Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe 408 MHz B3.1 Survey
154
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a new 408 MHz survey (B3.1) carried out with the Croce del Nord radiotelescope in Bologna. The survey coordinates limits are $-2^circ 00^prime$ to $+2^circ 15^prime$ in Dec. and 21h to 24h, 00h to 17h in R.A., equivalent to 0.388 sr. The B3.1 is complete to 0.15 Jy but many sources down to 0.1 Jy are included. Our aim was to select a new and complete sample of Ultra Steep Spectrum (USS) radio sources, as they proved to be good candidates to find high-z radiogalaxies and their surrounding protoclusters. The observations and the reduction procedure are described and the observational errors are discussed. A cross-identification with the NVSS survey was performed to obtain the spectral index $alpha_{408}^{1400}$ and radio size of the sources. We found no evidence of a change of the spectral index distribution as radio flux decreases. The B3.1 USS sample contains 185 sources down to 0.1 Jy and it is about one order of magnitude deeper in flux with respect to the 4C USS sample. For 146 B3.1 USS sources no optical counterpart was found on the POSS-I sky survey. A cross-correlation with the FIRST survey gave maps for a subset of 50 USS sources, and their optical ID search was also made on the POSS-II, resulting in 39 empty fields
rate research
Read More
Diffuse Galactic emission at low frequencies is a major contaminant for studies of redshifted $21$ cm line studies. Removal of these foregrounds is essential for exploiting the signal from neutral hydrogen at high redshifts. Analysis of foregrounds and its characteristics is thus of utmost importance. It is customary to test efficacy of foreground removal techniques using simulated foregrounds. Most simulations assume that the distribution of the foreground signal is a Gaussian random field. In this work we test this assumption by computing the binned bispectrum for the all-sky $408$ MHz map. This is done by applying different brightness temperature ($T$) thresholds in order to assess whether the cooler parts of the sky have different characteristics. We find that regions with a low brightness temperature $T < 25$ K indeed have smaller departures from a Gaussian distribution. Therefore, these regions of the sky are ideal for future H{sc i} intensity mapping surveys.
The all-sky 408 MHz map of Haslam et al. is one the most important total-power radio surveys. It has been widely used to study diffuse synchrotron radiation from our Galaxy and as a template to remove foregrounds in cosmic microwave background data. However, there are a number of issues associated with it that must be dealt with, including large-scale striations and contamination from extragalactic radio sources. We have re-evaluated and re-processed the rawest data available to produce a new and improved 408 MHz all-sky map. We first quantify the positional accuracy ($approx 7$ arcmin) and effective beam ($56.0pm1.0$ arcmin) of the four individual surveys from which it was assembled. Large-scale striations associated with $1/f$ noise in the scan direction are reduced to a level $ll 1$ K using a Fourier-based filtering technique. The most important improvement results from the removal of extragalactic sources. We have used an iterative combination of two techniques -- two-dimensional Gaussian fitting and minimum curvature spline surface inpainting -- to remove the brightest sources ($gtrsim 2$ Jy), which provides a significant improvement over previo
We present a correlation between the ACME/SP94 CMB anisotropy data at 25 to 45 GHz with the IRAS/DIRBE data and the Haslam 408 MHz data. We find a marginal correlation between the dust and the Q-band CMB data but none between the CMB data and the Haslam map. While the amplitude of the correlation with the dust is larger than that expected from naive models of dust emission it does not dominate the sky emission.
A new sample of very powerful radio galaxies is defined from the Molonglo Reference Catalogue, according to the criteria S (408 MHz) > 5 Jy, -30 < Dec < 10 degrees, |b| > 10 degrees. The sample is selected to have similar properties to the northern 3CR revised sample, and to be visible to a combination of existing northern telescopes such as the Very Large Array radio interferometer and large southern hemisphere telescope facilities. The sample contains 178 sources, of which spectroscopic redshifts are available in the literature for 128. For the remaining 50 sources, new radio imaging, optical imaging and spectroscopic observations are presented to identify the host galaxies and determine their redshifts. With these new observations the total sample is 100% optically identified and redshifts are available for 174 (98%) of the sources. The sample consists of one starburst galaxy, one Seyfert galaxy, 127 radio galaxies and 49 quasars. Basic properties of the sample, such as the distributions of the quasar and radio galaxy populations in redshift and their locations on the radio power versus linear size (P-D) diagram, show no significant differences from the revised 3CR sample. The equatorial location and the high spectroscopic completeness of this sample make it a valuable resource for detailed studies of the nature and environments of these important objects with the new generation of southern hemisphere telescopes.
A new catalogue of extended radio sources has been prepared based on arcminute-resolution 1420 MHz images from the Canadian Galactic Plane Survey (CGPS). The new catalogue provides both 1420 MHz and 408 MHz flux density measurements on sources found near the Galactic plane in the second quadrant of our Galaxy. In addition cross-identifications are made with other major radio catalogues and information is provided to facilitate the recovery of CGPS image data associated with each catalogued source. Numerous new radio sources are identified and the catalogue provides a comprehensive summary of both newly discovered and previously known HII regions and supernova remnants in the outer Galaxy. The catalogue should be of use both for synoptic studies of Galactic structure and for placing higher resolution observations, at radio and other wavelengths, in context.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
