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2MASS Atlas Image Gallery: Miscellaneous Objects

2MASS All Sky Aitoff projection of the three-color composite JHKs source count map of the entire sky, based on 95,851,173 stars with Ks 13.5. What appears most prominently are the Galactic plane and the Galactic bulge. The plane is cut by dark dust lanes and clouds, even in the near-infrared, and several dusty regions, including Orion, are conspicuous. One can also see the two Magellanic Clouds, Large and Small. (Note the prominent bar and incipient spiral structure of the Large Cloud.) Near the Small Magellanic Cloud is the globular cluster 47 Tucanae. Cutting almost north-south through one side of the bulge is the dwarf Sagittarius galaxy, which, along with the Clouds, is a satellite of the Milky Way. 2MASS has completed the observational part of the survey and is now preparing to reprocess all of the data for a Final public Release, in late 2002. The source generation was performed by M.F. Skrutskie (UMass; Principal Investigator, 2MASS), the flux maps were compiled by J.M. Carpenter (Caltech), and the color composite was assembled by R. Hurt (IPAC/Caltech). It is this composite flux map that comprises the new 2MASS logo, seen above. (Image size 2.0 Mb!)

Galactic Center Atlas Image mosaic showing the Galactic Plane (the Plane of the Milky Way). The Galactic Center is the very luminous Ks-bright (reddish) source south of the image center. (The image is centered at RA=17h46m22.0s Dec=-27d58m20s [J2000].) This mosaic contains more than 1 million stars. Visible, even in the near-infrared, are the obscuring dust lanes that fill the Plane between us and the Galactic Center, located about 8.1 kpc (26400 light-years) away. However, with 2MASS, we are able to see farther through this dust than can be accomplished at visible wavelengths. Image mosaic by E. Kopan (IPAC). (Field size 2.2° × 3.9°. Image size 626 kb.)

2MASS-MSX Galactic Center The Spatial Infrared Imaging Telescope, SPIRIT III, was the primary instrument for gathering mid-infrared data during the Midcourse Space Experiment (MSX) mission. 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), Ks (green), and MSX Band A (6 - 11 µm; red) imaging of this region (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. 2MASS Image mosaic and 2MASS-MSX image combination by E. Kopan (IPAC). Featured as an Astronomy Picture of the Day! (Field size 2° [galactic latitude] × 5° [galactic longitude]. Image size 10.5 Mb! For the full-resolution 11.6-Mb version of this image, click here.)

FEST 1-457 Is it the Black Hole of Calcutta? No, it's a dark, obscuring cloud of dust near the Galactic Plane (the cloud is at RA=17h35m46.84s Dec=-25d33m10.8s, J2000; in galactic coordinates, l=1.62, b=+3.77). The cloud is the entry ``1-457'' in the catalog by Feitzinger & Stuwe (1984, A&AS, 58, 365) of dark nebulae, hence, the SIMBAD designation Fest 1-457. Based on the (J-H, H-Ks) color-color diagram, we estimate that the extinction toward the center of the cloud is AV>20 mag. (Field size 8.2´ × 12.5´. Image size 424 kb.)

IDC 11.11-0.12 Atlas Image mosaic of the filamentary, or snake-like, infrared dark cloud G11.11-0.12. This is an example of various regions in the Milky Way Galaxy with very high visual extinction, in excess of 25 magnitudes. They were discovered by routine survey observations of the Galactic plane by the Infrared Space Observatory and the Midcourse Space Experiment. From the lack of emission between 8 and 100 μm and high mid-infrared opacities, Egan et al. (1998, ApJ, 494, L199) concluded that the infrared dark clouds contain cold (T<13 K) dust and suggested that they are dense molecular cores. Carey et al. (2000, ApJ, 543, L157) find strong submillimeter bright, compact sources in eight dark clouds, using SCUBA at the JCMT, and these authors suggest that these highly embedded sources are potentially the sites for very early star formation in the Galaxy. These clouds, of course, look very dark on the near-infrared 2MASS images. Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Data Release! (Field size 25´ × 31´. Image size 3.0 Mb!)

M 1-67 The Wolf-Rayet ring nebula M1-67. Several Wolf-Rayet (W-R) stars, which represent the final evolutionary stages of very massive stars, have surrounding them thick shells of matter called "ring nebulae." The W-R star 124 (van der Hucht et al. 1981, SpSciRev, 28, 227) has a relatively young ejection nebula (M1-67). In this 2MASS image, the bright Ks-band emission seen around the bright W-R star (near the center of the image) is likely to be molecular H2. The molecular gas excitation is due to either ultraviolet flourescence, as photons from the star are intercepted by the ring, or to shocks interacting with surrounding gas. The nebula was recently imaged in H-alpha by the Hubble Space Telescope (Grosdidier et al. 1998, ApJ, 506, L127). Grosdidier et al. find unprecented structure never seen before, including what appear to be hot, dense clumps in the wind coming from the star. (Field size 5.6´ × 7.2´. Image size 179 kb.)

