Circumzenithal sky region survey at the frequency of 30 GHz with 32-element radiometer matrix of the RATAN-600

We report the preliminary results of a deep sky survey in the field of 00^h < RA < 24^h, 40 _. ^° 5 < 42 _. ^° 5 with the RATAN-600 and its new focal 32-feed receiver matrix at the limiting radio frequency of 30 GHz, with the resolution up to 5″ in right ascension and 30″ in declination. The first results, including new estimates of the anisotropy of background radiation at the scales of (l > 3000) and noise from discrete radio sources in the wavelength range between the NVSS and IRAS catalogs are listed.     

Small-scale galactic emission fluctuation observations with RATAN-600 radio telescope

We present the estimates of Galactic synchrotron and free-free emission power at intermediate and small scales (500 < l < 1000, 20′ < θ < 40′), based on the RATAN-600 radio telescope observations (SAO RAS). The observations were conducted in the frequency range of 2.3–11.2 GHz using the transit scan mode, in the declination range of 40.7° s δ < 42.3°. The power spectrum estimates of synchrotron and free-free components were obtained. They can be further used in the data processing stage of the high-resolution cosmological experiments like Planck.     

Centimeter-wave radio emission of a high-latitude prominence

The results of observations of the radio emission of a high-latitude prominence located in the NE part of the solar limb are discussed. Observations were performed on the radio telescope RATAN-600 using its Northeastern sector and Southern sector with a periscope during the maximum phase (0.998) of the solar eclipse of March 29, 2006. The prominence was studied in the wavelength interval 1.03 ÷ 5.0 cm. The absence of the background illumination from the solar disk allowed us to study the parameters of the radio emission of the high-latitude prominence (? = 45°, NE limb of the Sun). Observations of the solar limb at the time of the maximum phase made it possible to record very small radio fluxes from the prominence, which amounted to 0.05 ÷ 0.01 s.f.u. in the wavelength interval from 1.84 to 5.0 cm. The position of the maximum of the radio emission of the prominence coincides, according to the results of observations performed on both sectors, with the summit of the prominence as seen on the solar image taken in the He II 304 Å line (SOHO, ? = 45°, NE limb of the Sun). The degree of polarization is P ≈ 7 ÷ 16% at 1.88 ÷ 5.0 cm. If interpreted in terms of the thermal mechanism considered here, polarized emission corresponds to a magnetic-field strength of H ? (550 ÷ 100) G in the prominence region.     

Spectral characteristics of radio sources near the North Celestial Pole

We have used the RATAN-600 radio telescope to study the spectral characteristics of a uniform sample of 504 radio sources from the NVSS catalog near the North Celestial Pole at six frequencies from 1.1 to 21.7 GHz, with the aim of selecting sources possessing inverted spectra near 22 GHz, to be included in the program of the Radio Astron future space VLBI mission. We found 17 radio sources with the desired spectral characteristics. Data from spectral studies over a wide wavelength range testify that the spectral behavior of our sample differs from that for a complete sample of sources with the same initial parameters but selected at 20 GHz. We find a 6% deficit of inverted-spectrum sources, which can be explained as an effect of the spectral characteristics of “sub-threshold” sources that were not included in the initial sample at 1.4 GHz.     

Radio spectra of objects in the RATAN-600 RZF catalog and a population analysis of faint radio sources

Results of centimeter-wavelength RATAN-600 observations of several hundred NVSS objects with a wide range of flux densities are presented. Changes in spectral-index distributions from strong-to faint-object populations are estimated. In the transition from strong to faint radio sources, the number of steep-and ultrasteep-spectrum objects decreases and the minimum between steep-and flat-spectrum objects, which was first discovered in the 1970s, becomes less distinct. A less certain increase in the fraction of inverted-spectrum objects is also found. Comparison with theoretical models of radio-source evolution suggests that the decrease in the number of steep-and ultrasteep-spectrum objects can be naturally explained by a sharp decrease in the fraction of classical FRII radio galaxies. The decrease in the sharpness of the minimum may be due to the growing contribution from the population with spectral indices 0.7–0.5, which is usually identified with starbust galaxies. The small increase in the fraction of inverted-spectrum radio sources can be attributed to the growing number of objects with active nuclei. Our spectrum-based conclusions are confirmed by the morphology of the FIRST Catalog images. The number of radio sources associated with supermassive black holes in the Early Universe is estimated using data from the SDSS Catalog.     

