119401808
SPHERICAL STATISTICS FOR WIMP DIRECT DETECTION
16034831
Probing the width of the MACHO mass function
The simplest interpretation of the microlensing events observed towards the Large Magellanic Cloud is that approximately half of the mass of the Milky Way halo is in the form of MAssive Compact Halo Objects with $M \sim 0.5 M_{\odot}$. This poses severe problems for stellar MACHO candidates, and leads to the consideration of more exotic objects such as primordial black holes (PBHs). Constraining the MACHO mass function will shed light on their nature. Using the current data we find, for four halo models, the best fit delta-function, power law and PBH mass functions. The best fit PBH mass functions, despite having significant finite width, have likelihoods which are similar to, and for one particular halo model greater than, those of the best fit delta functions. We also find that if the correct halo model is known then $\sim$ 500 events will be sufficient to determine whether the MACHO mass function has significant width, and will also allow determination of the mass function parameters to $\sim 5%$.
55672557
WIMP physics with ensembles of direct-detection experiments
if dierent classes of experiments see consistent signals and infer the same WIMP properties. In this work, we review the ideas, methods, and status of direct-detection searches. We focus in particular on extracting WIMP physics (WIMP interactions and phase-space distribution) from direct-detection data in the early discovery days when multiple experiments see of order dozens to hundreds of events. To demonstrate the essential complementarity of dierent direct-detection experiments in this context, we create mock data intended to represent the data from the near-future Generation 2 experiments. We consider both conventional supersymmetry-inspired benchmark points (with spin-independent and -dependent elastic cross sections just below current limits), as well as benchmark points for other classes of models (inelastic and eective-operator paradigms). We also investigate the eect on parameter estimation of loosening or dropping the assumptions about the local WIMP phase-space distribution. We arrive at two main conclusions. Firstly, teasing out WIMP physics with experiments depends critically on having a wide set of detector target materials, spanning a large range of target nuclear masses and spin-dependent sensitivity. It is also highly desirable to obtain data from low-threshold experiments. Secondly, a general reconstruction of the local WIMP velocity distribution, which will only be achieved if there are multiple experiments using dierent target materials, is critical to obtaining a robust and unbiased estimate of the WIMP mass.
119021467
PRIMORDIAL BLACK HOLES AND EARLY COSMOLOGY
We describe the changes to the standard primordial black hole constraints on density perturbations if there are modifications to the standard cosmology between the time of formation and nucleosynthesis.
117989592
Extracting Information about WIMP Properties from Direct Detection Experiments: Astrophysical Uncertainties
WIMP direct detection experiments probe the ultra-local dark matter density and velocity distribution. We review how uncertainties in these quantities affect the accuracy with which the WIMP mass and cross-section can be constrained or determined.
8787684
Determining the WIMP mass from a single direct detection experiment
The energy spectrum of nuclear recoils in Weakly Interacting Massive Particle (WIMP) direct detection experiments depends on the underlying WIMP mass (strongly for light WIMPs, weakly for heavy WIMPs). We discuss how the accuracy with which the WIMP mass could be determined by a single direct detection experiment depends on the detector configuration and the WIMP properties. In particular we examine the effects of varying the underlying WIMP mass, the detector target nucleus, exposure, energy threshold and maximum energy, the local velocity distribution and the background event rate and spectrum.
119092259
Environs of Bilateral Supernova Remnants with Neutron Stars
We report on Australia Telescope Compact Array (ATCA) HI observations carried out in the direction of bilateral supernova remnants (SNRs) with associated neutron stars: G296.5+10.0 and G320.4--1.2, in a search for the origin of such morphology. From these studies we conclude that in the case of G296.5+10.0, located far from the Galactic plane, the HI distribution has not influenced the present morphology of the SNR. In the case of G320.4--1.2, evolving in a denser medium, the combined action of the central pulsar, PSR B1509-58, with the peculiar distribution of the surrounding medium, has determined the observed characteristics of the SNR.
