ELAIS-N1 master catalogue¶
Preparation of UKIRT Infrared Deep Sky Survey / Deep Extragalactic Survey (UKIDSS/DXS)¶
The catalogue comes from dmu0_UKIDSS-DXS_DR10plus.
In the catalogue, we keep:
- The identifier (it's unique in the catalogue);
- The position;
- The stellarity;
- The magnitude for each band in apertude 3 (2 arcsec).
- The kron magnitude to be used as total magnitude (no “auto” magnitude is provided).
The magnitudes are “Vega like”. The AB offsets are given by Hewett et al. (2016):
| Band | AB offset |
|---|---|
| J | 0.938 |
| H | 1.379 |
| K | 1.900 |
A query to the UKIDSS database with 242.9+55.071 position returns a list of images taken between 2007 and 2009. Let's take 2008 for the epoch.
In [1]:
from herschelhelp_internal import git_version
print("This notebook was run with herschelhelp_internal version: \n{}".format(git_version()))
In [2]:
%matplotlib inline
#%config InlineBackend.figure_format = 'svg'
import matplotlib.pyplot as plt
plt.rc('figure', figsize=(10, 6))
from collections import OrderedDict
import os
from astropy import units as u
from astropy.coordinates import SkyCoord
from astropy.table import Column, Table
import numpy as np
from herschelhelp_internal.flagging import gaia_flag_column
from herschelhelp_internal.masterlist import nb_astcor_diag_plot, remove_duplicates
from herschelhelp_internal.utils import astrometric_correction, mag_to_flux
In [3]:
OUT_DIR = os.environ.get('TMP_DIR', "./data_tmp")
try:
os.makedirs(OUT_DIR)
except FileExistsError:
pass
RA_COL = "dxs_ra"
DEC_COL = "dxs_dec"
I - Column selection¶
In [4]:
imported_columns = OrderedDict({
'sourceid': 'dxs_id',
'RA': 'dxs_ra',
'Dec': 'dxs_dec',
'JAPERMAG3': 'm_ap_ukidss_j',
'JAPERMAG3ERR': 'merr_ap_ukidss_j',
'JKRONMAG': 'm_ukidss_j',
'JKRONMAGERR': 'merr_ukidss_j',
'KAPERMAG3': 'm_ap_ukidss_k',
'KAPERMAG3ERR': 'merr_ap_ukidss_k',
'KKRONMAG': 'm_ukidss_k',
'KKRONMAGERR': 'merr_ukidss_k',
'PSTAR': 'dxs_stellarity'
})
catalogue = Table.read(
"../../dmu0/dmu0_UKIDSS-DXS_DR10plus/data/UKIDSS-DR10plus_ELAIS-N1.fits")[list(imported_columns)]
for column in imported_columns:
catalogue[column].name = imported_columns[column]
epoch = 2008
# Clean table metadata
catalogue.meta = None
In [5]:
# Adding flux and band-flag columns
for col in catalogue.colnames:
if col.startswith('m_'):
errcol = "merr{}".format(col[1:])
# DXS uses a huge negative number for missing values
catalogue[col][catalogue[col] < -100] = np.nan
catalogue[errcol][catalogue[errcol] < -100] = np.nan
# Vega to AB correction
if col.endswith('j'):
catalogue[col] += 0.938
elif col.endswith('k'):
catalogue[col] += 1.900
else:
print("{} column has wrong band...".format(col))
flux, error = mag_to_flux(np.array(catalogue[col]), np.array(catalogue[errcol]))
# Fluxes are added in µJy
catalogue.add_column(Column(flux * 1.e6, name="f{}".format(col[1:])))
catalogue.add_column(Column(error * 1.e6, name="f{}".format(errcol[1:])))
# Band-flag column
if "ap" not in col:
catalogue.add_column(Column(np.zeros(len(catalogue), dtype=bool), name="flag{}".format(col[1:])))
# TODO: Set to True the flag columns for fluxes that should not be used for SED fitting.
In [6]:
catalogue[:10].show_in_notebook()
Out[6]:
II - Removal of duplicated sources¶
We remove duplicated objects from the input catalogues.
In [7]:
SORT_COLS = ['merr_ap_ukidss_j', 'merr_ap_ukidss_k']
FLAG_NAME = 'dxs_flag_cleaned'
nb_orig_sources = len(catalogue)
catalogue = remove_duplicates(catalogue, RA_COL, DEC_COL, sort_col=SORT_COLS, flag_name=FLAG_NAME)
nb_sources = len(catalogue)
print("The initial catalogue had {} sources.".format(nb_orig_sources))
print("The cleaned catalogue has {} sources ({} removed).".format(nb_sources, nb_orig_sources - nb_sources))
print("The cleaned catalogue has {} sources flagged as having been cleaned".format(np.sum(catalogue[FLAG_NAME])))
III - Astrometry correction¶
We match the astrometry to the Gaia one. We limit the Gaia catalogue to sources with a g band flux between the 30th and the 70th percentile. Some quick tests show that this give the lower dispersion in the results.
In [8]:
gaia = Table.read("../../dmu0/dmu0_GAIA/data/GAIA_ELAIS-N1.fits")
gaia_coords = SkyCoord(gaia['ra'], gaia['dec'])
In [9]:
nb_astcor_diag_plot(catalogue[RA_COL], catalogue[DEC_COL],
gaia_coords.ra, gaia_coords.dec)
In [10]:
delta_ra, delta_dec = astrometric_correction(
SkyCoord(catalogue[RA_COL], catalogue[DEC_COL]),
gaia_coords
)
print("RA correction: {}".format(delta_ra))
print("Dec correction: {}".format(delta_dec))
In [11]:
catalogue[RA_COL] += delta_ra.to(u.deg)
catalogue[DEC_COL] += delta_dec.to(u.deg)
In [12]:
nb_astcor_diag_plot(catalogue[RA_COL], catalogue[DEC_COL],
gaia_coords.ra, gaia_coords.dec)
IV - Flagging Gaia objects¶
In [13]:
catalogue.add_column(
gaia_flag_column(SkyCoord(catalogue[RA_COL], catalogue[DEC_COL]), epoch, gaia)
)
In [14]:
GAIA_FLAG_NAME = "dxs_flag_gaia"
catalogue['flag_gaia'].name = GAIA_FLAG_NAME
print("{} sources flagged.".format(np.sum(catalogue[GAIA_FLAG_NAME] > 0)))
V - Saving to disk¶
In [15]:
catalogue.write("{}/UKIDSS-DXS.fits".format(OUT_DIR), overwrite=True)