J/A+A/678/A151 LoTSS DR2 optical IDs (Hardcastle+, 2023)
The LOFAR Two-Metre Sky Survey.
VI. Optical identifications for the second data release.
Hardcastle M.J., Horton M.A., Williams W.L., Duncan K.J., Alegre L.,
Barkus B., Croston J.H., Dickinson H., Osinga E., Roettgering H.J.A.,
Sabater J., Shimwell T.W., Smith D.J.B., Best P.N., Botteon A., Brueggen M.,
Drabent A., de Gasperin F., Guerkan G., Hajduk M., Hale C.L., Hoeft M.,
Jamrozy M., Kunert-Bajraszewska M., Kondapally R., Magliocchetti M.,
Mahatma V.H., Mostert R.I.J., O'Sullivan S.P., Pajdosz-Smierciak U.,
Petley J., Pierce J.C.S., Prandoni I., Schwarz D.J., Shulewski A.,
Siewert T.M., Stott J.P., Tang H., Vaccari M., Zheng X., Bailey T.,
Desbled S., Goyal A., Gonano V., Hanset M., Kurtz W., Lim S.M., Mielle L.,
Molloy C.S., Roth R., Terentev I.A., Torres M.
<Astron. Astrophys. 678, A151 (2023)>
=2023A&A...678A.151H 2023A&A...678A.151H (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs; Radio continuum ; Radio sources ; Redshifts ;
Optical
Keywords: catalogs - radio continuum: galaxies
Abstract:
The second data release of the LOFAR Two-Metre Sky Survey (LoTSS)
covers 27% of the northern sky, with a total area of ∼5700deg2. The
high angular resolution of LOFAR with Dutch baselines (6 arcsec)
allows us to carry out optical identifications of a large fraction of
the detected radio sources without further radio followup; however,
the process is made more challenging by the many extended radio
sources found in LOFAR images as a result of its excellent sensitivity
to extended structure. In this paper we present source associations
and identifications for sources in the second data release based on
optical and near-infrared data, using a combination of a
likelihood-ratio cross-match method developed for our first data
release, our citizen science project Radio Galaxy Zoo: LOFAR, and new
approaches to algorithmic optical identification, together with
extensive visual inspection by astronomers. We also present
spectroscopic or photometric redshifts for a large fraction of the
optical identifications. In total 4116934 radio sources lie in the
area with good optical data, of which 85% have an optical or infrared
identification and 58% have a good redshift estimate. We demonstrate
the quality of the dataset by comparing it with earlier optically
identified radio surveys. This is by far the largest ever optically
identified radio catalogue, and will permit robust statistical studies
of star-forming and radio-loud active galaxies.
Description:
Combines data from LOFAR, WISE, Legacy Survey, and assorted
spectroscopic surveys. This is version 1.1 of the catalogue, released
with the description paper. For updates to IDs and redshifts see the
LoTSS DR2 release site https://lofar-surveys.org/dr2_release.html .
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 2037 4167359 Value-added optical identification catalogue
for LoTSS DR2
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See also:
J/A+A/659/A1 : LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)
http://lofar-surveys.org/dr2_release.html : LOFAR surveys website
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Source Object identifier (ILT name)
(Source_Name)
25- 48 F24.20 deg RAdeg Radio right ascension (mean position)
(J2000) (RA)
50- 67 F18.15 deg DEdeg Radio declination (mean position)
(J2000) (DEC)
69- 91 F23.20 arcsec e_RAdeg Error on radio right ascension (E_RA)
93- 115 F23.20 arcsec e_DEdeg Error on radio declination (E_DEC)
117- 141 F25.19 mJy Ftot 144-MHz total flux density (Total_flux)
143- 163 E21.16 mJy e_Ftot Error on total flux density
(ETotalflux)
165- 188 F24.18 mJy/beam Fpeak 144-MHz peak flux density (Peak_flux)
190- 211 F22.19 mJy/beam e_Fpeak Error on peak flux density
(EPeakflux)
