IX. Systematic comparison between lens modelling software programs: Time-delay prediction for WGD 2038-4008
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IX. Systematic comparison between lens modelling software programs : Time-delay prediction for WGD 2038-4008. / Shajib, A. J.; Wong, K. C.; Birrer, S.; Suyu, S. H.; Treu, T.; Buckley-Geer, E. J.; Lin, H.; Rusu, C. E.; Poh, J.; Palmese, A.; Agnello, A.; Auger-Williams, M. W.; Galan, A.; Schuldt, S.; Sluse, D.; Courbin, F.; Frieman, J.; Millon, M.
In: Astronomy & Astrophysics, Vol. 667, A123, 15.11.2022.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - IX. Systematic comparison between lens modelling software programs
T2 - Time-delay prediction for WGD 2038-4008
AU - Shajib, A. J.
AU - Wong, K. C.
AU - Birrer, S.
AU - Suyu, S. H.
AU - Treu, T.
AU - Buckley-Geer, E. J.
AU - Lin, H.
AU - Rusu, C. E.
AU - Poh, J.
AU - Palmese, A.
AU - Agnello, A.
AU - Auger-Williams, M. W.
AU - Galan, A.
AU - Schuldt, S.
AU - Sluse, D.
AU - Courbin, F.
AU - Frieman, J.
AU - Millon, M.
PY - 2022/11/15
Y1 - 2022/11/15
N2 - The importance of alternative methods for measuring the Hubble constant, such as time-delay cosmography, is highlighted by the recent Hubble tension. It is paramount to thoroughly investigate and rule out systematic biases in all measurement methods before we can accept new physics as the source of this tension. In this study, we perform a check for systematic biases in the lens modelling procedure of time-delay cosmography by comparing independent and blind time-delay predictions of the system WGD 2038-4008 from two teams using two different software programs: GLEE and LENSTRONOMY. The predicted time delays from the two teams incorporate the stellar kinematics of the deflector and the external convergence from line-of-sight structures. The un-blinded time delay predictions from the two teams agree within 1.2o-, implying that once the time delay is measured the inferred Hubble constant will also be mutually consistent. However, there is a similar to 4o-discrepancy between the power-law model slope and external shear, which is a significant discrepancy at the level of lens models before the stellar kinematics and the external convergence are incorporated. We identify the difference in the reconstructed point spread function (PSF) to be the source of this discrepancy. When the same reconstructed PSF was used by both teams, we achieved excellent agreement, within similar to 0.6o-, indicating that potential systematics stemming from source reconstruction algorithms and investigator choices are well under control. We recommend that future studies supersample the PSF as needed and marginalize over multiple algorithms or realizations for the PSF reconstruction to mitigate the systematics associated with the PSF. A future study will measure the time delays of the system WGD 2038-4008 and infer the Hubble constant based on our mass models.
AB - The importance of alternative methods for measuring the Hubble constant, such as time-delay cosmography, is highlighted by the recent Hubble tension. It is paramount to thoroughly investigate and rule out systematic biases in all measurement methods before we can accept new physics as the source of this tension. In this study, we perform a check for systematic biases in the lens modelling procedure of time-delay cosmography by comparing independent and blind time-delay predictions of the system WGD 2038-4008 from two teams using two different software programs: GLEE and LENSTRONOMY. The predicted time delays from the two teams incorporate the stellar kinematics of the deflector and the external convergence from line-of-sight structures. The un-blinded time delay predictions from the two teams agree within 1.2o-, implying that once the time delay is measured the inferred Hubble constant will also be mutually consistent. However, there is a similar to 4o-discrepancy between the power-law model slope and external shear, which is a significant discrepancy at the level of lens models before the stellar kinematics and the external convergence are incorporated. We identify the difference in the reconstructed point spread function (PSF) to be the source of this discrepancy. When the same reconstructed PSF was used by both teams, we achieved excellent agreement, within similar to 0.6o-, indicating that potential systematics stemming from source reconstruction algorithms and investigator choices are well under control. We recommend that future studies supersample the PSF as needed and marginalize over multiple algorithms or realizations for the PSF reconstruction to mitigate the systematics associated with the PSF. A future study will measure the time delays of the system WGD 2038-4008 and infer the Hubble constant based on our mass models.
KW - gravitational lensing
KW - strong - methods
KW - data analysis - galaxies
KW - elliptical and lenticular
KW - cD - distance scale
KW - EARLY-TYPE GALAXIES
KW - HUBBLE CONSTANT
KW - DARK-MATTER
KW - ACS SURVEY
KW - ELLIPTIC GALAXIES
KW - DENSITY PROFILE
KW - MASS
KW - COSMOGRAPHY
KW - H-0
KW - PRECISION
U2 - 10.1051/0004-6361/202243401
DO - 10.1051/0004-6361/202243401
M3 - Journal article
VL - 667
JO - Astronomy & Astrophysics
JF - Astronomy & Astrophysics
SN - 0004-6361
M1 - A123
ER -
ID: 329235028