J/A+A/712/A182 Euclid accretion properties of X-ray AGN (Euclid Coll.+, 2026)
Euclid Quick Data Release (Q1)
XL. The impact of AGN emission on SED-derived physical properties.
Euclid Coll., Laloux B., Bongiorno A., Salvato M., Allevato V., Mezcua M.,
Roster W., Matamoro Zatarain T., Paltani S., Shirley R., Tarsitano F.,
Saulder C., Fotopoulou S., Andonie C., Buchner J., La Franca F., Le Brun V.,
Ricci F., Scott D., Shankar F., Siudek M., Sorce J.G., Spinoglio L.,
Toba Y., Viitanen A., Wang L., Zamorani G., Andreon S., Auricchio N.,
Baccigalupi C., Baldi M., Balestra A., Bardelli S., Battaglia P.,
Biviano A., Branchini E., Brescia M., Camera S., Canas-Herrera G.,
Capobianco V., Carbone C., Carretero J., Casas S., Castellano M.,
Castignani G., Cavuoti S., Chambers K.C., Cimatti A., Colodro-Conde C.,
Congedo G., Conselice C.J., Conversi L., Copin Y., Costille A., Courbin F.,
Courtois H.M., Cropper M., Da Silva A., Degaudenzi H., De Lucia G., Dole H.,
Dubath F., Duncan C.A.J., Dupac X., Escoffier S., Fabricius M., Farina M.,
Farinelli R., Ferriol S., Finelli F., Fosalba P., Fourmanoit N., Frailis M.,
Franceschi E., Fumana M., Galeotta S., George K., Gillis B., Giocoli C.,
Gracia-Carpio J., Grazian A., Grupp F., Gwyn S., Haugan S.V.H., Hoekstra H.,
Holmes W., Hormuth F., Hornstrup A., Jahnke K., Jhabvala M., Joachimi B.,
Kermiche S., Kiessling A., Kubik B., Kuemmel M., Kunz M., Kurki-Suonio H.,
Le Brun A.M.C., Ligori S., Lilje P.B., Lindholm V., Lloro I., Mainetti G.,
Maino D., Maiorano E., Mansutti O., Marcin S., Marggraf O., Martinelli M.,
Martinet N., Marulli F., Massey R.J., Medinaceli E., Mei S., Mellier Y.,
Meneghetti M., Merlin E., Meylan G., Mora A., Moresco M., Moscardini L.,
Nakajima R., Neissner C., Nichol R.C., Niemi S.-M., Padilla C., Pasian F.,
Pedersen K., Percival W.J., Pettorino V., Pires S., Polenta G., Poncet M.,
Popa L.A., Pozzetti L., Racca G.D., Raison F., Renzi A., Rhodes J.,
Riccio G., Romelli E., Roncarelli M., Saglia R., Sakr Z., Sapone D.,
Sartoris B., Schneider P., Schrabback T., Scodeggio M., Secroun A.,
Seidel G., Serrano S., Sihvola E., Simon P., Sirignano C., Sirri G.,
Steinwagner J., Tallada-Crespi P., Taylor A.N., Tereno I., Tessore N.,
Toft S., Toledo-Moreo R., Torradeflot F., Tutusaus I., Valenziano L.,
Valiviita J., Vassallo T., Veropalumbo A., Wang Y., Weller J., Zacchei A.,
Zucca E., Ballardini M., Bolzonella M., Bozzo E., Burigana C., Cabanac R.,
Calabrese M., Cappi A., Castro T., Escartin Vigo J.A., Gabarra L.,
Garcia-Bellido J., Maoli R., Martin-Fleitas J., Maturi M., Mauri N.,
Metcalf R.B., Pezzotta A., Poentinen M., Porciani C., Risso I., Scottez V.,
Sereno M., Tenti M., Viel M., Wiesmann M., Akrami Y., Andika I.T.,
Angora G., Anselmi S., Archidiacono M., Atrio-Barandela F., Bazzanini L.,
Bertacca D., Bethermin M., Bisigello L., Blanchard A., Blot L., Bonici M.,
Brown M.L., Bruton S., Calabro A., Camacho Quevedo B., Caro F.,
Carvalho C.S., Cogato F., Conseil S., Cooray A.R., Davini S., De Paolis F.,
Desprez G., Diaz-Sanchez A., Di Domizio S., Diego J.M., Elkhashab M.Y.,
Enia A., Fang Y., Finoguenov A., Fontanot F., Franco A., Gasparetto T.,
Gaztanaga E., Giacomini F., Gianotti F., Gozaliasl G., Guidi M.,
