Carina Nebula Mosaic in SHORGB

The Carina Nebula (NGC 3372, Caldwell 92) [1] is a well evolved HII region located only 8.5 kly away according to Gaia DR2 measurements [2, 3] at which distance the image scale translates to 0.016 ly / px = 1.0 kAU / px or 167 ly by 182 ly for the whole FOV of the image which is covering the patch of the sky 1.14 deg. by 1.23 deg. across in the central part of the complex. The Carina Nebula, while being currently observed after the peak of star formation is already completed and its progenitor molecular cloud mostly dispersed, is hosting the Car OB1 [4] star association and numerous related star clusters that are between 1-10 Myr old [5, 6]. Yet, in spite of that process, the region still has prominent neutra gas and dust clouds present in the area, forming a V-shaped dust lane separating it the region into the Northern (upper part of the FOV) and Southern (lower part of the FOV) suggesting a bipolar physical structure for this nebula complex [7, 8]. Evidence from IR observations with MSX, Spitzer and Herschel space telescopes suggest that the star formation in the region continues in the “triggered mode” at the average rate of 0.008 solar masses per year, driven by the interaction of the expanting HII region with the surrounding molecular clouds and radiative compression by the massive stars within [9-12]. Most of the present day star formation activity in the central part of the region appears to be concentrated around Cl Trumpler 14 [13] and Cl Trumpler 16 [14] opens star clusters [11, 12, 15, 16].

Being one the the largest and brightest nebulae in the entire sky, it is naturally one of the most studied ones, with more than 18,000 objects catalogued in the circle of 70 arc.min radius from the center which makes the detailed annotated versions of the image very challenging. After filtering out most of the individual stellar objects and leaving non-stellar objects from the visible spectrum the following objects remain in the FOV of the image, as illustrated in Fig. 1:

48 star clusters and associations (red markers and text) of which the most prominent are the aforementioned Cl Trumpler 14 [13], Cl Trumpler 16 [14] open clusters as well as Cl Trumpler 15 [17], Cl Collinder 228 [18], Cl Collinder 232 [19] open clusters.
52 emission nebulae (gold markers and text), of which the Homunculus Nebula [20-25] - a compact bipolar HII region surrounding Eta Carinae hypergiant star [26] and the Keyhole Nebula [27] located North of it.
597 dark nebulae (white markers and text) - including dozens of Herbig-Haro objects, dark pillars [28, 29] (particularly remarkable in the South-East portion of the nebula complex - in the lower left quadrant of the FOV), and numerous compact neutral gas clouds, such as dense cores, “clumps” and “knots” of neutral gas, cometary globules, and various dark filamentary structures distributed all over the FOV.
2 planetary nebulae / PN candidates (magenta markers and text) plus 4 background galaxies (cyan markers and text) - none of these are large / bright enough to show at this image scale.

Many compact DNs located inside of Carina Nebula are famous in their own right and have been targeted by the Hubble Space Telescope and large aperture ground telescopes on many occasions, namely:

The Treasure Chest [30] - a compact nebula at the top of a dark pillar, containing a young star cluster emerging from it [31, 32].
The Mystic Mountain [33, 34] - a monumental set of gas pillars complete with a Herbig-Haro object at the “top” with a very well defined jet protruding on both sides.
The Defiant Finger [35-37] - a rather peculiarly shaped compact photoevaporating globule near the Keyhole nebula.
The Caterpillar [38] - another compact bright rim globule near the Keyhole nebula.

It’s very interesting to note the apparent lack of the visible SNR structures inside this region: the only SNR identified in its inner volume is the SNR G287.8-00.5 (Carina SNR) [39], and as stated in [40, 41]:

“The Carina Nebula (NGC 3372) is our richest nearby laboratory in which to study feedback through UV radiation and stellar winds from very massive stars during the formation of an OB association, at an early phase in the evolution of the surrounding proto-superbubble before supernova explosions have influenced the environment. …In the next 1-2 Myr, there will be several very energetic SNe in the Carina Nebula, which will carve out an even larger cavity in the ISM and form a giant superbubble in the Galactic plane … ”

However the possibility is suggested by the Chandra X-ray data [42, 43] that multiple neutron stars and black holes could be hidden in the Carina Nebula resulting from an earlier major episode of massive star formation in this region [44, 45].

