Schmidt Telescope Research Articles

Using the 6dF Galaxy Redshift Survey to Detect Gravitationally-lensed Quasars

AbstractIt is possible to detect gravitationally-lensed quasars spectroscopically if the spectra obtained during galaxy surveys are searched for the presence of quasar emission lines. The up-coming 6 degree Field (6dF) redshift survey on the United Kingdom Schmidt Telescope will involve obtaining ~105 spectra of near-infrared selected galaxies to a magnitude limit of K = 13. Applying previously developed techniques implies that at least one lens should be discovered in the 6dF survey, but that as many as ten could be found if quasars typically have BJ – K ~ 8. In this model there could be up to fifty lensed quasars in the sample, but most of them could only be detected by infrared spectroscopy.

Substructure and Dynamics of the Fornax Cluster

We present the first dynamical analysis of a galaxy cluster to include a large fraction of dwarf galaxies. Our sample of 108 Fornax Cluster members measured with the UK Schmidt Telescope FLAIR-II spectrograph contains 55 dwarf galaxies (15.5 > b(j) > 18.0 or -16 > M-B > -13.5). H alpha emission shows that of the dwarfs are star forming, twice the fraction implied by morphological classifications. The total sample has a mean velocity of 1493 +/- 36 kms s(-1) and a velocity dispersion of 374 +/- 26 km s(-1). The dwarf galaxies form a distinct population: their velocity dispersion (429 +/- 41 km s(-1)) is larger than that of the giants () at the 98% confidence level. This suggests that the dwarf population is dominated by infalling objects whereas the giants are virialized. The Fornax system has two components, the main Fornax Cluster centered on NGC 1399 with cz = 1478 km s(-1) and sigma (cz) = 370 km s(-1) and a subcluster centered 3 degrees to the southwest including NGC 1316 with cz = 1583 km s(-1) and sigma (cz) = 377 km s(-1). This partition is preferred over a single cluster at the 99% confidence level. The subcluster, a site of intense star formation, is bound to Fornax and probably infalling toward the cluster core for the first time. We discuss the implications of this substructure for distance estimates of the Fornax Cluster. We determine the cluster mass profile using the method of Diaferio, which does not assume a virialized sample. The mass within a projected radius of 1.4 Mpc is (7 +/- 2) x 10(13) M-., and the mass-to-light ratio is 300 +/- 100 M-./L-.. The mass is consistent with values derived from the projected mass virial estimator and X-ray measurements at smaller radii.

An Optical Nebula Associated with a Young X-Ray Supernova Remnant in Vela

A remarkable filamentary nebula (RCW 37) in the close vicinity of the newly discovered X-ray-emitting supernova remnant in Vela (RX J0852.0-4622) is investigated. This supernova explosion is arguably the nearest in recent history. A comparison is made between deep United Kingdom Schmidt Telescope optical images of the region and the ROSAT X-ray data in which the remnant was discovered. This reveals that RCW 37 is most likely directly associated with an X-ray projection from RX J0852.0-4622. This interpretation is strengthened by new long-slit echelle spectrometry of the edge of RCW 37 in the light of [S II] λ6716. A systematic increase in the velocity splitting of the line profiles, from the nebular edge toward its center, of 100 km s-1 is found. The structure bears morphological and kinematical similarities to the famous Crab Nebula funnel.

Spherical primary telescope with aspheric correction at a small internal pupil

The aspheric plate at the center of curvature of a spherical primary is replaced by a small aspheric corrector at a minified pupil located inside a reimaging camera. The correctors are identical for each reimaging camera because the spherical aberration of the primary sphere is identical and symmetrical for all field positions. The magnitude of the field aberrations is evaluated over a range of primary focal ratios and minified pupil diameters. The major term is the increased field angle through the minified aspheric corrector. The field and chromatic aberrations in such a camera are compared with the equivalent full-aperture Schmidt corrector. Field-of-view partitioning enables each subfield to be designed for specific observational requirements, such as multiple-fiber spectrography or CCD imaging. Field partitioning is shown to be a powerful means for the replacement of the large aspheric corrector of a Schmidt telescope by a multiplicity of small reimaging subsystems. The cost to fill the typical wide field of a Schmidt telescope with reimaging modules is approximately 1% the cost of a Schmidt aspheric plate.

