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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