What are IOU- and ROR- RGB images?

RAD-RGB images are false-colored images of astronomical objects.

The astronomical study involves a multi-wavelength analysis of the object from the radio part of the electromagnetic spectrum to X-rays. Astronomers access these data from various archival data services which are sky survey data on a particular wavelength taken by a particular telescope. No telescope can observe in all bands of electromagnetic spectrum. Different telescope images have different sensitivity, resolution (angular/frequency) and many other parameters. Each RGB image is a combination of these imaging survey data in Red, Green, and Blue color channels, with their respective intensities at each pixel, resulting in a false-colored image. Conventionally in RAD@home, the surveys are selected so that the order of wavelength of each data and colour of the channels are in same order i.e survey data in the red channel has a wavelength higher than that in green and green has a wavelength greater than that in blue. This is followed in optical- and IOU-RGB images, and ROR-RGB image has an exception allowed for green channel only.

The two widely used RAD-RGB images in our analysis are:

How to use the RAD-RGB Maker Tool:

RAD-RGB Maker Tool is a very simple to use tool. All you need is the name of the astronomical object of interest or its coordinates, the angular radius of the image, and what sort of images you would like to make.

Here is a brief description of each label provided in the form:

Contour Map

contour maps are lines which joins the pixels with same pixel-value of a given image or lines of equal intensity.  

Radio survey data contains a range of values as spectral flux density (unit of the pixel value in radio images is Jansky per beam). These values contain signal or real bright sources in the sky along with background noise data or the empty part.  Each sky survey provides a RMS (Root Mean Squared or 1-sigma) value or an accepted signal (3-5 sigma) value for the sky region. Three times the RMS value or a region above 3-sigma is usually taken as detection of the radio source signal and can be studied further. The contour map helps represent a 4th image along with three channels Red-Green-Blue (RGB) image. Its absolutely essential for radio images and if a source is not seen with contours with 3 sigma or above, it is considered unreliable. 

Table with details of a few radio surveys :

Frequency Survey  3 sigma Detection Resolution
- - Jy/beam (arcsec)
1.4 GHz VLA FIRST 0.0005 Jy 5 x 5
1.4 GHz VLA NVSS 0.0015 Jy 45 x 45
150 MHz TGSS ADR1 0.015 Jy 25 x 25
74 MHz VLSSr 0.3 Jy 75 x 75
325 MHz WENSS 0.018 Jy 54 x 54
843 MHz SUMSS 0.010 Jy 45 x 45

Please check the RAD-RGB acknowledgment at the bottom of the page for further details : RAD-RGB Maker Tool Acknowledgement