Rotating elephant trunks

Gahm, G. F.; Carlqvist, Per; Johansson, Lars; Nikolić, S.

doi:10.1051/0004-6361:20054494

Cited by 44 publications

(75 citation statements)

References 50 publications

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“…The observation in the lower left panel (d) (Hester et al 1996) has the same physical length scale as the zoomed simulated pillars to the right (e). the observed 9.2 M in the Dancing Queen trunk in NGC 7822 (Gahm et al 2006). In addition, the simulated line widths with a standard mean deviation of ≈ 0.38 km s −1 , corresponding to a FWHM 0.94 km s −1 , are in excellent agreement with the observed FWHM 1.2 km s −1 .…”

Section: Resultssupporting

confidence: 80%

“…Some filaments run diagonal across the pillars, suggesting a complex twist into a helical structure (Carlqvist et al 2003). This is also supported by spectroscopic measurements of the line-of-sight (LOS) gas velocity: the pillars show a bulk motion away from the ionizing stellar sources with a superimposed complex shear flow that could be interpreted as corkscrew rotation (Gahm et al 2006). Occasionally, close to the tip of the head small spherical gas clumps are observed to break off and float into the hot HII region.…”

Section: Introductionmentioning

confidence: 55%

“…Thin, elongated pillars connect the head with the main body of the molecular cloud. They have typical widths of 0.1 − 0.7 pc and are 1 − 4 pc long (Gahm et al 2006, Schuller et al 2006. Observations show that the pillars are not smooth, but built of small substructures, filaments and clumps (Pound 1998).…”

Section: Introductionmentioning

confidence: 99%

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Pillars, Jets and Dynamical Features

et al. 2010

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Abstract. We present high resolution simulations on the impact of ionizing radiation on turbulent molecular clouds. The combination of hydrodynamics, gravitational forces and ionization in the tree-SPH code iVINE naturally leads to the formation of elongated filaments and clumps, which are in excellent agreement with the pillars observed around HII regions. Including gravity the formation of a second generation of low-mass stars with surrounding protostellar disks is triggered at the tips of the pillars, as also observed. A parameter study allows us to determine the physical conditions under which irregular structures form and whether they resemble large pillars or a system of small, isolated globules.

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Section: Resultssupporting

confidence: 80%

Section: Introductionmentioning

confidence: 55%

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Pillars, Jets and Dynamical Features

et al. 2010

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“…The object designated Claw E forms the eastern part of a yaw-like structure, composed of twisted and very thin filaments. The western part of the Claw was included in the CO survey by Gahm et al (2006) of the adjacent "Wrench Trunk", which also has an yaw-like end (Carlqvist et al 2003).…”

Section: Selected Objectsmentioning

confidence: 99%

Mass and motion of globulettes in the Rosette Nebula

Gahm

Persson

Mäkelä

et al. 2013

A&A

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Context. Tiny molecular clumps are abundant in many H ii regions surrounding newborn stellar clusters. In optical images these so-called globulettes appear as dark patches against the background of bright nebulosity. The majority of the globulettes were found to be of planetary mass in a previous optical investigation, while the largest objects may contain more than half a solar mass. Aims. We aim to clarify the physical nature of globulettes by deriving densities and masses, and to determine their velocities as a function of position over the nebula. This information will provide clues to the question of origins, evolution, and fate of globulettes. The Rosette Nebula is relatively rich in globulettes, and we selected a sample of well-confined objects of different sizes for the present investigation. Methods. Radio observations were made of molecular line emission from 16 globulettes combined with near-infrared (NIR) broadband JHKs and narrow-band Paschen β and H 2 imaging. Ten objects, for which we collected information from several transitions in 12 CO and 13 CO, were modelled using a spherically symmetric model. Results. Practically all globulettes were detected in our CO survey. The observed 12 CO (3-2) and (2-1) line temperatures range from 0.6 K to 6 K, the 13 CO being a third of this. As a rule, the lines are narrow, ∼1.0 km s −1 . The best fit to observed line ratios and intensities was obtained by assuming a model composed of a cool and dense centre and warm and dense surface layer. This model provides estimates of maximum and minimum mass; the average masses range from about 50 to 500 Jupiter masses, which is similar to earlier estimates based on extinction measures. The selected globulettes are dense, n H ∼ 10 4 cm −3 , with very thin layers of fluorescent H 2 emission, showing that the gas is in molecular form just below the surface. The NIR data show that several globulettes are very opaque and contain dense cores. No infrared-excess stars in the fields are associated with globulettes. Internal gas motions are weak, but some larger objects show velocity-shifted components associated with tails. However, most globulettes show no signs of tails or pronounced bright rims in contradiction to current numerical simulations of clumps exposed to intense stellar radiation. Because of the high density encountered already at the surface, the rims become thin, as evidenced by our Pβ images, which also show extended emission that most likely comes from the backside of the globulettes. We conclude that the entire complex of shells, elephant trunks, and globulettes in the northern part of the nebula is expanding with nearly the same velocity of ∼22 km s −1 , and with a very small spread in velocity among the globulettes. We note that the velocities observed for background shells do not fit into a spherically expanding nebular complex. Conclusions. Some globulettes are in the process of detaching from elephant trunks and shells, while other more isolated objects must have detached long ago and are lagging b...