213 A1 --- SCode [SCMZ] PyBDSF source code or Z for
composite source (S_Code) (1)
215- 225 A11 --- MosaicID LoTSS mosaic of source image
(Mosaic_ID)
227- 248 F22.17 arcsec Maj ? Major axis of fitted Gaussian (Maj)
250- 270 F21.16 arcsec Min ? Minor axis of fitted Gaussian (Min)
272- 294 E23.17 deg PA ? Position angle of fitted Gaussian
(PA)
296- 320 F25.20 arcsec e_Maj ? Error on major axis (E_Maj)
322- 345 F24.20 arcsec e_Min ? Error on minor axis (E_Min)
347- 369 E23.17 deg e_PA ? Error on position angle (E_PA)
371- 392 F22.17 arcsec DCMaj ? Deconvolved major axis of fitted
Gaussian (DC_Maj)
394- 417 F24.19 arcsec DCMin ? Deconvolved minor axis of fitted
Gaussian (DC_Min)
419- 440 E22.16 deg DCPA ? Deconvolved position angle of fitted
Gaussian (DC_PA)
442- 462 F21.18 mJy/beam Islrms rms noise in island (Isl_rms)
464- 465 I2 --- FlagW [-1/23] Flag for workflow status
(internal) (FLAG_WORKFLOW)
467- 469 I3 --- IDFlag [-99/14]?=-1 Flag for workflow status
(internal) (ID_flag) (2)
471- 473 I3 --- PreFilt [-99/14] Prefilter status (internal)
(Prefilter) (2)
475 I1 --- PostFilt [0/6] Postfilter status (internal)
(Postfilter)
477- 499 E23.17 --- likefin ? Final likelihood ratio value
(internal) (lr_fin)
501- 525 F25.20 deg RAOdeg ? Optical right ascension (J2000)
(see r_RAOdeg) (optRA)
527- 545 F19.15 deg DEOdeg ? Optical declination (J2000)
(see r_RAOdeg) (optDec)
547- 569 F23.17 arcsec CompSize ? Max size of convex hull surrounding
components for composite sources
(Composite_Size)
571- 595 F25.19 arcsec CompWidth ? Transverse size of convex hull
surrounding components for composite
sources (Composite_Width)
597- 619 F23.18 deg CompPA ? Position angle on the sky of longest
axis of convex hull (Composite_PA)
621- 623 I3 --- Assoc Number of components used to form
composite source (Assoc)
625- 643 F19.16 --- IDQual ? Quality of association from RGZ(L)
(ID_Qual)
645- 663 F19.16 --- AssocQual ? Quality of association from RGZ(L)
(Assoc_Qual)
665- 685 F21.18 --- BlendProb ? Blend probability from RGZ(L) or
manual flagging) (Blend_prob)
687- 707 F21.18 --- OtherProb ? Other problem probability from RGZ(L)
(Other_prob)
709- 732 A24 --- Created Origin of radio component assignment
(Created)
734- 750 A17 --- r_RAOdeg Origin of optRA, optDec (Position_from)
752- 774 A23 --- Renamed Original name e.g. in RGZ if a
composite source (Renamed_from)
776- 800 F25.20 deg RAIdeg ? Right ascension (J2000) of positional
match in Legacy/WISE crossmatch
catalogue (ID_RA)
802- 820 F19.15 deg DEIdeg ? Declination (J2000) of positional
match in Legacy/WISE crossmatch
catalogue (ID_DEC)
822- 837 A16 --- UIDL ?=-1 Legacy ID if any (UID_L)
839- 854 A16 --- UNWISE UNWISE ID if any (UNWISE_OBJID)
856- 871 A16 --- IDName Legacy ID if present else WISE ID else
blank if no ID exists (ID_NAME)
873- 895 E23.17 --- Sep ? Offset between optRA, optDec and
ID_RA, ID_DEC (non-zero only for
visual inspection) (Separation)
897- 912 I16 --- LegacyID ?=-1 Unique source ID combining
release, brick ID and objid
(Legacy_ID)
914- 916 I3 --- HPX [16/303] Healpix of Legacy brick
(internal) (HPX)
918- 921 I4 --- Release [8000/8001]? Legacy release number
(release)
923- 928 I6 --- BrickId [422713/641534]? Legacy brick ID
(brickid)
930- 934 I5 --- ObjId ? Legacy object ID (objid)
936- 940 I5 --- Maskbits ? Bitwise mask indicating that an
object touches a pixel in the
`coadd/*/*/*maskbits*` maps, as
catalogued on the DR8 bitmasks page
(maskbits)
942- 965 E24.17 --- fracFg ? Profile-weighted fraction of the
flux from other sources divided by the
total flux in g (fracflux_g)
967- 990 E24.17 --- fracFr ? Profile-weighted fraction of the
flux from other sources divided by the
total flux in r (fracflux_r)
992-1015 E24.17 --- fracFz ? Profile-weighted fraction of the
flux from other sources divided by the
total flux in z (fracflux_z)
