9431739
New calculation of the mass fraction of primordial black holes
We revisit the calculation of the abundance of primordial black holes (PBHs) formed from primordial density perturbations, using a formation criterion derived by Shibata and Sasaki which refers to a metric perturbation variable rather than the usual density contrast. We implement a derivation of the PBH abundance which uses peaks theory, and compare it to the standard calculation based on a Press-Schechter-like approach. We find that the two are in reasonable agreement if the Press-Schechter threshold is in the range Δth≃0.3 to 0.5, but advocate use of the peaks theory expression which is based on a sounder theoretical footing.
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.
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 $\sim 5%$.
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.
14984275
SNR G320.4–01.2 and PSR B1509–58: new radio observations of a complex interacting system
We describe radio continuum and spectral-line observations of the source G320.4–01.2 (MSH 15–52) and the coincident young pulsar B1509–58 made with the Australia Telescope Compact Array. Based on a comparison between X-ray and radio observations, we argue that the two main radio components of G320.4–01.2 are a single supernova remnant (SNR), which H I absorption indicates is at a distance of 5.2 ± 1.4 kpc. A high-resolution correspondence between radio and X-rays argues that the pulsar is interacting with the SNR via an opposed pair of collimated outflows. The outflow itself is seen as an elongated X-ray feature surrounded by a highly polarized radio sheath, while the interaction with the SNR manifests itself as a ring of radio/X-ray knots within the optical nebula RCW 89. We reject the hypothesis that the pulsar outflow powers the entire RCW 89 region. 
 
 
 
SNR G320.4–01.2 and PSR B1509–58 agree in distance and in rotation measure, and appear to be interacting. We thus conclude that the two objects are associated and have an age of 1700 yr. We propose that the SNR resulted from a high-energy or low-mass supernova that occurred near the edge of an elongated cavity. Such a model can account for the bilateral appearance of the SNR, its large apparent age, the significant offset of the pulsar from the centre of the SNR and the faintness of the pulsar-powered nebula at radio wavelengths.
17911645
Influence of the Neutron Star 1E 161348–5055 in RCW 103 on the Surrounding Medium
We have carried out a study of the neutral hydrogen in the direction of the X-ray source 1E 161348–5055, a compact central object (CCO) located in the interior of the supernova remnant (SNR) RCW 103. The H i 21 cm line observations were carried out using the Australia Telescope Compact Array, complemented with single dish data from the Parkes radio telescope to recover information at all spatial scales. We derive a distance to RCW 103 of 3.1 kpc, in agreement with previous distance measurements. We have also detected a small hole in the H i emission which is positionally and kinematically coincident with the location of the CCO which confirms the association between the SNR and the CCO. This is the third case of a depression in H i emission seemingly associated with CCOs in SNRs. The characteristic parameters of the holes such as their size, eccentricity and evacuated mass are similar in all three cases. We estimate the absorbing H I column density towards 1E 161348–5055 to be ∼6 × 10 21 cm –2 , a value compatible with a blackbody solution for the CCO X-ray emission. However, the implied temperature and luminosity are very high compared to most neutron stars. Moreover, the strong long-term variability in X-rays favours the hypothesis that 1E 161348–5055 is an accreting binary source rather than an isolated, cooling neutron star. An analysis of the continuum image obtained at 1.4 GHz from these observations shows no trace of a pulsar wind nebula around 1E 161348–5055, in spite of it being a young object.
119830513
Interacting supergiant shells in the Large Magellanic Cloud
We seek evidence for secondary star formation in the Large Magellanic Cloud (LMC) arising in gas compressed by the interactions between H supergiant shells (SGS) identified from the Australia Telescope Compact Array (ATCA) survey of Kim et al., using mid-infrared (MIR) images from the Midcourse Space Experiment (MSX), and radio continuum images from the Molonglo Observatory Synthesis Telescope (MOST). We identify a dense photodissociation region shaped like a bar that lies between the rims of LMC 4 and LMC 5 as a strong candidate for this process, and argue that it has produced the young associations LH 52 and 53 in the dense starfield of NGC 1948 within the past few Myr. No obvious stellar candidate matches the coincident 8.3-, 21.3-μm, and 843-MHz peaks in this bar, although this bright spot lies between two nebulous Ha patches. At least one other such H i-MIR bar exists in the LMC so that this mode of star formation is unlikely to have been a unique occurrence. We have found a correlation between 8.3-μm radiance and H I column density for the LMC in general that can be predicted from the Schmidt law for spiral galaxies.
15118609
High-resolution Observations of OH(1720 MHz) Masers Toward the Galactic Center
High-resolution VLA observations of 1720 MHz OH maser emission from Sagittarius A East and the circumnuclear disk with spatial and spectral resolutions of ≈25×13 and 0.27 km s-1 are reported. This follow-up observational study focuses on the recent discovery of a number of such OH maser features and their intense, circularly polarized maser lines detected toward these Galactic center sources. The 1720 MHz maser line of OH arises from collisionally excited gas behind a C-type shock and is an important diagnostic of the interaction process that may occur between molecular clouds and associated X-ray-emitting shell-type supernova remnants. The present observations have confirmed that the observed Stokes V signal is due to Zeeman splitting, and the OH masers are angularly broadened by the scattering medium toward the Galactic center. The scale length of the magnetic field fluctuations in the scattering medium toward the Galactic center is estimated to be greater than 0.1-0.2 pc using the correlation of the position angles of the scatter-broadened maser spots. In addition, the kinematics of the maser spots associated with Sgr A East are used to place a 5 pc displacement between this extended radio structure and the Galactic center.
9215987
High-resolution H i and radio continuum observations of the SNR G290.1−0.8
We have observed the supernova remnant (SNR) G290.1−0.8 in the 21-cm H I line and the 20-cm radio continuum using the Australia Telescope Compact Array (ATCA). The H I data were combined with data from the Southern Galactic Plane Survey to recover the shortest spatial frequencies. In contrast, H I absorption was analysed by filtering extended H I emission, with spatial frequencies shorter than 1.1 kλ. The low-resolution ATCA radio continuum image of the remnant shows considerable internal structure, resembling a network of filaments across its 13-arcmin diameter. A high-resolution ATCA radio continuum image was also constructed to study the small-scale structure in the SNR. It shows that there are no structures smaller than ∼17 arcsec, except perhaps for a bright knot to the south, which is probably an unrelated object. The H I absorption study shows that the gas distribution and kinematics in front of SNR G290.1−0.8 are complex. We estimate that the SNR probably lies in the Carina arm, at a distance 7 (±1) kpc. In addition, we have studied nearby sources in the observed field using archival multiwavelength data to determine their characteristics.