Brackett-γ mapping observation of RCW 38

Mizutani, K.; Shimada, Hiroshi; Takami, Hideki; Maihara, Toshinori; Sood, R. K.; Thomas, John A.; Shibai, Hiroshi; Okuda, H.

doi:10.1093/mnras/228.3.721

Cited by 3 publications

(5 citation statements)

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“…Whilst we cannot exclude the possibility that a cluster of several lower T eff stars could also provide a suitable match, the calculated ratios are very sensitive to the temperature and bolometric luminosity, and T eff could be lowered by only about 1000 K for either face. The suggestion of Mizutani et al (1987) of three O6 ZAMS stars ( T eff ∼ 41 000 K) is not consistent with our data. Indeed, between about 10 and 100 such stars would be required to fit just one of the ratios.…”

Section: Results and Analysiscontrasting

confidence: 99%

“…Similarly, the He i (λ=2.06 m)/Brγ ratio, which is often used as a constraint on massive star formation (e.g. Doyon, Puxley & Joseph 1992), is observed to be quite high in RCW 38 at 0.65 (Mizutani et al 1987), which also suggests a minimum effective stellar temperature around 40 000 K. This method for determining stellar temperature, however, may not be very reliable for hot stars, as Shields (1993) and Lumsden & Puxley (1996) find that the He i/Brγ ratio actually decreases rather than saturates at temperatures over 42 000K.…”

Section: Results and Analysismentioning

confidence: 99%

“…Unfortunately, there is little other published information on fine‐structure line measurements of RCW 38 made in a similar beamsize to ours, with which we might further constrain densities (e.g., electron density using lines from the same element and ionization stage) and the exciting source and/or abundances (e.g., using lines from the same element but different ionization stages). From optical observations in a 17 × 34" 2 beam of [S ii] and [O ii] Danziger (1974) infers an electron density of 4 × 10 3 cm −3 , and Mizutani et al (1987) derive 6 × 10 3 cm −3 from Brγ mapping, whilst Takami et al (1987) infer an electron density of 10 4 cm −3 for their single‐component model, and 5 × 10 4 cm −3 clumps embedded in 150 cm −3 ambient gas for their two‐component model. Our derived spectral type of the ionizing star is similar to that inferred by other authors for RCW 38, as noted above and in our introduction.…”

Section: Results and Analysismentioning

confidence: 99%

“…They suggested that an O5 star and little or no dust absorption of the continuum photons in the ionized region could fit the known parameters of RCW 38. Mizutani et al (1987) present a Brγ map of the region (15‐" resolution), and find that Brγ emission largely follows the structure of the 10‐m images. From their observations they deduce an electron temperature of about 8000 K. They argue that IRS2 represents three O6 (ZAMS) stars rather than a single O5 star, although they do not preclude the possibility of an O5 star with a cluster of embedded stars.…”

Section: Introductionmentioning

confidence: 97%

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Mid-infrared imaging and spectroscopy of the southern Hii region RCW 38

Smith

Bourke

Wright

et al. 1999

Monthly Notices of the Royal Astronomical Society

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We present mid‐infrared images and an 8‐‐13 μ m spectrum of the southern HII region RCW 38. We determine the dust colour temperature from both our spectrum and images at 10 and 20 μ m, and deduce the gas excitation from an image in the [SIV] fine‐structure line, as well as spectra of the [ArIII], [SIV] and [NeII] fine‐structure lines. Our observations are consistent with a complex of sources associated with the RCW 38 IRS1 region, which represent knots of material in a shell, or ridge, surrounding a cavity of about 0.1 pc in radius, which is itself created by the stellar wind of the hot young source IRS2. The dust temperature does not peak closest to IRS2, but rather along the centre of the ridge, and is remarkably uniform over the extent of our image. From photoionization models for the observed line ratios at IRS1 we deduce a stellar effective temperature and gas density of about 43 000‐‐48 000 K and 104 cm‐3 respectively. Whilst the star, or star cluster, IRS2 is ultimately responsible for the observed thermal and ionic emission, the relatively uniform dust temperature implies that the bulk of the dust heating in the region is provided by resonantly trapped Lyman α photons, rather than direct stellar photons. This then also implies that the dust is depleted with respect to the gas by a factor of at least 100 from its normal interstellar value. The small‐scale spatial variations in the continuum emission and temperature can be explained by changes in the density and/or gas‐to‐dust mass ratio.