AG Carinae Atlas Image of the star AG Carinae. This star is one of the prototypical luminous blue variable stars, or LBVs, which are massive, evolved supergiant stars, in life-ending transition from an O star, with a mass 40 solar masses, to a Wolf-Rayet star. AG Car, at a distance of 6 kpc (19560 light years), has over 1 million times the luminosity of the Sun, and changes in spectral type from early A to late O; the star has varied greatly in luminosity over the last two decades. More importantly, it shows a dusty circumstellar nebula, visible in the 2MASS image as the blue ring around the star. Smith et al. (1997, MNRAS, 290, 265), from a compositional study of the nebula, conclude that AG Car probably experienced an earlier, brief red supergiant phase, when it ejected its hydrogen-rich outer layers to form the ~1 pc-diameter ring nebula; the ring matter has subsequently been swept up by the present hot supergiant wind. (The purplish "star" to the north of AG Car's diffraction spike is a known persistence artifact; a similar red artifact can be seen to the north of the very red star, which is to the southwest of AG Car.) (Field size 6.0´ × 6.0´. Image size 154 kb.)

NGC 3199 Atlas Image mosaic of NGC 3199, in the constellation Carina, which is the wind-blown partial "ring" around the Wolf-Rayet (W-R) star WR 18 (aka HD 89358), the easternmost (leftmost) of the three bright blue stars near the center of the 2MASS image. NGC 3199 and WR 18 are at a distance of about 3.6 kpc (11,736 light years) from us. W-R stars represent the final evolutionary stages of very massive stars (with ~30 solar masses or greater). The nebula shows an asymmetric appearance, i.e., only one side (the western one) of the shell is bright, both in the optical and the near-infrared. The fainter, eastern side is there, but is much fainter. Some W-R ring nebulae can be seen in 2MASS images, such as the more complete ring around M1-67. But, NGC 3199 is particularly bright in the 2MASS data. Dyson & Ghanbari (1989, A&A, 226, 270) provided an explanation for the ring's appearance through a model where a moving WR 18 is blowing a strong stellar wind into a surrounding uniform interstellar medium. Vigorous mass loss of 10-5 to 10-4 solar masses per year is characteristic of W-R stars, as the star approaches the end of its short life, although not all are surrounded by ring nebulae. Image mosaic by S. Van Dyk (IPAC). (Field size 13´ × 19´. Image size 1.1 Mb!)

Portion of Baade's Window Atlas Image mosaic of a portion of Baade's Window centered at about l=1.0°, b=-3.9°. (The downloadable image mosaic has been shrunk by 50%, but is still 2.2 Mb in size.) This "window" through our Milky Way Galaxy, discovered by the German-American astronomer Walter Baade early in the last century, is an important region of the sky, because the interstellar extinction, due to intervening dust in the Galactic plane, is substantially lower than other regions of the Galaxy nearby to it. Stanek (1996, ApJ, 460, L37) estimates from optical data that the extinction ranges from 1.26 to 2.79 visual magnitudes. As a result, this window allows astronomers to more easily view and study stars in the Galactic bulge. The chemical composition, ages, masses, and kinematics of these stars can be determined, the distance to the Galactic center can be measured, microlensing events can be discovered and analyzed, and the presence of a stellar bar in the bulge can be inferred, all important aspects to understanding the nature of the Milky Way. The 2MASS near-infrared color-color diagram and color-magnitude diagram for the stars within 1° of (l,b)=(1.0,-3.9) also demonstrate the relatively low extinction for the stellar populations in a region at this general position in the Galaxy. (Shown on the color-color diagram are the Bessell & Brett 1988, PASP, 100, 1134, and Koorneef 1983, A&A, 128, 84, tracks for dwarf and giant stars, as well as the reddening vector from Rieke & Lebofsky 1985, ApJ, 288, 618). Image mosaic by S. Van Dyk (IPAC). These data are included in the Second Incremental Release! (Field size 0.64° × 1.15°. Image size 2.2 Mb!)

