The object of this thesis was to develop an imaging system using a CID Indium Antimonide (InSb) 33 element detector. Some interesting results were obtained on the rings of Saturn and the poles of Jupiter and the detector would have been used to scan the nuclear regions of galaxies. However, the array had a low sensitivity and a slow response which made it impractical to carry out any observations of galactic nuclei. Data, from single detector scans of NGC 2683, were provided by Dr. A. Adamson and Dr. D.J. Adams. These scans were performed to see if a halo exists around this galaxy. Two methods were used. The first was a deconvolution method which is shown to have a fault when deconvolving diffuse objects. The second method was to analyse the colour indices. This method indicated that there could be a spheroidal component causing the V-J colour to become redder out to approximately 90 arcseconds from the nucleus. Beyond 90 arcseconds, the colour becomes bluer possibly because the galaxy is not quite edge on and the blue disc begins to dominate the colour. The last chapter deals with the morphologically peculiar galaxies NGC 613, 1097, 1365 and 1808. The data on these galaxies were obtained on the AAT using a single detector which was scanned across the objects in a DC mapping mode. Maps were constructed, on a CYBER 73 at Leicester, from the J, H and K data. The data were then examined to see if these galaxies conform to the usual exponential disc and R1/4 laws. The three latter galaxies seem to exhibit nuclear colours similar to Seyfert's and NGC 613 may be either a weak active galaxy, or could just simply suffer from reddening.

Infrared and optical star counts have been obtained to investigate the stellar distribution in the plane of the Galaxy. The discovery of an obscured infrared cluster of sources is presented and a search technique for finding such obscured sources using visible and near-infrared plates is discussed. The techniques and mathematical treatment of star counting are described and, as an introduction, a literature review of the galactic structure is given. Optical star counts in a strip across the dark rift of the Galaxy, containing the line of sight to the galactic centre, indicate that the extinction in this direction starts to increase significantly at a distance of about 1500 pc, approximately at the distance of the Sagittarius arm. Counting the stars into reseau squares shows that the direction of the thickest extinction in the visible, for star counts to 18m .0, is not coincident with the plane of the Galaxy but about +1° in latitude away. Infrared star counts at 2.2 microns have been obtained for seven regions, spaced at 10o intervals, in the galactic plane. Away from the nucleus the star counts seem to fit a simple exponential disc model. At a longitude of 30o where the line of sight is tangential to a ring of molecular clouds, the disc population appears to be supplemented by an increase in density of late-type giants. Towards, the galactic centre the extinction at 2.2 microns is low enough for the dense core to be seen in the star counts, these dominating the star counts from the disc population.

In this thesis complete light curves, at both optical (V) and infrared (J, H, K) wavelengths, are presented for 15 pulsating variable stars. These include four dwarf Cepheids, six RR Lyraes and five Cepheids. In addition, radial velocity curves are also presented for three stars. Using this data, and existing radial velocity curves taken from the literature, we derive radii for all the stars using a variant of the Baade-Wesselink method. The value of the infrared for radius determination is illustrated by the fact that no previous attempts to apply Baade-Wesselink type methods, in an empirical manner, to short period (P <1 day) variables have been successful. From these results the following conclusions are drawn: 1. Metal poor RR Lyraes have ? 0.55 and the metal rich, shorter period variables appear to be &sim;0.3 - 0.4 mags fainter. These results and data secured recently for the globular clusters M5 and M107 show that RR Lyraes obey a period-luminosity relation in the infrared of the form = -1.01 - 2.80 log P The Cepheid period-luminosity relation from our data requires that the Cepheid zero point from cluster main sequence fitting should be reduced by ~0.1. With this revision a distance modulus of 18.50 +/- 0.15 for the LMC is given by both RR Lyraes and Cepheids. The "pulsation" masses of both the RR Lyraes and Cepheids are systematically smaller than the "evolutionary" masses by &sim;15%. The "pulsation" masses of dwarf Cepheids depend on the assumed pulsation mode. For those stars of known (or suspected) pulsation mode, low masses are derived. If this is generally true then dwarf Cepheids and delta Scutis are dissimilar. Further evidence in support of this conclusion is provided by, firstly, a comparison of the observed pulsation characteristics (periods and amplitudes) of the two groups of stars and, secondly, a comparison of the observed period changes of dwarf Cepheids with the theoretically calculated period changes.

A review of the classification of asteroids according to their orbital and physical properties is presented and the technique of numerical taxonomy is applied to catalogued optical data. The size distribution of minor bodies is of fundamental importance for theories of the origin and formation of the Solar System. Methods of diameter determination are reviewed with particular reference to the radiometric method. Thermal emission models of asteroids are essential for the reduction of infrared observations to obtain radiometric diameters and albedos. Various thermal models are described, with an emphasis on the assumptions made, and their limitations. The models are applied to observations in the 8-13?m region to examine possible variations of emissivity with wavelength, to remove the thermal component from reflection spectra in the 3-4?m region, and to determine the nature of the surface of the unusual asteroid (3200) 1983TB. The Infrared Astronomical Satellite (IRAS) was launched in 1983 to provide an all-sky survey in four infrared wavebands. In order to prevent detections of the thermal emission from moving objects from being lost, software was written to search the rejected survey data in near real-time. As well as detecting several hundred numbered asteroids and five known comets, two main belt asteroids, two Apollo asteroids, six comets and an infrared tail on comet Tempel-2 were discovered. A description of the moving object software and its implementation is presented, together with estimates of the selection effects and completeness of the search, and analysis of the data. The ground-based observations of the Apollo asteroid (3200) 1983TB do not support the cometary nucleus hypothesis inferred from its orbital characteristics. A preliminary analysis of some IRAS additional observations of asteroids is also presented.

