OR 3: LMC Sampler from Australia

Steve Gottlieb

There's absolutely nothing comparable in the northern hemisphere with numerous LMC fields packed with 10 or more clusters and/or HII regions. While the brightest several dozen globulars in M31 are visible in an 18" scope, they appear at best as a fuzzy mag 14 or 15 "star". Not so in the LMC, where bright clusters may be partially or well resolved in larger scopes and the Tarantula Nebula region rivals the best HII regions in our own galaxy. Although the LMC was high on my priority list while I was in Australia a month ago, it was already well past the meridian in early April evenings, so I worked quickly to log over a 100 objects over a few nights. Just identifying all the objects in these rich fields can be challenging, so detailed star charts or images are a requirement. A UHC filter was also very helpful in bringing out structure in HII complexes. Here's a sampler of 8 fields to give a flavor of the LMC treasures. These fields included many additional objects (and this report is long as is), so if anyone is interested in complete notes send me a personal note. Steve

NGC 1850 field:
N1850: at 350x I was stunned by the view of this huge, extremely bright cluster! The outer halo (5' in diameter) was resolved into dozens of faint stars in irregular star chains that appear to stream out of the core. A single brighter mag 13 star is superimposed on the west side. The center is highly concentrated with an extremely bright 1' core that appears elongated, irregular and clumpy with a curved outline. A small, 20" diffuse glow is embedded at the N edge of the halo (open cluster S-L 260). N1850 lies in a very impressive region of the LMC (near the outskirts of the central bar) with 13 additional NGC clusters/nebulae within 30' including N1854 6' SE, N1858 10' SE, N1856 22' SSE and several others including N1836, N1839, N1847, N1860, N1863, N1865.

N1854 appeared very bright, large, round, with a brilliant core. At 350x, it was resolved into numerous faint stars around the edges of the intense core. Up to a couple of dozen very faint stars popped in and out of visibility. The core is noticeably elongated N-S and is surrounded by a large, much fainter halo. There is a small clump of stars at the NW edge. The large star cluster and nebulosity N1858 lies 4' SE.

N1858 would be a fascinating nebula and cluster if it were isolated, but is even more striking situated at the SE end of a wonderful chain with the bright cluster N1854 and N1850. At 346x about two dozen stars were superimposed over an elongated glow and many other stars are just outside the glow. At 200x with a UHC filter, the nebula is very bright overall with a 30" very high surface brightness patch at the N end. The nebula is brightest along the W and E border and weaker in the center. The elongation is towards a mag 12 star on the south side. N1854 lies 4.5' NW.

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NGC 1872 field:
N1872: this bright globular was the first LMC object I viewed in the 24" and the view and surrounding field was very striking. At 200x, the cluster appeared very bright, fairly large, round, 1.25' diameter, with a very bright core and a mottled halo. Just to the east is a fairly rich scattering of stars including a 6' N-S curving chain that includes several mag 11-12 stars with a nice mag 12 pair at the N end (NGC 1881). The southern end of the chain is near an impressive complex of 5 HII regions (N1874, 76, 77, 80) located ~4' S and 5' SSE of N1872.

N1876/1874/1877/1880: N1876 is the largest and brightest in an impressive complex of HII regions just 3' south of the globular cluster N1872. At 200x and a UHC filter it appeared very bright with a slightly irregular outline, ~1.2' diameter, brightest along the north rim where there is a brighter knot. Another prominent section, N1874, lies only 1' SW, and appeared bright, round, ~1' diameter, even surface brightness. N1877 is a similar distance SSE and appeared faint, fairly small, elongated 2:1 NW-SE, with several stars involved. N1877 forms the SE vertex of a small equilateral triangle with N1874 and N1876. Finally, N1880 lies another 1.5' ESE of N1877. It appeared as a moderately bright, small, round haze surrounding a star (a brighter star ~40" SW is free of nebulosity). Very faint haze is visible extending to the east and northeast. A long curving chain of stars curves to the NE of the complex and ends near N1881.

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NGC 1910 field:
N1910 is a large, bright cluster or star cloud that contains the variable S Doradus (8.6-11.5), the brightest star in the LMC and one of the brightest known stars (absolute mag -9). At 200x, roughly 100 stars mag 11-15 were resolved in a 7' region with some extensions increasing the diameter another couple of arc minutes. S Dor is the brightest star in the main portion of the cluster, though there are several mag 12 stars. On the north side is a small, bright knot (S-L 360) that is clearly non-stellar and surrounded by a thin, fainter halo (ring of faint stars on the DSS).

The cluster is embedded in a very large, bright emission nebula (N 119). The most prominent section of the nebula is a very bright 3' patch to the east of S-L 360 and a wing to the south of S-L 360 that responds well to a UHC filter at 200x. Nebulosity is also visible on the west side of S Dor. This section curves N-S to S-L 360 and also south of S Dor. To the south of N1910, on a NW to SE stream extending a couple of degrees, are dozens of LMC clusters with N1903, an impressive globular, situated 10' SW.

