query on (whereas with catalogs, you almost always need a sky-position based query tool).

Any feature you can change on the Splatalogue web form can be modified in the query_lines() tool.

For any Splatalogue query, you must specify a minimum/maximum frequency. However, you can do it with astropy units, so wavelengths are OK too.

>>> from astropy import units as u
>>> CO1to0 = Splatalogue.query_lines(115.271*u.GHz,115.273*u.GHz)
>>> CO1to0.pprint()
      Species        Chemical Name   Freq-GHz ... E<sub>U</sub> (K) Linelist
------------------- --------------- --------- ... ----------------- --------
              COv=0 Carbon Monoxide        -- ...           5.53211     CDMS
              COv=0 Carbon Monoxide        -- ...           5.53211      JPL
              COv=0 Carbon Monoxide  115.2712 ...               0.0    Lovas
              COv=0 Carbon Monoxide  115.2712 ...           5.53211    SLAIM
         CH3CHOvt=1    Acetaldehyde 115.27182 ...         223.65667    SLAIM
         CH3CHOvt=1    Acetaldehyde        -- ...         223.65581      JPL
CH3O13CHO(TopModel)  Methyl Formate  115.2728 ...         272.75041 TopModel

Querying just by frequency isn’t particularly effective; a nicer approach is to use both frequency and chemical name. If you can remember that CO 2-1 is approximately in the 1 mm band, but you don’t know its exact frequency (after all, why else would you be using splatalogue?), this query works:

>>> CO2to1 = Splatalogue.query_lines(1*u.mm, 2*u.mm, chemical_name=" CO ")
>>> CO2to1.pprint()
Species  Chemical Name   Freq-GHz ... E<sub>U</sub> (K) Linelist
------- --------------- --------- ... ----------------- --------
  COv=1 Carbon Monoxide        -- ...        3100.11628     CDMS
  COv=1 Carbon Monoxide 228.43911 ...        3100.11758    SLAIM
  COv=0 Carbon Monoxide        -- ...          16.59608     CDMS
  COv=0 Carbon Monoxide        -- ...          16.59608      JPL
  COv=0 Carbon Monoxide   230.538 ...               0.0    Lovas
  COv=0 Carbon Monoxide   230.538 ...          16.59608    SLAIM

Of course, there’s some noise in there: both the vibrationally excited line and a whole lot of different line lists. Start by thinning out the line lists used:

>>> CO2to1 = Splatalogue.query_lines(1*u.mm, 2*u.mm, chemical_name=" CO ",only_NRAO_recommended=True)
>>> CO2to1.pprint()
Species  Chemical Name   Freq-GHz ... E<sub>U</sub> (K) Linelist
------- --------------- --------- ... ----------------- --------
  COv=1 Carbon Monoxide 228.43911 ...        3100.11758    SLAIM
  COv=0 Carbon Monoxide   230.538 ...          16.59608    SLAIM

Then get rid of the vibrationally excited line by setting an energy upper limit in Kelvin:

>>> CO2to1 = Splatalogue.query_lines(1*u.mm, 2*u.mm, chemical_name=" CO ",
                                     only_NRAO_recommended=True,
                                     energy_max=50, energy_type='eu_k')
>>> CO2to1.pprint()
Species  Chemical Name  Freq-GHz ... E<sub>U</sub> (K) Linelist
------- --------------- -------- ... ----------------- --------
  COv=0 Carbon Monoxide  230.538 ...          16.59608    SLAIM

Reference/API

Splatalogue Catalog Query Tool

Author:Adam Ginsburg (adam.g.ginsburg@gmail.com) Originally contributed by:  Magnus Vilehlm Persson (magnusp@vilhelm.nu)

Splatalogue(**kwargs)