Gutierrez C.M., Hall A., Hernandez-Monteagudo C., Hildebrandt H., Hjorth J.,
Hunt L.K., Kajava J.J.E., Kang Y., Kansal V., Karagiannis D., Kiiveri K.,
Kim J., Kirkpatrick C.C., Kruk S., Lattanzi M., Legrand L., Lepori F.,
Leroy G., Lesci G.F., Lesgourgues J., Leuzzi L., Liaudat T.I., Liu S.J.,
Lopez Lopez X., Macias-Perez J., Magliocchetti M., Magnier E.A., Mancini C.,
Manjon-Garcia A., Mannucci F., Martins C.J.A.P., Maurin L., Miluzio M.,
Monaco P., Montoro A., Moretti C., Morgante G., Murray C., Nadathur S.,
Naidoo K., Natoli P., Navarro-Alsina A., Nesseris S., Paoletti D.,
Passalacqua F., Paterson K., Pisani A., Potter D., Pratt G.W., Quai S.,
Radovich M., Rodighiero G., Rojas K., Sacquegna S., Sahlen M., Sanders D.B.,
Sarpa E., Schneider A., Sciotti D., Sellentin E., Smith L.C., Tanidis K.,
Tao C., Testera G., Teyssier R., Tosi S., Troja A., Tucci M., Venhola A.,
Vergani D., Verza G., Vielzeuf P., Vinciguerra S., Walton N.A.
<Astron. Astrophys. 712, A182 (2026)>
=2026A&A...712A.182E 2026A&A...712A.182E (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Active gal. nuclei ; Redshifts ; Optical ; Infrared
Keywords: techniques: photometric - catalogs - galaxies: active
Abstract:
The Euclid Quick Data Release (Q1) is a powerful dataset to study
active galactic nuclei (AGN) and their host galaxies. Deriving their
physical properties through multi-component spectral energy
distribution (SED) fitting is a challenging task for AGN, but it is
greatly aided by the Euclid near-infrared photometry. Here we present
a new method of quantifying the reliability of SED-derived parameters,
such as AGN bolometric and monochromatic luminosities, host's
stellar mass (M*), star-formation rate (SFR), and specific
star-formation rate (sSFR), by using mock SEDs of AGN built by
combining observed SEDs of QSOs and galaxies. We applied this
methodology to the ∼1 million Q1 AGN candidates, constructing a
catalogue of AGN and host galaxy properties, alongside their
respective reliability values. With a reliability threshold at 0.5, we
find 88% of sources to have robust stellar masses and 76% to have
reliable AGN luminosities. Moreover, through SED fitting we also
measured the AGN fraction (fAGN) of the total mid-infrared flux and we
used its lower-limit to select AGN. A fAGN,ow>0.075 threshold yields
85% completeness and purity. Comparable to colour-colour AGN
selections, this method has the advantage of being less affected by
redshift evolution and exploring fainter magnitudes. Additionally, by
comparing the AGN and host galaxy parameters across different
identification methods, we find that the probed range in stellar mass
and AGN luminosity can be quite different. This highlights the
importance of combining different approaches and accounting for their
selection biases when studying AGN and their role in galaxy evolution.
Finally, for the X-ray detected sample, we present the X-ray to mid-IR
luminosity relation, and the correlation between stellar mass and
bolometric luminosity as a function of redshift, in good agreement
with previous results.
Description:
The catalogue of the physical properties of the ∼1 million sources
analysed in this work and the catalogue of the full photometric z-PDF.