The incredible complexity and the sheer number of small scale structures contained in this region allows one to produce many cropped views of interest in the FOV of the original image, and we settled on 23 regions of interest subdivided into 6 groups labeled C1-6 as illustrated in Fig. 2-8. These regions of interest are listed below.

Group C1 (frame previews are in Fig. 2):

Views C1 (Fig. 5) and C1.1 (Fig. 7): broad views to the North portion of the nebula containing Cl Trumpler 14 [13] cluster, the Mystic Mountain [33, 34] formation and multiple compact DNs and emission nebulae filaments.
Views C1.2 and C1.3 (Fig. 4): sub-regions of view C1 focused on the large dark pillar and ionisation fronts in the North-Western portion of the original image.
View C1.4 (Fig. 4, 200% of original resolution): closer view to the Mystic Mountain [33, 34].
View C1.5 (Fig. 4, 200% of original resolution): closer view to the peculiar compact DNs embedded in the North-Western wall of the region.

Group C2 (frame previews are in Fig. 2):

Views C2 (Fig. 5) and C2.1 (Fig. 4): broad views to the South portion of the nebula containing remarkable dark pillars including the one hosting the Treasure Chest [30] cluster.
View C2.2 (Fig. 4) and C2.3 (Fig. 4, 200% of original resolution): closer look to the Western side of view C2.1, containing some remarkable dark pillars and compact DNs.
View C2.4 (Fig. 4) and C2.5 (Fig. 4, 200% of original resolution): closer look to the dark filaments and compact DNs on the East side of view C2.

Group C3 (frame previews are in Fig. 3):

Views C3 and C3.1 (Fig. 6): closer look at the emission nebulae in the South-West side of the nebula.
View C3.2 (Fig. 4): peculiar wave pattern dark filaments in the South part of the nebula.
View C3.3 (Fig. 4): two remarkable dark pillars in the South-East part of the nebula
View C3.4 (Fig. 4): the “dragon pit” of Carina Nebula - a remarkable network of dark filaments in the South-East part of the nebula
View C3.5 (Fig. 4): ionisation fronts and compact DNs in the East wall of the region.

Group C4 (frame previews are in Fig. 3):

Views C4 (Fig. 4) and C4.2 (Fig. 8): views focused on the Eta Carinae [26] and the Keyhole Nebula [27], also featuring the Homunculus Nebula [20-25], the Defiant Finger [35-37] and the Caterpillar [38] compact DNs.While Homunculus Nebula is too small to reveal significant amount of details at this image scale, it’s bipolar structure is visible and several knots of ionized gas are also visible in its vicinity.
View C4.1 (Fig. 4, 400% of original resolution): closer look at the Defiant Finger [35-37] compact DN.

Group C5 (frame previews are in Fig. 3):

View C5 (Fig. 4): closer look to the emission nebulae and ionization fronts in the North side of the nebula.

Group C6 (frame previews are in Fig. 3):

View C6 (Fig. 4): closer looks to the dark filaments and pillars in the West side of the nebula.

Image Processing and Data Collection

<TBD>

Enjoy the view!

Fig. 1.Annotated version of the image (at 100% of original resolution).

Fig. 2. Original image with overlays showing the position of various cropped views into its subregions: sets C1 and C2 (at 100% of original resolution).

Fig. 3. Original image with overlays showing the position of various cropped views into its subregions: sets C3-6 (at 100% of original resolution).

Fig. 4. Close-up cropped views into most remarkable sub-regions of the image (at 100% of original resolution by default, unless otherwise noted).

Fig. 5. Cropped regions C1 (top) and C2 (bottom) shown at 100% of original resolution.

Fig. 6. Cropped regions C3.1 (top) and C3 (bottom) shown at 100% of original resolution.

Fig. 7. Cropped region C1.1 shown at 100% of original resolution.

Fig. 8. Cropped region C4.2 shown at 100% of original resolution.

[1] https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=NGC+3372&submit=SIMBAD+search

[2] https://arxiv.org/abs/1807.02115

[3] https://arxiv.org/pdf/1807.02115

[4] https://simbad.cds.unistra.fr/simbad/sim-id?Ident=car+ob1&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id

[5] https://arxiv.org/abs/1011.2904

[6] https://arxiv.org/pdf/1011.2904