Precision astrometry with schmidt telescopes

Schmidt telescopes currently provide nearly the only means to obtain positions of faint objects with respect to the standard ICRS reference system. However, the lack of adequate astrometric calibration methods to account for the specific properties of Schmidt telescopes leads to residual systematic errors of up to 1″. The main source of systematic errors is plate bending during exposure. A high-precision reduction technique to account for this effect is proposed. Application of this technique to observations acquired with the Schmidt telescopes of the Palomar and Anglo-Australian Observatories reduced the systematic errors by a factor of 2.5 and gave them a simpler structure, while simultaneously decreasing the number of unknowns in the reduction model threefold. Application of the new method, with appropriate account for the design of the particular plateholder used, will make it possible to use Schmidt telescopes to determine high-precision positions for virtually all objects detected in photographic surveys.

The KPNO International Spectroscopic Survey. I. Description of the Survey

The KPNO International Spectroscopic Survey (KISS) is a new objective-prism survey for extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys that were carried out with Schmidt telescopes using photographic plates with the advantages of modern CCD detectors. It is the first purely digital objective-prism survey, and extends previous photographic surveys to substantially fainter flux limits. In this, the first paper in the series, we give an overview of the survey technique, describe our data processing procedures, and present examples of the types of objects found by KISS. Our first H�-selected survey list detects objects at the rate of 18.1 per square degree, which is 181 times higher than the surface density of the Markarian survey. Since the sample is line-selected, there is an imposed redshift limit of z < � 0.095 due to the filter employed for the objective-prism observations. We evaluate the quality of the observed parameters derived from the survey data, which include accurate astrometry, photometry, redshifts, and line fluxes. Finally, we describe some of the many applications the KISS database will have for addressing specific questions in extragalactic astronomy. Subsequent papers in this series will present our survey lists of emission-line galaxy candidates. Subject headings: galaxies: emission-lines — galaxies: Seyfert — galaxies: starburst — surveys

Spatially Resolved Spectrophotometry of M81: Age, Metallicity, and Reddening Maps

In this paper we present a multicolor photometric study of the nearby spiral galaxy M81, using images obtained with the Beijing Astronomical Observatory 60/90 cm Schmidt telescope in 13 intermediate-band filters from 3800 to 10000 A. The observations cover the whole area of M81, with a total integration of 51 hr from 1995 to 1997 February. This provides a multicolor map of M81 in pixels of 17 × 17. Using theoretical stellar population synthesis models, we demonstrate that some BATC (Beijing-Arizona-Taiwan-Connecticut Multicolor Sky Survey) colors and color indices can be used to disentangle the age and metallicity effect. We compare in detail the observed properties of M81 with the predictions from population synthesis models and quantify the relative chemical abundance, age, and reddening distributions for different components of M81. We find that the metallicity of M81 is about Z = 0.03, with no significant difference over the whole galaxy. In contrast, an age gradient is found between stellar populations of the central regions and of the bulge and disk regions of M81: the stellar population in its central regions is older than 8 Gyr, while the disk stars are considerably younger (~2 Gyr). We also give the reddening distribution in M81. Some dust lanes are found in the galaxy bulge region, and the reddening in the outer disk is higher than that in the central regions.

A Finding List of Faint UV‐bright Stars in the Galactic Plane. V.

