IV/35 Gaia DR2-WISE Galactic Plane Matches (Wilson+, 2018)
A contaminant-free catalogue of Gaia DR2-WISE Galactic plane matches:
Including the effects of crowding in the cross-matching of photometric
catalogues.
Wilson T.J., Naylor T.
<Mon. Not. R. Astron. Soc. 481, 2148-2167 (2018)>
=2018MNRAS.481.2148W 2018MNRAS.481.2148W
=2018yCat.4035....0W 2018yCat.4035....0W
ADC_Keywords: Positional data; Cross identifications; Galactic plane; Photometry
Keywords: methods: statistical - techniques: photometric - catalogues -
surveys - astrometry - stars: statistics
Abstract:
Faint, hidden contaminants in the point-spread functions (PSFs) of
stars cause shifts to their measured positions. Wilson & Naylor
(2017MNRAS.468.2517W 2017MNRAS.468.2517W) showed failing to account for these shifts can
lead to a drastic decrease in the number of returned catalogue matches
in crowded fields. Here we highlight the effect these perturbations
have on cross-matching, for matches between Gaia DR2 and WISE stars in
a crowded Galactic plane region. Applying the uncertainties as quoted
to Gaussian-based astrometric uncertainty functions (AUFs) can lead,
in dense Galactic fields, to only matching 55% of the counterparts. We
describe the construction of empirical descriptions for AUFs, building
on the cross-matching method of Wilson & Naylor (2018MNRAS.473.5570W 2018MNRAS.473.5570W),
utilising the magnitudes of both catalogues to discriminate between
true and false counterparts. We apply the improved cross-matching
method to the Galactic plane |b|<10. We provide the most likely
counterpart matches and their respective probabilities. We also
analyse several cases to verify the robustness of the results,
highlighting some important caveats and considerations. Finally, we
discuss the effect PSF resolution has by comparing the intra-
catalogue nearest neighbour separation distributions of a sample of
likely contaminated WISE objects and their corresponding Spitzer
counterpart. We show that some WISE contaminants are resolved in
Spitzer, with smaller intra-catalogue separations. We have highlighted
the effect contaminant stars have on WISE, but it is important for all
photometric catalogues, playing an important role in the next
generation of surveys, such as LSST.
Description:
Source IDs, positions, magnitudes, cross-identification probabilities,
and WISE contamination probabilities and levels for sources
cross-matched between the AllWISE and Gaia DR2 catalogues with Gaia
DR2 Galactic coordinates |b|<10.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
wn18_b10.dat 283 118964029 IDs, positions, magnitudes and probabilities
wn18_b10.fit 2880 7435257 Fits version of the catalog
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/328 : AllWISE Data Release (Cutri+ 2013)
Byte-by-byte Description of file: wn18_b10.*
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Bytes Format Units Label Explanations
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1- 19 I19 --- GAIA ID of Gaia source, as given by the Gaia DR2
catalogue (GAIA_ID)
21- 39 A19 --- WISE ID of WISE object, as given by the AllWISE
catalogue (WISE_ID)
41- 55 F15.11 deg RAdeg Right Ascension of Gaia source (ICRS at epoch
2015.5), as given by the Gaia DR2 catalogue
(GAIA_RA)
57- 71 F15.11 deg DEdeg Declination of Gaia source (ICRS at epoch
2015.5), as given by the Gaia DR2 catalogue
(GAIA_DEC)
73- 87 F15.11 deg RAWdeg Right Ascension of WISE source (J2000), as
given by the AllWISE catalogue (WISE_RA)
89-103 F15.11 deg DEWdeg Declination of WISE source (J2000), as given
by the AllWISE catalogue (WISE_DEC)
105-113 F9.6 mag gmag Gaia G magnitude, as given by the Gaia
DR2 catalogue (G_MAG)
115-121 F7.3 mag W1mag WISE w1mpro magnitude, as given by the
AllWISE catalogue (W1_MAG)
123-129 F7.3 mag W2mag ?=- WISE w2mpro magnitude, as given by the
AllWISE catalogue (W2_MAG)
131-137 F7.3 mag W3mag ?=- WISE w3mpro magnitude, as given by the
AllWISE catalogue (W3_MAG)
139-145 F7.3 mag W4mag ?=- WISE w4mpro magnitude, as given by the
AllWISE catalogue (W4_MAG)
147-168 E22.17 --- MatchP Overall probability that the Gaia and
WISE sources are detections of the same
object, as given by equation 26
of Wilson & Naylor (2018MNRAS.473.5570W 2018MNRAS.473.5570W)
(MATCH_P)
170-191 E22.17 --- eta Photometric logarithmic likelihood ratio of
Gaia-WISE match, as described by equation 37
of Wilson & Naylor (2018MNRAS.473.5570W 2018MNRAS.473.5570W)
(ETA)
193-214 E22.17 --- xi Astrometric logarithmic likelihood ratio of
Gaia-WISE match, as described by equation 38
of Wilson & Naylor (2018MNRAS.473.5570W 2018MNRAS.473.5570W) (XI)
216-237 E22.17 --- ContP1 Probability of WISE source having contaminant
of at least 1% relative flux given its
separation from its corresponding Gaia
detection, as given by equation 12 of Wilson
& Naylor (2018b, this paper) (CONT_P1)
239-260 E22.17 --- ContP10 Probability of WISE source having contaminant
of at least 10% relative flux given its
separation from its corresponding Gaia
detection (CONT_P10)
262-283 E22.17 --- avgCont Mean contaminating relative flux within PSFs
when constructing h_offsets for WISE sources
at the local density, magnitude and intrinsic
positional uncertainty of the primary source
(AVG_CONT)
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Acknowledgements:
Tom J. Wilson, twilson(at)astro.ex.ac.uk
(End) Patricia Vannier [CDS] 22-Aug-2018