N1903, a this showpiece globular, is located just 10' SW of the N1910 complex containing S Doradus. At 350x, it appeared very bright, ~1' diameter, with a blazing 20" core. Perhaps 20 stars are resolved in the halo at this power with single brighter star at the edge of the core on the south side. N1916, another bright globular, lies 8' SE. This cluster is located in a wonderful section of the LMC and panning south and to the west yields field upon field filled with both bright and fainter clusters of all sizes, along with nebulous HII glows.

N1913: on the south edge of this interesting LMC cluster and nebula is a small triangle of mag 13-14 stars (12"-15" on each side) and another three stars within the cluster are resolved. The cluster is involved an elongated bright nebulous glow NNW to SSE and at 350x additional nebulosity surrounds the main glow for a total size of 1.5'x1.0'. A mag 11.7 star lies 1.7' E and a mag 10 star 2.2' SW. Continuing SW for 2' beyond the mag 10 star I also picked up S-L 362.

N1918 is a combination LMC cluster and nebula (listed in SIMBAD as a supernova remnant). At 200x a striking double star sits within the glow with a third star in a line and an additional 20 stars are resolved in the cluster. These stars are immersed in a diffuse nebulous glow that responds well to a UHC filter. The brightest section is a patch to the east of the double star (LMC N120C), but nebulosity extends throughout the cluster as an elongated glow of ~5' length. On images this nebula appears more like an arc or rim with some filamentary structure.

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NGC 1934 field:
N1929: this HII knot is the first in an impressive star cluster/ emission complex that extends over 7' in size and includes N1935, 1936, 1937, and IC 2126. At 260x it appeared as a bright, moderately large, round glow of ~50" diameter surrounding a mag 13 star. This is a symmetrical superbubble (http://www.universetoday.com/am/publish/ gemini_interstellar_cavern.html)

N1935: this emission glow forms the NW pair with N1936 in a very striking field of clusters and HII patches. At 200x and UHC filter it appeared as a very bright, round glow of uniform high surface brightness. The size is slightly smaller than N1936, perhaps 45"-50" in diameter. Good response to the UHC filter. Nebulosity also extends off to the NW of N1935 and a locally brighter patch (N1934) involves a couple of brighter stars. Superimposed on this entire complex of HII knots is a rich concentration of stars.

N1936 appeared as a very bright, round glow, ~1' diameter with a very high, uniform surface brightness at 200x using a UHC filter. Situated at the south end of a large cluster and HII complex. Additional fainter nebulosity sweeps to the south and is connected with a fainter (anonymous) patch to the west by 1'. This extension increases the total size to 2' to 2.5'.

N1937 is the furthest NE in a gorgeous field of stars and HII regions. N1937 is a large nebulous patch, ~3.7'x2.7' in size, with ~20 stars resolved over the bright glow. Excellent contrast gain using a UHC filter at 200x. The cluster includes a string of stars oriented WSW-ENE that passes through the center including a mag 11 star. N1936, a very bright nebulous glow, lies 5' S, and other sections of the N44 superbubble complex lie to the SW.

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NGC 1962-65-66-70 field:
N1962 is the bright western patch of the N1962-65-66-70 cluster and emission nebula. At 200x it appeared as a large, fairly bright glow on the west side of the complex, ~2' in diameter. A few faint stars are peppered across the glow. Excellent contrast gain using the UHC filter which increased the visibility to a prominent glow. N1965 is a bright, 20" knot that surrounds two stars on the NW side of the complex. N1966 is a small, bright glow surrounding three stars on the NE side, elongated WNW-ESE, ~40"x15". Fainter nebulosity is attached extending to the west for 1.5' and connecting to N1965.

At 200x using a UHC filter, this is a fascinating emission complex as the entire 5' region is awash in bright nebulosity and there are faint, irregular extensions beyond the main portion, particularly to the north (the outer portions form a faint bubble on images). A 10th mag star is involved, though the cluster itself (S-L 476) does not stand out significantly.

N1953 is a bright, moderately large globular cluster, round,~50" diameter, with a brighter core. At 350x, it was grainy with a couple stars easily resolved at the edges of the halo. The nucleus appears offset from center towards the E. The interesting N1962-65-66-70 HII complex and cluster follows with N1970 4.5' due E and stretching quite a distance to the E and SE lie a huge number of clusters, star clouds and HII regions.

