CFHT Research Articles

Evaluation Of The RCA 640 X1024 Charge-Coupled-Device Imager For Astronomical Use

A double-density (15 µm X15 µm pixels) RCA charge-coupled device has been tested and commissioned for astronomical imaging and spectroscopy at the Canada-France-Hawaii telescope (CFHT). This thinned device has had its support glass removed and has received a broadband antireflection coating to improve the UV and blue response. Presented here are characterization measurements resulting from 10 months of laboratory testing and use at the telescope. Although the read noise is not as low as with other CCDs available, the high pixel density and the permanent quantum efficiency enhancements provided by this RCA device give some advantages over other sensors when used at the CFHT.

Is 3C324 the first gravitationally lensed giant galaxy?

The radiogalaxy 3C324 has recently raised considerable interest as one of the most distant (redshift z = 1.206) and luminous known galaxies. Here we report new observations of this object at Canada–France–Hawaii Telescope which confirm our previous predictions of the presence of an intervening gravitational lens. First, a multiple structure is revealed by our charge-coupled device (CCD) broadband imagery. Second, following our previous identification in the 3C324 spectrum of an additional line system at z=0.84, subsequent CCD observation through interferential filters were planned. In a wavelength range corresponding to an emission line at z=0.84 only the central component is detected, while only outer components are seen in a range corresponding to a line redshifted by z=1.206. These observations are interpreted as the first example of gravitational multiple imaging of a giant radiogalaxy by a foregound object. So galaxy 3C324 seems to be a gravitational mirage—though further spectroscopic observations will be needed to establish whether the two images have similar spectra.

The structure of a cometary Type I tail: Ground‐based and ice observations of P/Giacobini‐Zinner

The in situ magnetic field and plasma measurements from the International Cometary Explorer (ICE) Mission obtained on September 11, 1985 are compared with CCD images of P/Giacobini‐Zinner (G‐Z) acquired with the 3.6 m Canada‐France‐Hawaii Telescope (CFHT) on Mauna Kea, Hawaii and a slit spectrogram from Lick Observatory during the same period. The CFHT image at ∼3.5 hr after the ICE encounter showed a short central ion tail with a diameter of ∼3 × 10³ km and a length of ∼2 × 104 km as observed in the H2O+ bandpass centered at 7025 Å. There was no distinct evidence of fine structure or ray activity. The Lick spectrogram of the H2O+ emissions taken ∼0.5 hr post‐encounter with the slit perpendicular to the sun‐comet line showed an ion tail with a diameter of 1.2 × 104 km. The ICE observations revealed a well defined 9.6 × 10³ km diameter magnetotail composed of two magnetic lobes in pressure equilibrium with a high beta central plasma sheet. These differing measures of tail width are found to be mutually consistent if the ion emissions observed at Earth originate in a slab‐shaped plasma sheet whose orientation is controlled by the direction of the interplanetary magnetic field. The results of this study also suggest that some thinning and thickening of cometary type I tails, usually attributed to plasma instabilities, may be due to changes in the angle at which the plasma sheet is viewed as IMF direction varies.

TWO PRIME-FOCUS SPECTROGRAPHS USING HOLOGRAPHIC GRATINGS

ABSTRACT Two simple low-resolution prime-focus spectrographs have been built and used at the Canada-France-Hawaii Telescope (CFHT). Both employ a concave holographic grating as the principal optical component. The spectrographs have typical efficiencies of 30 percent and operate over a 5000 A wavelength range. One spectrograph, a user instrument at the CFHT, allows both imaging and spectroscopy with a single detector. The second uses separate detectors for imaging and spectroscopy. Both are capable of limited two-dimensional long-slit spectroscopy with good images being obtained up to 2 mm off-axis.

More dark matter around Uranus and Neptune?

In addition to their natural satellites, the giant planets possess a surprisingly rich population of moonlets, rings, arcs and diffuse haloes of dust1–6, the dynamics of which involves gravitational interactions7 and radiation and magnetic forces8,9. Recent analyses (by A.B., W. Hubbard, F.R. and B.S.) of isolated events observed around Neptune indicate the existence of an incomplete or at least a highly azimuthally variable ring or ‘arc’ around Neptune. Similar phenomena may be detectable around Uranus. In order to look for yet undetected dark matter around Uranus and Neptune, the best signal-to-noise ratio stellar occultations have been reanalysed. To be confirmed, an ‘event’ should be observed with more than one telescope on the same site since the Fresnel scale (see below) is about 2–3 km at the level of Uranus and Neptune, and it should also be observed from widely separated observatories (100–1,000 km) to have an idea of the spatial extent of the occulting object, and to distinguish between satellites and ring-like structures. Moreover, theoretical models of diffracting bars or circular objects provide useful tests to reject some isolated events as being incompatible with real and celestial events10. We report here an investigation of the surroundings of Uranus and Neptune using stellar occulations observed at the European Southern Observatory (ESO) on 22 April 1982 and at the Canada France Hawaii Telescope (CFHT) on 15 June 1983, respectively. The high signal-to-noise ratio of these observations sets stringent limits on the presence of matter around these planets.

