D. A. Green

LIMITATIONS IMPOSED ON STATISTICAL STUDIES OF GALACTIC SUPERNOVA REMNANTS BY OBSERVATIONAL SELECTION EFFECTS

The selection effects that apply to the identification of Galactic supernova remnants are reviewed together with the limitations that they impose on statistical studies. Emphasis is given to problems with recent discussions of the number, birthrate, and distribution of remnants within the Galaxy. The distribution of high-surface-brightness remnants is concentrated in a nuclear disk that is even more well-defined than that noted by van den Bergh 1988a,b. Also presented, as an appendix, are revisions to the catalog of Galactic supernova remnants presented in Green 1988. The revised catalog contains 174 remnants.

STAGES: the Space Telescope A901/2 Galaxy Evolution Survey

We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multicluster system at z similar to 0.165 has been the subject of an 80-orbit F606W Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) mosaic covering the full 0 degrees.5 x 0 degrees.5 (similar to 5 x 5 Mpc(2)) span of the supercluster. Extensive multiwavelength observations with XMM-Newton, GALEX, Spitzer, 2dF, Giant Metrewave Radio Telescope and the 17-band COMBO-17 photometric redshift survey complement the HST imaging. Our survey goals include simultaneously linking galaxy morphology with other observables such as age, star formation rate, nuclear activity and stellar mass. In addition, with the multiwavelength data set and new high-resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the system. By examining all aspects of an environment we will be able to evaluate the relative importance of the dark matter haloes, the local galaxy density and the hot X-ray gas in driving galaxy transformation. This paper describes the HST imaging, data reduction and creation of a master catalogue. We perform the Sersic fitting on the HST images and conduct associated simulations to quantify completeness. In addition, we present the COMBO-17 photometric redshift catalogue and estimates of stellar masses and star formation rates for this field. We define galaxy and cluster sample selection criteria, which will be the basis for forthcoming science analyses, and present a compilation of notable objects in the field. Finally, we describe the further multiwavelength observations and announce public access to the data and catalogues.

Far‐infrared and submillimetre observations of the Crab nebula

We present far-infrared (FIR) and submillimetre images of the Crab nebula, taken with the ISOPHOT instrument onboard the Infrared Space Observatory (ISO) and with the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. The ISOPHOT observations were made in the bands centred at 60, 100 and 170 µm, with FWHM of equivalent area Gaussian beams of 44, 47 and 93 arcsec, respectively. The 850-µm SCUBA image was processed using a maximum-entropy method algorithm and has a Gaussian FWHM of 17 arcsec. The 60- and 100-µm images show clear excess of emission, above that expected from an extrapolation of the synchrotron spectrum of the Crab nebula from lower frequencies, as previously seen from IRAS observations. The superior angular resolution of the ISOPHOT images reveal that about half this excess is attributable to two peaks, separated by ≈80 arcsec. We also present spectra taken using the Long-wavelength Spectrometer onboard ISO, which show that the FIR excess is not due to line emission. The lower-resolution 170-µm image does not show any excess emission, but is possibly fainter, particularly in the NW, than expected from an extrapolation of the lower-frequency synchrotron emission. These findings are consistent with a picture in which the FIR excess is due to emission from a small amount of ‐

RADIOACTIVE SCANDIUM IN THE YOUNGEST GALACTIC SUPERNOVA REMNANT G1.9+0.3

We report the discovery of thermal X-ray emission from the youngest Galactic supernova remnant G1.9+0.3, from a 237 ks Chandra observation. We detect strong K? lines of Si, S, Ar, Ca, and Fe. In addition, we detect a 4.1 keV line with 99.971% confidence which we attribute to 44Sc, produced by electron capture from 44Ti. Combining the data with our earlier Chandra observation allows us to detect the line in two regions independently. For a remnant age of 100 yr, our measured total line strength indicates synthesis of (1-7) ? 10?5 M ? of 44Ti, in the range predicted for both Type Ia and core-collapse supernovae (SNe), but somewhat smaller than the 2 ? 10?4 M ? reported for Cas A. The line spectrum indicates supersolar abundances. The Fe emission has a width of about 28,000 km s?1, consistent with an age of ~100 yr and with the inferred mean shock velocity of 14,000 km s?1 deduced assuming a distance of 8.5 kpc. Most thermal emission comes from regions of lower X-ray but higher radio surface brightness. Deeper observations should allow more detailed spatial mapping of 44Sc, with significant implications for models of nucleosynthesis in Type Ia SNe.