Quasars have been used as efficient probes of high-redshift galaxy clustering as they are known to favour overdense environments. Quasars may also trace the largescale structure of the early universe (0.4 1< z <1 2) in the form of Large Quasar Groups(LQGs), which have comparable sizes (r.J 100-200hMpc) to the largest structures seen at the present epoch. This thesis describes an ultra-deep, wide-field optical study of a region containing three quasars from the largest known LJQG, the Clowes-Campusano LQG of at least 18 quasars at z 1.3, to examine their galaxy environments and to find indications of any associated large-scale structure in the form of galaxies. The optical data were obtained using the Big Throughput Camera (BTC) on the 4-m Blanco telescope at the Cerro Tololo Interamerican Observatory (CTIO) over two nights in April 1998, resulting in ultra-deep V, I imaging of a 40.6 x 34.9 arcmin 2 field centred at l0L47m30s, +05 0 30'00" containing three quasars from the LQG as well as four quasars at higher redshifts. The final catalogues contain 10 sources and are 50% complete to V 26.35 and I 25.85 in the fully exposed areas. The Cluster Red Sequence method of Gladders & Yee (2000) is used to identify and characterise galaxy clusters in the BTC field. The method is motivated by the observation that the bulk of early-type galaxies in all rich clusters lie along a tight, linear colour-magnitude relation - the cluster red sequence - which evolves with redshift, allowing the cluster redshift to be estimated from the colour of the red sequence. The method is applied to the detection of high-redshift clusters in the BTC field through the selection of galaxies redder than the expected colour of the z = 0.5 red sequence. A 2c excess of these red galaxies is found in the BTC field in comparison to the 27arcmin 2 ETS-DEEP HDF-South field. These galaxies are shown from the EIS-DEEP UBVRIJHK 3 photometry to hearly-type galaxies at 0.7 1< z 1.5. This excess, corresponding to 1000 extra red galaxies over the BTC field, along with the 3c excess of Mgti absorbers observed at 1.2 < z < 1.3(Williger et al., 2000), supports the hypothesis that the Clowes-Campusano LQG traces a large-scale structure in the form of galaxies at z 1.3. Four high-redshift cluster candidates are found, one of which is confirmed by additional K data to be at z = 0.8 + 0.1. Two of the high-redshift clusters are associated with quasars: the z = 1.426 quasar is located on the periphery of a cluster of V - I 3 galaxies; and the z = 1.226 LQC quasar is found within a large-scale structure of 100-150 red galaxies extending over 2-3h'Mpc. Additional K imaging confirms their association with the quasar, with red sequences at V - K 6.9 and I - K 4.3 indicating a population of 15-18 massive ellipticals at z = 1.2 ± 0.1 that are concentrated in two groups on either side of the quasar. The four z ± 1.3 quasars in the BTC field are found in a wide variety of environments,from those indistinguishable from the field, to being associated with rich clusters, but are on average in overdense regions comparable to poor clusters. These results are similar to those of previous studies of quasars at these redshifts, and are consistent with the quasars being hosted by massive ellipticals which trace mass in the same biased manner. It is also notable how the quasars associated with clustering are located on the cluster peripheries rather than in the high-density cluster cores, a result which is initially surprising given that quasars are thought to be hosted by massive elliptical galaxies, but in retrospect can be understood in the framework of both galaxy interaction and galaxy formation quasar triggering mechanisms.

This thesis investigates the evolution of galaxies as a function of look-back time, concentrating on early-type cluster galaxies. We demonstrate that selecting galaxies in the near-infrared produces samples that are representative of the galaxy population at intermediate and high redshift, and that such samples are likely to contain approximately the same proportion of all galaxy classes independently of z, avoiding the biases introduced by optical selection criteria. We have developed observing and data processing techniques using infrared arrays that yield high precision near-infrared photometry to very faint limits. Combining such data with optical photometry for the galaxy samples, we have been able to quantify the amount of colour evolution in early-type cluster galaxies up to redshifts z ~ 0.9.At z = 0.37 the mean colour-luminosity (c-L) relation for early-type cluster galaxies is compatible in slope and zero point with that of present-day ellipticals, indicating that the bulk of the stellar population at that epoch does not show any significant colour evolution. However, the scatter around the main c-L line is significantly larger than the observational errors, and distinctively non-Gaussian. We interpret this as evidence that a large fraction (~ 60%) of the early-type members have suffered a burst of star formation (involving ~ 10% of the galaxy mass) ~ 1 Gyr prior to the epoch of observation. In the redshift range 0.5 < z < 0.9, we detect systematic colour evolution with redshift in the red cluster galaxies. In particular, at z ~ 0.9 there are no galaxies as red as present day ellipticals at all wavelengths. The detected evolution is compatible with the passive ageing of stellar populations formed before z = 2. Superimposed on that, there is evidence for subsequent bursts of star formation happening on a substantial fraction of the cluster galaxies, but affecting only a small fraction of the total galaxy mass. We suggest this may be related to the Butcher-Oemler effect observed at lower redshifts. We did not detect significant amounts of galaxy luminosity evolution at 2µm, in contrast with the results for radio galaxies. We finally propose and test three new approaches to the study of normal field and cluster galaxies beyond z = 1: a study of gravitationally lensed galaxies, a search for galaxies producing clustered metallic absorption lines in QSOs and an infrared follow-up of ROSAT X-ray detected high redshift clusters.

No description available.

No description available.

No description available.

No description available.