2MASS Picture of the Week Archive Captions

Atlas Image mosaic, covering 11.0´ × 16.8´ on the sky, of NGC 205 (Messier 110), a dwarf elliptical companion of the giant spiral Andromeda Galaxy (Messier 31; M31), in the Local Group of galaxies. NGC 205 is peculiar in that evidence exists for recent star formation in what nominally should be a galaxy composed of old stars. The evidence is in the form of centrally-concentrated bright early type stars, neutral and molecular gas, and dust, much of it in clouds and some of it very cold (Haas 1998, A&A, 337, L1). From HST imaging, Cappellari et al. (1999, ApJ, 515, L17) determined that the quite modest star formation episode occurred over the last 100 million years; Welch, Sage, & Mitchell (1998, ApJ, 499, 209) found that it ended only a few million yr ago. Where the star-forming gas originally came from is a mystery, possibly from interaction with M31 or from the environment of the M31 system. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release!


Atlas Image mosaic, covering 15.3´ × 17´ on the sky, of IRAS 20306+4005, an object in the Infrared Astronomical Satellite (IRAS) catalog of sources. Little is known about this object, but it appears to be a region of current massive star formation in the Galactic plane and near the Cygnus 0B2 stellar association. This is the first known near-infrared image of this source. Infrared-bright filaments of gas surround a young cluster of stars and young stellar objects still embedded in their natal dusty molecular cloud. A large patch of heavily-obscuring dust is seen to the north of the nebula. 2MASS is ideal for investigating the nature of many IRAS objects and other very young star-forming regions throughout the Galaxy. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release!


Atlas Image mosaic, covering 7´ × 7´ on the sky, of a small, stellar cluster in the constellation Cygnus, consisting of the optically-bright Herbig Be star BD +40° 4124 (V1685 Cygni=MWC 340; center of image), V1686 Cyg (LkH 224; southeast of center), and V1318 Cyg (LkH 225; just east of V1686 Cyg). Herbig Ae/Be stars are young, intermediate-mass stars exhibiting mass loss, as seen from their optical line emission. This stellar group is about 1 kpc (3260 light years) from us, along the Cygnus spiral arm. V1686 Cyg and V1318 Cyg are also optical emission-line objects. V1318 Cyg, as seen in the 2MASS image, is actually two objects; Aspen, Sandell, & Weintraub (1994, A&A, 282, L25) suggest that the pair form a possibly-interacting binary of pre-main-sequence objects. A water maser source and bipolar molecular outflow are associated with V1318 Cyg (Palla et al. 1995, A&A, 293, 521). Many more highly-embedded objects are seen around this group of stars, which can be seen to be surrounded by infrared-bright nebulosity; the cluster of objects shows both a significant spread in stellar mass (both low and high, forming simultaneously) and age (~3 Myr; Hillenbrand et al. 1995, AJ, 109, 280). The infrared-bright yellowish star further southeast is unidentified. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release!


Atlas Image mosaic, covering 14.3´ × 14.3´ on the sky, of the Tarantula, or 30 Doradus, Nebula (also known as NGC 2070). This nebula, in the Large Magellanic Cloud, is the closest example to us of a giant ionized hydrogen (H II) region, covering several hundred parsecs in diameter. The closest analog in our Milky Way Galaxy is the H II region NGC 3603. Clusters of hundreds of young, massive O and B stars, particularly the dense central "super star" cluster, R136, provide the ultraviolet photons which ionize and photoevaporate the large filamentary cloud. A number of other stellar populations, including red supergiants and Wolf-Rayet stars, coexist in 30 Doradus. Detailed studies in the optical of the nebula and its stellar contents shows a complex history of recent star formation. In the near-infrared, Rubio et al. (1998, AJ, 116, 1708) point out that pre-main-sequence objects are also found, particularly along the Ks-bright molecular hydrogen (H2) line-emitting filaments in the nebula's periphery, which can be seen in the 2MASS image. What emerges is a scenario of new generations of stars triggered by the energy input from the massive stellar clusters, which is likely a characteristic picture for star-forming regions of this scale in galaxies. Image mosaic by E. Kopan (IPAC). These data are included in the Second Incremental Release!


Atlas Image mosaic, covering 9.2´ × 9.2´ on the sky, of the Sombrero, Messier 104 (M104). The galaxy derives its nickname from its appearance, as a nearly edge-on disk system with a "rim" of dark, obscuring dust. The "rim" are the dust lanes within the disk of this early-type spiral galaxy, which are still particularly visible, even in this 2MASS near-infrared image. As is true for other spiral galaxies as seen by 2MASS, the overall apparent structure of the galaxy is much smoother in the near-infrared than in the optical. M104 shows an extended halo of emission above and below the plane of the galaxy's disk. The faint, purplish "stars" emanating both due north and due south of the galaxy's nucleus are known persistence artifacts. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release!
































Return to the 2MASS Home Page