Table of contents

The CORNISH project is the highest resolution radio continuum survey of the Galactic plane to date. It is the 5 GHz radio continuum part of a series of multi-wavelength surveys that focus on the northern GLIMPSE region (10° < l < 65°), observed by the Spitzer satellite in the mid-infrared. Observations with the Very Large Array in B and BnA configurations have yielded a 15 resolution Stokes I map with a root mean square noise level better than 0.4 mJy beam⁻¹. Here we describe the data-processing methods and data characteristics, and present a new, uniform catalog of compact radio emission. This includes an implementation of automatic deconvolution that provides much more reliable imaging than standard CLEANing. A rigorous investigation of the noise characteristics and reliability of source detection has been carried out. We show that the survey is optimized to detect emission on size scales up to 14'' and for unresolved sources the catalog is more than 90% complete at a flux density of 3.9 mJy. We have detected 3062 sources above a 7σ detection limit and present their ensemble properties. The catalog is highly reliable away from regions containing poorly sampled extended emission, which comprise less than 2% of the survey area. Imaging problems have been mitigated by down-weighting the shortest spacings and potential artifacts flagged via a rigorous manual inspection with reference to the Spitzer infrared data. We present images of the most common source types found: H ii regions, planetary nebulae, and radio galaxies. The CORNISH data and catalog are available online at http://cornish.leeds.ac.uk.

We present a new series of supernova neutrino light curves and spectra calculated by numerical simulations for a variety of progenitor stellar masses (13–50 M_☉) and metallicities (Z = 0.02 and 0.004), which would be useful for a broad range of supernova neutrino studies, e.g., simulations of future neutrino burst detection by underground detectors or theoretical predictions for the relic supernova neutrino background. To follow the evolution from the onset of collapse to 20 s after the core bounce, we combine the results of neutrino-radiation hydrodynamic simulations for the early phase and quasi-static evolutionary calculations of neutrino diffusion for the late phase, with different values of shock revival time as a parameter that should depend on the still unknown explosion mechanism. We describe the calculation methods and basic results, including the dependence on progenitor models and the shock revival time. The neutrino data are publicly available electronically.

A Newtonian model of non-conductive, charged, perfect fluid tori orbiting in combined spherical gravitational and dipolar magnetic fields is presented and stationary, axisymmetric toroidal structures are analyzed. Matter in such tori exhibits a purely circulatory motion and the resulting convection carries charges into permanent rotation around the symmetry axis. As a main result, we demonstrate the possible existence of off-equatorial charged tori and equatorial tori with cusps that also enable outflows of matter from the torus in the Newtonian regime. These phenomena qualitatively represent a new consequence of the interplay between gravity and electromagnetism. From an astrophysical point of view, our investigation can provide insight into processes that determine the vertical structure of dusty tori surrounding accretion disks.

We investigate the signal-to-noise ratio (S/N) of a new incoherent dedispersion algorithm optimized for FPGA-based architectures intended for deployment on the Australian SKA Pathfinder and other Square Kilometre Array precursors for fast transients surveys. Unlike conventional CPU- and GPU-optimized incoherent dedispersion algorithms, this algorithm has the freedom to maximize the S/N by way of programmable dispersion profiles that enable the inclusion of different numbers of time samples per spectral channel. This allows, for example, more samples to be summed at lower frequencies where intra-channel dispersion smearing is larger, or it could even be used to optimize the dedispersion sum for steep spectrum sources. Our analysis takes into account the intrinsic pulse width, scatter broadening, spectral index and dispersion measure of the signal, and the system's frequency range, spectral and temporal resolution, and number of trial dedispersions. We show that the system achieves better than 80% of the optimal S/N where the temporal resolution and the intra-channel smearing time are smaller than a quarter of the average width of the pulse across the system's frequency band (after including scatter smearing). Coarse temporal resolutions suffer a Δt^−1/2 decay in S/N, and coarse spectral resolutions cause a Δν^−1/2 decay in S/N, where Δt and Δν are the temporal and spectral resolutions of the system, respectively. We show how the system's S/N compares with that of matched filter and boxcar filter detectors. We further present a new algorithm for selecting trial dispersion measures for a survey that maintains a given minimum S/N performance across a range of dispersion measures.

We develop a new method for identifying young stellar objects (YSOs) from star-forming regions using the photometry data from Spitzer's c2d Legacy Project. The aim is to obtain YSO lists as complete as possible for studying statistical properties such as the star formation rate (SFR) and lifetimes of YSOs in different evolutionary stages. The largest obstacle in identifying YSOs comes from background galaxies with similar spectral energy distributions to YSOs. Traditionally, selected color–color and color–magnitude criteria are used to separate YSOs and galaxies. However, since there is no obvious boundary between YSOs and galaxies in color–color diagrams and color–magnitude diagrams (CMDs), those criteria may exclude faint YSOs near the boundary. In this paper, we separate the YSOs and galaxies in a multi-dimensional (multi-D) magnitude space, which is equivalent to using all variations of CMDs simultaneously. Comparing sources from molecular clouds to Spitzer's SWIRE data, which have a negligible amount of YSOs, we can naturally identify YSO candidates (YSOc) located outside of the galaxy-populated regions in the multi-D space. In the five c2d surveyed clouds, we select 322 new YSOc and miss/exclude 33 YSOc compared to Evans et al., and this results in 1313 YSOc in total. As a result, SFR increases 28% correspondingly, but the lifetimes of YSOs in different evolutionary stages remain unchanged. Compared to theories by Krumholz & McKee, our derived SFR suggests that star formation at a large scale is dominated by supersonic turbulence rather than magnetic fields. Furthermore, we identify seven new very low luminosity objects.