ABSTRACTFour additional plates from the Sandage Two‐Color Survey of the Galactic Plane have been examined, yielding identifications of 108 UV‐bright stars. The plates examined were obtained using the Palomar 48 inch Oschin Schmidt telescope and cover a field of view of 6.°6 × 6 .°6. The plates were centered at the Galactic longitude (l) and latitude (b) coordinates of (80.°4, +0°), (80.°4, −6°), (100°, +4°), and (104.°1, +6°). Identified sources range in U−B color from U−B∼ - 0.1 to U−B∼ - 1.0 and in magnitude from mB∼10 to ∼20. Accurate J2000 coordinates and finding charts are provided for all the UV candidates included, and some of the more interesting sources are discussed. Previously identified objects referenced in the literature are noted.

Spectral evolution of the peculiar Ic Supernova 1998bw

Supernova 1998bw holds the record for the most energetic Type Ic explosion, one of the brightest radio supernovae and probably the first supernova associated with a γ-ray burst. In this paper we present spectral observations of SN 1998bw observed in a cooperative monitoring campaign using the Anglo-Australian Telescope, the UK Schmidt Telescope and the Siding Springs Observatories 2.3-m telescope. We investigate the evolution of the spectrum between 7 and 94 d after V-band maximum in comparison with well-studied examples of Type Ic SNe in order to quantify the unusual properties of this supernova event. Though the early spectra differ greatly from observations of classical Ic supernovae (SNe), we find that the evolution from the photospheric to nebular phases is slow but otherwise typical. The spectra differ predominantly in the extensive line blending and blanketing which has been attributed to the high velocity of the ejecta. We find that by day 19, the absorption line minima blueshifts are 10–50 per cent higher than other SNe and on day 94 emission lines are 45 per cent broader, as expected if the progenitor had a massive envelope. However, it is difficult to explain the extent of line blanketing entirely by line broadening, and we argue that an additional contribution from other species is present, indicating unusual relative abundances or physical conditions in the envelope.

Lightcurve and color of near-earth-asteroid 1989ML

The asteroid of 1989ML is an Amor type near-earth-asteroid, which is one of the most accessible asteroids by spacecraft, and consequently it has been selected as a backup target of the Japanese sample return mission, MUSES-C. In January 1996, the brightness of 1989ML had been brighter than 20-magnitude in R-band and we succeeded to observe it using a 1.05-m schmidt telescope with 1K CCD detector at Kiso Observatory, Japan. From the analysis of the data obtained for four nights, it is found that the rotational period of 1989ML may be 19 or 32 hours, and the amplitude of its brightness variation is about 1 magnitude in R-band. We have performed also VRI band colorimetry and found that the color of 1989ML is similar to that of C-type asteroid.

Automated detection and classification of objective prism stellar spectra

Abstract The spectral classification of stars in galaxies is a method of studying their stellar content. In particular, the distribution of spectral types in the stellar systems is a powerful diagnostic for the estimation of their composition, age and evolutionary state. The observational materials mainly used are spectral plates obtained with Schmidt telescopes. Such plates contain, generally, thousands of spectra. There are prism-plate libraries and digitized databases in several astronomical centres that can be fully exploited only with automated processing. Such a system for automated processing of stellar spectra on digitized objective-prism plates is presented. It is developed as a context under the MIDAS environment and provides tools for digital preprocessing of the images (rotating, correcting the tilt, calibration, etc.), for interactive and automated detection of the spectra, for spectra extraction as one-dimensional scans, and finally, for automated classification. Here we particularly present...

