LHA 120-N55 emission nebula complex
by Zaytsev and Hanson
Full Image click for higher resolution
North-East of the Large Magellanic Cloud (LMC), a peculiar combination interstellar shell, emission nebulae, and a collection of shock fronts forming a structure that we called earlier a “Flying Owl Nebula” is located, for which an earlier image was obtained using the Chilescope T3 system (ASA-N D=0.5m, f/3.8) [1].
Here we present the close-up view on one of them - the LHA 120-N55 emission nebula complex / N55 molecular cloud of the LMC [2, 3], obtained with the Chilescope T1 system (ASA Ritchey-Chretien RC-1000: D=1m, f/6.8) comprised of the following tightly coupled structures
LHA 120-N55A star forming region [4],
DEM L 228{a, b} HII regions [5] arranged into a bi-polar shape with a bridge in the middle, that appears to be a nebula associated with WBBe LH 72 13 Be star candidate [6].
Fig. 1
Fig. 1. The central part of the image containing the following structures: (a) LHA 120-N55A star forming region [4] and (b) DEM L 228{a, b} HII regions [5] arranged into an unusual bi-polar shape with a bridge in the middle, that appears to be a nebula associated with WBBe LH 72 13 Be star candidate [6]. Shown at 100% of the original image resolution.
As LHA 120-N55 physically belongs to the Large Magellanic Cloud (LMC) [2, 3], the linear size of the side of the image of 18.5 arc.min can be estimated as 650 ly at the distance to LMC taken as 158 kly.
Fig. 2
Fig. 2 shows the part of the image containing the DEM L 228{a, b} HII regions and WBBe LH 72 13 Be star candidate at 150% of the original resolution.Two most striking features here is the spiral structure of the formed out of neutral gas clouds inside the DEM L 228b region and the “bridge” connecting the DEM L 228{a, b} regions of the estimated physical length of about 13 ly at the distance to the LMC. There appears to be a neutral gas tendril present inside that compact nebula extending from the central star to the periphery of the nebula as well.
Fig. 2. Part of the original image containing the DEM L 228{a, b} HII regions [5] and WBBe LH 72 13 Be star candidate [6]. Shown at 150% of the original image resolution.
Fig. 3
Fig. 3 shows the part of the image containing the LHA 120-N55A star forming region [4] hosting the majority of LH 72 OB star association [7, 8] and a rather beautiful collection of compact neutral gas clouds, ionization fronts and shock fronts. The brightest stars of the LH 72 appear to have shock fronts or compact toroidal diffuse structures associated with them. The linear scale estimate for both structures is in the 9.4-9.7 ly range given the distance to the LMC.
Fig. 3. Part of the original image containing the LHA 120-N55A star forming region [4], shown at 200% of the original image resolution. Shock front (a) and toroidal diffuse structure (b) associated with bright stars of the LH 72 OB association [7, 8].
The highest resolution image available up to date for this OB association is one obtained by the Hubble Space Telescope (HST) WFC2 / WFC3 instruments using Ha, UV and visual spectrum data [9].
Fig. 4
Fig. 4 shows the cropped version of the original image at 200% resolution with the HST image [9] added as a semi-transparent overlay thus making it easy to identify all of the small structural features of this region detected in both images. This entire nebula complex is undoubtedly a good candidate for study with even larger apertures, particularly for the interior part of the LHA 120-N55A region and the compact nebula surrounding the WBBe LH 72 13.
Fig. 4. Part of the original image containing the LHA 120-N55A star forming region [4], shown at 200% of the original image resolution with the overlay of the HST image [9] added in matching mirroring and orientation..
Data and initial calibration/integration: Alexandr Zaytsev https://www.astrobin.com/users/m57ring/
ASA Ritchey-Chretien RC-1000: D=1m, f/6.8 on alt-azimuthal direct drive fork mount, FLI ProLine 16803 with secondary mirror based motorized focusing and automatic de-rotation (Telescope #1 system of ChileScope observatory, Río Hurtado Valley, Chile).
14x Ha + 11x OIII + 11x SII guided 1200 sec exposures (12h of combined integral) collected over 8 imaging sessions carried out on Aug 6, 8, 9, 10, 11, 12, 13, 14, 2024 using Chilescope Telescope #1 system.
Image Processing: Mark Hanson
Enjoy, Mark and Alex
[1] https://www.astrobin.com/lobsen/
[2] https://arxiv.org/abs/1801.01653
[3] https://arxiv.org/pdf/1801.01653
[4] https://simbad.cds.unistra.fr/simbad/sim-id?Ident=LHA+120-N+55A&
[5] https://simbad.cds.unistra.fr/simbad/sim-id?Ident=DEM+L+228a& , https://simbad.cds.unistra.fr/simbad/sim-id?Ident=DEM+L+228b&
[6] https://simbad.cds.unistra.fr/simbad/sim-id?Ident=%405126669&Name=WBBe%20LH%2072%2013&submit=submit
[7] https://arxiv.org/abs/astro-ph/0102444