J/A+A/707/A239 Discovery of bright z~=7 LBGs in Euclid COSMOS (Varadaraj+, 2026)
Euclid Discovery of bright z~=7 Lyman-break galaxies in UltraVISTA and Euclid
COSMOS.
Varadaraj R.G., Bowler R.A.A., Jarvis M.J., Weaver J.R., Banados E.,
Holloway P., Caputi K.I., Wilkins S.M., Yang D., Milvang-Jensen B.,
Gabarra L., Oesch P.A., Amara A., Andreon S., Auricchio N., Baccigalupi C.,
Baldi M., Bardelli S., Biviano A., Branchini E., Brescia M., Camera S.,
Canas-Herrera G., Capobianco V., Carbone C., Carretero J., Castellano M.,
Castignani G., Cavuoti S., Chambers K.C., Cimatti A., Colodro-Conde C.,
Congedo G., Conselice C.J., Conversi L., Copin Y., 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., Dusini S., Escoffier S., Farina M.,
Farinelli R., Faustini F., 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., Guzzo L.,
Haugan S.V.H., Hoar J., Hoekstra H., Holmes W., Hook I.M., Hormuth F.,
Hornstrup A., Jahnke K., Jhabvala M., Joachimi B., Keihanen E., Kermiche S.,
Kiessling A., Kilbinger M., Kubik B., Kummel 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., Marggraf O., Martinelli M., Martinet N.,
Marulli F., Massey R.J., Medinaceli E., Mei S., Melchior M., Mellier Y.,
Meneghetti M., Merlin E., Meylan G., Mora A., Moresco M., Moscardini L.,
Nakajima R., Neissner C., Niemi S.-M., Padilla C., Paltani S., Pasian F.,
Pedersen K., Percival W.J., Pettorino V., Pires S., Polenta G., Poncet M.,
Popa L.A., Pozzetti L., Raison F., Renzi A., Rhodes J., Riccio G.,
Romelli E., Roncarelli M., Rossetti E., Saglia R., Sakr Z., Sapone D.,
Sartoris B., Schirmer M., Schneider P., Schrabback T., Secroun A.,
Seidel G., Serrano S., Simon P., Sirignano C., Sirri G., Stanco L.,
Starck J.-L., Steinwagner J., Tallada-Crespi P., Taylor A.N., Teplitz H.I.,
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., Zamorani G., Zerbi F.M., Zucca E., Martin-Fleitas J.,
Scottez V., Viel M.
<Astron. Astrophys. 707, A239 (2026)>
=2026A&A...707A.239V 2026A&A...707A.239V (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Positional data ; Redshifts ; Equivalent widths ;
Magnitudes, absolute ; Photometry ; Optical ; Infrared
Keywords: galaxies: evolution - galaxies: formation - galaxies: high-redshift -
galaxies: luminosity function, mass function - galaxies: photometry
Abstract:
We present a search for z ~= 7 Lyman-break galaxies using the 1.72 deg2
near-infrared UltraVISTA survey in the COSMOS field, reaching 5 σ
depths in Y of 26.2. We incorporate deep Euclid optical and
Euclid + Spitzer NIR imaging for a full spectral energy distribution
(SED) fitting analysis. We find 289 candidate galaxies at 6.5 ≤ z ≤ 7.5
covering -22.6 ≤ MUV ≤ -20.2, faint enough to overlap with Hubble
Space Telescope studies. We conduct a separate selection by including
complementary Euclid performance verification imaging (reaching 5 σ
depths of 26.3), yielding 140 galaxies in 0.65 deg2, with 38 sources
unique to this sample. We compute the rest-frame UV luminosity
function (UV LF) from our samples, extending below the knee
(M*=-21.14). We find that the shape of the UV LF is consistent with
both a Schechter function and double-power law (DPL) at the magnitudes
probed by this sample, with a DPL preferred at MUV < -22.5 when
bright-end results are included. The UltraVISTA+Euclid sample provides
a clean measurement of the LF due to the overlapping near-infrared
filters identifying molecular absorption features in the SEDs of
ultra-cool dwarf interlopers, and a dditional faint galaxies are
recovered. A comparison with JWST LFs at z > 7 suggests a gentle
evolution in the bright-end slope, although this is limited by a lack
of robust bright-end measurements at z > 9. We forecast that in the
Euclid Deep Fields, the removal of contaminant ultra-cool dwarfs as
point sources will be possible at JE < 24.5. Finally, we present a
high-equivalent-width Lyman-α emitter candidate identified by
combining HSC, VISTA, and Euclid broadband photometry, highlighting
the synergistic power t hese instruments will have in the Euclid
Auxiliary Fields for identifying extreme sources in the Epoch of
Reionisation.
