J/A+A/705/A13 TDCOSMO XXI SL2S spectra for accurate vel. disp. (Mozumdar+, 2026)
TDCOSMO XXI. Accurate stellar velocity dispersions of the SL2S lens sample and
the fundamental plane of the lensing mass.
Mozumdar P., Knabel S., Treu T., Sonnenfeld A., Shajib A. J., Cappellari M.,
Nipoti C.
<Astron. Astrophys. 705, A13 (2026)>
=2026A&A...705A..13M 2026A&A...705A..13M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Gravitational lensing ; Galaxies, spectra ;
Spectroscopy ; Optical ; Infrared
Keywords: gravitational lensing: strong - techniques: spectroscopic -
galaxies: elliptical and lenticular, cD - galaxies: evolution -
galaxies: fundamental parameters - galaxies: kinematics and dynamics
Abstract:
We reanalyzed spectra that were taken as part of the SL2S lens galaxy
survey with the goal to obtain the stellar velocity dispersion with a
precision and accuracy sufficient for time-delay cosmography. In order
to achieve this goal, we imposed stringent cuts on the signal-to-noise
ratio (S/N), and employed recently developed methods to mitigate and
quantify residual systematic errors that are transferred from template
libraries and fitting process. We also quantified the covariance
across the sample. For galaxy spectra with S/N > 20/Å, our new
measurements have an average random uncertainty of 3-4%, an average
systematic uncertainty of 2%, and a covariance across the sample of
1%. We find a negligible covariance between spectra taken with
different instruments. The systematic uncertainty and covariance need
to be included when the sample is used as an external dataset in
time-delay cosmography. We revisited empirical scaling relations of
lens galaxies based on the improved kinematics. We show that the SL2S
sample, the TDCOSMO time-delay lens sample, and the lower-redshift
SLACS sample follow the same correlation of the effective radius,
stellar velocity dispersion, and lensing mass, known as the
lensing-mass fundamental plane, as the previously derived correlation
that assumed isothermal mass profiles for the deflectors. We also
derived for the first time the lensing-mass fundamental plane assuming
free power-law mass density profiles, and we show that the three
samples also follow the same correlation. This is consistent with a
scenario in which massive galaxies evolve by growing their radii and
mass, but stay within the plane.
Description:
In this paper, we reanalyze the spectra that were taken a
decade ago as part of the 'Strong Lensing Legacy Survey' (SL2S) with
the goal of implementing the recent improvements in the derivation
of stellar kinematics to obtain accurate measurements and estimates of
the systematic errors and covariance between galaxies. SL2S is a very
valuable external dataset for cosmography because it is well matched
to the time-delay lenses in terms of redshift distribution and
provides information that is helpful for breaking the mass-sheet
degeneracy. We also took advantage of the new measurements to investigate
whether the SL2S sample galaxies obey the same lensing mass fundamental
plane as the SLACS sample.
For this study, we provided the 47 new acquired observations spectra
respectively from Keck Low-Resolution Imaging Spectrometer (LRIS) for
31 spectra covering 2 bands (blue and red) in a wavelength range of
3000-10000Å (sufficient spectral resolution and S/N for determining
the stellar velocity dispersions), Keck DEep Imaging Multi-Object
Spectrograph (DEIMOS) for 3 spectra covering a band in a wavelength
range of 4500-9500 Å (with sufficient spectral resolution and S/N
ratio for determining the stellar velocity dispersions) and VLT
Xshooter spectrograph (XSHOOTER) for 13 spectra covering 3 bands (UVB,
VIS, and NIR) in a wavelength range of 3000-25000 Å (with a
sufficient spectral resolution and S/N for determining the stellar
velocity dispersions, i.e see more in section SL2S spectroscopic data
as well as method and results in section Method for new kinematic
measurements and section New measurements and uncertainties, linked to
appendix tables).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table.dat 88 47 SL2S lens galaxies with sufficient spectral res.
