astroquery:docs

ALMA Queries (astroquery.alma)

Getting started

astroquery.alma provides the astroquery interface to the ALMA archive. It supports object and region based querying and data staging and retrieval.

You can get interactive help to find out what keywords to query for:

>>> from astroquery.alma import Alma
>>> Alma.help()
Valid ALMA keywords:

Position
  Source name (Sesame)             : source_name_sesame
  Source name (ALMA)               : source_name-asu
  RA Dec                           : raDecCoordinates

Energy
  Frequency                        : energy.frequency-asu
  Bandwidth                        : energy.bandwidth-asu
  Spectral resolution              : energy.resolution-asu
  Band                             : band-asu

Time
  Observation date                 : start_date-asu
  Integration time                 : int_time-asu

Polarisation
  Polarisation type                : energy.pol_num-asu

Observation
  Water vapour                     : pwv-asu

Project
  Project code                     : project_code-asu
  Project title                    : project.title-substr
  PI name                          : project.pi_name-substr

Options
  View:                            : viewFormat
  [x] public data only             : publicFilterFlag     = public
  [x] science observations only    : scan_intent-asu      = =%TARGET%

Authentication

Users can log in to acquire proprietary data products. Login is performed via the ALMA CAS (central authentication server).

>>> from astroquery.alma import Alma
>>> alma = Alma()
>>> # First example: TEST is not a valid username, it will fail
>>> alma.login("TEST") 
TEST, enter your ALMA password:

Authenticating TEST on asa.alma.cl...
Authentication failed!
>>> # Second example: pretend ICONDOR is a valid username
>>> alma.login("ICONDOR", store_password=True) 
ICONDOR, enter your ALMA password:

Authenticating ICONDOR on asa.alma.cl...
Authentication successful!
>>> # After the first login, your password has been stored
>>> alma.login("ICONDOR") 
Authenticating ICONDOR on asa.alma.cl...
Authentication successful!

Your password will be stored by the keyring module. You can choose not to store your password by passing the argument store_password=False to Alma.login. You can delete your password later with the command keyring.delete_password('astroquery:asa.alma.cl', 'username').

Querying Targets and Regions

You can query by object name or by circular region:

>>> from astroquery.alma import Alma
>>> m83_data = Alma.query_object('M83')
>>> print(len(m83_data))
225
>>> m83_data.colnames
['Project_code', 'Source_name', 'RA', 'Dec', 'Band',
'Frequency_resolution', 'Integration', 'Release_date', 'Frequency_support',
'Velocity_resolution', 'Pol_products', 'Observation_date', 'PI_name',
'PWV', 'Member_ous_id', 'Asdm_uid', 'Project_title', 'Project_type',
'Scan_intent']

Region queries are just like any other in astroquery:

>>> from astropy import coordinates
>>> from astropy import units as u
>>> galactic_center = coordinates.SkyCoord(0*u.deg, 0*u.deg,
...                                        frame='galactic')
>>> gc_data = Alma.query_region(galactic_center, 1*u.deg)
>>> print(len(gc_data))
82

Downloading Data

You can download ALMA data with astroquery, but be forewarned, cycle 0 and cycle 1 data sets tend to be >100 GB!

>>> import numpy as np
>>> uids = np.unique(m83_data['Asdm_uid'])
>>> print(uids)
        Asdm_uid
 -----------------------
 uid://A002/X3b3400/X90f
 uid://A002/X3b3400/Xaf3
 uid://A002/X3fbe56/X607
 uid://A002/X4b29af/X24c
  uid://A002/X4b29af/X5c

You can then stage the data and see how big it is (you can ask for one or more UIDs):

>>> link_list = Alma.stage_data(uids[0:2])
>>> Alma.data_size(link_list)
INFO: Staging files... [astroquery.alma.core]
<Quantity 146.51379712000002 Gbyte>

You can then go on to download that data. The download will be cached so that repeat queries of the same file will not re-download the data. The default cache directory is ~/.astropy/cache/astroquery/Alma/, but this can be changed by changing the cache_location variable:

>>> myAlma = Alma()
>>> myAlma.cache_location = '/big/external/drive/'
>>> myAlma.download_files(link_list, cache=True)

You can also do the downloading all in one step:

>>> myAlma.retrieve_data_from_uid(uids[0])

Downloading FITS data

If you want just the QA2-produced FITS files, you can download the tarball, extract the FITS file, then delete the tarball:

>>> from astroquery.alma.core import Alma
>>> from astropy import coordinates
>>> from astropy import units as u
>>> orionkl = coordinates.SkyCoord('5:35:14.461 -5:21:54.41', frame='fk5',
...                                unit=(u.hour, u.deg))
>>> result = Alma.query_region(orionkl, radius=0.034*u.deg)
>>> uid_url_table = Alma.stage_data(result['Asdm_uid'], cache=False)
>>> # Extract the data with tarball file size < 1GB
>>> small_uid_url_table = uid_url_table[uid_url_table['size'] < 1]
>>> # get the first 10 files...
>>> filelist = Alma.download_and_extract_files(small_uid_url_table[:10]['URL'])

You might want to look at the READMEs from a bunch of files so you know what kind of S/N to expect:

>>> filelist = Alma.download_and_extract_files(uid_url_table['URL'], regex='.*README$')

Reference/API

astroquery.alma Module

ALMA Archive service.

Classes

AlmaClass()
Conf Configuration parameters for astroquery.alma.