1017-1020 A4 --- Type Morphological model (type) (3)
1022-1046 F25.20 deg RALdeg ? Right ascension (J2000) of match in
Legacy catalogue (ra)
1048-1066 F19.15 deg DELdeg ? Declination (J2000) of match in
Legacy catalogue (dec)
1068-1090 E23.17 --- pstar [0/1]? Star likelihood based on GMM
modelling (type='PSF' sources only)
(pstar)
1092-1096 A5 --- Star [True-False ] Likely star based on
pstar or proper motion (deprecated),
blank if no match (star)
1098-1102 A5 --- MaskOpt [True-False ] Bitwise mask set if the
central pixel from any image satisfies
each condition in any of g, r or z as
catalogued on the DR8 bitmasks page
(ANYMASK_OPT)
1104-1105 A2 --- GMMcomp Gaussian Mixture Model component to
which source belongs (and hence the
gpz++ class used for prediction)
(gmmcomp)
1107-1120 E14.7 --- zphot [-3.73/8.28]? Photo-z estimate (zphot)
1122-1143 F22.19 --- e_zphot [-0.01/7.6]? Predicted 1-sigma
uncertainty on photometric redshift
(after magnitude calibration)
(zphot_err)
1145-1157 E13.7 --- varDensity [0.0/1.22]? gpz++ predicted variance
from density of training set
(var.density)
1159-1171 E13.7 --- varTrNoise [0.0/66.83]? gpz++ predicted variance
from noise in training set
(var.tr.noise)
1173-1185 E13.7 --- varInNoise [0.0/3.89]? gpz++ predicted variance
from noise in fluxes used in
prediction (var.in.noise)
1187 I1 --- FlagQual [0/1]? Predicted photo-z quality flag,
0 if bad, 1 if good (flag_qual) (4)
1189-1204 E16.9 --- zspecSDSS [-0.01/5]? SDSS spectroscopic redshift
if available (zspec_sdss)
1206-1208 I3 --- zwarnSDSS ? 0 if SDSS redshift is good,
1 if bad (zwarning_sdss)
1210-1214 I5 --- PlateSDSS ? SDSS plate number (plate_sdss)
1216-1220 I5 --- MJDSDSS ? SDSS MJD (mjd_sdss)
1222-1225 I4 --- FiberSDSS ? SDSS fibre ID (fiberid_sdss)
1227-1238 F12.9 --- zHETDEX [0.01/4.15]? HETDEX spectroscopic
redshift if available (z_hetdex)
1240-1252 E13.7 --- zHETDEXConf ? HETDEX spectroscopic redshift
confidence (zhetdexconf)
1254-1266 I13 --- HETDEX ? HETDEX source ID (hetdex_sourceid)
1268-1291 E24.17 --- zDESI [-0.01/4.84]? DESI spectroscopic
redshift if available (z_desi)
1293-1315 E23.17 --- e_zDESI [0.0/0.01]? DESI spectroscopic
redshift error (zdesierr)
1317-1335 I19 --- DESI ? DESI source ID (desi_sourceid)
1337-1357 A21 --- 2RXS ID in 2RXS (2RXS_ID)
1359-1381 A23 --- XMMSL2 ID in XMM source catalogue (XMMSL2_ID)
1383 I1 --- Resolved [0/1] Boolean flag to indicate whether
source is resolved (Resolved)
1385-1406 F22.17 arcsec LAS Estimate of angular size, only valid
for sources with Resolved≡True (LAS)
1408-1430 E23.17 --- zbest [0/6.6]? Spec-z if available and good,
else photo-z if available and good,
else blank (z_best) (5)
1432-1437 A6 --- r_zbest String describing origin of z_best
(z_source)
1439-1460 E22.16 kpc Size ? LAS times angular size distance
(Size)
1462-1484 E23.17 W/Hz L144 ? Radio luminosity at 144MHz for
alpha=0.7 (L_144) (6)
1486-1491 A6 --- Field Which of the two fields the data come
from (Field)
1493 I1 --- LegacyCov Flag to say whether source is in the
DESI Legacy sky area (Legacy_Coverage)
1495-1518 F24.18 mJy LMFlux Flux density from LoMorph code
(LM_flux)
1520-1541 F22.16 arcsec LMSize ? Size from LoMorph code (LM_size)
1543 I1 --- fLMflux [0/1] Flag to say that LoMorph flux
is bad (BadLMflux)
1545 I1 --- fLMimage [0/1] Flag to say that LoMorph mask
is bad (BadLMimage)
1547-1556 A10 --- r_LAS Source for the LAS column (LAS_from)
1558-1568 F11.7 mag gmag ? Magnitude in g-band (mag_g)
1570-1583 E14.8 mag e_gmag ? Magnitude error in g-band,
or blank for upper limit (magerr_g)
1585-1595 F11.7 mag rmag ? Magnitude in r-band (mag_r)
1597-1610 E14.8 mag e_rmag ? Magnitude error in r-band,
or blank for upper limit (magerr_r)
1612-1622 F11.7 mag zmag ? Magnitude in z-band (mag_z)
1624-1637 E14.8 mag e_zmag ? Magnitude error in z-band,