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NGC 2018 field:
Fascinating, showpiece HII complex with a cluster and a large, detailed nebula appearing like a fainter version of M8 -- of course, in another galaxy! At 200x the cluster (S-L 533) is ~8' in diameter and includes a couple of dozen mag 11-15 stars. The stars are involved in the glow of a bright HII complex that has an excellent response to a UHC filter. Using the filter, the brightest region (N2018) is a very prominent 1' circular patch on the east end with fainter wings extending north and south, increasing the size to 3'x1'. A wide pair of stars including a brighter star (HD 269676) is at the west edge of this patch. Three additional elongated patches (each 1' to 1.5' in diameter) are strung out in a NW to SE line along the SW side of the complex (BSDL 2005, 2048 and 2120). Another glowing patch of nebulosity, ~45" diameter, is to the west of of the brightest region and surrounds a couple of brighter stars. Finally there is an isolated, elongated patch on the north end of the complex that seems detached (BSDL 2129). Weaker sections of the nebulosity give the impression of dark lanes. Surprisingly, Herschel's description applies only to the brightest region at the east end of this entire complex.

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Seagull Nebula (NGC 2030, 2032, 2035, 2040):
N2030: The Seagull Nebula is a bright, highly structured 7'x5' emission nebula. N2030, the NW component, consists of a bright streak elongated E-W extending west from mag 12.3 HD 269810. A large mass of nebulosity spreads to the north from this streak in a more circular 2' patch. This object is incorrectly identified as N2029 in modern catalogues and atlases.

N2032 is possibly the brightest section of the Seagull Nebula and consists of a very bright, elongated ~SSW-NNE patch, 2'x1', with an unusual kidney-bean shape, indented or concave on the east side. N2032 is just separated to N2035 by an elongated SSW-NNE on the east side. A faint, thin streamer of nebulosity shoots to the north from N2032. Mag 11.4 HD 269808 is off the SW side.

N2035 is the southeast section and appeared very bright, moderately large, with a very irregular shape similar to an anvil. The very knotty, complex structure was elongated N-S, 1.6'x1.0', with the widest part of the anvil on the south end. A very faint streamer attached on the NE side flows to the north (N2032 has a similar but brighter streamer). A fairly small detached patch, ~1.2' in diameter, is close SE (= LHA 120-N 59C).

N2040 is a bright, irregularly round glow, ~2' diameter, located ~4' ENE of the Seagull Nebula and part of the same emission complex. This irregular nebulosity surrounds a cluster of roughly 15 stars. The DSS reveals delicate filaments to the south forming a large loop or shell (possibly a SNR shell).

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NGC 2077 – NGC 2086 nebulous field:
This is an amazing field of nebulous glows located ~35' SSE of the Tarantula Nebula and an outlying part of the same huge complex. N2077 is the SW component of a very bright, impressive 2' emission patch with N2080. At 200x and UHC filter it appeared bright, moderately large, elongated 2:1 E-W, ~1.2'x0.6'. Without a filter, three fainter stars are involved in the glow. N2080 is an extremely bright nebulous glow just 1' NW with an irregular shape, ~1.5' diameter, slightly elongated. The brightest section is encased in a larger, fainter nebulous glow that extends mostly to the south. At 350x the view is fascinating with 3 or 4 stars involved (possibly one a knot) and the HII knot took on a curdled texture. A couple of brighter stars are off the NW side and a number of stars trail off to the E and NE. Another smaller pair of bright glows, N2085 and N2086, lies 3' and 4' ESE.

N2078 is the northwest component of an impressive 4' emission nebula filled with bright knots with several of the brighter knots forming a curving "S" shape. At 200x and UHC filter it appeared as a fairly bright, moderately large glow surrounding a mag 12 star and two fainter stars. This knot is elongated ~E-W, ~1.2'x0.8' and is encased in a fainter outer halo that extends perhaps 1.5', mostly to the north. An extremely bright isolated patch, N2079, lies 1.7' S and N2083 is a similar distance to the east.

N2079 is the brightest section on the SW side of an impressive 4' collection of perhaps 8 different emission knots encased in a diffuse glow (only 4 NGC numbers). At 200x and UHC filter it appeared extremely bright, with a uniform very high surface brightness. The outline has an unusual triangular shape (one vertex at the N end) with a well-defined border and ~1' in diameter. Without a filter, a very faint star is located at the center of the glow.

N2083 is the NE section of the N2078/79/83/84 complex. At 214x and UHC filter, it appeared as a bright, large, slightly elongated glow surrounding a mag 12.5 star, ~1.8' diameter. A brighter knot is embedded within the glow on the west side (LMC N159I) on a line with N2078. Removing the filter, the mag 12.5 star has a very faint companion and another brighter star is also embedded at the edge.

N2084 forms the SE region of the complex and it's composed of several nearby components. At the NE end of this extended region is a moderately bright, round knot, ~45" diameter (N159G). Without a filter a star is involved with this glow. The second, brighter embedded "glow" is close WSW on a direct line with N2079. This knot (N159C-east) corresponds with John Herschel's position for N2084 and appeared very bright, fairly large, elongated, ~1.2'x1.0'. Removing the filter a couple of stars are involved (with one brighter star). A fainter stream of nebulosity connects this glow with another glowing knot in essentially the center of the entire complex, 1.5' W of N2084 (N159C-west). This third knot is fairly bright, moderately large, round, 45" diameter.--