A guide to TAURUS-2 Fabry–Perot data reduction

The data reduction process for optical emission-line observations of galaxies using the TAURUS-2 Fabry–Perot interferometer mounted on the 3.9-m Anglo-Australian Telescope is described in detail. The initial steps (bias subtraction, flat-fielding, etc.) are the same as for calibration of CCD images, and the wavelength calibration is similar to that in optical spectroscopy. The final steps are specific to Fabry–Perot instruments, and include the fitting of several instrumental parameters and a phase correction to convert the raw ( x ,  y ,  z ) data cube into a useful position–velocity ( α ,  δ ,  v ) cube. Software has been written to assist with the latter steps of the data reduction. H α observations of NGC 1808, NGC 2442 and Circinus are used to demonstrate the reduction process.     

The 2dF Galaxy Redshift Survey: the nature of the relative bias between galaxies of different spectral type

We present an analysis of the relative bias between early- and late-type galaxies in the Two-degree Field Galaxy Redshift Survey (2dFGRS) – as defined by the η parameter of Madgwick et al., which quantifies the spectral type of galaxies in the survey. We calculate counts in cells for flux-limited samples of early- and late-type galaxies, using approximately cubical cells with sides ranging from 7 to  42 h ⁻¹ Mpc  . We measure the variance of the counts in cells using the method of Efstathiou et al., which we find requires a correction for a finite volume effect equivalent to the integral constraint bias of the autocorrelation function. Using a maximum-likelihood technique we fit lognormal models to the one-point density distribution, and develop methods of dealing with biases in the recovered variances resulting from this technique. We then examine the joint density distribution function,   f (δ_E, δ_L)  , and directly fit deterministic bias models to the joint counts in cells. We measure a linear relative bias of ≈1.3, which does not vary significantly with ℓ. A deterministic linear bias model is, however, a poor approximation to the data, especially on small scales  (ℓ≤ 28  h ⁻¹ Mpc)  where deterministic linear bias is excluded at high significance. A power-law bias model with index   b ₁≈ 0.75  is a significantly better fit to the data on all scales, although linear bias becomes consistent with the data for  ℓ≳ 40  h ⁻¹ Mpc  .     

H 0 from an orientation-unbiased sample of Sunyaev–Zel'dovich and X-ray clusters

We have observed the Sunyaev–Zel'dovich (SZ) effect in a sample of five moderate-redshift clusters with the Ryle Telescope, and used them in conjunction with X-ray imaging and spectral data from ROSAT and ASCA to measure the Hubble constant. This sample was chosen with a strict X-ray flux limit using both the Bright Cluster Sample and the Northern ROSAT All-Sky Survey (RASS) cluster catalogues to be well above the surface brightness limit of the RASS, and hence to be unbiased with respect to the orientation of the cluster. This controls a major potential systematic effect in the SZ/X-ray method of measuring H ₀. Taking the weighted geometric mean of the results and including the main sources of error, namely the noise in the SZ measurement, the uncertainty in the X-ray temperatures and the unknown ellipticity and substructure of the clusters, we find   H ₀= 59⁺¹⁰₋₉ (random)⁺⁸₋₇(systematic) km s⁻¹ Mpc⁻¹  assuming a standard cold dark matter model with  Ω_M= 1.0, Ω_Λ= 0.0  or   H ₀= 66⁺¹¹₋₁₀ ⁺⁹₋₈ km  s⁻¹ Mpc⁻¹  if  Ω_M= 0.3, Ω_Λ= 0.7  .     

A survey for planetary transits in the field of NGC 7789

We present results from 30 nights of observations of the open cluster NGC 7789 with the Wide Field Camera on the Isaac Newton Telescope, La Palma. From ∼900 epochs, we obtained light curves and Sloan   r '− i '  colours for ∼33 000 stars, with ∼2400 stars having better than 1 per cent precision. We expected to detect ∼2 transiting hot Jupiter planets if 1 per cent of stars host such a companion and a typical hot Jupiter radius is  ∼1.2  R _J  . We find 24 transit candidates, 14 of which we can assign a period. We rule out the transiting planet model for 21 of these candidates using various robust arguments. For two candidates, we are unable to decide on their nature, although it seems most likely that they are eclipsing binaries as well. We have one candidate exhibiting a single eclipse, for which we derive a radius of  1.81^+0.09_−0.00  R _J  . Three candidates remain that require follow-up observations in order to determine their nature.     