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Section: Results and Analysiscontrasting

confidence: 99%

Section: Results and Analysismentioning

confidence: 99%

Section: Results and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Mid-infrared imaging and spectroscopy of the southern Hii region RCW 38

Smith

Bourke

Wright

et al. 1999

Monthly Notices of the Royal Astronomical Society

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“…Persson et al (1976) revisited this region using narrow band photometry and found no evidence of silicates. Other narrow line infrared imaging such as Br-γ at 2.16 µm also indicated an open center morphology centered on IRS 2 with enhanced emission toward IRS 1 (Mizutani et al 1987).…”

Section: Irsmentioning

confidence: 85%

The Embedded Massive Star Forming Region RCW 38

Wolk,

Bourke,

Vigil

2008

Preprint

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RCW 38 is a uniquely young (<1 Myr), embedded (A V ∼ 10) stellar cluster surrounding a pair of early O stars (∼O5.5) and is one of the few regions within 2 kpc other than Orion to contain over 1000 members. X-ray and deep near-infrared observations reveal a dense cluster with over 200 X-ray sources and 400 infrared sources embedded in a diffuse hot plasma within a 1 pc diameter. The central O star has evacuated its immediate surroundings of dust, creating a wind bubble ∼0.1 pc in radius that is confined by the surrounding molecular cloud, as traced by millimeter continuum and molecular line emission. The interface between the bubble and cloud is a region of warm dust and ionized gas, which shows evidence for ongoing star formation. Extended warm dust is found throughout a 2-3 pc region and coincides with extended X-ray plasma. This is evidence that the influence of the massive stars reaches beyond the confines of the O star bubble. RCW 38 appears similar in structure to RCW 49 and M 20 but is at an earlier evolutionary phase. RCW 38 appears to be a blister compact HII region lying just inside the edge of a giant molecular cloud. Figure 2. Mid-infrared image of RCW 38, about 11.5 ′ (5.7 pc) on a side, from Spitzer/IRAC observations. IRAC Band 1 (3.6 µm) is assigned to blue, Band 2 (4.5 µm) to green, and Band 3 (5.6 µm) to red. [3.6] band = blue, [4.5] band = green and [5.6] band = red. Voids in the 5.6 µm image tend to be filled by 4.5 µm emission. The yellow box is 2.5 ′ on a side and is shown in more detail in Figures 3 and 5.

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Molecular Clouds Toward the Super Star Cluster NGC 3603; Possible Evidence for a Cloud-Cloud Collision in Triggering the Cluster Formation

Fukui

Ohama

Hanaoka

et al. 2013

ApJ

175

170

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We present new large field observations of molecular clouds with NANTEN2 toward the super star cluster NGC3603 in the transitions 12 CO(J=2-1, J=1-0) and 13 CO(J=2-1, J=1-0). We suggest that two molecular clouds at 13 km s −1 and 28 km s −1 are associated with NGC3603 as evidenced by higher temperatures toward the H II region as well as morphological correspondence. The mass of the clouds is too small to gravitationally bind them, given their relative motion of ∼20 km s −1 . We suggest that the two clouds collided with each other a Myr ago to trigger the formation of the super star cluster. This scenario is able to explain the origin of the highest mass stellar population in the cluster which is as young as a Myr and is segregated within the central sub-pc of the cluster. This is the second super star cluster along side Westerlund2 where formation may have been triggered by a cloud-cloud collision. Subject headings: ISM: clouds -open clusters and associations -individual: (NGC3603)the large turbulence excited by the shock interaction. This is the second case of formation of a super star cluster by triggering in a cloud-cloud collision along side Westerlund2 NANTEN2 is an international collaboration of ten universities, Nagoya University,

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Brackett-γ mapping observation of RCW 38

Cited by 3 publications

References 0 publications

Mid-infrared imaging and spectroscopy of the southern Hii region RCW 38

Mid-infrared imaging and spectroscopy of the southern Hii region RCW 38

The Embedded Massive Star Forming Region RCW 38

Molecular Clouds Toward the Super Star Cluster NGC 3603; Possible Evidence for a Cloud-Cloud Collision in Triggering the Cluster Formation

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