The large-scale Structure and dynamics of the local universe

This thesis investigates the dynamics of the local Universe with particular reference to discovering the source of the Local Group (LG) motion. A redshift survey of the Great Attractor (GA) region, thought responsible for a significant fraction of the LG motion, is presented. Over 3053 galaxies, located in both clusters and filaments, were targeted using the 2dF on the AAT. Velocity distributions and mass estimates for nine clusters are reported. Together with redshifts from the literature, this survey reveals the dominant feature in the core of the GA to be a large filament extending from Abell S0639 (l= 281º, b=+11º) towards a point at I ~ 5º b ~ -50º , encompassing the Cen-Crux, CIZA J1324.7-5736, Norma and Pavo II clusters. A new model of the local velocity field out to ՅՕՕh(^-1) Мрc is derived from the combined REFLEX, BCS and CIZA surveys: the RBC catalogue. This is the first all-sky, X-ray selected galaxy cluster sample. The reconstruction includes an intrinsic correction for the bias of clusters in tracing the total density field. The velocity fields from both this reconstruction and that of the PSCz survey are compared to the observed peculiar velocities of 98 local type la supernovae (SNIa). The best fits are respectively found for values of βRBC(= Ω(^0.6)m /(^b)RBC) = 0.39±0.20 and βι = 0.55±0.06. These results are found to be robust to culls of the SNIa sample by distance, host-galaxy extinction and the reference frame in which the comparison is carried out. As the PSCz preferentially samples late-type galaxies, the derived density field under- Samples the contributions from regions of greatest over density, precisely the regions traced by the RBC survey. When combined in the ratio 78% PSCz, 22% RBC these two complimentary reconstructions are a better fit to the ресuliar velocities of the same SNIa sample than either one alone. Compared to galaxy surveys, which only see contributions to the LG motion from structures within -60h(^-1) Мрc, previous cluster surveys have argued that sources at much greater distances (~150h(^-1) Mpc) influence local dynamics. However, the RBC reconstruction presented here shows similar contributions from the same depths as the PSCz, which is partly attributed to the intrinsic bias correction and inclusion of the Virgo cluster in the RBC. The extended GA region, defined as the volume enclosed by 250 < / <350º, 一45 < ь < 45º and 2000 <cz< 6000 km s (^-1) is found to be responsible for 65% of the LG motion, whilst the more distant (~ 145h(^-1) Mpc) SSC only accounts for 12%

X-ray emission from the Sombrero galaxy: discrete sources

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200 ks. With a detection limit of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30 kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray binaries (LMXBs). We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-low indices (~1.1 for the GC-LF and ~1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC LF at fainter luminosities down to 1E35 erg/s. The derived index rules out a faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum