On the Mass Spectrum of Giant Molecular Clouds in the Large Magellanic Cloud

Fukui, Y.; Mizuno, N.; Yamaguchi, Ryuichi; Mizuno, Akira; Onishi, Toshikazu

doi:10.1093/pasj/53.6.l41

Cited by 84 publications

(93 citation statements)

References 15 publications

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“…The slope of the power law cloud mass spectrum in the LMC (index almost −2) was found to be considerably steeper than that of the cloud mass spectrum in our direct vicinity in the Galaxy which has a power law index of −1.5 (Fukui 2001). This difference may be due to a higher UV radiation field (Israel 1986) in the LMC compared to the Galaxy which causes a drastic depletion of lower-mass GMCs (Fukui 2001). The GMC sizes in the LMC are huge with sizes of up to 200 pc.…”

Section: Introductionmentioning

confidence: 55%

Star formation in the LMC: Comparative CCD observations of young stellar populations in two giant molecular clouds

Ruppert

Zinnecker

2009

Astron Nachr

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This work deals with a CCD imaging study at optical and near-infrared wavelength of two giant molecular clouds (plus a control field) in the southern region of the Large Magellanic Cloud, one of which shows multiple signs of star formation, whereas the other does not. The observational data from VLT FORS2 (R band) and NTT SOFI (Ks band) have been analyzed to derive luminosity functions and color-magnitude diagrams. The young stellar content of these two giant molecular clouds is compared and confirmed to be different, in the sense that the apparently "starless" cloud has so far formed only low-luminosity, low-mass stars (fainter than mKs ∼ 16.5 mag, not seen by 2MASS), while the other cloud has formed both faint low-mass and luminous high-mass stars. The surface density excess of low-luminosity stars (∼ 2 per square arcmin) in the "starless" cloud with respect to the control field is about 20% whereas the excess is about a factor of 3 in the known star-forming cloud. The difference may be explained theoretically by the gravo-turbulent evolution of giant molecular clouds, one being younger and less centrally concentrated than the other.

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Section: Introductionmentioning

confidence: 55%

Star formation in the LMC: Comparative CCD observations of young stellar populations in two giant molecular clouds

Ruppert

Zinnecker

2009

Astron Nachr

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“…Because solid CO has a low sublimation temperature, much of the CO may have been desorbed off the dust grains and out of the ice phase in the relatively warm regions around a massive YSO. Alternatively, there is evidence that CO is underabundant in the LMC (Fukui et al 2001), meaning that the lower contribution of the CO:CO 2 component could be due to an overall underabundance of CO-containing ices in the LMC. The distribution of CO:CO 2 mixing ratios is similar to that found in the Pontoppidan et al (2008) study of low-mass and high-mass Galactic YSOs.…”

Section: Five-component 152 μM Fitmentioning

confidence: 99%

“…A higher CO 2 /H 2 O ratio in LMC massive YSOs than in Milky Way massive YSOs is a surprising result. The LMC is a lowmetallicity galaxy; thus, CO is expected to be underabundant (Fukui et al 2001). Because CO is considered an important parent molecule of CO 2 (for a recent review of CO 2 production routes see Pontoppidan et al 2008), one might expect a lower CO 2 abundance in the LMC.…”

Section: Co 2 Abundancementioning

confidence: 99%

The Evolution of Massive Young Stellar Objects in the Large Magellanic Cloud. Ii. Thermal Processing of Circumstellar Ices

Seale

Looney

Chen

et al. 2010

ApJ

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We present Spitzer Space Telescope spectroscopy of the CO 2 ice absorption feature at 15.2 μm toward 41 high-mass young stellar objects in the Large Magellanic Cloud (LMC). As the shape of the CO 2 absorption profile is a measure of both the composition and thermal history of the ice, we have performed a decomposition of the spectral profiles to determine the nature of the CO 2 ice. We fit the absorption profiles to laboratory analogues of ice spectra with two different methods: (1) a five-component fit with polar and apolar ices and (2) a two-component fit with a polar and an annealed H 2 O:CH 3 OH:CO 2 ice mixture. Many of the LMC sources have a pronounced double peak in their CO 2 feature profiles analogous to that seen from pure CO 2 or annealed CO 2 laboratory ice mixtures; these represent the first direct detections of the characteristic double peak in an extragalactic environment. Fits to annealed laboratory ices suggest that the ices around massive LMC young stellar objects (YSOs) have been warmed and thermally processed. We find that a majority of the CO 2 is embedded in a polar ice matrix; however, the observations suggest that a lower fraction of CO 2 is locked in polar ices in the LMC compared to the Milky Way, which is in agreement with the proposed lower LMC abundance of water ice. In addition, we find that the ices are best fit with laboratory ice mixtures composed of less than 50% methanol, and most absorption spectra can be fit by ices with no methanol. Finally, we corroborate mounting evidence of an enhanced CO 2 ice abundance in the LMC relative to the Milky Way, and determine a CO 2 /H 2 O ratio of 0.33 ± 0.01 by combining the column densities of these observations with those in the literature.

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“…There are also some reports on the GMCMF variation along the galactocentric radii (e.g., in the Galaxy (Rice et al 2016) and in M33 (Rosolowsky et al , 2007; c.f. the outer Galaxy (Heyer et al 2001), LMC (Fukui et al 2001), and M83 (Hirota et al in prep. )) Presumably, this type of statistical GMC studies will proceed further down to both smaller mass scales 10 4 M and smaller spatial scales thanks to ongoing latest observations (e.g., in Atacama Large Millimeter/Submillimeter Array (ALMA); c.f., Tosaki et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Evolutionary Description of Giant Molecular Cloud Mass Functions on Galactic Disks

Kobayashi

Inutsuka

Kobayashi

et al. 2017

ApJ

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Recent radio observations show that the giant molecular cloud (GMC) mass functions noticeably vary across galactic disks. High-resolution magnetohydrodynamics simulations show that multiple episodes of compression are required for creating a molecular cloud in the magnetized interstellar medium. In this article, we formulate the evolution equation for the GMC mass function to reproduce the observed profiles, for which multiple compression are driven by the network of expanding shells due to HII regions and supernova remnants. We introduce the cloud-cloud collision (CCC) terms in the evolution equation in contrast to the previous work (Inutsuka et al. 2015). The computed time evolution suggests that the GMC mass function slope is governed by the ratio of GMC formation timescale to its dispersal timescale, and that the CCC effect is limited only in the massive-end of the mass function. In addition, we identify a gas resurrection channel that allows the gas dispersed by massive stars to regenerate GMC populations or to accrete onto the pre-existing GMCs. Our results show that almost all of the dispersed gas contribute to the mass growth of pre-existing GMCs in arm regions whereas less than 60% in inter-arm regions. Our results also predict that GMC mass functions have a single power-law exponent in the mass range < 10 5.5 M (where M represents the solar mass), which is well characterized by GMC self-growth and dispersal timescales. Measurement of the GMC mass function slope provides a powerful method to constrain those GMC timescales and the gas resurrecting factor in various environment across galactic disks.

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On the Mass Spectrum of Giant Molecular Clouds in the Large Magellanic Cloud

Cited by 84 publications

References 15 publications

Star formation in the LMC: Comparative CCD observations of young stellar populations in two giant molecular clouds

Star formation in the LMC: Comparative CCD observations of young stellar populations in two giant molecular clouds

The Evolution of Massive Young Stellar Objects in the Large Magellanic Cloud. Ii. Thermal Processing of Circumstellar Ices

Evolutionary Description of Giant Molecular Cloud Mass Functions on Galactic Disks

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