The Two Micron All Sky Survey at IPAC

The Two Micron All Sky Survey (2MASS) is surveying the entire sky in the near-infrared from Mt. Hopkins and Cerro Tololo. The cameras on the two automated 1.3-m telescopes observe in three channels, J (1.25 µm), H (1.65 µm), and K_s (2.17 µm), simultaneously, using 256 × 256 HgCdTe detector arrays, sampling the sky in 6° × 8.3´ strips. Coadded images, with 7.8-s total integration, are produced from six dithered frames, after rebinning to 1´´ pixels. The 2MASS Production Processing System provides final Atlas Images and source extractions with precise photometric calibration and astrometric positions, with 10 sensitivities of 15.8 mag at J, 15.1 at H, and 14.3 at K_s.

The Spatial Infrared Imaging Telescope, SPIRIT III, was the primary instrument for gathering mid-infrared data during the Midcourse Space Experiment (MSX) mission. SPIRIT III is a 33-cm aperture, high off-axis rejection telescope with a five-color, high-spatial resolution (18´´), 4.2 to 26 µm multi-spectral radiometer and a six-channel, 2.5 to 28 µm Fourier transform spectrometer.

One of the main targets for MSX and a fascinating target for 2MASS is the Galactic Center. This image is a composite of 2MASS J (blue), K_s (green), and MSX Band A (6 - 11 µm; red) imaging of this region, and is 2° in galactic latitude by 5° in galactic longitude. (The 2MASS image mosaic has been binned to 2´´ × 2´´ pixels.) The Galactic plane runs horizontally along the image, and the Galactic center is the bright (yellow) object near the middle. The infrared can peer through the dense obscuring dust that hides the Galactic center in the optical. The near-infrared is sensitive to the photospheric emission from the very large number of, particularly cooler, stars seen toward this region, and also gives us a glimpse of the mass of stars and gas that comprise the very center of the Milky Way. The mid-infrared is ideal for measuring the thermal emission from the cool dust in nebular ionized (H II) regions and molecular clouds, producing the extended clumpy and filamentary emission surrounding the center. Although MSX Band A is still sensitive to stellar emission, the cool extended emission becomes apparent, relative to the 2MASS bands, and the Galactic center becomes more obvious. Even with the penetrating power of these infrared wavelengths, however, large ``holes'' can be seen throughout the image, where no emission in any of these bands can emerge from objects behind the dark dust.

The 2MASS Picture of the Week uses the NED, SIMBAD, and ADS databases.

Return to the 2MASS Home Page