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تسجيل مستخدم جديدYebes 40 m radio telescope and the broad band NANOCOSMOS receivers at 7 mm and 3 mm for line surveys
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F. Tercero
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Yebes 40,m radio telescope is the main and largest observing instrument at Yebes Observatory and it is devoted to Very Long Baseline Interferometry (VLBI) and single dish observations since 2010. It has been covering frequency bands between 2,GHz and 90,GHz in discontinuous and narrow windows in most of the cases, to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). Nanocosmos project, a European Union funded synergy grant, opened the possibility to increase the instantaneous frequency coverage to observe many molecular transitions with single tunnings in single dish mode. This reduces the observing time and maximises the output from the telescope. We present the technical specifications of the recently installed 31.5-50 GHz (Q band) and 72-90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We have observed IRC+10216, CRL 2688 and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single dish mode. The results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers a signal to noise ratio never seen before for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL,618 in the W band demonstrates that the 40~m radio telescope produces comparable results to those from the IRAM 30~m radio telescope, although with a smaller sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity.
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This review arose from the European Radio Astronomy Technical Forum (ERATec) meeting held in Firenze, October 2015, and aims to highlight the breadth and depth of the high-impact science that will be aided and assisted by the use of simultaneous mm-w
avelength receivers. Recent results and opportunities are presented and discussed from the fields of: continuum VLBI (observations of weak sources, astrometry, observations of AGN cores in spectral index and Faraday rotation), spectral line VLBI (observations of evolved stars and massive star-forming regions) and time domain observations of the flux variations arising in the compact jets of X-ray binaries. Our survey brings together a large range of important science applications, which will greatly benefit from simultaneous observing at mm-wavelengths. Such facilities are essential to allow these applications to become more efficient, more sensitive and more scientifically robust. In some cases without simultaneous receivers the science goals are simply unachievable. Similar benefits would exist in many other high frequency astronomical fields of research.
We present observational data of a molecular line survey toward the nearby galaxies NGC 1068, NGC 253, and IC 342 at the wavelengths of 3 mm ($sim$85--116 GHz) obtained with the Nobeyama 45 m radio telescope. In IC 342 the line survey with high spect
ral resolution at the 3 mm region was reported for the first time. NGC 1068 is a nearby gas-rich galaxy with X-rays from an active galactic nucleus (AGN), and NGC 253 and IC 342 are nearby gas-rich galaxies with prototypical starbursts. These galaxies are useful to study the impacts of X-rays and ultraviolet radiation on molecular abundances. The survey was carried out with the resulting rms noise level of a few mK ($Trm{_A^*}$). As a result we could obtain almost complete data of these galaxies at the 3 mm region: We detected 19--23 molecular species depending on the galaxies including several new detections (e.g., cyclic-C$_3$H$_2$ in IC 342). We found that the intensities of HCN, CN, and HC$_3$N relative to $^{13}$CO are significantly strong in NGC 1068 compared to those in NGC 253 and IC 342. On the other hand, CH$_3$CCH was not detected in NGC 1068. We obtained these results with the narrow beam (15$$.2--19$$.1) of the 45 m telescope among the single-dish telescopes, and in particular selectively observed the molecular gas close to the circumnuclear disk (CND) in NGC 1068. Our line intensities in NGC 1068 were compared to those obtained with the IRAM 30 m radio telescope already reported. As a result, the intensity ratio of each line was found to have information on the spatial distribution. Our observations obtained the line intensities and stringent constraints on the upper limit for the three galaxies with such narrow beam, and consequently, the data will be a basis for further observations with high spatial resolution.
