Examinando por Autor "Tudorica, A."
Mostrando 1 - 2 de 2
Resultados por página
Opciones de ordenación
Ítem Galaxy Merger Candidates in High-redshift Cluster Environments(Institute of Physics Publishing, 2017-07) Delahaye, A.G.; Webb, T.M.A.; Nantais, J.; Degroot, A.; Wilson, G.; Muzzin, A.; Yee, H.K.C.; Foltz, R.; Noble, A.G.; Demarco, R.; Tudorica, A.; Cooper, M.C.; Lidman, C.; Perlmutter, S.; Hayden, B.; Boone, K.; Surace, J.We compile a sample of spectroscopically and photometrically selected cluster galaxies from four high-redshift galaxy clusters (1.59 < z < 1.71) from the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS), and a comparison field sample selected from the UKIDSS Deep Survey. Using near-infrared imaging from the Hubble Space Telescope, we classify potential mergers involving massive (M∗ ≥ 3 × 1010M⊙) cluster members by eye, based on morphological properties such as tidal distortions, double nuclei, and projected near neighbors within 20 kpc. With a catalog of 23 spectroscopic and 32 photometric massive cluster members across the four clusters and 65 spectroscopic and 26 photometric comparable field galaxies, we find that after taking into account contamination from interlopers, 11+7.0-5.6% of the cluster members are involved in potential mergers, compared to 24.7+5.3-4.6% of the field galaxies. We see no evidence of merger enhancement in the central cluster environment with respect to the field, suggesting that galaxy-galaxy merging is not a stronger source of galaxy evolution in cluster environments compared to the field at these redshifts.Ítem Weak lensing magnification of SpARCS galaxy clusters(EDP Sciences, 2017) Tudorica, A.; Hildebrandt, H.; Tewes, M.; Hoekstra, H.; Morrison, C.B.; Muzzin, A.; Wilson, G.; Yee, H.K.C.; Lidman, C.; Hicks, A.; Nantais, J.; Erben, T.; Van Der Burg, R.F.J.; Demarco, R.Context. Measuring and calibrating relations between cluster observables is critical for resource-limited studies. The mass-richness relation of clusters offers an observationally inexpensive way of estimating masses. Its calibration is essential for cluster and cosmological studies, especially for high-redshift clusters. Weak gravitational lensing magnification is a promising and complementary method to shear studies, that can be applied at higher redshifts. Aims. We aim to employ the weak lensing magnification method to calibrate the mass-richness relation up to a redshift of 1.4. We used the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) galaxy cluster candidates (0.2 < z < 1.4) and optical data from the Canada France Hawaii Telescope (CFHT) to test whether magnification can be effectively used to constrain the mass of high-redshift clusters. Methods. Lyman-break galaxies (LBGs) selected using the u-band dropout technique and their colours were used as a background sample of sources. LBG positions were cross-correlated with the centres of the sample of SpARCS clusters to estimate the magnification signal, which was optimally-weighted using an externally-calibrated LBG luminosity function. The signal was measured for cluster sub-samples, binned in both redshift and richness. Results. We measured the cross-correlation between the positions of galaxy cluster candidates and LBGs and detected a weak lensing magnification signal for all bins at a detection significance of 2.6-5.5σ. In particular, the significance of the measurement for clusters with z> 1.0 is 4.1σ; for the entire cluster sample we obtained an average M200 of 1.28 -0.21 +0.23 × 1014 M⊙. Conclusions. Our measurements demonstrated the feasibility of using weak lensing magnification as a viable tool for determining the average halo masses for samples of high redshift galaxy clusters. The results also established the success of using galaxy over-densities to select massive clusters at z > 1. Additional studies are necessary for further modelling of the various systematic effects we discussed.