Deep 7.6 cm RATAN-600 sky surveys at the declination of SS 433 during the 1980–1999 period. Catalog of radio sources in the right-ascension interval 2<Superscript>h</Superscript> ≤ RA &lt; 7<Superscript>h</Superscript>

We present a catalog of radio sources extending the RCR (RATAN Cold Refined) catalog to the right-ascension interval 2^h ≤ RA < 7^h. The list of objects was obtained in the process of a reprocessing of the observations of the “Cold” experiment conducted in 1980–1981 on RATAN-600 radio telescope at the declination of SS433, and the reduction of the 1987–1999 surveys of the same experiment.We report the right ascensions and integrated flux densities for 237 sources found at 7.6 cm (3.94 GHz) and their spectral exponents at 3.94 and 0.5 GHz. Twenty-nine sources of the list, which are mostly weaker than 30 mJy at 3.94 GHz, have available data only at two frequencies—1.4 and 3.94 Hz.We approximated the spectra of the sources using all catalogs available in the CATS and VizieR databases that meet the survey strip, and, in some cases, using the flux densities estimates from VLSSr,GLEAM, TGSS, and GB6 survey maps.We constructed the histograms of the spectral indices of the sources and verified the reliability of the identifications of sources found in the scans by comparing the coordinates and integrated flux densities with the corresponding parameters listed in the NVSS catalog. In the right ascension interval considered we found no objects at the 10–15 mJy level lacking in decimeter-wave catalogs.     

Statistical radio astronomy of the 21st century

The exponential development of radio-astronomy methods (sensitivity, resolution, depth of surveys, etc) has led to the need for new methods aimed at distinguishing weak signals in the midst of numerous background signals, as has long been the case for radio astronomy at meter wavelengths. Centimeter-wavelength data accumulated with existing radio telescopes (such as the RATAN-600 reflector—the largest radio telescope in Russia) are presented, and expected problems for major new radio telescopes of the 21st century, such as the Square Kilometer Array, are discussed. The effectiveness of using certain tested methods to derive astrophysically important results through reasonable statistical processing of large datasets is shown. In experiments conducted with RATAN-600, these methods lead to an enhancement in sensitivity by an order of magnitude compared with the sensitivity of a resolving element.     

A high-resolution study of Jupiter at a frequency of 30 GHz

We present the results of our study of Jupiter and its radiation belts with a resolution of 6 arcsec at a frequency of 30 GHz using the RATAN-600 radio telescope and a MARS matrix radiometer with a sensitivity of about 6 mK ^?1/2. We monitored the integrated emission from the Jovian disk with a signal-to-noise ratio of more than 1000 for 30 days and showed its radio emission to be highly stable (≈1%). Based on daily data for the one-dimensional radio brightness distribution over the disk, we mapped the longitudinal radio brightness distribution over 100 rotation periods of Jupiter around its axis. Neither hot nor cold spots with a temperature contrast of more than 1 K were detected; their contribution to the total radio flux from the Jovian disk was no more than 0.2%. The one-dimensional latitudinal (longitude-averaged) distribution obtained on VLA with a similar resolution is shown to be an order of magnitude less uniform than the one-dimensional longitudinal (latitude-averaged) distribution obtained on RATAN-600. We have studied the radiation belts at such high frequencies for the first time and estimated their intensities and variability levels under the effect of external factors. The variable component of the radiation belts was shown to have not exceeded 0.5% of the integrated spectrum of Jupiter over the entire period of its observations. We estimated the contribution of the Galilean satellites (“Galilean noise”) in low-resolution observations; the accuracy of allowing for this noise is determined by the accuracy of estimating the temperatures of the satellites at the observing frequency. The uncertainty in the total flux does not exceed 0.1%.     

Detection of Five New RRATs at 111 MHz

Results of 111-MHz monitoring observations carried out on the Big Scanning Antenna of the Pushchino Radio Astronomy Observatory during September 1–28, 2015 are presented. Fifty-four pulsating sources were detected at declinations ?9° < δ < 42°. Forty-seven of these are known pulsars, five are new sources, and two are previously discovered transients. Estimates of the peak flux densities and dispersion measures are presented for all these sources.     

The “X component” of the radio background

The recent publication of evidence for a new mechanism producing background radio emission of the Galaxy at centimeter wavelengths (in addition to synchrotron radiation, free—free transitions in ionized gas, and the weak radio emission of standard dust) gave rise to a strong reaction among observers, and requires independent experimental verification. This signal is of special concern in connection with studies of the polarization of the cosmic microwave background (CMB) using new-generation experiments. We have derived independent estimates of the validity of the “spinning-dust” hypothesis (dipole emission of macromolecules) using multi-frequency RATAN-600 observations. Test studies in the Perseus molecular cloud show evidence for anomalous extended emission in the absence of strong radio sources (compact HII regions) that could imitate an anomalous radio spectrum in this region. A statistical analysis at centimeter wavelengths over the Ratan Zenith Field shows that the upper limit for the polarized noise from this new component in the spinning-dust hypothesis is unlikely to exceed 1 µK at wavelengths of 1 cm or shorter on the main scales of the EE mode of Sakharov oscillations. Thus, this emission should not hinder studies of this mode, at least to within several percent of the predicted level of polarization of the CMB emission.