catalog.dat: the first columns contain information that were available
prior to the SED fit, mainly coordinates, redshift information and AGN
selection criteria. The last columns contain the data products from
the SED fitting, mainly the parameter estimates and uncertainties
along the reliability informations. For sources with spectroscopic
redshift, the parameter estimates and uncertainties are directly set
to the values returned by CIGALE. For sources with photometric
redshift, the parameter estimates correspond to the median value of
the Gaussian mixture as explained in Sec. 3.3. The 1-sigma lower and
upper uncertainties correspond to the difference between 16th and 84th
percentile to the median value, respectively.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 1487 1112013 Accretion properties of X-ray AGN
zphpdf.dat 131 1033837 zphot PDF
zphot_PDF.fits 2880 2034653 fits version of zphot PDF with
the 701 zPDF values
--------------------------------------------------------------------------------
See also:
J/ApJS/234/23 : The WISE AGN candidates catalogs (Assef+, 2018)
J/ApJ/796/60 : ECDFS galaxies photometric redshifts + counterparts (Hsu+,2014)
J/A+A/711/A16 : X-ray point-like sources of Euclid (Q1) (Euclid Coll.+, 2026)
Byte-by-byte Description of file: catalog.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- ID Euclid ID (id)
21- 39 F19.15 deg RAdeg Right ascension (J2000) of the
Euclid source
(rightascensioneuclid)
41- 59 F19.15 deg DEdeg Declination (J2000) of the Euclid
source (declination_euclid)
61- 64 A4 --- Field The source is within Euclid Deep
Field North (EDFN), South (EDFS),
or Fornax (EDFF) (field)
66- 86 F21.19 --- zbest ?=- Best redshift estimate, equal
to best_zspec if available
(best_z)
88- 108 E21.19 --- zspbest ?=- Best spectroscopic redshift
(see confidence order from paper)
(best_zspec)
110- 129 F20.18 --- zphbest ?=- Best photometric redshift
(see confidence order from paper
) (best_zphot)
131- 150 F20.18 --- zph ?=- Photometric redshift computed
in this work (zphotthiswork)
152- 156 A5 --- GoodFlags Absence of photometric flags
(Matamoro et al., 2025, in prep.)
(good_flags)
158- 178 F21.19 mag E(B-V)gal Milky-Way E(B-V) attenuation
(galebvebv)
180- 201 E22.20 mag/arcsec2 mumax-mag ?=- If below -2.6, the source is
considered point-like (Matamoro et
al., 2025, in prep.)
(mumaxminusmag_euclid)
202 A1 --- n_mumax-mag [I] I for Infinity
203- 220 F18.15 mag VISmag ?=- Magnitude in the VIS band
(mag_VIS)
222- 226 A5 --- SampleA The source belongs to sample A
(has spectroscopic redshift)
(Sample_A)
228- 232 A5 --- SampleB The source belongs to sample B
(is an X-ray AGN candidates)
(Sample_B) (1)
234- 238 A5 --- SampleC The source belongs to sample C
(is an AGN candidate) (Sample_C)
240- 244 A5 --- StarCandE Flag of star candidates
(starcandidateeuclid)
246- 250 A5 --- b24AE Bisigello et al.
(2024A&A...691A...1E 2024A&A...691A...1E)
AGN selection A
(bisigello24aeuclid)
252- 256 A5 --- b24BE Bisigello et al.
(2024A&A...691A...1E 2024A&A...691A...1E)
AGN selection B
(bisigello24beuclid)
258- 262 A5 --- JHVISYE Euclid-based color-color selection
from Matamoro et al., 2025,
in prep. (jhvisy_euclid)
264- 268 A5 --- VISHGZE Euclid-based color-color selection
from Matamoro et al., 2025,
in prep. (vishgz_euclid)
270- 274 A5 --- A18C75A C75 mid-infrared AGN selection from
Assef et al., 2018ApJS..234...23A 2018ApJS..234...23A,
Cat. J/ApJS/234/23
(assef18c75allwise)
276- 280 A5 --- A18R90A R90 mid-infrared AGN selection from
Assef et al., 2018ApJS..234...23A 2018ApJS..234...23A,
Cat. J/ApJS/234/23
(assef18r90allwise)
282- 286 A5 --- QSO-PRF Random forest AGN selection
(Tucci et al., 2025, in prep.)
