A RATAN-600 Zenith-Field sky survey. Catalog of radio sources

A catalog of radio sources detected in a deep RATAN-600 survey is presented. The catalog was obtained in the region 0^h ≤ RA_2000.0 ≤ 24^h, Dec_2000.0 = 41°30′42″ ± 2′, at the declination of the bright radio source 3C 84. There were nine sessions of multi-wavelength observations at wavelengths λ = 1–55 cm, and more than 300 daily scans were accumulated at each wavelength. This is the first stage in the reduction of an extensive database accumulated by the Cosmological Gene Project. The RATAN-600 Zenith Field (RZF) catalog was obtained at the central wavelength of 7.6 cm, and contains 437 radio sources, virtually all of which have been identified with NVSS objects. Most of the flux densities for the catalog sources are above the 5σ level. Noise from faint (mainly new) background sources at a level of about 0.8 mJy has been detected. The minimum flux density of the catalog, 2.5 mJy, is comparable to the flux-density linit of the NVSS catalog. The catalog is more than 80% complete for sources with flux densities >3 mJy.     

Six-day modulation of the quiescent radio emission of SS 433

Two daily sets of monitoring data of the Galactic X-ray binary SS 433 (V1343 Aql) obtained on the RATAN-600 radio telescope (117 days in 1997 and 120 days in 1999) show variations in its quiescent radio emission with a period of 6.05±0.1 days at six frequencies from 0.96 to 22 GHz. This 10–15% modulation in the quiescent radio light curves differs significantly from the well-known 6.28-day periodicity in the emission of moving spectral features and in optical photometric data, which are related to nodding motions of the jets and accretion-disk wobble. This period coincides almost exactly with the theoretical value for the harmonic f=2(I _o+I _p), related to the orbital (T _o=13.08 days) and precessional (T _p=162.4 days) periods for slaved accretion-disk models. The 6.06-day period corresponds to the combined frequency. It is proved that the modulation of the radio flux of SS 433 may be associated with relativistic boosting of the jet emission due to periodic variation of the orientation of the jets, which are nodding with a period of six days. The synchrotron emission of the two jets contributes to the quiescent radio flux of SS 433, and the six-day harmonic has the same radio spectrum as the quiescent radio flux: S _v ～v ^?0.6.     

Multi-frequency survey of background radiations of the Universe. The “Cosmological Gene” project. First results

The results of the first stage of the “Cosmological Gene” project of the Russian Academy of Sciences are reported. These results consist in the accumulation of multi-frequency data in 31 frequency channels in the wavelength interval 1–55 cm with maximum achievable statistical sensitivity limited by the noise of background radio sources at all wavelengths exceeding 1.38 cm. The survey region is determined by constraints 00 ^h < RA < 24 ^h and 40°30′ < DEC < 42°30′. The scientific goals of the project are refined in view of recent proposals to use cosmological background radiation data for the development of a unified physical theory. Experimental data obtained with the RATAN-600 radio telescope are used to refine the contribution of the main “screens” located between the observer and the formation epoch of cosmic background radiation (z = 1100). Experimental data for synchrotron radiation and free-free noise on scales that are of interest for the anisotropy of cosmic microwave background are reported as well as the contribution of these noise components in millimeter-wave experiments to be performed in the nearest years. The role of dipole radio emission of fullerene-type dust nanostructures is shown to be small. The most precise estimates of the role of background radio sources with inverted spectra are given and these sources are shown to create no serious interference in experiments. The average spectral indices of the weakest sources of the NVSS and FIRST catalogs are estimated. The “saturation” data for all wavelengths allowed a constraint to be imposed on the Sunyaev-Zeldovich noise (the SZ noise) at all wavelengths, and made it possible to obtain independent estimates of the average sky temperature from sources, substantially weaker than those listed in the NVSS catalog. These estimates are inconsistent with the existence of powerful extragalactic synchrotron background associated with radio sources. Appreciable “quadrupole” anisotropy in is detected in the distribution of the spectral index of the synchrotron radiation of the Galaxy, and this anisotropy should be taken into account when estimating the polarization of the cosmic microwave background on small l. All the results are compared to the results obtained by foreign researchers in recent years.     

