arXiv subjects
Publications and source records attributed to I. M. Hook.
The Supernova Cosmology Project has discovered over twenty-eight supernovae (SNe) at 0.35 = 0.2, we find that H_0^G < 70 km/s/Mpc in a Lambda=0 universe and H_0^G < 78 km/s/Mpc in a flat universe, correcting the distant and local SN apparent magnitudes for light curve width. Lower results for H_0^G are obtained if the magnitudes are not width corrected.
We present optical spectroscopic data for a complete sample of 161 S_5GHz >= 0.2 Jy, flat-spectrum radio sources. The sources were observed as part of a survey for high redshift, radio-loud quasars, and were selected for spectroscopic follow-up based on criteria of red optical colour and unresolved optical counterpart, as measured from APM scans of POSS-I plates. 13 objects from the spectroscopic sample were found to be radio-loud quasars with z > 3, of which two were previously known. We give positions, E (red) magnitudes, O-E colours, 5GHz radio fluxes, radio spectral indices, optical spectra and redshifts where possible for the spectroscopic sample. We also give finding charts for the z > 3 QSOs. The highest redshift object found is a QSO with z = 4.30 (GB1508+5714, the subject of an earlier Letter). The sample also contains a z = 3.05 QSO, GB1759+7539, which is optically very luminous (E=16.1). In addition, spectra are given for 18 S_5GHz >= 0.2 Jy, flat-spectrum radio sources that do not form part of the complete sample.
We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived using a large subset of data from the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 square degrees. The survey spanned a $\sim 3$ week baseline and used images with $3σ$ limiting magnitude of $R\sim 23$. We present our methods for estimating the numbers of galaxies and the number of solar luminosities to which the survey is sensitive, and the supernova detection efficiency which is used to determine the control time, the effective time for which the survey is sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova rate at $z\sim0.4$ of $0.82\ {^{+0.54}_{-0.37}}\ {^{+0.37}_{-0.25}} $ $h^2$ SNu (1 SNu = 1 SN per century per $10^{10}$\Lbsun), where the first uncertainty is statistical and the second includes systematic effects. For the purposes of observers, we also determine the rate of SNe, per sky area surveyed, to be $ 34.4\ {^{+23.9}_{-16.2}}$ SNe\ $\rm year^{-1} deg^{-2}$ for SN magnitudes in the range $21.3 < R < 22.3$.
We report the discovery of a radio loud quasar with a redshift of 4.30. This object, which is the first radio selected quasar with a redshift greater than four, was discovered during an observational investigation into the evolution of the luminosity function of radio loud quasars. Here we describe results based on a sample of ~300, flat spectrum radio sources with S(5GHz) > 200mJy. In this study, rather than carry out an indiscriminate redshift campaign on all the radio sources, we have used the APM POSS catalogue to preselect a subset of stellar-like optical counterparts with red optical colours. Such a subsample is expected to contain a high fraction of high redshift quasars. 10 of the ~300 sources were selected for follow-up optical spectroscopy and three of these are identified as quasars with redshifts greater than 3.0. One of the radio sources, GB1508+5714, is a quasar with z=4.30 and m(R)~19.