and S/N for the stellar velocity dispersions
sp/* . 47 SL2S lens galaxy individual spectra
(with file names NameInstspec.dat)
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See also:
J/A+A/697/A139 : r-band light curves of 22 lensed QSOs (Dux+, 2025)
J/A+A/673/A9 : TDCOSMO XII. Resolved kinematics of lens galaxy
(Shajib+, 2023)
J/ApJ/785/144 : SL2S galaxy-scale sample of lens candidates (Gavazzi+, 2014)
J/ApJ/777/97 : SL2S galaxy-scale lens sample. III. (Sonnenfeld+, 2013)
J/ApJ/749/38 : CFHTLS-SL2S-ARCS strong lens candidates (More+, 2012)
J/ApJ/682/964 : Sloan lens ACS survey. V. (Bolton+, 2008)
J/MNRAS/371/703 : MILES library of empirical spectra (Sanchez-Blazquez+, 2006)
Byte-by-byte Description of file: table.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Name Name of SL2S lens galaxy designation as
SL2SJHHMMSS+DDMMSS(Name)
20- 21 I2 h RAh Right Ascension (J2000)
23- 24 I2 min RAm Right Ascension (J2000)
26- 30 F5.2 s RAs Right Ascension (J2000)
32 A1 --- DE- Declination sign (J2000)
33- 34 I2 deg DEd Declination (J2000)
36- 37 I2 arcmin DEm Declination (J2000)
39- 42 F4.1 arcsec DEs Declination (J2000)
44- 51 A8 --- Inst Spectroscopic instrument used (Instrument) (1)
53- 88 A36 --- FileName File name containing the spectrum in
subdirectory sp
--------------------------------------------------------------------------------
Note (1): Spectroscopic instruments are as follows:
LRIS = Keck Low-Resolution Imaging Spectrometer,
31 sources in our sample
XSHOOTER = VLT Xshooter spectrograph, 13 sources in our sample
DEIMOS = Keck DEep Imaging Multi-Object Spectrograph, 3 sources
in our sample
--------------------------------------------------------------------------------
Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 F19.13 0.1nm Wavelength Spectroscopic wavelength (Wavelength)
21- 43 E23.16 --- Flux Relative spectroscopic flux (Flux)
--------------------------------------------------------------------------------
References:
Millon et al., Paper I 2020A&A...639A.101M 2020A&A...639A.101M
Millon et al., Paper II 2020A&A...642A.193M 2020A&A...642A.193M
Gilman et al., Paper III 2020A&A...642A.194G 2020A&A...642A.194G
Birrer et al., Paper IV 2020A&A...643A.165B 2020A&A...643A.165B
Birrer et al., Paper V 2021A&A...649A..61B 2021A&A...649A..61B
Chen et al., Paper VI 2021A&A...652A...7C 2021A&A...652A...7C
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Gomer et al., Paper VIII 2022A&A...667A..86G 2022A&A...667A..86G
Shajib et al., Paper IX 2022A&A...667A.123S 2022A&A...667A.123S
Ertl et al., Paper X 2023A&A...672A...2E 2023A&A...672A...2E
Mozumdar et al., Paper XI 2023A&A...672A..20M 2023A&A...672A..20M
Shajib et al., Paper XII 2023A&A...673A...9S 2023A&A...673A...9S, Cat. J/A+A/673/A9
Yildirim et al., Paper XIII 2023A&A...675A..21Y 2023A&A...675A..21Y
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Wells et al., Paper XV 2024A&A...689A..87W 2024A&A...689A..87W
Wong et al., Paper XVI 2024A&A...689A.168W 2024A&A...689A.168W
Dux et al., Paper XVII 2025A&A...697A.139D 2025A&A...697A.139D, Cat. J/A+A/697/A139
Schmidt et al., Paper XVIII 2025A&A...700A..92S 2025A&A...700A..92S
Knabel et al., Paper XIX 2025A&A...703A.117K 2025A&A...703A.117K
Williams et al., Paper XX 2025A&A...703A.118W 2025A&A...703A.118W
Mozumdar et al., Paper XXII 2025arXiv250513962M 2025arXiv250513962M
Shajib et al., Paper XXIII 2025arXiv250621665S 2025arXiv250621665S
Paic et al., Paper XXIV 2025arXiv251203178P 2025arXiv251203178P
Acknowledgements:
Pritom Mozumdar, pmozumdar(at)astro.ucla.edu
(End) Pritom Mozumdar [Univ. of California], Luc Trabelsi [CDS] 02-Dec-2025