Description:
We provide tables of the UltraVISTA+Euclid and UltraVISTA-only samples
at z=7 in the COSMOS field. The Lyman-break galaxies are selected with
the dropout technique and SED fitting. We provide information such as
the source ID, position, photometric redshifts, results of SED
fitting, and photometry. We provide details of the secondary solutions
(low-redshift dusty galaxies and ultra-cool dwarfs, UCDs), but we note
that these solutions are not preferred compared to the high-redshift
(z>6.5) solution. The photometry is measured in circular apertures
with diameter 1.8 arcsec, apart from Spitzer/IRAC where a 2.8 arcsec
diameter aperture is used. We apply an aperture correction assuming a
point-spread function (PSF), and Euclid photometry is obtained after
PSF homogenising the imaging to match VISTA-Y, the broadest PSF of the
VISTA filters. We also provide 10x10 arcsec postage stamp cutouts of
the UltraVISTA+Euclid sample in the Euclid I_E, Y_E, J_E, and H_E
filters. These images are unconvolved with the VISTA PSF. The
UltraVISTA+Euclid data are in uviez7.dat while UltraVISTA-only data
are in uvistaz7.dat. Cutouts for the 4 Euclid filters for each 140
UltraVISTA+Euclid sources are in fits subdirectory, list.dat lists all
the cutouts informations.
Objects:
----------------------------------------------------------------------------
RA (2000) DE Designation(s)
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10 00 28.59 +02 12 21.0 NAME COSMOS Field
----------------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
uviez7.dat 691 140 UltraVISTA+Euclid selection of LGB candidates
for SED fit with HSC+VISTA+Spitzer/IRAC+Euclid
(table 3)
uvistaz7.dat 578 289 UltraVISTA-only selection LGB candidates for SED
fit with HSC+VISTA+Spitzer/IRAC without Euclid
(table 3)
list.dat 142 560 List of fits cutouts of the UltraVISTA+Euclid
sample in the Euclid IE, YE, JE, and HE filters
fits/* . 560 Individual LGB euclid fits cutout images in each
4 Euclid filters
--------------------------------------------------------------------------------
See also:
J/A+A/704/A339 : COSMOS2025 (Shuntov+, 2025)
J/A+A/697/A16 : Euclid ERO LBG and ERS candidate lists (Weaver+, 2025)
J/MNRAS/515/3126 : REBELS. Dust Continuum Detections at z>6.5 (Inami+, 2022)
J/MNRAS/440/2810 : Galaxy luminosity function at z ≃ 7 (Bowler+, 2014)
J/MNRAS/432/2696 : Galaxy luminosity function at z = 7-9 (McLure+, 2013)
J/ApJ/975/162 : Spectra of brown dwarf candidates in ONC from JWST
(Luhman+, 2024)
J/ApJ/810/71 : UV mag of candidate galaxies at 3~<z~<8.5
(Finkelstein+, 2015)
J/ApJ/803/34 : z∼4-10 galaxies from HST legacy fields (Bouwens+, 2015)
J/ApJ/793/115 : UV-continuum slopes beta for z∼4-8 galaxies (Bouwens+, 2014)
J/ApJS/259/20 : GOLDRUSH. IV. z∼3-7 galaxies (Harikane+, 2022)