Optical counterparts for X-ray sources in M31

view Abstract Citations (32) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optical counterparts for X-ray sources in M 31. Crampton, D. ; Cowley, A. P. ; Hutchings, J. B. ; Schade, D. J. ; van Speybroeck, L. P. Abstract Einstein Observatory X-ray position (both IPC and HRI) for 117 sources around M31 have been examined with 1000 A/mm slitless spectral plates obtained at the prime focus of the Canada-France-Hawaii Telescope (CFHT). A variety of possible counterparts is found within the error circles of the source positions, including globular clusters, foreground stars, faint blue stars, and a compact galaxy. For about half of the sources, no candidate object sufficiently near the X-ray position was visible on the plates which reach to a B-mag of about -3.5. Crowding in the nucleus of M31 made it impossible to examine the source positions less than 2 to 3 arcmin from the center of the galaxy. This paper lists all sources with their suggested optical identifications and gives finding charts for some of the stars. A brief comparison is made among the X-ray sources in M31, the Magellanic Clouds, and the Galaxy. Publication: The Astrophysical Journal Pub Date: September 1984 DOI: 10.1086/162448 Bibcode: 1984ApJ...284..663C Keywords: Andromeda Galaxy; Blue Stars; Globular Clusters; Radio Sources (Astronomy); Supernova Remnants; X Ray Sources; B Stars; Compact Galaxies; Magellanic Clouds; Milky Way Galaxy; O Stars; Optical Emission Spectroscopy; Astronomy full text sources ADS | data products SIMBAD (86) NED (2)

Halfway to space

It is now nearly three years since three new telescopes were completed alongside the University of Hawaii's 88–inch instrument, to enhance the prospects of the observatory at Mauna Kea in Hawaii. These were the 3 m infrared telescope facility (IRTF) belonging to NASA, and operated by the University of Hawaii; the 3.6 m Canada–France–Hawaii telescope (CFHT); and the 3.8 m United Kingdom infrared telescope (UKIRT) – see Physics Bulletin December 1979 p501.

Optical morphology of 13 QSOs

view Abstract Citations (44) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optical morphology of 13 QSOs. Hutchings, J. B. ; Crampton, D. ; Campbell, B. ; Pritchet, C. Abstract Faint, underlying structures have been detected and mapped around all (10) QSOs with z less than 0.3 for which good, red, sensitive plates were obtained at the prime focus of the Canada-France-Hawaii Telescope (CFHT). In some cases the 'fuzz' is circular or elliptical, giving the object the appearance of a Seyfert or N galaxy, while in others, particularly the radio-loud sources, the extent of the fuzz is larger and has a jetlike appearance. Surface photometry of the objects shows that the radial intensity distribution falls off exponentially in the outer regions, while in the inner regions it is impossible to distinguish between a spheroidal, r to the -1/4, distribution or an exponential disk. An analysis with simple models confirms that the intensity distribution of a disk plus point source is indistinguishable from a spheroidal plus point source on the basis of such data. Publication: The Astrophysical Journal Pub Date: August 1981 DOI: 10.1086/159085 Bibcode: 1981ApJ...247..743H Keywords: Astronomical Photometry; Galactic Structure; Quasars; X Ray Sources; Galactic Nuclei; Image Processing; Photosensitivity; Point Sources; Point Spread Functions; Astronomy full text sources ADS | data products NED (13) SIMBAD (8)

Some features of the Canada–France–Hawaii telescope. I. Before-foci optical design

The 3.6-m Canada–France–Hawaii telescope has some unusual before-focus optical features such as: (a) a three element prime focus corrector lens which can have a transmission grating on the last element, i.e., a grens, which gives a dispersion of 1000 Å/mm over a 1° field at F/4.2, and (b) a small-mirror coudé train, triplicated for high reflectance coatings, which can be adjusted to produce a small, 15 mm, collimated beam suitable for insertion of a polarization modulator before the declination axis.