Discovery of the Optical Transient of GRB 990308

The optical transient of the faint gamma-ray burst GRB 990308 was detected by the QUEST camera on the Venezuelan 1 m Schmidt telescope starting 3.28 hr after the burst. Our photometry gives V = 18.32 ± 0.07, R = 18.14 ± 0.06, B = 18.65 ± 0.23, and R = 18.22 ± 0.05 for times ranging from 3.28 to 3.47 hr after the burst. The colors correspond to a spectral slope of close to fν ∝ ν1/3. Within the standard synchrotron fireball model, this requires that the external medium be less dense than 104 cm-3, the electrons contain more than 20% of the shock energy, and the magnetic field energy be less than 24% of the energy in the electrons for normal interstellar or circumstellar densities. We also report upper limits of V > 12.0 at 132 s (with LOTIS), V > 13.4 from 132 to 1029 s (with LOTIS), V > 15.3 at 28.2 minutes (with Super-LOTIS), and a 8.5 GHz flux of less than 114 μJy at 110 days (with the Very Large Array). Wisconsin-Indiana-Yale-NOAO 3.5 m and Keck 10 m telescopes reveal this location to be empty of any host galaxy to R > 25.7 and K > 23.3. The lack of a host galaxy likely implies that it is either substantially subluminous or more distant than a redshift of ~1.2.

A UKST survey of blue objects towards the galactic centre – a search for early-type stars

We have begun a search for early-type stars towards the galactic centre which are potentially young objects situated within the inner few kiloparsecs of the disk. U and V (or I) band photographic photometry from the UK Schmidt Telescope has been obtained to identify the bluest candidates in nineteen Schmidt elds (centred close to the galactic centre). We have spectroscopically observed these targets for three elds with the FLAIR multi-bre system to determine their spectral types. In particular, ten early B-type stars have been identied and equivalent width measurements of their Balmer and He i lines have been used to estimate atmospheric parameters. These early-type objects have magnitudes in the range 11:5 V 16:0, and our best estimates of their distance (given probable highly variable reddening in this direction together with errors in the plate photometry) suggest that some of them originated close to (i.e Rg < 3 kpc), or even beyond the galactic centre. Future high-resolution spec- troscopy of these stars will provide reliable atmospheric parameters and element abundances, in order to map the current chemical composition of the inner galaxy.

Newly Discovered Herbig-Haro Objects in the NGC 2068 and NGC 2071 Regions

Taking the advantage of the large field of view at the 60/90 cm Schmidt telescope of Beijing Astronomical Observatory, we were able to carry out a wide-held survey of Herbig-Haro (HH) objects in nearby star-forming regions, including Perseus, Taurus, Orion, and others. In a 58' x 58' field centered on NGC 2068 and NGC 2071 (M78), two active regions of star formation in the giant molecular cloud complex L1630, we found 17 HH objects exhibiting prominent [S II] emission but without continuum emission. Among these, we confirmed all the 11 known HH objects listed in the General Catalogue of Herbig-Haro Objects in this field. In addition, we discovered another six new HH objects, including HH 437, 438A-C, 440A/B, 442, 443, and 452A/B. These objects exhibit a variety of morphological structures, from knot to nebula. The discovery of these HH objects demonstrates strong activity of young stellar objects in the region we are studying. The large-scale spatial distribution of HH objects in the region is discussed by combination of our results and previous data.

Investigation of flare stars in the pleiades by the method of stellar tracks. I

Observations of the Pleiades cluster by the method of stellar tracks, carried out on the 40-inch Schmidt telescope of Byurakan Astrophysical Observatory, have resulted in the detection of 49 flares from 38 stars, 17 of which were not previously known to be flare stars. It is shown that for bright stars (U ≤ 16.0) the detection of flares in observations by the method of stellar tracks is at least three times more efficient than for observations by the method of stellar chains. Another advantage of the first method is that one can detect brief flares that last less than 6 min. The visual stellar magnitude at the minimum for the brightest of the flare stars that we found is 11.92. This raised the upper luminosity limit of known flare stars in the Pleiades by 0.21 magnitude. A comparison of the expected number of bright flare stars in the Pleiades with the number of all bright members of the cluster (falling in the range from V ≈ 12.0 toV ≈16.0) suggested that all these stars evidently must be flare stars.

