Atlas Image mosaic of GGD 27. This object is the center of an active young star formation region obscured optically by dense molecular gas and dust along our line of sight. In the 2MASS near-infrared image a number of point sources in this region can be seen, along with the extended and wispy bipolar reflection nebulosity, which corresponds to a bipolar molecular outflow, with a dynamical age of about 105 years (Yamashita et al. 1989, ApJ, 347, 894). Particularly noticeable is the reddish core region of the source, where the most embedded star formation is taking place. Imaging of this core region at slightly longer wavelengths than the 2MASS bandpasses (3.8 and 4.7 µm) by Aspin et al. (1994, A&A, 292, L9) reveal several sources so obscured they are not seen at 2 µm. Image mosaic by S. Van Dyk (IPAC). (Field size 12.0´ × 12.0´. Image size 510 kb.) 


 Atlas Image mosaic of the Herbig Ae/Be star R Coronae Australis. Herbig Ae/Be stars are the intermediate-mass (2 to 8 solar masses) counterparts of T Tauri stars. The emission-line star highlights the Corona Australis molecular cloud complex and is embedded within it. The complex, at a distance of only ~130 pc (424 light years) is one of the nearest star-forming regions. The densest part of the molecular cloud core, containing about 50 solar masses of gas, has high visual extinction, about 35 magnitudes. The bright star just to the southeast of R CrA (at image center) is T CrA, and the two stars to the northeast, enshrouded in bluish reflection nebulosity near the image edge, are TY CrA (northern-most) and HD 176386 (southern-most). Stars are forming throughout the cloud, highlighted by several young stellar objects (YSOs), the most prominent ten or so of which surrounding R CrA have been dubbed the Coronet; starting clockwise from north the brighter reddish YSOs comprising the Coronet are IRS 6, IRS 5, IRS 2, Herbig-Haro (HH) 100 IR, and T Cr A itself. (The "sources" emanating due north and south of R CrA, with decreasing brightness are latent image artifacts, produced by the mode of the survey scanning; diffraction spike artifacts from R CrA are also seen in the image.) A number of other fainter YSOs and HH objects (IRS 10 through 15, HH 99, and HH 104) are also seen; Wilking et al. (1997, AJ, 114, 2029) recently produced a similar, yet deeper near-infrared map of this region and identified the various sources in the cloud. They find reflection or HH nebulae associated with most of the YSOs in the cloud, suggesting nearly coeval star formation in the cloud some 3 million years ago. They also find a shallower reddening vector slope than found for normal interstellar dust, implying the presence of larger than average dust grains throughout the cloud. Image mosaic by S. Van Dyk (IPAC). (Field size 10.0´ × 10.0´. Image size 289 kb.) 


 Atlas Image mosaic of the reflection nebula IC 2087. The bluish nebula has a arc-like appearance, fanning off to the east from the low-mass young stellar object (YSO) Elias 18 (aka Elias 3-18 and IRAS 04369+2539), within the Taurus molecular cloud, specifically the Heiles Cloud 2. Elias (1978, ApJ, 224, 857) found that this YSO is behind about 17 visual magnitudes of extinction. Shuping et al. (2001, ApJ, 547, L161) argue, based on near-infrared spectroscopy, that, since Elias 18 is associated with two Herbig-Haro objects (HH 395A and B) to the northeast (not seen in this image) and IC 2087, the YSO is near the front of Heiles Cloud 2 and that most of this extinction is in the form of a highly-inclined circumstellar disk around the YSO. Elias 18 has Ks=6.25, J-H=2.63, H-Ks=1.78 mag. Known diffraction spike artifacts are evident around, and persistence artifacts trail (in decreasing brightness) both due north and due south of, Elias 18. The infrared-bright source to the southwest in the 2MASS mosaic is the YSO TMC 1A (IRAS 04365+2535). Image mosaic by S. Van Dyk (IPAC). (Field size 12´ × 12´. Image size 583 kb.) 


 Atlas Image mosaic of the Herbig Ae/Be star LkH 198, at a distance of 600 to 900 pc. The Herbig Ae/Be stars are intermediate-mass pre-main sequence objects, showing emission lines in their optical spectra and appearing with associated nebulosity (they are more massive than their lower-mass counterparts, the T Tauri stars). LkH 198 is the bright object at the center of the image; 35´´ north of this star is another Ae/Be star, V376 Cas. Both stars can be seen in the near-infrared to be embedded in associated nebulous clouds. (Diffraction spike artifacts can be seen emanating from both bright objects; latent image artifacts, produced by the mode of the survey scanning, show a similar pattern of "red stars" both due north and due south of the two stars.) Both stars are thought to drive a low-velocity bipolar molecular outflow. LkH 198 also has an embedded infrared companion (unseen in the 2MASS image). Also seen in the 2MASS image is a blue elliptical loop associated with LkH 198 and a similar "sickle-shaped" nebula (weakly) seen to the west of V376 Cas; this extended emission is consistent with light scattering by small dust grains. A diagram of this complex region, showing the relationship of its various components, is provided by Koresko et al. (1997, ApJ, 485, 213; their Figure 7). Image mosaic by S. Van Dyk (IPAC). (Field size 6.7´ × 6.7´. Image size 188 kb.)