Example of querying Gaia DR2 from Python

Query_Gaia_DR2.ipynb

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   "source": [
    "Example of querying Gaia DR2 from Python. "
   ]
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   "execution_count": 11,
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   "source": [
    "# Silence warnings from deprecated VO fields in the Gaia astroquery output: \n",
    "import warnings\n",
    "warnings.filterwarnings(\"ignore\", module='astropy.io.votable.tree')\n",
    "warnings.filterwarnings(\"ignore\", message='.*unclosed..socket')\n",
    "\n",
    "from __future__ import print_function, division\n",
    "import astropy.units as u \n",
    "from astropy.coordinates import SkyCoord, ICRS\n",
    "from astroquery.gaia import Gaia\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {
    "collapsed": true
   },
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   "source": [
    "def gaia_query(ra, dec, radius=5 * u.arcsec):\n",
    "    '''Return an ADQL query string for Gaia DR2 + geometric distances \n",
    "        from Bailer-Jones et al. 2018 '''\n",
    "    query_string = '''SELECT *, DISTANCE(POINT('ICRS',g.ra, g.dec), \n",
    "                    POINT('ICRS', %s, %s)) as r\n",
    "                    FROM gaiadr2.gaia_source AS g, external.gaiadr2_geometric_distance AS d\n",
    "                    WHERE g.source_id = d.source_id AND CONTAINS(POINT('ICRS',g.ra, g.dec), \n",
    "                    CIRCLE('ICRS',%15.10f, %15.10f,%15.10f))=1 ORDER BY r ASC''' % \\\n",
    "        (ra, dec, ra, dec, radius.to(u.degree).value) \n",
    "    return(query_string)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4h21m59.4321s 19d32m06.42s\n"
     ]
    }
   ],
   "source": [
    "# Get coordinates by resolving the object name: \n",
    "object_name = 'T Tauri'\n",
    "coords = SkyCoord.from_name(object_name)\n",
    "print(coords.ra.to_string(u.hour), coords.dec.to_string(u.deg))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Launched query: 'SELECT  TOP 2000 *, DISTANCE(POINT('ICRS',g.ra, g.dec), \n",
      "                    POINT('ICRS', 65.49763375, 19.53511667)) as r\n",
      "                    FROM gaiadr2.gaia_source AS g, external.gaiadr2_geometric_distance AS d\n",
      "                    WHERE g.source_id = d.source_id AND CONTAINS(POINT('ICRS',g.ra, g.dec), \n",
      "                    CIRCLE('ICRS',  65.4976337500,   19.5351166700,   0.0013888889))=1 ORDER BY r ASC'\n",
      "Retrieving sync. results...\n",
      "Query finished.\n",
      "\n",
      "The distance to T Tauri is 144.32 pc, proper motion is 11.4, -14.8 mas/yr.\n"
     ]
    }
   ],
   "source": [
    "query_string = gaia_query(coords.ra.to_value(), coords.dec.to_value())\n",
    "job = Gaia.launch_job(query_string, verbose=False)\n",
    "a = job.get_results()\n",
    "if len(a)==0:\n",
    "    print(\"No results for star %s.\" % object_name)\n",
    "else:\n",
    "    print(\"\\nThe distance to %s is %0.2f pc, proper motion is %0.1f, %0.1f mas/yr.\" \\\n",
    "          % (object_name, 1000/a['parallax'][0], a['pmra'], a['pmdec']))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['solution_id',\n",
       " 'designation',\n",
       " 'source_id',\n",
       " 'random_index',\n",
       " 'ref_epoch',\n",
       " 'ra',\n",
       " 'ra_error',\n",
       " 'dec',\n",
       " 'dec_error',\n",
       " 'parallax',\n",
       " 'parallax_error',\n",
       " 'parallax_over_error',\n",
