Schmidt Telescope Research Articles

An Hα Survey of the Galactic Plane

We describe a major new Anglo-Australian proposal for a U.K. Schmidt Telescope (UKST) Hα survey of the Southern Galactic plane, Magellanic clouds and selected regions. The agreed survey will use a new 12 × 12 inch monolithic Hα interference filter of very high specification in combination with Tech Pan film. Tech Pan offers significant advantages for this work due to an inherent sensitivity at Hα and its extremely fine grain, high resolution, exceptional DQE, excellent imaging and low noise (e.g., Parker et al. 1994). The combination of Tech Pan and a narrow band Hα filter will provide a survey of unprecendented area coverage, depth and resolution, superior to any previous optical survey of ionized gas in the galaxy. It should to lead to exciting new discoveries and avenues of research.

Colour Equations for Techpan Films

The UK 1.2m Schmidt Telescope (UKST) at Siding Spring Observatory in Australia has been routinely using panchromatic Tech-Pan emulsion on film as a detector since 1992. Details of how the telescope was adapted to take film and how hypersensitization techniques have been modified for film have been described by Parker (1992). The film has a much finer grain than its equivalent spectroscopic emulsion on glass (IIIa-F) and consequently records images typically one magnitude fainter than IIIa-F when properly hypersensitized. The improved depth, resolution and low noise also permit better differentiation between stars and galaxies (see Parker et al. 1994). Consequently Tech-Pan film has become one of the most useful and commonly used emulsions at the UKST for a variety of passbands and may in time be used for a full or partial sky survey.

Optimizing Results from Automatic Objective-Prism Surveys

One of the most important results in observational cosmology is the galaxy star formation rate distribution, or its equivalent observable, the Hα luminosity function. The UCM-CIDA project has grown to address the problem of the poorly-known faint star forming galaxy population using the objective-prism technique along with a CCD mosaic in a Schmidt telescope. However, one tough problem when computing statistical properties of a selected sample are the selection effects. Here we present tools developed by us to undertake the analysis of objective-prism (OP) selected samples in an unbiased way and quantify the sensitivity of the survey to every object. The main tools for this purpose are simulations.

Arops : The ASIAGO Red Objective-Prism Survey

AROPS is an objective-prism survey conducted at high galactic latitudes with the 67/92 cm (f=205 cm) Schmidt telescope of the Asiago Astrophysical Observatory (Italy). The basic technical data are: – TP4415 high resolution plates, 20×20 cm, treated in forming gas (H2+N2) and covering 24 deg2 on sky– 4° UBK7 objective prism, for a dispersion of 1490 Åmm−1 at NaI D– blue side cut-off at 4980 Å using a 2mm GG14 filter, for a recorded λ range 5000–7000 Å– untrailed spectra to record V ∼ 16.5 mag stars with 40 min exposures

Background and First Results from the New AAO/UKST Hα Survey

AbstractThe UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory (AAO) has just embarked on a new Hα survey of the Southern Galactic Plane, Magellanic Clouds and selected regions using a specially designed, high-specification, monolithic, interference filter. It is probably the largest of its kind for astronomy. It is being used in combination with Kodak Tech Pan film-based emulsion. This emulsion not only has a useful sensitivity peak at Hα but also possesses extremely fine grain and an exceptionally high DQE for the hypersensitised product (∼10%). This leads to excellent imaging, sensitivity and low noise. It is clear that CCDs cannot yet match the wide-area coverage, uniformity and resolution of the UKST/Tech Pan combination for undertaking such a survey. The survey will initially include about 233 Galactic Plane and 40 Magellanic Cloud fields on 4-degree centres and will take about 3 years to complete. Some preliminary images from the new survey are presented and compared with the best previously available from the UKST. Examples of the first survey discoveries, new resolved Galactic planetary nebulae, are also given. This survey will have an unprecedented combination of area coverage, depth and resolution, superior to those of any previous optical survey of ionised gas in the Galaxy. Many new discoveries and research avenues are expected.

The Large Sky Area Multi-Object Fibre Spectroscopy Telescope (Lamost)

AbstractIn China, we will start to build a new spectroscopic survey telescope. It will be a meridian reflecting Schmidt telescope. The optical system is horizontal. The primary mirror is spherical and segmented. It faces towards the north. In its spherical center there is a plane mirror which is segmented too. The different shape of reflecting Schmidt plate is realized by active optics. The clear aperture is 4 m and f-ratio is 5. The angular field of view is 5 square degree, 4000 objects can be observed simultaneously by using optical fibre. The science goal is to make a 20000 square degrees spectroscopic survey, including ten million galaxies and stars, many variable objects and the identification of numerous objects found by radio, x-ray, IR and other survey in these sky areas.