Spectral line survey observations are conducted toward the high-mass protostar candidate NGC 2264 CMM3 in the 4 mm, 3 mm, and 0.8 mm bands with the Nobeyama 45 m telescope and the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope. In t
otal, 265 emission lines are detected in the 4 mm and 3 mm bands, and 74 emission lines in the 0.8 mm band. As a result, 36 molecular species and 30 isotopologues are identified. In addition to the fundamental molecular species, many emission lines of carbon-chain molecules such as HC5N, C4H, CCS, and C3S are detected in the 4 mm and 3 mm bands. Deuterated molecular species are also detected with relatively strong intensities. On the other hand, emission lines of complex organic molecules such as HCOOCH3, and CH3OCH3 are found to be weak. For the molecules for which multiple transitions are detected, rotation temperatures are derived to be 7-33 K except for CH3OH. Emission lines with high upper-state energies (Eu > 150 K) are detected for CH3OH, indicating existence of a hot core. In comparison with the chemical composition of the Orion KL, carbon-chain molecules and deuterated molecules are found to be abundant in NGC 2264 CMM3, while sulfur-bearing species and complex organic molecules are deficient. These characteristics indicate chemical youth of NGC 2264 CMM3 in spite of its location at the center of the cluster forming core, NGC 2264 C.
We have conducted a spectral line survey in the 3 mm and 2 mm bands toward two positions in a spiral arm of M51 (NGC 5194) with the IRAM 30 m telescope. In this survey, we have identified 13 molecular species, including CN, CCH, N2H+, HNCO, and CH3OH
. Furthermore, 6 isotopologues of the major species have been detected. On the other hand, SiO, HC3N, CH3CN, and the deuterated species such as DCN and DCO+ are not detected. The deuterium fractionation ratios are evaluated to be less than 0.8 % and 1.2 % for DCN/HCN and DCO+/HCO+, respectively. By comparing the results of the two positions with different star formation activities, we have found that the observed chemical compositions do not strongly depend on star formation activities. They seem to reflect a chemical composition averaged over the 1-kpc scale region including many giant molecular clouds. Among the detected molecules CN, CCH, and CH3OH are found to be abundant. High abundances of CN, and CCH are consistent with the above picture of a wide spread distribution of molecules, because they can be produced by photodissociation. On the other hand, it seems likely that CH3OH is liberated into the gas phase by shocks associated with large scale phenomena such as cloud-cloud collisions and/or by non-thermal desorption processes such as photoevaporation due to cosmic-ray induced UV photons. The present result demonstrates a characteristic chemical composition of a giant molecular cloud complex in the spiral arm, which can be used as a standard reference for studying chemistry in AGNs and starbursts.
We report the current status of the 1.85-m mm-submm telescope installed at the Nobeyama Radio Observatory (altitude 1400 m) and the future plan. The scientific goal is to reveal the physical/chemical properties of molecular clouds in the Galaxy by ob
taining large-scale distributions of molecular gas with an angular resolution of several arcminutes. A semi-automatic observation system created mainly in Python on Linux-PCs enables effective operations. A large-scale CO $J=$2--1 survey of the molecular clouds (e.g., Orion-A/B, Cygnus-X/OB7, Taurus-California-Perseus complex, and Galactic Plane), and a pilot survey of emission lines from minor molecular species toward Orion clouds have been conducted so far. The telescope also is providing the opportunities for technical demonstrations of new devices and ideas. For example, the practical realizations of PLM (Path Length Modulator) and waveguide-based sideband separating filter, installation of the newly designed waveguide-based circular polarizer and OMT (Orthomode Transducer), and so on. As the next step, we are now planning to relocate the telescope to San Pedro de Atacama in Chile (altitude 2500 m), and are developing very wideband receiver covering 210--375 GHz (corresponding to Bands 6--7 of ALMA) and full-automatic observation system. The new telescope system will provide large-scale data in the spatial and frequency domain of molecular clouds of Galactic plane and Large/Small Magellanic Clouds at the southern hemisphere. The data will be precious for the comparison with those of extra-galactic ones that will be obtained with ALMA as the Bands 6/7 are the most efficient frequency bands for the surveys in extra-galaxies for ALMA.
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