       " 'pmra',\n",
       " 'pmra_error',\n",
       " 'pmdec',\n",
       " 'pmdec_error',\n",
       " 'ra_dec_corr',\n",
       " 'ra_parallax_corr',\n",
       " 'ra_pmra_corr',\n",
       " 'ra_pmdec_corr',\n",
       " 'dec_parallax_corr',\n",
       " 'dec_pmra_corr',\n",
       " 'dec_pmdec_corr',\n",
       " 'parallax_pmra_corr',\n",
       " 'parallax_pmdec_corr',\n",
       " 'pmra_pmdec_corr',\n",
       " 'astrometric_n_obs_al',\n",
       " 'astrometric_n_obs_ac',\n",
       " 'astrometric_n_good_obs_al',\n",
       " 'astrometric_n_bad_obs_al',\n",
       " 'astrometric_gof_al',\n",
       " 'astrometric_chi2_al',\n",
       " 'astrometric_excess_noise',\n",
       " 'astrometric_excess_noise_sig',\n",
       " 'astrometric_params_solved',\n",
       " 'astrometric_primary_flag',\n",
       " 'astrometric_weight_al',\n",
       " 'astrometric_pseudo_colour',\n",
       " 'astrometric_pseudo_colour_error',\n",
       " 'mean_varpi_factor_al',\n",
       " 'astrometric_matched_observations',\n",
       " 'visibility_periods_used',\n",
       " 'astrometric_sigma5d_max',\n",
       " 'frame_rotator_object_type',\n",
       " 'matched_observations',\n",
       " 'duplicated_source',\n",
       " 'phot_g_n_obs',\n",
       " 'phot_g_mean_flux',\n",
       " 'phot_g_mean_flux_error',\n",
       " 'phot_g_mean_flux_over_error',\n",
       " 'phot_g_mean_mag',\n",
       " 'phot_bp_n_obs',\n",
       " 'phot_bp_mean_flux',\n",
       " 'phot_bp_mean_flux_error',\n",
       " 'phot_bp_mean_flux_over_error',\n",
       " 'phot_bp_mean_mag',\n",
       " 'phot_rp_n_obs',\n",
       " 'phot_rp_mean_flux',\n",
       " 'phot_rp_mean_flux_error',\n",
       " 'phot_rp_mean_flux_over_error',\n",
       " 'phot_rp_mean_mag',\n",
       " 'phot_bp_rp_excess_factor',\n",
       " 'phot_proc_mode',\n",
       " 'bp_rp',\n",
       " 'bp_g',\n",
       " 'g_rp',\n",
       " 'radial_velocity',\n",
       " 'radial_velocity_error',\n",
       " 'rv_nb_transits',\n",
       " 'rv_template_teff',\n",
       " 'rv_template_logg',\n",
       " 'rv_template_fe_h',\n",
       " 'phot_variable_flag',\n",
       " 'l',\n",
       " 'b',\n",
       " 'ecl_lon',\n",
       " 'ecl_lat',\n",
       " 'priam_flags',\n",
       " 'teff_val',\n",
       " 'teff_percentile_lower',\n",
       " 'teff_percentile_upper',\n",
       " 'a_g_val',\n",
       " 'a_g_percentile_lower',\n",
       " 'a_g_percentile_upper',\n",
       " 'e_bp_min_rp_val',\n",
       " 'e_bp_min_rp_percentile_lower',\n",
       " 'e_bp_min_rp_percentile_upper',\n",
       " 'flame_flags',\n",
       " 'radius_val',\n",
       " 'radius_percentile_lower',\n",
       " 'radius_percentile_upper',\n",
       " 'lum_val',\n",
       " 'lum_percentile_lower',\n",
       " 'lum_percentile_upper',\n",
       " 'datalink_url',\n",
       " 'epoch_photometry_url',\n",
       " 'source_id_2',\n",
       " 'r_est',\n",
       " 'r_lo',\n",
       " 'r_hi',\n",
       " 'r_len',\n",
       " 'result_flag',\n",
       " 'modality_flag',\n",
       " 'r']"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# The output array a has all the fields from Gaia DR2, plus those\n",
    "# from Bailer-Jones et al. and the distance from center r that\n",
    "# specified it should calculate: \n",
    "a.colnames"
   ]
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   "cell_type": "code",
   "execution_count": null,
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   "source": []
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