Session 1
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Leszek Blaszkiewicz
leszekb@astro.uni.torun.pl
Torun Center for Astronomy, Poland
I would like to present the status of spectral observations in Department of Radio Astronomy of Torun Centre for Astronomy. There are three persons in our spectral group: dr Marian Szymczak, Grzegorz Hrynek - student and Leszek Blaszkiewicz - PhD student.
The front end available for spectral observations with 32-meter antenna are 1.6, 5 and 6.7 GHz receiving systems. The back end is a Penny & Giles VLBA terminal controlled by a computer working under The Field System and a 512 channel autocorrelator.
At present we carry out some observing programs. These include (1) monitoring of particular OH/IR stars with OH maser emision, (2) regular long period observations (2 years) of W3(OH) and W49(OH) maser sources, (3) searching for new sources of maser emission in some IRAS objects in outer parts of Galaxy, (3) survey of CH3OH maser emission towards OH and SiO sources associated with late type stars.
Aznaur Botashev
bam@sao.ru
Special Astrophysical Observatory RAS, Russia
We conducted multi-frequency observations of complete sample of sources from the PMN catalogue at the RATAN-600 radio telescope in 1994-1996. A list included about 500 radio sources in an interval of declinations -21 deg. < delta < -17 deg. Observations were made on 6 frequencies simultaneously (0.96, 2.3, 3.95, 7.7, 11.2, 21.7 GHz). To detect a variable sources we compare an obtained flux densities with the data from the PMN and other catalogues. An investigation of the resulted spectra get an information for a further search for the counterparts in different non-radio catalogues. This observational program illustrate an astronomical potential of radio telescope RATAN-600. After improving of RA of the sources we began optical identification of these objects. Optical identifications for about 55% radio sources from the sample are presented.
Vladimir Frolov
fvn@isida.ipa.rssi.ru
Institute of Applied Astronomy Russian Academy of Science, Russia
The first Russian system for VLBI-data processing in S2 standard is working in IAA RAS since 1996. This system consist of Mk3 correlator TISS-1M and three PlayBack Terminals S2-PT. New software was written for this system. Software consists of two parts: for S2-PT and for correlator TISS-1M.
S2-PT software realizes the following functions:
Correlator software includes two basic fragments:
During processing radioastronomical data with the TISS-1M it is necessary to solve the following problems:
A subsystem, intended for results displaying allows to display all necessary diagrams and provides a possibility of the preliminary analysis of data processing results.
Some results of data processing are described in report.
Eduardo Gonzales-Solares
eglez@ll.iac.es
Instituto de Astrofisica de Canarias, Spain
The ELAIS (European Large Area ISO Survey) is a project to survey a wide area of the northern and southern sky with ISO at two wavelengths, 15 and 90 microm. The main areas were selected on the basis of: (i) low galactic cirrus contamination, (ii) visibility by ISO for more than 25% of the mission life time, (iii) high ecliptic latitude to avoid zodiacal contamination and (iv) absence of bright 12 microm sources. The main scientific aim is the detection of hifh redshift galaxies, the derivation of star formation history of the Universe between now and z = 1 and the compilation of unbiased samples of active galaxies.
We will use the main radio surveys (FIRST-VLA, NVSS, WENSS, ..) to study the radio properties of the sources detected in the ELAIS areas. We will show first results of the infrared survey and the association of the infrared sources with radio sources.
Heiko Hafok
hafok@zeus.ph1.uni-koeln.ed
Physikalisches Institut, Universität zu Köln, Germany
In 1996 the KOSMA (Kölner Observatorium für SubMillimeter Astronomie) 3-m-radiotelescope has been rebuilt. It is operated at Gornergrat/Zermatt (Switzerland) by the Universität zu Köln, supported by the Deutsche Forschungsgemeinschaft (grant SFB 301) and the Land Nordrhein-Westfalen.
The new telescope, an on-axis Cassegrain system, replaces the old 3-m-radiotelescope of the same type, which was in operation since 1985 on the Gornergrat (altitude 3125 m). Weather statistics and submillimetre observations have shown the excellent atmospheric conditions (very little water vapour) especially during winter time above the Gornergrat, which allow observations up to 1 THz.