J/ApJS/258/11 : The COSMOS2020 catalog (Weaver+, 2022)
J/ApJS/237/39 : Spitzer survey of UltraVISTA deep Stripes (SMUVS)
(Ashby+, 2018)
J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)
J/ApJS/219/15 : Morphologies of z=0-10 galaxies with HST data
(Shibuya+, 2015)
J/ApJS/218/33 : Spitzer-CANDELS catalog within 5 deep fields (Ashby+, 2015)
J/AJ/162/47 : UV luminosity in ∼25000 2<z<9 galaxies (Bouwens+, 2021)
J/PASJ/70/S10 : GOLDRUSH I. UV magnitudes (Ono+, 2018)
III/334 : VISTA Deep Extragalactic Observations (VIDEO) (Jarvis+,2013)
II/388 : Euclid final merged catalog. Q1 data release
(Euclid Coll., 2025)
II/373 : The fourth UltraVISTA data release (DR4) (Moneti+, 2019)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: uviez7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- EUCL The euclid source identifier designation
as EUCL JHHMMSS.ss+DDMMSS.s (SOURCE_ID)
26- 44 F19.15 deg RAdeg Right ascension (J2000) (RA)
46- 61 F16.14 deg DEdeg Declination (J2000) (DEC)
63- 69 F7.5 --- zph Photometric redshift of the lyman-break
galaxy solution (Zphot)
71- 77 F7.5 --- E_zph Upper uncertainty of zph (dZphot_sup)
79- 85 F7.5 --- e_zph Lower uncertainty of zph (dZphot_inf)
87- 94 F8.5 --- Chi2 The Chi2 of the best SED fitting process
of the lyman-break galaxy z>6.5 solution
(Chi2)
96-100 F5.2 --- zphsec Low photometric redshift of the
low-redshift dusty galaxy secondary
solution (Zphot_sec)
102-110 F9.4 --- Chi2sec The Chi2 value from SED fitting process
of the low-redshift dusty galaxy
secondary solution (Chi2_sec)
112-113 A2 --- SpType Spectral type for the stellar model of
ultra-cool dwarf interloper solution
(Stellar_model)
115-123 F9.5 --- Chi2star The Chi2 of the best SED fit process of
ultra-cool dwarf interloper solution
(Chi2_star)
125-143 F19.15 0.1nm EWLya ?=0 Computed equivalent width of the
Lyman-α emission line in
high-redshift template (LymanalphaEW)
145-161 F17.13 mag UVMag The measured absolute rest-frame UV
magnitude (MUV)
163-179 F17.15 mag E_UVMag Upper uncertainty of UVMag (dMuv_sup)
181-197 F17.15 mag e_UVMag Lower uncertainty of UVMag (dMuv_inf)
199-212 E14.7 mW/m2/Hz FHSCg HSC-SSP flux at g band optical filter
(fluxHSCG)
214-227 E14.7 mW/m2/Hz FHSCr HSC-SSP flux at r band optical filter
(fluxHSCR)
229-242 E14.7 mW/m2/Hz FHSCi HSC-SSP flux at i band optical filter
244-257 E14.7 mW/m2/Hz FHSCNB0816 HSC-SSP flux at NB816 optical filter
(fluxHSCNB0816)
259-272 E14.7 mW/m2/Hz FHSCz HSC-SSP flux at z band filter
(fluxHSCZ)
274-287 E14.7 mW/m2/Hz FHSCNB921 HSC-SSP flux at NB921 band filter
(fluxHSCNB0921)
289-302 E14.7 mW/m2/Hz FHSCY HSC-SSP flux at Y band filter
(fluxHSCY)
304-317 E14.7 mW/m2/Hz FVISIE Euclid VIS flux at IE band filter
(flux_IE)
319-332 E14.7 mW/m2/Hz FNISPYE Euclid NISP flux at YE band filter
