2MASS Picture of the Week Archive Captions

Atlas Image, covering 8.4´ × 17.1´ on the sky, of the region of the sky containing the red nebulous objects GGD 12-15 (Gyulbudaghian, Glushkov, & Denisyuk 1978, ApJ, 224, L137). These objects are part of an active star-forming region located in the Monoceros molecular cloud, about 1 kpc (3260 light years) away. The many Ks-bright objects in the region appear to be members of a still-forming star cluster. Associated with this cluster are a strong water maser, a compact H II region, and a bipolar molecular outflow, all signatures of active ongoing star formation. Many stellar objects are detected in the 2MASS Atlas Image. To see a JHKs color-color diagram for the detected point sources, click here. (The green stellar track is for dwarfs, the blue track is for giants; Bessell & Brett 1988, PASP, 100, 1134. The reddening vector is from Rieke & Lebofsky 1985, ApJ, 288, 618.) The embedded objects are obscured by up to at least 10 visual magnitudes of extinction. These data are included in the Second Incremental Release!


The planetary nebula NGC 6818. (Caption lost in Y2K frenzy....) These data are included in the Second Incremental Release!


Atlas Image mosaic, covering 23.3´ × 20.0´ on the sky, of the young open cluster IC 348. This cluster, at a distance of ~320 pc, is still embedded in its parental molecular gas cloud, which is part of the larger Perseus Molecular Cloud. Thus, many of the cluster members are obscured by dust and would go relatively undetected in optical imaging of the cluster. For such very young embedded clusters as IC 348, near-infrared imaging, such as by 2MASS, provides a more complete stellar census and determination of the stellar and cluster properties and histories. The bright star near the top center of the 2MASS image mosaic is omicron Persei. The main portion of IC 348 is toward the image mosaic center, just south of the star. From their JHK imaging, Lada & Lada (1995, AJ, 109, 1682) found ~380 members of the cluster, that the stellar density is consistent with other rich embedded clusters, and that ~20% of the members are infrared-excess objects, suggesting the presence of circumstellar disks. For a near-infrared color-color diagram for sources in the IC 348 field drawn from the release Point Source Catalog, click here. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release!


Atlas Image mosaic, covering 5.0´ × 5.0´ on the sky, of the famous Seyfert galaxy Messier 77 (NGC 1068). The nucleus of this galaxy is so bright in the infrared, particularly at longer wavelengths, that in the 2MASS mosaic, it has created persistence artifacts, seen as the two red "spots" due north and south of the galaxy center. (A pair of artifacts are seen, due to the mosaicing of images made by the two different scan directions.) The bright galactic bar is apparent in the image, with two or more dusty arms extending outward along the galaxy disk. Although classified as Seyfert 2, it has been recently speculated that the nucleus of this well-studied galaxy is actually the prototypical dust torus-obscured Seyfert 1 nucleus, where a powerful supermassive black hole is thought to reside. The extinction toward the nucleus may be as high as 40 visual magnitudes (Lumsden et al. 1999, MNRAS, 303, 209). The bar is the site of very active star formation, out to 10 kpc radius, and a relationship may exist between the spectacular activity of the nucleus and the copious gas and new stars around it. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release!


Atlas Image, covering 6.0´ × 6.0´ on the sky, of the Quintuplet star cluster near the Galactic Center. The Quintuplet is a young (~4 Myr old), very massive cluster of stars, formed during one of the recent bursts of star formation around the Milky Way's center. The cluster, seen behind about 29 magnitudes of visual extinction, actually consists of more than just five stars. The five bright stars that earned the cluster its name, however, have high luminosities in the near-infrared and are likely young, dust-enshrouded stars. Figer, McLean, & Morris (1999, ApJ, 514, 202) recently produced a census of the massive stars in the cluster, based on near-infrared photometry and spectroscopy. In addition to O- and B-type main-sequence and supergiant stars, a number of post-main-sequence decendants of massive stars, i.e., several Wolf-Rayet stars and Luminous Blue Variables (LBVs), have also been identified. The most famous of these LBVs is the Pistol Star (seen ~0.5´ due south of the main cluster in the center of the 2MASS image), imaged recently with HST/NICMOS and studied by Figer et al. (1998, ApJ, 506, 384). The Pistol Star appears to have 100-200 times the mass of the Sun, making it one of the most massive and luminous stars in the Milky Way! Considering the mass and number densities of stars in the cluster, the Quintuplet, also recently imaged with NICMOS, can be considered a small "super star cluster," examples of which are found in starbursts occurring in many other galaxies. Super star clusters are thought to be young globular clusters in the making. These data are included in the Second Incremental Release!
































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