Source subtraction for the extended Very Small Array and 33-GHz source count estimates

We describe the source subtraction strategy and observations for the extended Very Small Array (VSA), a cosmic microwave background interferometer operating at 33 GHz. A total of 453 sources were monitored at 33 GHz using a dedicated source subtraction baseline. 131 sources brighter than 20 mJy were directly subtracted from the VSA visibility data. Some characteristics of the subtracted sources, such as spectra and variability, are discussed. The 33-GHz source counts are estimated from a sample selected at 15 GHz. The selection of VSA fields in order to avoid bright sources introduces a bias into the observed counts. This bias is corrected and the resulting source count is estimated to be complete in the flux-density range 20–114 mJy. The 33-GHz source counts are used to calculate a correction to the VSA power spectrum for sources below the subtraction limit.     

Upper limits on the hot Jupiter fraction in the field of NGC 7789

We describe a method of estimating the abundance of short-period extra-solar planets based on the results of a photometric survey for planetary transits. We apply the method to a 21-night survey with the 2.5-m Isaac Newton Telescope of ∼32 000 stars in a ∼0.5 × 0.5 deg² field including the open cluster NGC 7789. From the colour–magnitude diagram, we estimate the mass and radius of each star by comparison with the cluster main sequence. We search for injected synthetic transits throughout the light curve of each star in order to determine their recovery rate, and thus calculate the expected number of transit detections and false alarms in the survey. We take proper account of the photometric accuracy, time sampling of the observations and criteria (signal-to-noise ratio and number of transits) adopted for transit detection. Assuming that none of the transit candidates found in the survey will be confirmed as real planets, we place conservative upper limits on the abundance of planets as a function of planet radius, orbital period and spectral type.     

The ratio between magnetotail height and neutral point height

The ratio between the magnetotail height and the neutral point height is exactly 2 in the classical calculation of the shape of the magnetopause following Chapman and Ferraro. This ratio is useful in assessing the results of calculations. There exist possibilities for improvement of magnetopause shape calculations, especially in the tail region or in the neutral point region for “tilted” cases.     

Fraunhofer line profiles

It is shown that comparing an observed Fraunhofer profile to a fitted gaussian yields more information on shape and asymmetry of the solar line than the simple bisector method.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

The relationship of soil 210Po and 210Pb geochemical dispersion patterns to uranium mineralization

²¹⁰Po and ²¹⁰Pb measurements of soils delineated uranium anomalies at three out of four test sites in Ontario, Canada. Measurements were made of ²¹⁰Po in solutions produced by both complete digestion and partial leaching of soil samples. Direct plating of ²¹⁰Po onto metal plates was followed by measuring the alpha activity. Subsequent plating of ²¹⁰Po in-grown from ²¹⁰Pb in solution several months later confirmed the anomalies.The ²¹⁰Po and ²¹⁰Pb anomalies at three of the test sites coincided with ²²⁶Ra and ²²²Rn anomalies. Samples from the fourth uranium occurrence associated with a known ²²²Rn anomaly failed to show either a ²²⁶Ra anomaly on the one hand, or ²¹⁰Po or ²¹⁰Pb anomalies on the other. This suggests that the ²¹⁰Po and ²¹⁰Pb anomalies were probably produced by the decay of ²²⁶Ra contained within secondary dispersion haloes.Although anomalies due to the ²¹⁰Po and ²¹⁰Pb products of ²²²Rn have now been documented, prospecting methods based on their use as direct tracers of the migration paths of ²²²Rn require much further development.