Deep 610‐MHz Giant Metrewave Radio Telescope observations of the Spitzer extragalactic First Look Survey field – I. Observations, data analysis and source catalogue

Observations of the Spitzer extragalactic First Look Survey field taken at 610 MHz with the Giant Metrewave Radio Telescope are presented. Seven individual pointings were observed, covering a total area of ∼4 deg 2 with a resolution of 5.8 x 4.7 arcsec 2 , PA 60°. The rms noise at the centre of the pointings is between 27 and 30 μJy before correction for the Giant Metrewave Radio Telescope (GMRT) primary beam. The techniques used for data reduction and production of a mosaicked image of the region are described, and the final mosaic, along with a catalogue of 3944 sources detected above ∼5σ, are presented. The survey complements existing radio and infrared data available for this region.

Jupiter's radio spectrum from 74 MHz up to 8 GHz

Abstract We carried out a brief campaign in September 1998 to determine Jupiter’s radio spectrum at frequencies spanning a range from 74 MHz up to 8 GHz. Eleven different telescopes were used in this effort, each uniquely suited to observe at a particular frequency. We find that Jupiter’s spectrum is basically flat shortwards of 1–2 GHz, and drops off steeply at frequencies greater than 2 GHz. We compared the 1998 spectrum with a spectrum (330 MHz–8 GHz) obtained in June 1994, and report a large difference in spectral shape, being most pronounced at the lowest frequencies. The difference seems to be linear with log(ν), with the largest deviations at the lowest frequencies (ν). We have compared our spectra with calculations of Jupiter’s synchrotron radiation using several published models. The spectral shape is determined by the energy-dependent spatial distribution of the electrons in Jupiter’s magnetic field, which in turn is determined by the detailed diffusion process across L -shells and in pitch angle, as well as energy-dependent particle losses. The spectral shape observed in September 1998 can be matched well if the electron energy spectrum at L = 6 is modeled by a double power law E − a (1+( E / E 0 )) − b , with a = 0.4, b = 3, E 0 = 100 MeV, and a lifetime against local losses τ 0 = 6 × 10 7 s. In June 1994 the observations can be matched equally well with two different sets of parameters: (1) a = 0.6, b = 3, E 0 = 100 MeV, τ 0 = 6 × 10 7 s, or (2) a = 0.4, b = 3, E 0 = 100 MeV, τ 0 = 8.6 × 10 6 s. We attribute the large variation in spectral shape between 1994 and 1998 to pitch angle scattering, coulomb scattering and/or energy degradation by dust in Jupiter’s inner radiation belts.

Testing Inflation with Large Scale Structure: Connecting Hopes with Reality

The statistics of primordial curvature fluctuations are our window into the period of inflation, where these fluctuations were generated. To date, the cosmic microwave background has been the dominant source of information about these perturbations. Large scale structure is however from where drastic improvements should originate. In this paper, we explain the theoretical motivations for pursuing such measurements and the challenges that lie ahead. In particular, we discuss and identify theoretical targets regarding the measurement of primordial non-Gaussianity. We argue that when quantified in terms of the local (equilateral) template amplitude

A REVISED REFERENCE CATALOGUE OF GALACTIC SUPERNOVA REMNANTS

f_{\rm NL}^{\rm loc}

The relationship between star formation rate and radio synchrotron luminosity at 0 < z < 2

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AMI observations of Lynds dark nebulae: Further evidence for anomalous cm-wave emission

f_{\rm NL}^{\rm eq}