Survey for Emission‐Line Galaxies: Universidad Complutense de Madrid List 3

A low-dispersion objective-prism survey for low-redshift emission-line galaxies (ELGs) is being carried out by the University Complutense de Madrid with the Schmidt telescope at the German-Spanish Observatory of Calar Alto (Almeria, Spain). A 4° full aperture prism, which provides a dispersion of 1950 A mm^-1, and IIIaF emulsion combination has been used to search for ELGs selected by the presence of H_α emission in their spectra. Our survey has proved to be able to recover objects already found by similar surveys with different techniques and, what is more important, to discover new objects not previously cataloged. A compilation of descriptions and positions, along with finding charts when necessary, is presented for 160 extragalactic emission-line objects. This is the first list, which contains objects located in a region of the sky covering 270 deg^2 in 10 fields near α = 0^h and δ = 20°.

Deep Intermediate-Band Surface Photometry of NGC 5907

We obtained very deep exposures of NGC 5907 with a Schmidt telescope, large-format CCD, and intermediate-band filters centered at 6660A and 8020A. These two filters, part of a 15-filter set, are custom-designed to avoid the brightest (and most variable) night sky lines, with the result that our images go deeper, with lower sky noise, than those taken with broad-band filters. Our errors of observation reach 1 mag/arcsec^2 at 29.00 mag/arcsec-2 in the 6660A image (= 28.7 in R-band), and 27.4 mag/arcsec^ in the 8020A image (same zero point as I-band). Fainter than R = 27 mag arcsec^, the surface brightness around NGC 5907 is strongly asymmetric, being mostly brighter the NW side of the galaxy midplane. This asymmetry rules out a halo for the origin of the faint surface brightness we see. Rather, this asymmetry is likely an artifact due to a combination of light from a faint ring around this galaxy (as described in Shang et al. 1998, ApJL 504, 23) and residual surface brightness at faint levels from stars that our star-masking procedure cannot completely eliminate. Good agreement with the surface photometry of NGC 5907 by Morrison et al. and other workers lead us to conclude that their data are similarly affected at faint levels by ring light and residual effects from their star masking procedures. Inspection of the images published by Morrison et al. and Sackett et al. confirm this to be the case. Thus, we conclude that NGC 5907 does not have a faint, extended halo.

Optical and Near‐infrared Observations of the Afterglow of GRB 980329 from 15 Hours to 10 Days

We report I-band observations of the GRB 980329 field made on March 29 with the 1.34-m Tautenberg Schmidt telescope, R-, J- and K-band observations made on April 1 with the APO 3.5-m telescope, R- and I-band observations made on April 3 with the Mayall 4-m telescope at KPNO, and J- and K-band observations made between April 6 - 8 with the Keck-I 10-m telescope. We show that these and other reported measurements are consistent with a power-law fading of the optical/near infrared source that is coincident with the variable radio source VLA J0702+3850. This firmly establishes that this source is the afterglow of GRB 980329.

A new faint Wolf-Rayet star in the Large Magellanic Cloud

A new faint WN3 star in the general field of the Large Magellanic Cloud has been identified on a UK Schmidt Telescope objective-prism plate. It is reddened and has weak emission lines.

Brown dwarfs in the Pleiades and the initial mass function across the stellar/substellar boundary

ABSTRA C T We present a new sample of brown dwarf (BD) candidates from a survey covering 68 · 68 centred on the Pleiades. The survey was constructed using I- and R-band photographic plates, from the United Kingdom Schmidt Telescope, measured using the new high-precision microdensitometer SuperCOSMOS at the Royal Observatory, Edinburgh. Objects as faint as or up to ,0:5 mag fainter than the Pleiades lithium boundary are selected on the basis of having extremely red photographic colours and proper motions consistent with cluster membership; follow-up near-infrared and infrared photoelectric photometry yields nine candidate BD Pleiads. Coordinates, magnitudes and finders are presented for these objects. We use these data and information on higher mass stars to construct a mass function having an increasingly shallow gradient towards and across the stellar/substellar boundary; a few of the candidates are found at distances of more than 28 from the nominal cluster centre. We discuss the implications of these results for future surveys.