(qso_PRF)
288- 292 A5 --- QSO-QUAIA QSO flag by QUAIA (qso_quaia)
294- 298 A5 --- QSO-GDR3 QSO flag from GAIA DR3 (qso_gdr3)
300- 304 A5 --- QSO-DESI QSO flag from DESI (qso_desi)
306- 310 A5 --- isAGNbroad Broad-line AGN from DESI DR1
(isagnbroad)
312- 316 A5 --- isAGNnarrow Narrow-line AGN from DESI DR1
(isagnnarrow)
318- 339 E22.19 --- redChi2 ?=- Reduced chi-square value from
the SED fitting (reduced_Chi2)
341- 363 F23.19 --- z ?=- Redshift value (redshift)
365- 386 F22.18 --- e_z []?=- Redshift value 1-sigma lower
uncertainty (redshifterrinf)
388- 409 F22.18 --- E_z ?=- Redshift value 1-sigma upper
uncertainty (redshifterrsup)
411- 430 F20.16 Msun Mstar ?=- Stellar mass estimate (Mstar)
432- 453 E22.19 Msun e_Mstar []?=- Stellar mass estimate 1-sigma
lower uncertainty (Mstarerrinf)
455- 475 E21.19 Msun E_Mstar ?=- Stellar mass estimate 1-sigma
upper uncertainty (Mstarerrsup)
477- 498 E22.19 Msun/yr SFR ?=- Star Formation Rate estimate
(SFR)
500- 524 F25.18 Msun/yr e_SFR []?=- Star Formation Rate estimate
1-sigma lower uncertainty
(SFRerrinf)
526- 549 F24.18 Msun/yr E_SFR ?=- Star Formation Rate estimate
1-sigma upper uncertainty
(SFRerrsup)
551- 569 F19.15 --- sSFR ?=- Specific Star Formation Rate
estimate (sSFR)
571- 595 F25.18 --- e_sSFR []?=- Specific Star Formation Rate
estimate 1-sigma lower uncertainty
(sSFRerrinf)
597- 621 F25.18 --- E_sSFR ?=- Specific Star Formation Rate
estimate 1-sigma upper uncertainty
(sSFRerrsup)
623- 642 F20.14 Gyr Age ?=- Host age estimate (age)
644- 666 E23.19 Gyr e_Age []?=- Host age estimate 1-sigma
lower uncertainty (ageerrinf)
668- 689 E22.19 Gyr E_Age ?=- Host age estimate 1-sigma
upper uncertainty (ageerrsup)
691- 712 E22.19 --- fAGN ?=- AGN fraction (5-20um) estimate
(fAGN)
714- 736 E23.19 --- e_fAGN []?=- AGN fraction (5-20um)
estimate 1-sigma lower uncertainty
(fAGNerrinf)
738- 759 E22.19 --- E_fAGN ?=- AGN fraction (5-20um) estimate
1-sigma upper uncertainty
(fAGNerrsup)
761- 779 F19.15 Lsun LAGN ?=- AGN bolometric luminosity
estimate (LAGN)
781- 802 F22.18 Lsun e_LAGN []?=- AGN bolometric luminosity
estimate 1-sigma lower uncertainty
(LAGNerrinf)
804- 825 F22.18 Lsun E_LAGN ?=- AGN bolometric luminosity
estimate 1-sigma upper uncertainty
(LAGNerrsup)
827- 845 F19.15 --- L6um ?=- 6-micron AGN luminosity
estimate (L6um)
847- 868 F22.18 --- e_L6um []?=- 6-micron AGN luminosity
estimate 1-sigma lower uncertainty
(L6umerrinf)
870- 891 F22.18 --- E_L6um ?=- 6-micron AGN luminosity
estimate 1-sigma upper uncertainty
(L6umerrsup)
893- 911 F19.15 --- L2500A ?=- 2500Å AGN luminosity
estimate (L2500A)
913- 934 F22.18 --- e_L2500A []?=- 2500Å AGN luminosity
estimate 1-sigma lower uncertainty
(L2500Aerrinf)
936- 957 F22.18 --- E_L2500A ?=- 2500Å AGN luminosity
estimate 1-sigma upper uncertainty
(L2500Aerrsup)
959- 978 F20.16 --- Inc ?=- AGN viewing angle estimate
(inclination)
980-1001 E22.19 --- e_Inc []?=- AGN viewing angle estimate
1-sigma lower uncertainty
(inclinationerrinf)
1003-1023 E21.19 --- E_Inc ?=- AGN viewing angle estimate
1-sigma upper uncertainty
(inclinationerrsup)
1025-1046 E22.19 mag E(B-V) ?=- E(B-V) attenuation estimate
(E_BV)
1048-1070 E23.19 mag e_E(B-V) []?=- E(B-V) attenuation estimate
1-sigma lower uncertainty
(EBVerr_inf)
1072-1093 E22.19 mag E_E(B-V) ?=- E(B-V) attenuation estimate
1-sigma upper uncertainty
(EBVerr_sup)
1095-1099 A5 --- SEDAGNCand AGN-candidate flag from SED fitting
(fAGN+fAGNerrinf>0.075,
sect 5.2) (SEDAGNcandidate)
1101-1115 A15 --- BandAvail Most similar combination of
available photometric bands to
selected corresponding reliability
functions (band_availability)
1117-1121 A5 --- W34flag WISE3 or WISE4 have flux
measurements with SNR>3 (W34_flag)
1123-1127 A5 --- ExtRelFlag If True, the source is located
outside the interpolation region
used during the reliability
function construction, i.e. the
reliability value should be taken
with a grain of salt.
