2841328
Model independent determination of the dark matter mass from direct detection experiments.
Determining the dark matter (DM) mass is of paramount importance for understanding dark matter. We present a novel parametrization of the DM speed distribution which will allow the DM mass to be accurately measured using data from weakly interacting massive particle (WIMP) direct detection experiments. Specifically, we parametrize the natural logarithm of the speed distribution as a polynomial in the speed v. We demonstrate, using mock data from upcoming experiments, that by fitting the WIMP mass and interaction cross section, along with the polynomial coefficients, we can accurately reconstruct both the WIMP mass and speed distribution. This new method is the first demonstration that an accurate, unbiased reconstruction of the WIMP mass is possible without prior assumptions about the distribution function. We anticipate that this technique will be invaluable in the analysis of future experimental data.
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.
119363323
Effect of halo modelling on WIMP exclusion limits
WIMP direct detection experiments are just reaching the sensitivity required to detect galactic dark matter in the form of neutralinos. Data from these experiments are usually analysed under the simplifying assumption that the Milky Way halo is an isothermal sphere with maxwellian velocity distribution. Observations and numerical simulations indicate that galaxy halos are in fact triaxial and anisotropic. Furthermore, in the cold dark matter paradigm galactic halos form via the merger of smaller subhalos, and at least some residual substructure survives. We examine the effect of halo modelling on WIMP exclusion limits, taking into account the detector response. Triaxial and anisotropic halo models, with parameters motivated by observations and numerical simulations, lead to significant changes which are different for different experiments, while if the local WIMP distribution is dominated by small scale clumps then the exclusion limits are changed dramatically.
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.
16776986
The Southern Galactic Plane Survey: the test region
The Southern Galactic Plane Survey (SGPS) is a project to image the H I line emission and 1.4 GHz continuum in the fourth quadrant of the Milky Way at high resolution using the Australia Telescope Compact Array and the Parkes Radio Telescope. This paper describes the survey details and goals, presents 21 cm continuum data, and discusses H I absorption and emission characteristics of the SGPS test region (325.5d<=l<=333.5d -0.5d<=b<=+3.5d). We explore the effects of massive stars on the interstellar medium through a study of H I shells and the H I environments of H II regions and supernova remnants (SNRs). We find an H I shell surrounding the H II region RCW 94, which indicates that the region is embedded in a molecular cloud. We give lower limits for the kinematic distances to SNRs G327.4+0.4 and G330.2+1.0 of 4.3 and 4.9 kpc, respectively. We find evidence of interaction with the surrounding H I for both of these remnants. We also present images of a possible new SNR G328.6-0.0. Additionally, we have discovered two small H I shells with no counterparts in continuum emission.
118680225
Ultra- and hyper-compact H ii regions at 20 GHz
We present radio and infrared observations of 4 hyper-compact HII regions and 4 ultracompact HII regions in the southern Galactic plane. These objects were selected from a blind survey for UCHII regions using data from two new radio surveys of the southern sky; the Australia Telescope 20 GHz survey (AT20G) and the 2nd epoch Molonglo Galactic Plane Survey (MGPS-2) at 843 MHz. To our knowledge, this is the first blind r adio survey for hyper- and ultra-compact HII regions. We have followed up these sources with the Australia Telescope Compact Array to obtain H70� recombination line measurements, higher resolution images at 20 GHz and flux density measurements at 30, 40 and 95 GHz. From this we have determined sizes and recombination line temperatures as well as modeling the spectral energy distributions to determine emission measures. We have classified the sources as hyper-compact or ultra-compact on the basis of their physical parameters, in comparison with benchmark parameters from the literature. Several of these bright, compact sources are potential cali brators for the Low Frequency Instrument (30 70 GHz) and the 100-GHz channel of the High Frequency Instrument of the Planck satellite mission. They may also be useful as calibrators for the Australia Telescope Compact Array, which lacks good non-variable primary flux ca librators at higher frequencies and in the Galactic plane region. Our spectral energy distri butions allow the flux densities within the Planck bands to be determined, although our high frequency observations show that several sources have excess emission at 95 GHz (3 mm) that can not be explained by current models.
15932808
High-resolution radio polarimetry of Vela X
We present high-resolution 1.4 GHz Australia Telescope Compact Array polarimetric observations of Vela X, the pulsar wind nebula of the Vela SNR. We find that the linearly polarized emission is only partially correlated with total intensity. There are many depolarization features, some of which are coincident with foreground H-alpha filaments. Further study of these should provide measurements of the magnetic field in the remnant's shell.
18300265
Distant Extended Spiral Arm in the Fourth Quadrant of the Milky
Using data from the Southern Galactic Plane Survey we present a possible distant spiral arm in the fourth quadrant of the Milky Way. The very distinct and cohesive feature can be traced for over 70 • as the most extreme positive velocity feature in the longitude-velocity diagram. The feature is at a Galactic radius between 18 and 24 kpc and appears to be the last major structure before the end of the H i disk. We compare the feature with a Galactic spiral model and show that it is well reproduced by a spiral arm of pitch angle, i ∼ 9 •. The arm is quite well confined to the Galactic plane, dropping at most 1 kpc below the Galactic equator. Over most of its length the arm is 1-2 kpc thick.
15340760
Multiwavelength observations of the supernova remnant G349.7+0.2 interacting with a molecular cloud
We present molecular-line observations at millimetre, centimetre and infrared wavelengths of the region containing OH(1720 MHz) masers in the supernova remnant (SNR) G349.7+0.2, using the Australia Telescope (AT) Mopra antenna, the Swedish-ESO Submillimeter Telescope, the AT Compact Array and the UNSW Infrared Fabry-Perot narrow-band filter installed on the Anglo Australian Telescope. Several molecular transitions were observed between 1.6 and 3 mm to constrain the physical parameters of the molecular cloud interacting with the SNR and to investigate the effects of the SNR shock on the gas chemistry. We detected shockexcited near-infrared H2 emission towards the centre of the SNR, revealing highly clumped molecular gas and a good correlation with published mid-infrared images from the Spitzer Space Telescope. An excellent correlation between the H2 clumps and OH(1720 MHz) maser positions supports the shock excitation of the OH(1720 MHz) maser emission. Furthermore, we detected OH absorption at 1665 and 1667 MHz which shows a good correlation with the shocked H2 emission and the masers. We found maser emission at 1665 MHz near the OH(1720 MHz) masers in this SNR, which is found to be associated with a GLIMPSE source SSTGLMC G349.7294+00.1747. We also detected 1665 and 1667 MHz OH masers, and weak 4.8 GHz H2CO absorption towards the ultra-compact H II region IRAS 17147‐3725 located to the southeast of the SNR. We found no 4.7- or 6-GHz excited-state OH masers or 6-GHz CH3OH maser towards either the SNR or the H II region.