The relationship between acculturative stress and Korean immigrants’ travel experiences

TTRA 2017 Graduate Student Research Colloquium: The relationship between acculturative stress and Korean immigrants’ travel experiences Abstract The purpose of this exploratory study is to examine how acculturative stress affects onsite leisure travel experience of first-generation Korean immigrants. This study contributes to the literature by advancing the study of leisure constraints by providing proof-of-concept of the stress-coping model in travel experiences and immigrants’ responses in coping with acculturative stress during travel periods.By exploring what factors influence immigrant travelers’ appraisal process, empirically verifying that the acculturative stress does create stress for the immigrants, and learning preferred coping strategies and responses, tourism managers, planners and marketers will be better able to make informed decisions to mitigate stress among immigrant travelers

Galaxy alignments: Observations and impact on cosmology

Galaxy shapes are not randomly oriented, rather they are statistically aligned in a way that can depend on formation environment, history and galaxy type. Studying the alignment of galaxies can therefore deliver important information about the physics of galaxy formation and evolution as well as the growth of structure in the Universe. In this review paper we summarise key measurements of galaxy alignments, divided by galaxy type, scale and environment. We also cover the statistics and formalism necessary to understand the observations in the literature. With the emergence of weak gravitational lensing as a precision probe of cosmology, galaxy alignments have taken on an added importance because they can mimic cosmic shear, the effect of gravitational lensing by large-scale structure on observed galaxy shapes. This makes galaxy alignments, commonly referred to as intrinsic alignments, an important systematic effect in weak lensing studies. We quantify the impact of intrinsic alignments on cosmic shear surveys and finish by reviewing practical mitigation techniques which attempt to remove contamination by intrinsic alignments.Comment: 52 pages excl. references, 16 figures; minor changes to match version published in Space Science Reviews; part of a topical volume on galaxy alignments, with companion papers arXiv:1504.05456 and arXiv:1504.0554

CFHTLenS: A Weak Lensing Shear Analysis of the 3D-Matched-Filter Galaxy Clusters

We present the cluster mass-richness scaling relation calibrated by a weak lensing analysis of >18000 galaxy cluster candidates in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Detected using the 3D-Matched-Filter cluster-finder of Milkeraitis et al., these cluster candidates span a wide range of masses, from the small group scale up to $\sim10^{15} M_{\odot}$, and redshifts 0.2 $\lesssim z\lesssim$ 0.9. The total significance of the stacked shear measurement amounts to 54$\sigma$. We compare cluster masses determined using weak lensing shear and magnification, finding the measurements in individual richness bins to yield 1$\sigma$ compatibility, but with magnification estimates biased low. This first direct mass comparison yields important insights for improving the systematics handling of future lensing magnification work. In addition, we confirm analyses that suggest cluster miscentring has an important effect on the observed 3D-MF halo profiles, and we quantify this by fitting for projected cluster centroid offsets, which are typically $\sim$ 0.4 arcmin. We bin the cluster candidates as a function of redshift, finding similar cluster masses and richness across the full range up to $z \sim$ 0.9. We measure the 3D-MF mass-richness scaling relation $M_{200} = M_0 (N_{200} / 20)^\beta$. We find a normalization $M_0 \sim (2.7^{+0.5}_{-0.4}) \times 10^{13} M_{\odot}$, and a logarithmic slope of $\beta \sim 1.4 \pm 0.1$, both of which are in 1$\sigma$ agreement with results from the magnification analysis. We find no evidence for a redshift-dependence of the normalization. The CFHTLenS 3D-MF cluster catalogue is now available at cfhtlens.org.Comment: 3D-MF cluster catalog is NOW AVAILABLE at cfhtlens.org. Magnification-shear mass comparison in Figure 10. 19 pages, 10 figures. Accepted to MNRA

Optical Absorption of CuO3_3 antiferromagnetic chains at finite temperatures

We use a high-statistic quantum Monte Carlo and Maximum Entropy regularization method to compute the dynamical energy correlation function (DECF) of the one-dimensional (1D) $S=1/2$ antiferromagnetic Heisenberg model at finite temperatures. We also present a finite temperature analytical ansatz for the DECF which is in very good agreement with the numerical data in all the considered temperature range. From these results, and from a finite temperature generalisation of the mechanism proposed by Lorenzana and Sawatsky [Phys. Rev. Lett. {\bf 74}, 1867 (1995)], we compute the line shape for the optical absorption spectra of multimagnon excitations assisted by phonons for quasi 1D compounds. The line shape has two contributions analogous to the Stokes and anti-Stokes process of Raman scattering. Our low temperature data is in good agreement with optical absorption experiments of CuO$_3$ chains in Sr$_2$CuO$_3$. Our finite temperature results provide a non trivial prediction on the dynamics of the Heisenberg model at finite temperatures that is easy to verify experimentally.Comment: 7 pages, 5 figure

Consistent cosmic shear in the face of systematics: a B-mode analysis of KiDS-450, DES-SV and CFHTLenS

We analyse three public cosmic shear surveys; the Kilo-Degree Survey (KiDS-450), the Dark Energy Survey (DES-SV) and the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Adopting the “COSEBIs” statistic to cleanly and completely separate the lensing E-modes from the non-lensing B-modes, we detect B-modes in KiDS-450 and CFHTLenS at the level of ∼2.7σ. For DES-SV we detect B-modes at the level of 2.8σ in a non-tomographic analysis, increasing to a 5.5σB-mode detection in a tomographic analysis. In order to understand the origin of these detected B-modes we measure the B-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modelling errors, camera-based additive shear bias and photometric redshift selection bias. We show that any correlation between photometric-noise and the relative orientation of the galaxy to the point-spread-function leads to an ellipticity selection bias in tomographic analyses. This work therefore introduces a new systematic for future lensing surveys to consider. We find that the B-modes in DES-SV appear similar to a superposition of the B-mode signatures from all of the systematics simulated. The KiDS-450 and CFHTLenS B-mode measurements show features that are consistent with a repeating additive shear bias