(flux_YE)
334-346 E13.7 mW/m2/Hz FNISPJE Euclid NISP flux at JE band filter
(flux_JE)
348-361 E14.7 mW/m2/Hz FNISPHE Euclid NISP flux at HE band filter
(flux_HE)
363-375 E13.7 mW/m2/Hz FNIRY UltraVISTA flux at Y NIR band (flux_Y)
377-389 E13.7 mW/m2/Hz FNIRJ UltraVISTA flux at J NIR band (flux_J)
391-404 E14.7 mW/m2/Hz FNIRH UltraVISTA flux at H NIR band (flux_H)
406-419 E14.7 mW/m2/Hz FNIRKs UltraVISTA flux at Ks NIR band (flux_Ks)
421-434 E14.7 mW/m2/Hz FIRAC1 Spitzer/IRAC flux at IRAC1 IR band
(flux_IRAC1)
436-449 E14.7 mW/m2/Hz FIRAC2 Spitzer/IRAC flux at IRAC2 IR band
(flux_IRAC2)
451-463 E13.7 mW/m2/Hz e_FHSCg Error of FHSCg (errHSCG)
465-477 E13.7 mW/m2/Hz e_FHSCr Error of FHSCr (errHSCR)
479-491 E13.7 mW/m2/Hz e_FHSCi Error of FHSCi (errHSCI)
493-505 E13.7 mW/m2/Hz e_FHSCNB0816 Error of FHSCNB0816 (errHSCNB0816)
507-519 E13.7 mW/m2/Hz e_FHSCz Error of FHSCz (errHSCZ)
521-533 E13.7 mW/m2/Hz e_FHSCNB921 Error of FHSCNB921 (errHSCNB0921)
535-547 E13.7 mW/m2/Hz e_FHSCY Error of FHSCY (errHSCY)
549-561 E13.7 mW/m2/Hz e_FVISIE Error of FVISIE (err_IE)
563-575 E13.7 mW/m2/Hz e_FNISPYE Error of FNISPYE (err_YE)
577-589 E13.7 mW/m2/Hz e_FNISPJE Error of FNISPJE (err_JE)
591-603 E13.7 mW/m2/Hz e_FNISPHE Error of FNISPHE (err_HE)
605-617 E13.7 mW/m2/Hz e_FNIRY Error of FNIRY (err_Y)
619-631 E13.7 mW/m2/Hz e_FNIRJ Error of FNIRJ (err_J)
633-645 E13.7 mW/m2/Hz e_FNIRH Error of FNIRH (err_H)
647-659 E13.7 mW/m2/Hz e_FNIRKs Error of FNIRKs (err_Ks)
661-675 E15.7 mW/m2/Hz e_FIRAC1 ?=-99 Error of FIRAC1 (err_IRAC1)
677-691 E15.7 mW/m2/Hz e_FIRAC2 ?=-99 Error of FIRAC2 (err_IRAC2)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: uvistaz7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- UVISTA The UVISTA source identifier designation
as UVISTA JHHMMSS.ss+DDMMSS.s (SOURCE_ID)
(1)
28- 43 F16.12 deg RAdeg Right ascension (J2000) (RA)
45- 60 F16.14 deg DEdeg Declination (J2000) (DEC)
62- 68 F7.5 --- zph Photometric redshift of the lyman-break
galaxy solution (Zphot)
70- 76 F7.5 --- E_zph Upper uncertainty of zph (dZphot_sup)
78- 84 F7.5 --- e_zph Lower uncertainty of zph (dZphot_inf)
86- 94 F9.6 --- Chi2 The Chi2 of the best SED fitting process
of the lyman-break galaxy z>6.5 solution
(Chi2)
96-100 F5.2 --- zphsec Low photometric redshift of the
low-redshift dusty galaxy secondary
solution (Zphot_sec)
102-111 F10.5 --- Chi2sec The Chi2 value from SED fitting process
of the low-redshift dusty galaxy
secondary solution (Chi2_sec)
113-114 A2 -- SpType Spectral type for the stellar model of
ultra-cool dwarf interloper solution
(Stellar_model)
116-124 F9.5 --- Chi2star The Chi2 of the best SED fit process of
ultra-cool dwarf interloper solution
(Chi2_star)
126-144 F19.15 0.1nm EWLya ?=0 Computed equivalent width of the
Lyman-α emission line in