7776074
H2O Maser Observations of Candidate Post-AGB Stars and Discovery of Three High-Velocity Water Sources
We present the results of 22 GHz H2O maser observations of a sample of 85 post-asymptotic giant branch (post-AGB) candidate stars, selected on the basis of their OH 1612 MHz maser and far-infrared properties. All sources were observed with the Tidbinbilla 70 m radio telescope, and 21 detections were made; 86 GHz SiO Mopra observations of a subset of the sample are also presented. Of the 21 H2O detections, 15 are from sources that are likely to be massive AGB stars and most of these show typical, regular H2O maser profiles. In contrast, nearly all the detections of more evolved stars exhibited high-velocity H2O maser emission. Of the five sources seen, v223 (W43A, IRAS 18450-0148) is a well-known "water-fountain" source that belongs to a small group of post-AGB stars with highly collimated, high-velocity H2O maser emission. A second source in our sample, v270 (IRAS 18596+0315), is also known to have high-velocity emission. We report the discovery of similar emission from a further three sources, d46 (IRAS 15445-5449), d62 (IRAS 15544-5332), and b292 (IRAS 18043-2116). The source d46 is an evolved post-AGB star with highly unusual maser properties. The H2O maser emission from d62 is probably associated with a massive star. The source b292 is a young post-AGB star that is highly likely to be a water-fountain source, with masers detected over a velocity range of 210 km s-1.
119374948
OH (1720 MHz) Maser Search toward the Large Magellanic Cloud
We have carried out a sensitive search for OH (1720 MHz) masers in the Large Magellanic Cloud (LMC) toward five regions using the Australia Telescope Compact Array. Our source list includes the 30 Doradus region and four supernova remnants (SNRs): N44, N49, N120, and N132D. These data have a typical resolution of ~8'' and rms noise levels of 5–10 mJy beam-1. We have detected OH (1720 MHz) masers in the northeast part of 30 Doradus and toward the SNR N49. The OH (1720 MHz) maser emission in 30 Doradus is coincident with a cluster of young stars known as "knot 1" and is almost certainly of the star formation variety. Our spectral resolution (0.68 km s-1) is insufficient to detect the Zeeman effect from the strongest (~320 mJy beam-1) of the 30 Doradus OH (1720 MHz) masers, leading to an upper limit to the field strength of 6 mG. The weak OH (1720 MHz) maser emission (35 mJy beam-1) detected toward the LMC SNR N49 is located just west of a previously identified CO cloud and is indicative of an interaction between the SNR and the molecular cloud. Although the statistics are low, the detection rate seems consistent with that seen for Galactic star-forming region and SNR type OH (1720 MHz) masers—both of which are low.
16871130
Observations of the neutral hydrogen surrounding the radio-quiet neutron star RX J0822-4300 in Puppis A
We have observed the H I distribution in an area 40 × 40 arcmin 2 around the neutron star candidate RX J0822-4300, which is located in the supernova remnant Puppis A. The observations of the λ21-cm line were obtained with the Australia Telescope Compact Array and were combined with single-dish data from the Southern Galactic Plane Survey. The spatial resolution is 90 arcsec, and the velocity resolution is 1 km s - 1 . A sensitivity of ∼0.7 K was achieved. The results revealed a double-lobed feature of reduced emission at +16 km s - 1 , centred on the central compact object (CCO), and aligned with an H I hole blueshifted by 13 km s - 1 . The H I depressions have probably been created by the sweeping up of ∼2 M O .. The alignment between the lobes and the optical expansion centre of Puppis A suggests that the CCO could be ejecting two opposite jets. The velocity at which the two lobes are best defined has allowed us to confirm that the distance to Puppis A is 2.2 kpc, based on a systemic velocity of +16 km s - 1 . The hydrogen column density computed using this systemic velocity is consistent with estimates from models for X-ray spectra, thus reinforcing our conclusion that the kinematic distance is 2.2 kpc.
17676935
ENHANCED SMALL-SCALE FARADAY ROTATION IN THE GALACTIC SPIRAL ARMS
We present an analysis of the rotation measures (RMs) of polarized extragalactic point sources in the Southern Galactic Plane Survey. This work demonstrates that the statistics of fluctuations in RM differ for the spiral arms and the interarm regions. Structure functions of RM are flat in the spiral arms, while they increase in the interarms. This indicates that there are no correlated RM fluctuations in the magnetoionized interstellar medium in the spiral arms on scales larger than ~05, corresponding to ~17 pc in the nearest spiral arm probed. The nonzero slopes in interarm regions imply a much larger scale of RM fluctuations. We conclude that fluctuations in the magnetoionic medium in the Milky Way spiral arms are not dominated by the mainly supernova-driven turbulent cascade in the global ISM but are probably due to a different source, most likely H II regions.