However, the surface accuracy (50 microm rms) and the stiffness of the old main reflector limited the highest observable frequency to 500 GHz. To extend this instrumential frequency limit, the new main reflector consists of 18 aluminium panels (accuracy 3..8 microm rms), supported by a carbon fibre backstructure.The stability of the complete structure guarantees a mirror accuracy of below 10 microm rms under all load conditions including gravity and thermal cycling. This is sufficient for observations up into the highest frequency atmospheric window at 1 THz accessible from the ground.
We have fabricated SIS mixer elements and integrated them into receivers for frequencies as high as 800 GHz. These receivers have been successfully in operation and are available for the new telescope.
Wendy Lane
wlane@astro.rug.nl
Rijksuniversiteit Groningen, Kapteyn Astronomical Institute, The Netherlands
We report preliminary results from a survey for HI 21cm absorption in MgII-selected systems at 0.2 < z < 1. Using the new UHF-high system at the Westerbork Synthesis Radio Telescope (WSRT), we have identified two HI 21cm absorbers from the first twenty systems studied. This is consistent with previous numbers for the incidence of HI 21cm absorption in MgII-selected systems. (cf. Briggs and Wolfe, 1983, ApJ, 268, 76). The two new HI 21cm absorption systems, one at z = 0.221 towards the quasar OI 363 (B0738+313), and the other at z = 0.313 towards the quasar PKS 1127-145, are presented. Recent HST/FOS spectra identify damped Ly alpha absorption in both systems (Rao and Turnshek, 1997, in prep.). By comparing the column density from the damped Ly alpha line with that from the HI 21cm line, we calculate the spin temperature, Ts, and find Ts = 1000 K for both systems. Implications for a change in Ts with redshift and the practicality of calculating Ts in this manner at high redshift are discussed.
O. L. Ivantyshyn, V. V. Koshovy, A. B. Lozynsky, Yury V.
Romanchev
Dep23@ah.ipm.Lviv.ua
Karpenko Physico-Mechanical Institute of National Academy of Sciences of Ukraine, Ukraine
Radio telescope URAN-3 was created in 1991 as a part of global Ukrainian VLBI system URAN for investigations of radio sources radiation in decameter waveband. Using this radio telescope the angular resolution near 2 arcsec was obtained. In this paper the parameters, construction and abilities of the radio telescope URAN-3 and two additionally created radio physical complexes -- short base interferometer (SBI) and ionosphere diagnostic center (IDC) is describing. SBI include basic radio telescope URAN-3 with 256-antennas field and movable (up to 40 km baseline) 16-antennas array with variable configuration (4x4, 2x8, etc.). On this instrument a new measurement of CasA visibility function on 25 MHz were made. IDC include URAN-3 and SBI antennas systems with addional apparature and program ware. On IDC were investigated ionosphere phenomena from 5 up to 30 MHz, including disturbances of ionosphere plasma by the ground based acoustic radiator.
Svetlana Veselkova and Dmitriy Ivanov
ipatov@isida.ipa.rssi.ru
Institute of Applied Astronomy Russian Academy of Science, Russia
The quality of scientific results, that are obtained by interferometric methods, are determined in many respects by receivers. The aim of our work is researches of receiving system (S/X cryoreceivers for Russian VLBI network), which mainly determines the sensitivity of all interferometric devices. Basic characteristics of cryoreceiver are gain and noise temperature. Contributions into the noise temperature from different receiver elements were calculated, and measuremed by means of different methods. We have got almost complete coincidence of calculated and measured noise temperature, that shows receiver is ready for work. In the interferometry to have rectangular amplitude-frequency characteristic (AFC) and linear phase-frequency characteristic of receiver is very important. Maximum AFC slope of our S/X receivers is 2 dB at 100 MHz bandwidth, which is only 0.04 dB at frequency band of registration in narrow channel. Deviation of phase characteristic from linearity does not exceed 5% in 100 MHz bandwidth in both frequency bands and does not influence on the result of interferometric processing in narrows channels. Since receivers are used both in interferometric and single dish modes, problems of unstability of gain and noise temperature of receivers were investigated in details.