J/A+A/710/A207 JWST Bullet Cluster redshifts and spectra (Rihtarsic+, 2026)
Mapping dark matter in the Bullet Cluster using JWST imaging and spectroscopy.
Rihtarsic G., Bradac M., Desprez G., Harshan A., Martis N.S., Willott C.J.,
Asada Y., Sarrouh G.T.E., Cornil-Baiotto C., Biviano A., Clowe D.,
Gonzalez A.H., Jones C., Judez J., Kim S.Y., Lemaux B.C., Lombardi M.,
Marchesini D., Markevitch M., Markov V., Noirot G., Peter A.H.G.,
Randall S.W., Robertson A., Sawicki M., Tripodi R.
<Astron. Astrophys. 710, A207 (2026)>
=2026A&A...710A.207R 2026A&A...710A.207R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Gravitational lensing ; Redshifts ; Infrared
Keywords: gravitational lensing: strong - galaxies: distances and redshifts -
galaxies: clusters: individual: Bullet Cluster -
galaxies: clusters: individual: 1E 0657-56 - dark matter
Abstract:
The Bullet Cluster (1E 0657-56), located at a redshift of 0.296, is
among the best-known merging galaxy clusters and a key laboratory for
dark matter studies. Although the mass distribution in the Bullet
Cluster has been modelled using an increasing number of multiply
imaged galaxies, only six systems had spectroscopic redshifts
published prior to this work, which are essential for system
confirmation and as lens model constraints. We present an updated
gravitational lens model of the Bullet cluster, obtained by combining
JWST NIRCam imaging and NIRSpec spectroscopy. Our lens model has been
constrained on the basis of a catalogue of 135 secure multiple images
from 27 background galaxies with spectroscopic redshifts, uniformly
covering both subclusters and a wide redshift range of 0.9-6.7. We
also provide a catalogue of 199 multiple image candidates. We modelled
the cluster with the parametric lens modelling code Lenstool. We
incorporated several large-scale halos, cluster member galaxies,
intracluster gas, and group-scale halos surrounding the cluster core,
motivated by spectroscopic studies of cluster member kinematics. We
describe the main cluster component with a complex, elongated
double-peaked distribution, along with the subcluster, modelled using
a single large-scale halo coinciding closely with the brightest
cluster galaxy at a projected separation of 4-2+3kpc. The
uncertainty of the displacement has been improved three-fold thanks to
the addition of JWST systems. The addition of group-scale
substructures, roughly following the two axes of cluster assembly,
improves the fit to the multiple image positions and provides a
physically motivated alternative to a constant shear component. Our
lens model shows the closest agreement with previous studies in
aperture mass profiles at ∼60kpc from the brightest cluster
galaxies (BCGs), but exhibits significant differences in the detailed
mass distribution as a result of different lens-modelling strategies
and adopted constraints. The differences are reflected in small, but
spatially coherent deviations between the new spectroscopic redshifts
and redshifts predicted by earlier lens models.
Description:
A catalogue of strongly lensed multiple images, derived from JWST
program GO 4598 (PI Bradac) with associated spectroscopic redshifts
and 1D NIRSpec spectra. The catalog also contains multiple image
systems and redshifts reported in Cha et al. (2025ApJ...987L..15C 2025ApJ...987L..15C),
Paraficz et al. (2016A&A...594A.121P 2016A&A...594A.121P) and Richard et al.
(2021A&A...646A..83R 2021A&A...646A..83R, cat. J/A+A/646/A83)
Objects:
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RA (2000) DE Designation(s)
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06 58 26.87 -55 58 20.9 1E 0657-55.8 = Bullet Cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 95 199 Catalogue of multiple images
sp/* . 46 Individual spectra
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See also:
J/A+A/646/A83 : 12 massive lensing clusters MUSE observations (Richard+, 2021)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Id Multiple image identified
8- 17 F10.6 deg RAdeg Right ascension (ICRS)
19- 28 F10.6 deg DEdeg Declination (ICRS)
30- 34 F5.3 --- zNIRSpec ? NIRSpec redshift
36- 40 F5.3 --- e_zNIRSpec ? Lower uncertainty on zNIRSpec
42- 46 F5.3 --- E_zNIRSpec ? Upper uncertainty on zNIRSpec
48- 56 A9 --- f_zNIRSpec NIRSpec redshift flag (stacked/confirmed)
58- 63 F6.4 --- zold ? Archival redshift
65- 70 F6.4 --- zsys ? System redshift used in the lens model
72 A1 --- Class [GSB] Quality class
74- 78 A5 --- IdCha25 Cha et al. (2025ApJ...987L..15C 2025ApJ...987L..15C) identifier
80- 95 A16 --- FileName Name of the fits spectrum file in
subdirectory sp
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Acknowledgements:
Gregor Rihtarsic, gregor.rihtarsic(at)fmf.uni-lj.si
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 27-Apr-2026