KiDS+VIKING-450 and DES-Y1 combined::Mitigating baryon feedback uncertainty with COSEBIs

We present cosmological constraints from a joint cosmic shear analysis of the Kilo-Degree Survey (KV450) and the Dark Energy Survey (DES-Y1), conducted using Complete Orthogonal Sets of E/B-Integrals (COSEBIs). With COSEBIs we isolate any B-modes which have a non-cosmic shear origin and demonstrate the robustness of our cosmological E-mode analysis as no significant B-modes are detected. We highlight how COSEBIs are fairly insensitive to the amplitude of the non-linear matter power spectrum at high $k$-scales, mitigating the uncertain impact of baryon feedback in our analysis. COSEBIs, therefore, allow us to utilise additional small-scale information, improving the DES-Y1 joint constraints on $S_8=\sigma_8(\Omega_{\rm m}/0.3)^{0.5}$ and $\Omega_{\rm m}$ by $20\%$. Adopting a flat $\Lambda$CDM model we find $S_8=0.755^{+0.019}_{-0.021}$, which is in $3.2\sigma$ tension with the Planck Legacy analysis of the cosmic microwave background.Comment: Accepted for publication in A&A. 15 pages, 7 figure

RCSLenS: testing gravitational physics through the cross-correlation of weak lensing and large-scale structure

The unknown nature of ‘dark energy’ motivates continued cosmological tests of large-scale gravitational physics. We present a new consistency check based on the relative amplitude of non-relativistic galaxy peculiar motions, measured via redshift-space distortion, and the relativistic deflection of light by those same galaxies traced by galaxy–galaxy lensing. We take advantage of the latest generation of deep, overlapping imaging and spectroscopic data sets, combining the Red Cluster Sequence Lensing Survey, the Canada–France–Hawaii Telescope Lensing Survey, the WiggleZ Dark Energy Survey and the Baryon Oscillation Spectroscopic Survey. We quantify the results using the ‘gravitational slip’ statistic EG, which we estimate as 0.48 ± 0.10 at z = 0.32 and 0.30 ± 0.07 at z = 0.57, the latter constituting the highest redshift at which this quantity has been determined. These measurements are consistent with the predictions of General Relativity, for a perturbed Friedmann–Robertson–Walker metric in a Universe dominated by a cosmological constant, which are EG = 0.41 and 0.36 at these respective redshifts. The combination of redshift-space distortion and gravitational lensing data from current and future galaxy surveys will offer increasingly stringent tests of fundamental cosmology

CFHTLenS: a weak lensing shear analysis of the 3D-Matched-Filter galaxy clusters

We present the cluster mass-richness scaling relation calibrated by a weak lensing analysis of ≳ 18000 galaxy cluster candidates in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Detected using the 3D-Matched-Filter (MF) cluster-finder of Milkeraitis etal., these cluster candidates span a wide range of masses, from the small group scale up to∼1015 M⊙, and redshifts 0.2≲z≲0.9. The total significance of the stacked shear measurement amounts to 54σ. We compare cluster masses determined using weak lensing shear and magnification, finding the measurements in individual richness bins to yield 1σ compatibility, but with magnification estimates biased low. This first direct mass comparison yields important insights for improving the systematics handling of future lensing magnification work. In addition, we confirm analyses that suggest cluster miscentring has an important effect on the observed 3D-MF halo profiles, and we quantify this by fitting for projected cluster centroid offsets, which are typically∼0.4arcmin. We bin the cluster candidates as a function of redshift, finding similar cluster masses and richness across the full range up to z∼0.9. We measure the 3D-MF mass-richness scaling relation M200=M0(N200/20)β. We find a normalization $M_0 \sim (2.7^{+0.5}_{-0.4}) \times 10^{13} \,\mathrm{M}_{{\odot }}$, and a logarithmic slope of β∼1.4±0.1, both of which are in 1σ agreement with results from the magnification analysis. We find no evidence for a redshift dependence of the normalization. The CFHTLenS 3D-MF cluster catalogue is now available at cfhtlens.or

Chalcopyrite ZnSnSb_2: A Promising Thermoelectric Material

Ternary compounds with a tetragonal chalcopyrite structure, such as CuGaTe2, are promising thermoelectric (TE) materials. It has been demonstrated in various chalcopyrite systems, including compounds with quaternary chalcopyrite-like structures, that the lattice parameter ratio, c/a, being exactly 2.00 to have a pseudo-cubic structure is key to increase the degeneracy at the valence band edge and ultimately achieve high TE performance. Considering the fact that ZnSnSb_2 with a chalcopyrite structure is reported to have c/a close to 2.00, it is expected to have multiple valence bands leading to a high p-type zT. However, there are no complete investigations on the high temperature TE properties of ZnSnSb_2 mainly because of the difficulty of obtaining a single-phase ZnSnSb_2. In the present study, pure ZnSnSb_2 samples with no impurities are synthesized successfully using a Sn flux-based method and TE properties are characterized up to 585 K. Transport properties and thermal analysis indicate that the structure of ZnSnSb_2 remains chalcopyrite with no order–disorder transition and clearly show that ZnSnSb_2 can be made to exhibit a high zT in the low-to-mid temperature range through further optimization