V713 Mon Atlas Image of the carbon star V713 Monocerotis. This star, also known as AFGL 935 and IRAS 06230-0930, is an example of asymptotic giant branch (AGB) stars which are surrounded by an expanding shell. The AGB stars have evolved from main sequence stars in the mass range 1.2-1.6 solar masses (Claussen et al. 1987), but a significant population come from 2.5-4 solar mass main sequence stars (Barnbaum, Kastner, & Zuckerman 1991, AJ, 102, 289). The bright red color of the star in the 2MASS image indicates a general infrared excess due to carbon-rich dust formation in the shell. (The fainter red "star" to the south is a latent image artifact, produced by the mode of the survey scanning; diffraction spike artifacts are also seen in the image.) The dust is subject to pressure from the star's radiation and is dragged outward with the atmospheric gas, and is the cause for the mass loss from the star. The evolved star experiences pulsations and is variable with a long period; the variability and the amount of mass loss appears correlated for the carbon stars. Although the dust formation mechanism is not known, it appears that the dust is induced by the stellar pulsations. LeBertre (1997, A&A, 324, 1059) finds that the infrared colors of carbon stars shed light on the processes of dust formation and mass loss. V713 Mon, at a distance of 2240 pc (from its 494-day pulsation period), has a shell expansion velocity of 13.7 km s-1 and a mass-loss rate of 2.8×10-6 solar masses per year. LeBertre finds a correlation between the mass-loss rate for this and other carbon stars and the stars' near-infrared colors. 2MASS is particularly well-suited for not only finding many carbon stars throughout the Galaxy, but can also assist in characterizing the nature of their evolution. (Field size 5.0´ × 5.0´. Image size 139 kb.)

L dwarf 2MASSW J0326137+295015 The L dwarf 2MASSW J0326137+295015. (Field size 5.4´ × 5.4´. Image size 152 kb.)

L dwarf 2MASSW J1632291+190441 The L dwarf 2MASSW J1632291+190441. (Field size 5.8´ × 5.8´. Image size 161 kb.)

Gliese 570D Atlas Image mosaic of the T-type methane brown dwarf, Gliese 570D (Gl 570D), companion to the Gl 570ABC triple star system. Gl 570D is widely separated from the main system and is indicated with an arrow. Its brightness is overwhelmed by Gl 570ABC, seen as the two bright stars in the 2MASS image (the Gl 570BC binary system is unresolved in the image). T dwarfs are so cool that the methane in the object's atmosphere dominates the absorption spectrum, which peaks in the near-infrared. The strong methane absorption, particularly at 2 µm, results in less light in the Ks band, relative to J and H, such that the dwarfs look quite blue in the near-infrared. Their appearance is very similar to the methane-rich gas planets in our own solar system, Uranus and Neptune. Their color and relative faintness make them distinct in the 2MASS database. What makes Gl 570D so particularly interesting is that it is significantly cooler and less luminous than any other known brown dwarf, including the prototype T dwarf, Gl 229B. Burgasser et al. (2000, ApJ, 531, L57) find that temperature and luminosity of Gl 570D is 750 K and 2.8 × 10-6 the luminosity of the Sun, respectively, and they infer a mass for the brown dwarf of ~50 Jupiter masses. (Field size 6.7´ × 6.7´. Image size 214 kb.)

SS 433 Atlas Image, covering 8´ × 8´ on the sky of SS 433 and its environs. The 433rd entry in the Stephenson-Sanduleak (1977, ApJS, 33, 459) catalog of H emission stars in the Milky Way, aka V1343 Aquilae, is one of the most peculiar and possibly unique objects in the Galaxy (it is seen as the relatively bright star at the center of the 2MASS image). The strong emission lines seen in the spectrum of SS 433 appear as two sets which alternately redshift and blueshift in a smooth and regular fashion. The line sets, when redshifted, reach an impressive maximum of 50,000 km s-1, while the sets, when blueshifted, reach a maximum of 30,000 km s-1. These velocities both are a significant fraction of the speed of light! The basic model hypothesizes that the emission arises from two opposing collimated jets of matter, which rotate once every 164 days. The jets emanate from an accretion disk around a neutron star in an interacting binary system, possibly with a B-type companion star. That the compact object is likely a neutron star is consistent with the likely association of SS 433 with the supernova remnant W50; the jets interact with the nebula (Dubner et al. 1998, AJ, 116, 1842). SS 433, on the date that the routine 2MASS southern operations observed it (1999 Aug 11 UT), had magnitudes J=9.40, H=8.75, Ks=8.18. Kodaira, Nakada, & Backman (1985, ApJ, 296, 232) found the near-infrared emission to be, not unexpectedly, variable and likely mostly arising from the disk. The 2MASS color-color and color-magnitude diagrams (SS 433 is the red star on the latter diagram) indicate that the recent radio distance (Dubner et al.) of ~3.0 kpc (9780 light years) and a visual extinction of 8 to 9 magnitudes are consistent with the brightnesses and colors of many of the stars in SS 433's environment. (Field size 8´ × 8´. Image size 267 kb.)

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