An Astronomical Image Mosaic of the Sky at 21 cm

While attending a meeting in Charlottesville, I chatted to Brian Kent, who has been doing some exciting work with the Montage image mosaic engine. He is part of a team that has been building mosaics of the sky at the radio wavelength of 21 cm. The observations are being made with the Arecibo 1000-ft (305 m) radio telescope in Puerto Rico, the world’s largest radio telescope.

1500 square degree equal area Aitoff projection mosaic, computed with Montage, of galactic neutral hydrogen observed with the ALFALFA survey near the North Galactic Pole (NGP). Image courtesy of Dr. Brian Kent and the ALFALFA collaboration.

When complete, the Arecibo Legacy Fast ALFA survey (ALFALFA) will cover 7000 square degrees of sky. The 100 MHz bandbass detects neutral hydrogen (HI) in both the Milky Way and external galaxies. The survey will detect over 20,000 sources out to 250 megaparsecs in HI and make the largest collection of HI catalogs, images, and high quality radio spectra ever obtained by astronomers.

ALFALFA has used Montage to create a large wide-field mosaic of high galactic latitude HI (b > 20 degrees). Montage allows for the combination and re-projection of over 1200 images in dual polarization from data obtained by the survey’s observing team. The project collaboration, led by Cornell University, consists of many faculty, postdocs, and graduate and undergraduate students working on a wide variety of science projects.

I wish to thank Dr. Brian Kent for permission to use the image shown  and for contributing content to this post.

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2 Responses to An Astronomical Image Mosaic of the Sky at 21 cm

  1. Bubak says:

    Montage seems to be interesting. Would you know how does it compare to Skyview?

  2. astrocompute says:

    Hello and thanks for your comment. Skyview and Montage are very different animals. Skyview is a front-end to browse quality images from many different surveys (browse quality means in this sense that the images are intended for visualization rather than for science analysis). Some of the images in Skyview are in fact small scale mosaics. Montage is an engine for producing science-grade mosaics. Science grade in this context means that the mosaic preserves the flux and positional accuracy of the original images. Montage is, by design, portable and highly scalable: it can handle mosaics of a few images as well as mosaics, e.g., the whole sky as measured by 2MASS. I hope this helps! Let me know if you need further information.

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