RATAN-600 7.6-cm deep sky strip surveys at the declination of the SS433 source during the 1980–1999 period. Data reduction and the catalog of radio sources in the right-ascension interval 7h ≤ R.A. < 17h

We use two independent methods to reduce the data of the surveys made with RATAN-600 radio telescope at 7.6 cm in 1988–1999 at the declination of the SS433 source. We also reprocess the data of the “Cold” survey (1980–1981). The resulting RCR (RATAN COLD REFINED) catalog contains the right ascensions and fluxes of objects identified with those of the NVSS catalog in the right-ascension interval 7 ^h ≤ R.A. < 17 ^h . We obtain the spectra of the radio sources and determine their spectral indices at 3.94 and 0.5 GHz. The spectra are based on the data from all known catalogs available from the CATS, Vizier, and NED databases, and the flux estimates inferred from the maps of the VLSS and GB6 surveys. For 245 of the 550 objects of the RCR catalog the fluxes are known at two frequencies only: 3.94 GHz (RCR) and 1.4 GHz (NVSS). These are mostly sources with fluxes smaller than 30mJy. About 65% of these sources have flat or inverse spectra (α > −0.5). We analyze the reliability of the results obtained for the entire list of objects and construct the histograms of the spectral indices and fluxes of the sources. Our main conclusion is that all 10–15 mJy objects found in the considered right-ascension interval were already included in the decimeter-wave catalogs.     

Galactic synchrotron emission according to the data of the RZF survey conducted at the RATAN-600 radio telescope

Deep 1–49 cm surveys of the circumzenithal sky area performed using the RATAN-600 radio telescope allowed the spectral index of Galactic synchrotron emission in the 7.6–49 cm wavelength interval to be refined. The data obtained are inconsistent with the model of synchrotron emission adopted to interpret the results of the first year of the WMAP mission, which led to the hypothesis of the early secondary ionization of the Universe at redshifts Z > 10–30. New observations made with the RATAN-600 demonstrated the possibility of deep studies of the intensity and polarization of the microwave background (the E component) in ground-based experiments at short centimeter wavelengths. Galactic synchrotron emission may as well limit the possibilities of space- and ground-based studies of the polarization of cosmic microwave background radiation arising as a result of scattering induced by relic gravitational waves (the B component). The sky area studied with the RATAN-600 is intended to be used to interpret the PLANCK mission data in order to ensure a more detailed account of the role of the Galactic synchrotron emission.     

The field of view and flux sensitivity of RATAN-600

The refined data on the diffraction scattering of RATAN-600 allowed the telescope field of view to be increased substantially at large elevations. Amethod, which can be used to reconstruct the parameters of the sources passing at angular distances fromthe beamaxis that are several dozen times greater than the half-power width of the beam, is analyzed. The knowledge about wide scattering of RATAN-600 allowed the noise from background radio sources at zenith to be reduced by one order of magnitude and flux sensitivity of the radio telescope to be increased by the same factor without resorting to two-dimensional mapping. Methods for cleaning one-dimensional records of the RZF survey are suggested that use model scans based on the data of the NVSS survey and MHAT filtering. The latter proved to be an especially efficient tool for suppressing sky noise and identifying sources in the central section of the survey. The flux sensitivity of RATAN-600 is estimated with new opportunities taken into account.     