(extrapolatedreliaflag)
1129-1133 A5 --- ExtReGALFlag If True, the source is located
outside the interpolation region
used during the reliability
function construction, i.e. the
reliability value should be taken
with a grain of salt for inactive
galaxy candidates (Sect 4.4)
(extrapolatedreliaGAL_flag)
1135-1155 E21.19 --- RelMstar Stellar mass reliability for AGN
candidates (reliability_Mstar)
1157-1177 E21.19 --- RelMstarGAL Stellar mass reliability for
inactive galaxy candidates
(reliabilityMstarGAL)
1179-1199 F21.18 --- e_RelMstar []?=- Stellar mass lower
uncertainty to reach at least 68%
reliability (Sect 4.6.1)
(realisticMstarerr_inf)
1201-1222 F22.18 --- e_RelMstarGAL []?=- Stellar mass lower
uncertainty to reach at least 68%
reliability for inactive galaxy
candidates (Sect 4.6.1)
(realisticMstarerrinfGAL)
1224-1243 F20.18 --- E_RelMstar ?=- Stellar mass upper uncertainty
to reach at least 68%
reliability (Sect 4.6.1)
(realisticMstarerr_sup)
1245-1264 F20.18 --- E_RelMstarGAL ?=- Stellar mass upper uncertainty
to reach at least 68% reliability
for inactive galaxy candidates
(Sect 4.6.1)
(realisticMstarerrsupGAL)
1266-1286 F21.19 --- RelLAGN Reliability of the AGN bolometric
luminosity (reliability_LAGN)
1288-1308 E21.19 --- RelL6um Reliability of the AGN luminosity
at 6um (reliability_L6um)
1310-1330 E21.19 --- RelL2500A Reliability of the AGN luminosity
at 2500Å (reliability_L2500A)
1332-1352 E21.19 --- RelSFR SFR reliability for AGN
(reliability_SFR)
1354-1374 E21.19 --- RelSFRGAL SFR reliability for inactive galaxy
candidates (reliabilitySFRGAL)
1376-1397 E22.19 Msun/yr SFRcor ?=- Bias-corrected SFR estimate for
AGN candidates (Sect 4.6.2)
(corrected_SFR)
1399-1421 F23.17 Msun/yr e_SFRcor []?=- Bias-corrected SFR estimate
lower uncertainty for AGN
candidates (Sect 4.6.2)
(correctedSFRerr_inf)
1423-1444 F22.17 Msun/yr E_SFRcor ?=- Bias-corrected SFR estimate
upper uncertainty for AGN
candidates (Sect 4.6.2)
(correctedSFRerr_sup)
1446-1466 F21.19 --- RelsSFR Specific SFR reliability for AGN
(reliability_sSFR)
1468-1487 F20.18 --- RelsSFRGAL Specific SFR reliability for
inactive galaxy candidates
(reliabilitysSFRGAL)
--------------------------------------------------------------------------------
Note (1): from Roster et al., 2026A&A...711A..16R 2026A&A...711A..16R, Cat. J/A+A/711/A16 or
Hsu et al., 2014ApJ...796...60H 2014ApJ...796...60H, Cat. J/ApJ/796/60)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: zphpdf.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- ID Euclid ID (id)
21- 35 F15.11 deg RAdeg Right ascension (J2000) Euclid
(rightascensioneuclid)
37- 51 F15.11 deg DEdeg Declination (J2000) Euclid
(declination_euclid)
53- 56 A4 --- Field Field (field)
58- 74 F17.15 --- zbest Best redshift estimate (best_z)
76- 94 F19.15 --- zspbest ?=- Best spectroscopic redshift(best_zspec)
96-112 F17.15 --- zphbest Best photometric redshift (best_zphot)
114-130 F17.15 --- zph Photometric redshift computed in this work
(zphotthiswork)
--------------------------------------------------------------------------------
Acknowledgements:
Brivael Laloux, brivael.laloux(at)inaf.it
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 02-Jun-2026