A CO Survey of the LMC with NANTEN: II. Catalog of Molecular Clouds

Mizuno, N.; Yamaguchi, Ryuichi; Mizuno, Akira; Rubio, M.; Abe, Rihei; Saito, Hiro; Onishi, Toshikazu; Yonekura, Yoshinori; Yamaguchi, Nobuyuki; Ogawa, Hideo; Fukui, Y.

doi:10.1093/pasj/53.6.971

Cited by 123 publications

(169 citation statements)

References 45 publications

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“…Although the map is still rather noisy, some well known clouds such as the 30 Dor complex, LMC-114, and LMC-154 (Fukui et al 2008) are clearly detected. The CO arc discovered by Mizuno et al (2001) using the NANTEN telescope is also seen. We show in Sect.…”

Section: Derivation Of the Extinction Mapmentioning

confidence: 79%

Extinction and dust/gas ratio in LMC molecular clouds

Dobashi

Bernard

Hughes

et al. 2008

A&A

125

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Aims. The goal of this paper is to measure the dust content and distribution in the Large Magellanic Cloud (LMC) by comparing extinction maps produced in the near-infrared wavelengths and the spatial distribution of the neutral and molecular gas, as traced by H i and CO observations.Methods. In order to derive an extinction map of the LMC, we have developed a new method to measure the color excess of dark clouds, using the 2MASS all-sky survey. Classical methods to measure the color excess (including the NICE method) tend to underestimate the true color excess if the clouds are significantly contaminated by unreddened foreground stars, as is the case in the LMC. We propose a new method that uses the color of the X percentile reddest stars and which is robust against such contamination. Using this method, it is possible to infer the positions of dark clouds with respect to the star distribution by comparing the observed color excess as a function of the percentile used and that predicted by a model. Results. On the basis of the resulting extinction map, we perform a correlation analysis for a set of dark molecular clouds. Assuming similar infrared absorption properties for the dust in the neutral and molecular phases, we derive the absorption-to-column density ratio A V N H and the CO-to-H 2 conversion factor X CO . We show that A V N H increases from the outskirts of the LMC towards the 30 Dor star-forming region. This can be explained either by a systematic increase of the dust abundance, or by the presence of an additional gas component not traced by H i or CO, but strongly correlated to the H i distribution. If dust abundance is allowed to vary, the derived X CO factors for the selected regions are several times lower than those derived from a virial analysis of the CO data. This could indicate that molecular clouds in the LMC are not gravitationally bound, or that they are bounded by substantial external pressure. However, the X CO values derived from absorption can be reconciled with the virial results assuming a constant value for the dust abundance and the existence of an additional, unseen gas component. These results are in agreement with those derived for the LMC from diffuse far-infrared emission.

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Section: Derivation Of the Extinction Mapmentioning

confidence: 79%

Extinction and dust/gas ratio in LMC molecular clouds

Dobashi

Bernard

Hughes

et al. 2008

A&A

125

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“…The analysis of supergiants reveals that this shell is very young (10−15 Myr, Grebel & Brandner 1998), and in the spatial distribution of supergiants the interaction region between SGS 19 (LMC 2) and SGS 12 (LMC 3) is clearly visible. Mizuno et al (2001b) find that most of the CO clouds in the LMC are distributed in dense parts of HI gas and over several HII regions. LMC CO clouds are often located at the outer edge of SGSs as for, e.g., SGS 11 (LMC 4) .…”

Section: Lmcmentioning

confidence: 84%

Ages and luminosities of young SMC/LMC star clusters and the recent star formation history of the Clouds