or blank for upper limit (magerr_z)
1639-1649 F11.7 mag W1mag ? Magnitude in WISE band 1 (mag_w1)
1651-1665 E15.9 mag e_W1mag ? Magnitude error in WISE band 1,
or blank for upper limit (magerr_w1)
1667-1677 F11.7 mag W2mag ? Magnitude in WISE band 2 (mag_w2)
1679-1692 E14.8 mag e_W2mag ? Magnitude error in WISE band 2,
or blank for upper limit (magerr_w2)
1694-1704 F11.7 mag W3mag ? Magnitude in WISE band 3 (mag_w3)
1706-1719 E14.8 mag e_W3mag ? Magnitude error in WISE band 3,
or blank for upper limit (magerr_w3)
1721-1731 F11.7 mag W4mag ? Magnitude in WISE band 4 (mag_w4)
1733-1746 F14.11 mag e_W4mag ? Magnitude error in WISE band 4,
or blank for upper limit (magerr_w4)
1748-1757 A10 --- r_WISE Origin of the WISE measurements
(WISE_Src) (3)
1759-1778 F20.16 [Msun] logMass ? Source host galaxy stellar mass
estimate estimate (Mass_median)
1780-1799 F20.16 [Msun] b_logMass ? 68% lower confidence bound on mass
(Mass_l68)
1801-1820 F20.16 [Msun] B_logMass ? 68% upper confidence bound on mass
(Mass_u68)
1822-1841 F20.16 mag gmagrest ? Rest-frame g-band magnitude from
SED fit (g_rest)
1843-1862 F20.16 mag rmagrest ? Rest-frame r-band magnitude from
SED fit (r_rest)
1864-1882 F19.15 mag zmagrest ? Rest-frame z-band magnitude from
SED fit (z_rest)
1884-1903 F20.16 mag Umagrest ? Rest-frame U-band magnitude from
SED fit (U_rest)
1905-1923 F19.15 mag Vmagrest ? Rest-frame V-band magnitude from
SED fit (V_rest)
1925-1943 F19.15 mag Jmagrest ? Rest-frame J-band magnitude from
SED fit (J_rest)
1945-1964 F20.16 mag Kmagrest ? Rest-frame K-band magnitude from
SED fit (K_rest)
1966-1984 F19.15 mag W1magrest ? Rest-frame WISE band-1 magnitude from
SED fit (w1_rest)
1986-2005 F20.16 mag W2magrest ? Rest-frame WISE band-1 magnitude from
SED fit (w2_rest)
2007-2020 E14.8 arcsec r50 ? Half-light radius of Legacy optical
exponential/DeVaucouleurs/composite
model (r_50)
2022-2035 E14.8 arcsec e_r50 ? 1-sigma uncertainty on r_50
(r50err)
2037 I1 --- q_logMass [0/1] 1 if a mass is measured and
reliable (flag_mass)
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Note (1): Code as follows:
S = indicates an isolated source that is fit with a single Gaussian
C = represents sources that are fit by a single Gaussian but are within an
island of emission that also contains other sources
M = is used for sources with are extended and fit with multiple Gaussians
Z = composite source
Note (2): Flag as follows:
-99 = Outside Legacy optical coverage
1 = LR ID
2 = Match with large optical galaxy
3 = ID from RGZ(L)
5 = Faint source not visually inspected
6 = Sent for deblend
8 = Uncatalogued host after prefilter
9 = Automatic or visually selected deblend
10 = Blend workflow
11 = Second blend workflow
12 = Too zoomed in workflow
13 = Ridge line code
14 = Deduplicate workflow
Note (3): Type as follows:
PSF = stellar
REX = round exponential galaxy
DEV = de Vaucouleur
EXP = exponential
COMP = composite
Note (4): selects sources with reliable redshifts, with reasonable uncertainty,
minimal contamination from nearby sources, low star-likelihood and free from
imaging artefacts based on maskbits.
Note (5): Non-blank z_best combines SDSS spec-z with reliable photo-z.
Note (6): Cosmology is the standard cosmology for this paper.
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Acknowledgements:
Martin Hardcastle, m.j.hardcastle(at)herts.ac.uk
References:
Shimwell et al., Paper I 2017A&A...598A.104S 2017A&A...598A.104S, Cat. J/A+A/598/A104
Shimwell et al., Paper II 2019A&A...622A...1S 2019A&A...622A...1S, Cat. J/A+A/622/A1
Williams et al., Paper III 2019A&A...622A...2W 2019A&A...622A...2W
Duncan et al., Paper IV 2019A&A...622A...3D 2019A&A...622A...3D
Shimwell et al., Paper V 2022A&A...659A...1S 2022A&A...659A...1S, Cat. J/A+A/659/A1
(End) Patricia Vannier [CDS] 04-Sep-2023