high-redshift template (LymanalphaEW)
146-162 F17.13 mag UVMag The measured absolute rest-frame UV
magnitude (MUV)
164-180 F17.15 mag E_UVMag Upper uncertainty of UVMag (dMuv_sup)
182-198 F17.15 mag e_UVMag Lower uncertainty of UVMag (dMuv_inf)
200-213 E14.7 mW/m2/Hz FHSCg HSC-SSP flux at g band optical filter
(fluxHSCG)
215-228 E14.7 mW/m2/Hz FHSCr HSC-SSP flux at r band optical filter
(fluxHSCR)
230-243 E14.7 mW/m2/Hz FHSCi HSC-SSP flux at i band optical filter
(fluxHSCI)
245-258 E14.7 mW/m2/Hz FHSCNB0816 HSC-SSP flux at NB816 optical filter
(fluxHSCNB0816)
260-273 E14.7 mW/m2/Hz FHSCz HSC-SSP flux at z band filter
(fluxHSCZ)
275-288 E14.7 mW/m2/Hz FHSCNB921 HSC-SSP flux at NB921 band filter
(fluxHSCNB0921)
290-303 E14.7 mW/m2/Hz FHSCY HSC-SSP flux at Y band filter
(fluxHSCY)
305-317 E13.7 mW/m2/Hz FNIRY UltraVISTA flux at Y NIR band (flux_Y)
319-331 E13.7 mW/m2/Hz FNIRJ UltraVISTA flux at J NIR band (flux_J)
333-346 E14.7 mW/m2/Hz FNIRH UltraVISTA flux at H NIR band (flux_H)
348-361 E14.7 mW/m2/Hz FNIRKs UltraVISTA flux at Ks NIR band (flux_Ks)
363-376 E14.7 mW/m2/Hz FIRAC1 Spitzer/IRAC flux at IRAC1 IR band
(flux_IRAC1)
378-391 E14.7 mW/m2/Hz FIRAC2 Spitzer/IRAC flux at IRAC2 IR band
(flux_IRAC2)
393-405 E13.7 mW/m2/Hz e_FHSCg Error of FHSCg (errHSCG) Column#29
(errHSCG)
407-420 E14.7 mW/m2/Hz e_FHSCr Error of FHSCr (errHSCR)
422-434 E13.7 mW/m2/Hz e_FHSCi Error of FHSCi (errHSCI)
436-448 E13.7 mW/m2/Hz e_FHSCNB0816 Error of FHSCNB0816 (errHSCNB0816)
450-462 E13.7 mW/m2/Hz e_FHSCz Error of FHSCz (errHSCZ)
464-476 E13.7 mW/m2/Hz e_FHSCNB921 Error of FHSCNB921 (errHSCNB0921)
478-490 E13.7 mW/m2/Hz e_FHSCY Error of FHSCY (errHSCY)
492-504 E13.7 mW/m2/Hz e_FNIRY Error of FNIRY (err_Y)
506-518 E13.7 mW/m2/Hz e_FNIRJ Error of FNIRJ (err_J)
520-532 E13.7 mW/m2/Hz e_FNIRH Error of FNIRH (err_H)
534-546 E13.7 mW/m2/Hz e_FNIRKs Error of FNIRKs (err_Ks)
548-562 E15.7 mW/m2/Hz e_FIRAC1 ?=-99 Error of FIRAC1 (err_IRAC1)
564-578 E15.7 mW/m2/Hz e_FIRAC2 ?=-99 Error of FIRAC2 (err_IRAC2)
--------------------------------------------------------------------------------
Note (1): Some of these sources overlap with the UltraVISTA+Euclid sample, so
will also have an ID from that catalogue. The name from the
UltraVISTA+Euclid catalogue (starting with EUCL) is preferred.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- EUCL The euclid source identifier designation as
EUCL JHHMMSS.ss+DDMMSS.s (SOURCE_ID)
26- 28 I3 --- Nx Number of pixels along X-axis
30- 32 I3 --- Ny Number of pixels along Y-axis
34- 35 I2 Kibyte size Size of FITS file
37- 67 A31 --- FileName Name of FITS file, in subdirectory fits
69- 142 A74 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Rohan Varadaraj, rohan.varadaraj(at)physics.ox.ac.uk
(End) Luc Trabelsi [CDS] 27-Jan-2026