Glatt

Grebel

Koch

2010

A&A

170

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Aims. In this paper we discuss the age and spatial distribution of young (age < 1 Gyr) Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC) clusters using data from the Magellanic Cloud Photometric Surveys. Luminosities are calculated for all age-dated clusters. Methods. The ages of 324 and 1193 populous star clusters in the SMC and the LMC were determined fitting Padova and Geneva isochrone models to their resolved color-magnitude diagrams. The clusters cover an age range between 10 Myr and 1 Gyr in each galaxy. For the SMC, a constant distance modulus of (m − M) 0 = 18.90 and a metallicity of Z = 0.004 were adopted. For the LMC, we used a constant distance modulus of (m − M) 0 = 18.50 and a metallicity of Z = 0.008. For both galaxies, we used a variable color excess to derive the cluster ages. Results. We find two periods of enhanced cluster formation in both galaxies at 160 Myr and 630 Myr (SMC) and at 125 Myr and 800 Myr (LMC). We present the spatially resolved recent star formation history of both Clouds based on young star clusters. The first peak may have been triggered by a close encounter between the SMC and the LMC. In both galaxies, the youngest clusters reside in the supergiant shells, giant shells, the intershell regions, and toward regions with a high Hα content, suggesting that their formation is related to expansion and shell-shell interaction. Most of the clusters are older than the dynamical age of the supergiant shells. No evidence of cluster dissolution was found. Computed V band luminosities show a trend toward fainter magnitudes with increasing age, as well as a trend toward brighter magnitudes with increasing apparent cluster radii.

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“…A full PDR model analysis will be presented in a follow-up paper (Okada et al in prep.). N159 is located south of 30 Dor as a part of the molecular ridge (Cohen et al 1988;Mizuno et al 2001). Three CO cores are identified (N159 W, E, and S; Johansson et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Velocity resolved [C ii], [C i], and CO observations of the N159 star-forming region in the Large Magellanic Cloud: a complex velocity structure and variation of the column densities

Okada

Requeña-Torres

Güsten

et al. 2015

A&A

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Context. The [C ii] 158 µm fine structure line is one of the dominant cooling lines in star-forming active regions. Together with models of photon-dominated regions, the data is used to constrain the physical properties of the emitting regions, such as the density and the radiation field strength. According to the modeling, the [C ii] 158 µm line integrated intensity compared to the CO emission is expected to be stronger in lower metallicity environments owing to lower dust shielding of the UV radiation, a trend that is also shown by spectral-unresolved observations. In the commonly assumed clumpy UV-penetrated cloud scenario, the models predict a [C ii] line profile similar to that of CO. However, recent spectral-resolved observations by Herschel/HIFI and SOFIA/GREAT (as well as the observations presented here) show that the velocity resolved line profile of the [C ii] emission is often very different from that of CO lines, indicating a more complex origin of the line emission including the dynamics of the source region. Aims. The Large Magellanic Cloud (LMC) provides an excellent opportunity to study in great detail the physics of the interstellar medium (ISM) in a low-metallicity environment by spatially resolving individual star-forming regions. The aim of our study is to investigate the physical properties of the star-forming ISM in the LMC by separating the origin of the emission lines spatially and spectrally. In this paper, we focus on the spectral characteristics and the origin of the emission lines, and the phases of carbon-bearing species in the N159 star-forming region in the LMC. Methods. We mapped a 4 ′ ×(3 ′ -4 ′ ) region in N159 in [C ii] 158 µm and [N ii] 205 µm with the GREAT instrument on board SOFIA. We also observed CO(3-2), (4-3), (6-5), 13 CO(3-2), and [C i] 3 P 1 -3 P 0 and 3 P 2 -3 P 1 with APEX. All spectra are velocity resolved. Results. The emission of all transitions observed shows a large variation in the line profiles across the map and in particular between the different species. At most positions the [C ii] emission line profile is substantially wider than that of CO and [C i]. We estimated the fraction of the [C ii] integrated line emission that cannot be fitted by the CO line profile to be 20% around the CO cores, and up to 50% at the area between the cores, indicating a gas component that has a much larger velocity dispersion than the ones probed by the CO and [C i] emission. We derived the relative contribution from C + , C, and CO to the column density in each velocity bin. The result clearly shows that the contribution from C + dominates the velocity range far from the the velocities traced by the dense molecular gas. Spatially, the region located between the CO cores of N159 W and E has a higher fraction of C + over the whole velocity range. We estimate the contribution of the ionized gas to the [C ii] emission using the ratio to the [N ii] emission, and find that the ionized gas contributes ≤ 19% to the [C ii] emission at its peak position, and ≤ 15% over the whol...

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A CO Survey of the LMC with NANTEN: II. Catalog of Molecular Clouds

Cited by 123 publications

References 45 publications

Extinction and dust/gas ratio in LMC molecular clouds

Extinction and dust/gas ratio in LMC molecular clouds

Ages and luminosities of young SMC/LMC star clusters and the recent star formation history of the Clouds

Velocity resolved [C ii], [C i], and CO observations of the N159 star-forming region in the Large Magellanic Cloud: a complex velocity structure and variation of the column densities

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