Radio Image Galactic Plane on Stars Galactic Center Cygnus Loop Region Rosette Nebula Region Expanded view of the Galactic Plane Sky Full of Stars with 8.35 GHz Galactic Plane Survey in Color. The Galactic center , Cygnus Region and Rosette Nebula regions are highlighted. Many of the most interesting features in the Radio Sky are invisible in the star map. Discover what you can not see, click on one of the expanded regions! Radio images of the Galactic center show a line of very bright of star forming regions along the galactic plane. In the outer galaxy few stars are born.

First Galactic Plane survey at 8.35 and 14.35 GHz

Glen Langston, Anthoney Minter, Larry D'Addario, Keri Eberhardt, Katrina Koski, and Julianne Zuber

We present the first images of the galactic plane ( |b| < 5 degree, l = -15 degree to 255 degree) at 8.35 and 14.35 GHz. These observations used the NRAO/NASA Green Bank Earth Station to survey the sky simultaneously at these frequencies. These are the first results from the Galactic Plane (GP) survey observations, a program to monitor the sky at 8.35 and 14.35 GHz. The GP survey series is intended to detect short lived radio sources. We present four independent observations of the galactic plane, combined to provide a set of reference images of the galactic plane. We compare the relative brightness of Cassiopeia A and Cygnus A and find the rate of decrease of Cassiopeia A is slower than previously reported. The first survey, GPA, covers 0.82 sr (6.5 \%) of the sky. A source list is presented for all sources brighter than 0.9 Jy at 8.35 GHz and also for all sources brighter than 2.5 Jy at 14.35 GHz. The FITS format images, residual images, source lists and archive data are available (8,500,000 Bytes each).

2000 June Astronomical Journal Vol 119, Page 2801

A postscript version of a description of the GPA survey is available. The LaTeX is also available. The 9 figures from the paper are presented below. A large (23 MB) color pdf version of the papers is available

Figure 1: Optics geometry for Green Bank Earth Station. The main antenna surface, M1, is left, the sub-reflector, M2, is below the prime focus. The frequency selective surface (FSS), M3, is above the 8.35 GHz horn. and the ellipsoidal mirror, M4, is above the 14.35 GHz horn. Both the 8.35 and 14.35 GHz horns view the same region of the sky simultaneously.

Figure 2: Schematic diagram showing the organization of data sampling for the 4 Sessions comprising the GPA survey. Samples are taken 9 times a second, every 2.4\arcm. Sections are labeled by the center galactic longitude (degrees).

Figure 3a: The 8.35 GHz image of the Cygnus Loop Region of galactic plane, showing calibration sources Cygnus A (north west), DR21 and NGC7027 (south east). The flux density range shown is -1.5 (dark blue) to 5 (red) Jy. Sources brighter than 5 Jy are shown in white and noise features more negative than -1.5 Jy are shown in black.

Figure 3b: The 14.35 GHz image of the Cygnus Loop Region. The de-convolved source size is shown with ovals, scaled by a factor of two for clarity. Upper limits on the source size are shown as circles. Due to source confusion along the galactic plane, source labels are located at b = 4 degees for sources with b > 0 and labels are located at b = -4 degrees for sources with b < 0. (Zoom in on the color 8.35 GHz and 14.35 GHz images.)

Figure 4: Image of the Galactic Center region of the Galactic Plane at 8.35 and 14.35 GHz. The figure shows Galactic Longitude from 345 to 30 degrees and | b | < 5 degrees. The flux density scale is -.5 to 5 Jy. Sources with flux density greater than 5 Jy are shown in red, while regions of little emission are shown in blue. The 8.35 GHz image is above of the 14.35 GHz image.

Figure 5: Image of Galactic Plane at 8.35 and 14.35 GHz. The figure shows Galactic Longitude from 30 to 75 degrees and | b | < 5 degrees.

Figure 6: Image of Galactic Plane at 8.35 and 14.35 GHz. The figure shows Galactic Longitude from 75 to 120 degrees and | b | < 5 degrees.

Figure 7: Image of Galactic Plane at 8.35 and 14.35 GHz. The figure shows Galactic Longitude from 120 to 165 degrees and | b | < 5 degrees.

Figure 8: Image of the Anti-Center region of the Galactic Plane at 8.35 and 14.35 GHz. The figure shows the Rosette Nebula in the Galactic Longitude range from 165 to 210 degrees and | b | < 5 degrees.

Figure 9: Image of Galactic Plane at 8.35 and 14.35 GHz. The figure shows Galactic Longitude from 210 to 255 degrees and | b | < 5 degrees.

The calibrated data samples (before gridding to produce images) are in the 4 files below:

Brightness temperature images

The GPA survey was carried out primarily to detect short lived, transient radio sources. However a number of groups are interested in the properties of molecular clouds and other extended objects in the Milky Way galaxy. These clouds have large angular extent and the GPA images (above) have reduced sensitivity to extended emission with size greather than 33 arc-minutes.

Below are JPG images and links to FITS format images with intensity scale calibrated in units of Kelvins/Beam for the 670 arc-second FWHM 8.35 GHz band images and the 480 arc-second FWHM 14.35 GHz band. These sky and system temperature contribution to these images is removed by subtracting median value from a 3 degree region centered on each scan data sample. These images are also contain an extra noise component due to compact structures (water vapor) in the atmosphere, that is more strongly suppressed by the 1 degree median window used for the GPA images. The brightness temperature of sources smaller than 1.5 degrees should not be decreased by the effects of the median filtering. A comparision with measured brightess temperature of Cassiopea A and Cygnus A with measured values indicates that the intensity scales are accurate to better than 10 % at 8.35 GHz and better than 20 % at 14.35 GHz. Galactic latitude range 75 to 165 degrees.
Extended emission structures from the gpa survey. Galactic latitude range -15 to 75 degrees. FITS format images calibrated in units of Kelvins/Beam are available at 8.35 GHz and 14.35 GHz. The image at left has be compressed by a factor of 5 in the galactic longitude direction.
Extended emission structures from the GPA survey. FITS format images calibrated in units of Kelvins/Beam are available at 8.35 GHz and 14.35 GHz.
Extended emission structures from the GPA survey. Galactic latitude range 165 to 255 degrees. FITS format images calibrated in units of Kelvins/Beam are available at 8.35 GHz and 14.35 GHz.

NRAO

The National Radio Astronomy Observatory (NRAO) is a facillity of the National Science Foundation operated under cooperative agreement with the Associated Universities, Inc.

glangsto@nrao.edu Last update: 2003 Feb 12