We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and 3 brown dwarfs with extremely red near-infrared colors that exhibit characteristics of both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7 ± 1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and 4 photometrically selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color–color and color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared spectra of the new discoveries are presented along with spectral classifications. To accommodate later T dwarfs we have modified the integrated flux method of determining spectral indices to instead use the median flux. Furthermore, a newly defined J-narrow index differentiates the early-type Y dwarfs from late-type T dwarfs based on the J-band continuum slope. The K/J indices for this expanded sample show that 32% of late-type T dwarfs have suppressed K-band flux and are blue relative to the spectral standards, while only 11% are redder than the standards. Comparison of the Y/J and K/J index to models suggests diverse atmospheric conditions and supports the possible re-emergence of clouds after the L/T transition. We also discuss peculiar brown dwarfs and candidates that were found not to be substellar, including two young stellar objects and two active galactic nuclei. The substantial increase in the number of known late-type T dwarfs provides a population that will be used to test models of cold atmospheres and star formation. The coolest WISE-discovered brown dwarfs are the closest of their type and will remain the only sample of their kind for many years to come.

We have investigated the role of the equation of state in resistive relativistic magnetohydrodynamics using a newly developed resistive relativistic magnetohydrodynamic code. A number of numerical tests in one dimension and multi-dimensions are carried out in order to check the robustness and accuracy of the new code. The code passes all the tests in situations involving both small and large uniform conductivities. Equations of state that closely approximate the single-component perfect relativistic gas are introduced. Results from selected numerical tests using different equations of state are compared. The main conclusion is that the choice of the equation of state as well as the value of the electric conductivity can result in considerable dynamical differences in simulations involving shocks, instabilities, and magnetic reconnection.

Polycyclic aromatic hydrocarbons (PAHs) are likely responsible for the family of infrared emission features seen in a wide variety of astrophysical environments. A potentially important subclass of these materials are PAHs whose edges contain excess H atoms (H_n-PAHs). This type of compound may be present in space, but it has been difficult to assess this possibility because of a lack of suitable laboratory spectra to assist with analysis of astronomical data. We present 4000–500 cm⁻¹ (2.5–20 μm) infrared spectra of 23 H_n-PAHs and related molecules isolated in argon matrices under conditions suitable for interpretation of astronomical data. Spectra of molecules with mixed aromatic and aliphatic domains show characteristics that distinguish them from fully aromatic PAH equivalents. Two major changes occur as PAHs become more hydrogenated: (1) aromatic C–H stretching bands near 3.3 μm weaken and are replaced with stronger aliphatic bands near 3.4 μm, and (2) aromatic C–H out-of-plane bending mode bands in the 11–15 μm region shift and weaken concurrent with growth of a strong aliphatic –CH₂– deformation mode near 6.9 μm. Implications for interpreting astronomical spectra are discussed with emphasis on the 3.4 and 6.9 μm features. Laboratory data is compared with emission spectra from IRAS 21282+5050, an object with normal PAH emission features, and IRAS 22272+5435 and IRAS 0496+3429, two protoplanetary nebulae with abnormally large 3.4 μm features. We show that "normal" PAH emission objects contain relatively few H_n-PAHs in their emitter populations, but less evolved protoplanetary nebulae may contain significant abundances of these molecules.

The cis-methyl formate molecule is a well known molecule found in interstellar space. Recently, rotational lines of methyl formate in the first CH₃ torsional excited state were observed in Orion KL and W51e2. It is quite natural to observe methyl formate in even higher vibrational states considering the temperature estimated in Orion KL and W51e2. Maeda et al. reported results on the laboratory spectroscopy of methyl formate including the spectral analysis in its second CH₃ torsional state. Their assignments were limited to a series of a-type R-branch lines and low K_a b-type R-branch transitions, and many assigned lines are excluded in the least-squares analysis. In the present study, we extended the line assignments of both the A- and E-species transitions in the second CH₃ torsional state especially in the frequency region below the 120 GHz region. By combining the present assignments and those made by Maeda et al., 1951 transitions in total for the second CH₃ torsional state, 1096 A-species transitions up to J = 39, and K_a = 15 and 855 E-species transitions up to J = 35 and K_a = 13, were least-squares analyzed by using the pseudo-principal-axis-method Hamiltonian with 42 parameters consisting of rotational, centrifugal distortion, and internal rotational constants in the second CH₃ torsional state. In addition, 1012 transitions out of 1096 A-species transitions could also be least-squares analyzed by using Watson's A-reduced Hamiltonian with 43 parameters, which can serve to calculate the energy levels of the A-species lines of molecules with the CH₃ internal rotation conveniently.