Browsing by Author "Kuijken, Konrad"

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    ACT-DR5 Sunyaev-Zel'dovich clusters: Weak lensing mass calibration with KiDS
    (2024) Robertson, Naomi Clare; Sifon, Cristobal; Asgari, Marika; Battaglia, Nicholas; Bilicki, Maciej; Richard Bond, John; Devlin, Mark J.; Dunkley, Jo; Giblin, Benjamin; Heymans, Catherine; Hildebrandt, Hendrik; Hilton, Matt; Hoekstra, Henk; Hughes, John P.; Kuijken, Konrad; Louis, Thibaut; Mallaby-Kay, Maya; Page, Lyman; Partridge, Bruce; Radovich, Mario; Schneider, Peter; Shan, Huanyuan; Spergel, David N.; Troster, Tilman; Wollack, Edward J.; Vargas, Cristian; Wright, Angus H.
    We present Weak Gravitational Lensing measurements of a sample of 157 clusters within the Kilo Degree Survey (KiDS), detected with a > 5 sigma thermal Sunyaev-Zel'dovich (SZ) signal by the Atacama Cosmology Telescope (ACT). Using a halo-model approach, we constrained the average total cluster mass, M-WL, accounting for the ACT cluster selection function of the full sample. We find that the SZ cluster mass estimate M-SZ, which was calibrated using X-ray observations, is biased with M-SZ/M-WL = (1 - b(SZ)) = 0.65 +/- 0.05. Separating the sample into six mass bins, we find no evidence of a strong mass dependency for the mass bias, (1 - b(SZ)). Adopting this ACT-KiDS SZ mass calibration would bring the Planck SZ cluster count into agreement with the counts expected from the Planck cosmic microwave background Lambda CDM cosmological model, although it should be noted that the cluster sample considered in this work has a lower average mass M-SZ,M- uncor = 3.64 x 10(14) M-circle dot compared to the Planck cluster sample which has an average mass in the range M-SZ,M- uncor = (5.5 - 8.5)x10(14) M-circle dot, depending on the sub-sample used.
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    HST proper motions on the far side of the Galactic bar-data
    (2023) Soto, Mario; Kuijken, Konrad; Rich, R. Michael; Clarkson, William, I; Castellon, Jose Luis Nilo; Fernandez-Trincado, Jose G.; Ramos, Rodrigo Contreras; Kunder, Andrea; Baravalle, Laura D.; Alonso, M. Victoria; Simion, Iulia T.; Johnson, Christian, I; Vieira, Katherine
    This is the third paper in a series that attempts to observe a clear signature of the Galactic bar/bulge using kinematic observations of the bulge stellar populations in low foreground extinction windows. We report on the detection of & SIM;100 000 new proper motions in four fields covering the far side of the Galactic bar/bulge, at negative longitudes. Our proper motions have been obtained using observations from the Advance Camera for Surveys (ACS), on board of the Hubble Space Telescope (HST), with a time-baseline of 8-9 years, which has produced accuracies better than 0.5 mas yr(-1) for a significant fraction of the stellar populations with F814W < 23 mag. Interestingly, as shown in previous works, the Hess diagrams show a strikingly similar proper motion distribution to fields closer to the Galactic center and consistent with an old stellar population. The observed kinematics point to a significant bulge rotation, which seems to predominate even in fields as far as l & SIME; -8 & DEG;, and is also reflected in the changes of the velocity ellipsoid in the l, b plane as a function of distance.