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“…In the H band the rims are less bright and especially in J the rims are not conspicuous because of strong background surface brightness in the images. The arc-minute-scaled elephant trunks called "the Wrench" and "the Claw" (nomenclature from Gahm et al 2006) RN 31,35,44,88,94,95,114,122,129) are seen in absorption against the bright background emission in J, indicating that these objects are very dense. The designations and locations of the globulettes can be found in G07.…”

Section: Jhks Imagingmentioning

confidence: 99%

Rosette globulettes and shells in the infrared

Mäkelä

Haikala

Gahm

2014

A&A

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Context. Giant galactic H ii regions surrounding central young clusters show compressed molecular shells, which have broken up into clumps, filaments, and elephant trunks interacting with UV light from central OB stars. Tiny, dense clumps of subsolar mass, called globulettes, form in this environment. Aims. We observe and explore the nature and origin of the infrared emission and extinction in these cool, dusty shell features and globulettes in one H ii region, the Rosette nebula, and search for associated newborn stars.Methods. We imaged the northwestern quadrant of the Rosette nebula in the near-infrared (NIR) through wideband JHKs filters and narrowband H 2 1-0 S(1) and Pβ plus continuum filters using the Son of Isaac (SOFI) instrument at the New Technology Telescope (NTT) at European Southern Observatory (ESO). We used the NIR images to study the surface brightness of the globulettes and associated bright rims. We used the NIR JHKs photometry to create a visual extinction map and to search for objects with NIR excess emission. In addition, archival images from Spitzer Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) 24 μm and Herschel Photoconductor Array Camera and Spectrometer (PACS) observations, covering several bands in the mid-infrared and far-infrared, were used to further analyze the stellar population, to examine the structure of the trunks and other shell structures and to study this Rosette nebula photon-dominated region in more detail. Results. The globulettes and elephant trunks have bright rims in the Ks band, which are unresolved in our images, on the sides facing the central cluster. An analysis of 21 globulettes, where surface brightness in the H 2 1-0 S(1) line at 2.12 μm is detected, shows that approximately a third of the surface brightness observed in the Ks filter is due to this line: the observed average of the H 2 /Ks surface brightness is 0.26 ± 0.02 in the globulettes' cores and 0.30 ± 0.01 in the rims. The estimated H 2 1-0 S(1) surface brightness of the rims is ∼3−8 × 10 −8 Wm −2 sr −1 μm −1 . The ratio of the surface brightnesses support fluorescence instead of shocks as the H 2 excitation mechanism. The globulettes have number densities of n(H 2 ) ∼ 10 −4 cm −3 or higher. We estimated masses of individual globulettes and compared them to the results from previous optical and radio molecular line surveys. We confirm that the larger globulettes contain very dense cores, that the density is also high farther out from the core, and that their mass is subsolar. Two NIR protostellar objects were found in an elephant trunk and one was found in the most massive globulette in our study.

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Rotating elephant trunks

Cited by 44 publications

References 50 publications

Pillars, Jets and Dynamical Features

Pillars, Jets and Dynamical Features

Mass and motion of globulettes in the Rosette Nebula

Rosette globulettes and shells in the infrared

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