New Membership Criteria For 437 Flare Stars in the Pleiades

Most of the flare stars (FSs) discovered in that field are very faint and are missing from all previously published lists of Pleiades cluster members. Reliable membership probabilities (MPs) were only determined for one third of these objects while the rest were supposed to be more or less probable members with a few exceptions. A recent proper motion survey of that field (Schilbach et al. 1995) based on plates taken with the Tautenburg Schmidt telescope and extended to an area of 16.5 square degrees provided new cluster MPs and also photometric data even for a number of the lowest luminosity stars (in fact the faintest object measured has V = 18.26). Of the 520 known FSs in the field 437 (85%) were successfully identified, their J2000.0 coordinates, high precision proper motion components and apparent photographic R magnitudes (and for the majority of them their V and B magnitudes too) determined. Based on these data new cluster MPs have been deduced which show that a considerable number (40%) of the so called Pleiades FSs are not members of that cluster at all. This conclusion follows the tendency already found: when we involve more and more faint FSs into the investigations the percentage of non-members monotonically increases (cf. Haro et al. 1982 and references therein).

Multicolor Survey For High Redshift Quasars By Kiso Schmidt Telescope

Several groups have been successful in the survey of high-redshift (z > 4) quasars. For example, Schneider et al. (1994) and Schmidt et al. (1995) were successful in detecting 90 quasars with 2.75 < z < 4.75, R < 21 for 62deg2 using Palomar Transit Grism. Among them, there are 9 quasars with z > 4.0. Storrie-Lombardi et al. (1996) were detected 31 quasars with z > 4.0, mT < 19 for 2500deg2 by APM photographic multicolor survey using UK Schmidt telescope. Survey observations of quasars up to now have to select one of the following conditions; wide field surveys using photographic Schmidt plate which cover large areas but do not go faint enough, or deep surveys using large telescopes which go faint magnitude but which cover relatively small areas.

Some Results of the BATC CCD Color Survey

The BATC (Beijing-Arizona-Taiwan-Connecticut) CCD color survey started 2 years ago. It is based on observations with the 60/90cm f/3 Schmidt Telescope of the Beijing Astronomical Observatory using a 2k×2k CCD and 15 intermediate band filters covering from 300nm to 1000nm to obtain the spectral energy distribution (SED) of all objects in 500 selected fields down to mV = 20 (Chen 1994). The basic framework of the survey including instrumentation, data acquisition system, archive data system, and the various steps of data reduction has been established. About 60 fields have been observed. Most fields are still short of observations in UV band. We are waiting for a new thinned CCD to improve the quantum efficiency.

High Density Requirements

I will consider here some practical astrometric requirements, from the perspective of an optical astronomer working on objects much fainter than the limits of the primary catalogues, i.e., from 15 mag down to 20 mag and fainter. I take ‘high density’ to mean surface densities of order 100 or more stars per square degree; these two criteria are roughly equivalent (Bahcall & Soneira, 1980). The positions of such objects are routinely available to an accuracy of around 0.5-1.0 arcsec, e.g. from various digitised versions of the Schmidt Telescope photographic sky surveys. However, these sky surveys themselves readily yield internal accuracies at the 0.1 arcsec level, as demonstrated by repeated measures of the same plates. The problem is that the discrepancies can be ten times larger than this when different machines or plates are used, when a wide magnitude range is covered, when relative positions are compared over distances of a degree or more, or when absolute positions are needed for comparison with, say, radio catalogues. The challenge now is to improve this accuracy; we should to be able to specify the absolute positions of all well-defined optical objects to better than 250 mas, anywhere in the sky, at any epoch and regardless of magnitude or colour.

A Search for Distant Satellites of Neptune

AbstractThe recent discovery of two distant satellites of Uranus suggests that there could be similar bodies orbiting Neptune. Previous surveys for distant satellites of Neptune have had relatively bright magnitude limits (BJ ≃ 20·5) and would have missed satellites with magnitudes and colours similar to the two recently discovered Uranian satellites (R ~ 20·4 and R ~ 21·9). We have searched for satellites of Neptune to a limiting magnitude of R ~ 21 in a 0·1□° region centred on the planet. This search is up to ~ 2 magnitudes deeper than the previous wide field search for distant satellites by the UK Schmidt Telescope. Nereid was easily recovered by the search and no large variations of its magnitude were detected.

