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Data Access

The FITS data cubes can be accessed by either entering a specific region in the table or by clicking on the integrated intensity image below. Enter either the range in latitude, longitude and velocity or a central (l,b,v) and size. Due to file size limitations, the maximum range in Galactic longitude is 2 degrees. By default, the full velocity coverage for a given patch of the GRS is returned if no velocity range is entered.

The following clickable image map shows an integrated intensity image of the GRS in the ¹³CO 1-0 line. Click on a part of the image to the download the nearest file. The files are divided into l x b = 2 degrees x 2 degrees fields centered at even integer values of Galactic longitudes and b=0. The cubes centered at Galactic longitudes < 40 degrees cover the velocity range from -5 to 135km s^{-1 .} Cubes centered at Galactic longitudes > 40 degrees cover the velocity range -5 to 85 km s-1.

GRS channel maps and the position-velocity (l-v) diagram are also available.

Details

Each field comprises spectra on a fully sampled 22" grid. The intensities are on a T_A* antenna temperature scale. To convert this to main beam temperatures, divide by the main beam efficiency of 0.48. The velocity resolution of the data is 0.25 km s^-1 (0.22 km s^-1 sampling). The cubes centered at Galactic longitudes < 40 degrees cover the velocity range from -5 to 135km s^-1. Cubes centered at Galactic longitudes > 40 degrees cover the velocity range -5 to 85 km s-1.

The coordinates are Galactic latitude and longitude. The center position for all files is the Galactic Center, (l,b)=(0,0). The positional grid is based on the 22.14 arcsecond spacing used to sample the sky. Therefore, the centers of each image in pixels will not necessarily fall at whole number or fraction longitude values. If you are processing data of this form for the first time, use double-precision variables.

For more information about the GRS see: "The Boston-University--Five College Radio Astronomy Observatory Galactic Ring Survey" Jackson, Rathborne, Shah, Simon, Bania, Clemens, Chambers, Johnson, Dormody, Lavoie, & Heyer [pdf].

Data Analysis Tools

We provide three IDL procedures to help visualize the GRS data. GRS_IntInt.pro will generate an integrated intensity image from a FITS cube over the input velocity range. You will also need to download total_1d.pro for GRS_IntInt.pro to work. GRS_spectrum.pro will generate either a single spectrum for a particular (l,b) position or averaged spectum over a region in (l,b). GRS_plotspectrum.pro will plot a spectrum.

Additional Data

We also have limited data from l = 14 deg to 18 deg. To access this data, click on a segment of the image below.

CS Data

A two square degree pilot field observed in the CS 2-1 line (Galactic Longitude from 44.3 to 46.3 degrees, Galactic Latitude from -0.5 to 0.5 degrees) is available. Click on the image below to go to the download section and follow the instructions. The field comprises about 62,000 spectra on a fully sampled 22" grid. The spectra are on a T_A* antenna temperature scale. To convert this to main beam temperatures, divide by the main beam efficiency of 0.50. The velocity resolution of the data is 0.26 km s^-1 (0.24 km s^-1 sampling).

Problems or Questions?

Contact Irena Stojimirovic (irena@bu.edu) or Alexis Johnson (alexj@bu.edu).

Please include the following acknowledgement in any published material that makes use of GRS data:

This publication makes use of molecular line data from the Boston University-FCRAO Galactic Ring Survey (GRS). The GRS is a joint project of Boston University and Five College Radio Astronomy Observatory, funded by the National Science Foundation under grants AST-9800334, AST-0098562, AST-0100793, AST-0228993, & AST-0507657.

The GRS is supported by the NSF via grants AST-9800334, AST-0098562 and AST-0507657

The FCRAO is supported by the NSF via AST-0100793 and AST-0228993.