STRIDES: Spectroscopic and photometric characterization of the environment and effects of mass along the line of sight to the gravitational lenses DES J0408-5354 and WGD 2038-4008 Academic Article uri icon


  • ABSTRACT In time-delay cosmography, three of the key ingredients are (1) determining the velocity dispersion of the lensing galaxy, (2) identifying galaxies and groups along the line of sight with sufficient proximity and mass to be included in the mass model, and (3) estimating the external convergence ext from less massive structures that are not included in the mass model. We present results on all three of these ingredients for two time-delay lensed quad quasar systems, DESJ04085354and WGD20384008. We use the Gemini, Magellan, and VLT telescopes to obtain spectra to both measure the stellar velocity dispersions of the main lensing galaxies and to identify the line-of-sight galaxies in these systems. Next, we identify 10 groups in DESJ04085354and two groups in WGD20384008using a group-finding algorithm. We then identify the most significant galaxy and galaxy-group perturbers using the flexion shift criterion. We determine the probability distribution function of the external convergence ext for both of these systems based on our spectroscopy and on the DES-only multiband wide-field observations. Using weighted galaxy counts, calibrated based on the Millennium Simulation, we find that DESJ04085354is located in a significantly underdense environment, leading to a tight (width $sim 3{{
    m per cent}}$), negative-value ext distribution. On the other hand, WGD20384008is located in an environment of close to unit density, and its low source redshift results in a much tighter ext of $sim 1{{
    m per cent}}$, as long as no external shear constraints are imposed.

published proceedings


altmetric score

  • 7.83

author list (cited authors)

  • Buckley-Geer, E. J., Lin, H., Rusu, C. E., Poh, J., Palmese, A., Agnello, A., ... Varga, T. N.

citation count

  • 4

complete list of authors

  • Buckley-Geer, EJ||Lin, H||Rusu, CE||Poh, J||Palmese, A||Agnello, A||Christensen, L||Frieman, J||Shajib, AJ||Treu, T||Collett, T||Birrer, S||Anguita, T||Fassnacht, CD||Meylan, G||Mukherjee, S||Wong, KC||Aguena, M||Allam, S||Avila, S||Bertin, E||Bhargava, S||Brooks, D||Carnero Rosell, A||Carrasco Kind, M||Carretero, J||Castander, FJ||Costanzi, M||da Costa, LN||De Vicente, J||Desai, S||Diehl, HT||Doel, P||Eifler, TF||Everett, S||Flaugher, B||Fosalba, P||García-Bellido, J||Gaztanaga, E||Gruen, D||Gruendl, RA||Gschwend, J||Gutierrez, G||Hinton, SR||Honscheid, K||James, DJ||Kuehn, K||Kuropatkin, N||Maia, MAG||Marshall, JL||Melchior, P||Menanteau, F||Miquel, R||Ogando, RLC||Paz-Chinchón, F||Plazas, AA||Sanchez, E||Scarpine, V||Schubnell, M||Serrano, S||Sevilla-Noarbe, I||Smith, M||Soares-Santos, M||Suchyta, E||Swanson, MEC||Tarle, G||Tucker, DL||Varga, TN

publication date

  • August 2020