Digital Colour Mapping of the Sky from Supercosmos

The major photographic surveys of the sky (undertaken with the ESO, Palomar and UK Schmidt telescopes) still hold enormous potential regarding the information content of the original plate material. The problem to date has been to extract that information in a meaningful and quantitative way, hence giving rise to the large number of digitisation programmes currently underway and which are reported elsewhere in this volume.

The Use of Photographs in Astronomical Instruction

For many years, copies on film of photographs, both direct and through objective prisms, taken with the 1.2 m United Kingdom Schmidt Telescope, have provided teaching material suitable for universities and colleges (Brück and Tritton, 1988). Table 1 outlines the various types of application to which the photographs may be put. With additional data, some real physics can be injected into the exercises, allowing students to perform quite elaborate projects.

Some Results of an Hα Survey in the Taurus Dark Clouds

AbstractFrom a series of 4° objective-prism plates obtained on the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory, 20 new Hα emission line stars were found. The intensity of Hα emission line was evaluated for these stars. An additional sample of probable Hα emission stars was also found. We present here details and some observational features of these stars. The total number of Hα emission line stars estimated for the surveyed area is about 80.

Wide Field Optical Imaging at CTIO

The CTIO 4-m and 0.6/0.9-m Schmidt telescopes provide a wide-field CCD imaging capability unequalled in the southern hemisphere. Characteristics of present and future CCD imaging systems for these telescopes are discussed.

Kiso Hα Imaging Observations of Nearby Galaxies

AbstractWe report Hα imaging observations of nearby galaxies with the Kiso Schmidt telescope. For spiral galaxy NGC 628, we found no clear correlation between Hα and CO intensities, and we discuss the star formation efficiency of this galaxy. No nuclear Hα emission in this galaxy was detected. This is consistent with spectroscopic observations which indicate that the nuclear region is in the post starburst phase. We also describe the Hα image of Hickson's compact group 92 in which diffuse emission is detected extending within the group system.

Dwarf Spheroidal Galaxies in the Virgo Cluster

We present a study of the smallest and faintest galaxies found in a very deep photographic R-band survey of regions of the Virgo Cluster, totalling over 3 deg2, made with the UK Schmidt Telescope. The objects we detect have the same physical sizes and surface brightnesses as Local Group dwarf spheroidal galaxies. The luminosity function of these extremely low luminosity galaxies (down to MR≃-11 or about 5×10−5L⋆) is very steep, with a power-law slope α≃-2, as would be expected in many theories of galaxy formation via hierarchical clustering, supporting previous observational evidence at somewhat higher luminosities in other clusters.

The Potsdam contribution to the extragalactic link of the Hipparcos proper motion system

Absolute proper motions of 360 Hipparcos stars in 24 fields well distributed over the northern sky were derived from measurements of photographic plates taken mainly with the Tautenburg Schmidt telescope (134/200/400 cm). In each field (about 10 square degrees) a large number of galaxies was used to link the proper motions to the extragalactic reference system. Because of systematic magnitude-dependent errors, which affect the proper motion determination of bright stars, only the 256 stars with were used to determine the spin parameters of the Hipparcos system. The accuracy of the final result is 0.5 mas/yr for all three spin parameters.

New m stars in the vicinity of dark nebulae. I

The results of a spectroscopic survey of late-type M stars in three regions of dark nebulae are given. The observations were made on the 1-m Schmidt telescope of Byurakan Observatory with a 4° preobjective prism. A method of detecting late-type M giants is developed on the basis of the presence of TiO absorption bands in their spectra. The area of the regions studied is 48 sq. deg. We found 96 new late-type M stars, 22 of which exhibited brightness variability during our observations and are new variable stars. The limiting magnitude on the plates obtained in red light is 16m.0, which enables us to state confidently that all late-type M stars (starting with M4) brighter than R = 15m.0 have been detected.

Analysis of seven face-on spiral galaxies

We continue in this work the study of nearby spiral galaxies started with NGC 628 (Natali 1992, here- after Paper I). A sample of seven face-on spiral galax- ies has been selected to obtain images in the U , B, V , R, I bands using a CCD detector at the 90 cm Schmidt telescope at Campo Imperatore Observatory. Surface pho- tometry using a dedicated software is used to derive both the surface brightness radial proles in each band and the colour indexes. The radial disk scalelengths obtained from the radial proles show a trend with wavelength which seems to highlight a huge presence of dust in the inner disk zone. For two galaxies of the sample the presence of dust is conrmed by the radial trend of colour in- dexes. The presence of galactic infall already detected for NGC 628, is conrmed, from the bluish (B V ), also for NGC 3184.