The KHOLOD experiment: A search for a new population of radio sources

Published data from long-term observations of a strip of sky at declination ?? ?? 5° carried out at 7.6 cm on the RATAN-600 radio telescope are used to estimate some statistical properties of radio sources. Limits on the sensitivity of the survey due to noise imposed by background sources, which dominates the radiometer sensitivity, are refined. The vast majority of noise due to background sources is associated with known radio sources (for example, from the NVSS with a detection threshold of 2.3 mJy) with normal steep spectra (?? = 0.7?C0.8, S ?? ?? ^??? ), which have also been detected in new deep surveys at decimeter wavelengths. When all such objects are removed from the observational data, this leaves another noise component that is observed to be roughly identical in independent groups of observations. We suggest this represents a new population of radio sources that are not present in known catalogs at the 0.6 mJy level at 7.6 cm. The studied redshift dependence of the number of steep-spectrum objects shows that the sensitivity of our survey is sufficient to detect powerful FRII radio sources at any redshift, right to the epoch of formation of the first galaxies. The inferred new population is most likely associated with low-luminosity objects at redshifts z < 1. In spite of the appearance of new means of carrying out direct studies of distant galaxies, searches for objects with very high redshifts among steep and ultra-steep spectrum radio sources remains an effective method for studying the early Universe.     

Deep RATAN-600 surveys at the declination of SS 433 carried out in 1987–2000 at 7.6 and 2.7 cm

We discuss the results of deep surveys of a ±10′ strip of the sky, centered on the declination of SS 433, carried out on the Northern sector of the RATAN-600 telescope at 2.7 and 7.6 cm in 1987–2000. The survey objects are cross-identified with sources in the NVSS catalog and the corresponding two-frequency spectral indices determined. We find a decrease in the mean spectral index in the transition from objects with flux densities S ₂₁ ≥ 30 mJy to those with 15 < S ₂₁ < 30 mJy. The constructed log N — logS relation at 2.7 cm has a slope of 3/2 at flux densities ≥300 mJy and flattens at weaker flux densities. The 1.4 GHz (NVSS), 3.94 GHz (RATAN-600), and 11.11 GHz (RATAN-600) data are used to estimate the number of objects per square degree at a wavelength of 1 cm.     

Macromolecules in the galaxy and the cosmic microwave background

A deep search for the predicted Galactic microwave dipole emission of spinning interstellar fullerene-type molecules has been conducted using the RATAN-600 radio telescope. This effect is of interest both in its own right and as a new form of Galactic screen between the cosmic microwave background (CMB) and the observer. The power of this noise component on angular scales of about 0.1° (l=1000) is estimated. These scales are of primary interest for the “Cosmological Gene of the Universe” (RATAN-600), PLANCK Surveyor Mission, and other projects. At the frequencies of the expected emission peak of this dust component, the small-scale noise is a factor of 20 weaker than the predicted noise. It is shown that the role of this dust component is negligible, at least at the main PLANCK frequencies. The first estimates of the contribution from Galactic polarization noise are given for λ=3.9 cm, where the theory predicts a maximum in the CMB polarization (l～1000). At wavelengths of ～1 cm and shorter, macromolecules contribute less than 1 µK, and should not hinder CMB polarization studies. Galactic synchrotron polarization, likewise, should not prevent CMB polarization experiments at the main PLANCK frequencies.     

Study of the power beam pattern of RATAN-600 during the deep RZF survey (1998–2003)

This paper proposes a method for constructing an experimental power beam pattern (PB) of RATAN-600 based on the sample of NVSS sources observed in the process of a deep sky survey near local zenith. The data obtained from observations of radio sources at λ7.6 cm in nine bands of the survey (the 2002 and 2003 sets) are used to construct vertical PB of the telescope at rather large offsets from the central horizontal section of the PB (±36′). The experimental PBs obtained using different methods are compared and the root-mean-square deviations of the experimental PB from the corresponding computed PB are determined. The stability of the power beam pattern in its central part (±6′) during the RATAN-600 Zenith Field (RZF) survey (1998–2003) and the accuracies of the fluxes of the sources observed within the framework of this survey and included into the RZF catalog are estimated [1].