12CO and 13CO J = 3–2 observations toward N11 in the Large Magellanic Cloud

Peña, M.; Paron, S.; Rubio, M.; Herrera, Cinthya N.; Ortega, M. E.

doi:10.1051/0004-6361/201935446

A&A

2019

DOI: 10.1051/0004-6361/201935446

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¹²CO and ¹³CO J = 3–2 observations toward N11 in the Large Magellanic Cloud

M. Peña

S. Paron

M. Rubio

et al.

Abstract: Aims. After 30 Doradus, N11 is the second largest and brightest nebula in the Large Magellanic Cloud (LMC). This large nebula has several OB associations with bright nebulae at its surroundings. N11 was previously mapped at the lowest rotational transitions of 12 CO (J=1-0 and 2-1), and in some particular regions pointings of the 13 CO J=1-0 and 2-1 lines were also performed. Observations of higher CO rotational transitions are needed to map gas with higher critical densities, useful to study in a more accurat… Show more

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Cited by 5 publications

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Using CO line ratios to trace compressed areas in bubble N131

Zhang

Zhou

et al. 2019

A&A

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Aims. N131 is a typical infrared dust bubble showing an expanding ring-like shell. We study the CO line ratios that can be used to trace the interaction in the expanding bubble. Methods. We carried out new CO (3 − 2) observations toward bubble N131 using the 15m JCMT, and derived line ratios by combining these observations with our previous CO (2 − 1) and CO (1 − 0) data from IRAM 30m observations. To trace the interaction between the molecular gas and the ionized gas in the HII region, we used RADEX to model the dependence of the CO line ratios on kinetic temperature and H 2 volume density, and examined the abnormal line ratios based on other simulations. Results. We present CO (3 − 2), CO (2 − 1), and CO (1 − 0) integrated intensity maps convolved to the same angular resolution (22.5 ). The three different CO transition maps show a similar morphology. The line ratios of W CO (3−2) /W CO (2−1) mostly range from 0.2 to 1.2 with a median of 0.54 ± 0.12, while the line ratios of W CO (2−1) /W CO (1−0) range from 0.5 to 1.6 with a median of 0.84 ± 0.15. The high CO line ratios W CO (3−2) /W CO (2−1) 0.8 and W CO (2−1) /W CO (1−0) 1.2 are beyond the threshold predicted by numerical simulations based on the assumed density-temperature structure for the inner rims of the ring-like shell, where the compressed areas are located in bubble N131. Conclusions. These high CO integrated intensity ratios, such as W CO (3−2) /W CO (2−1) 0.8 and W CO (2−1) /W CO (1−0) 1.2, can be used as a tracer of gas-compressed regions with a relatively high temperature and density. This further suggests that the non-Gaussian part of the line-ratio distribution can be used to trace the interaction between the molecular gas and the hot gas in the bubble.

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Using CO line ratios to trace compressed areas in bubble N131

Zhang

Zhou

et al. 2019

A&A

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SuperCAM CO(3–2) APEX survey at a 6 pc resolution in the Small Magellanic Clouds

Saldaño,

Rubio,

Bolatto

et al. 2024

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The Small Magellanic Cloud (SMC) is an ideal laboratory for studying the properties of star-forming regions thanks to its low metallicity, which has an impact on the molecular gas abundance. However, a small number of molecular gas surveys of the entire galaxy have been carried out in the last few years, limiting the measurements of interstellar medium (ISM) properties in a homogeneous manner. We present the CO($3-2$) APEX survey at a $6$ pc resolution of the bar of the SMC, observed with the SuperCAM receiver attached to the APEX telescope. This high-resolution survey has allowed us to study certain properties of the ISM and to identify CO clouds in the innermost parts of the H$_2$ envelopes. We black adopted the CO analysis in the SMC bar comparing the CO($3-2$) survey with that of the CO($2-1$) of a similar resolution. We studied the CO($3-2$)-to-CO($2-1$) ratio ($R_ $), which is very sensitive to the environment properties (e.g., star-forming regions). We analyzed the correlation of this ratio with observational quantities that trace the star formation such as the local CO emission, the Spitzer color $ $, and the total IR surface brightness measured from the Spitzer and Herschel bands. For the identification of the CO($3-2$) clouds, we used the CPROPS algorithm, which allowed us to measure the physical properties of the clouds. We analyzed the scaling relationships of such physical properties. black We obtained $R_ 0.02$ for the SW bar and a slightly higher ratio 0.1,$ for N66 in the SMC. We found that $R_ $ varies from region to region, depending on the star formation activity. In regions dominated by HII and photo-dissociated regions (e.g., N22, N66) $R_ $ tends to be higher than the median values. Meanwhile, lower values were found toward quiescent clouds. We also found that $R_ black is correlated with the IR color $ $ and the total IR surface brightness. This finding indicates that $R_ $ increases with environmental properties, such as the dust temperature, total gas density, and radiation field. We identified $225$ molecular clouds with sizes of $R > 1.5$ pc and signal-to-noise ratios (S/N) of $> 3$ black of which only $17$ black are well resolved CO($3-2$) clouds black with S/N $ 5$. These $17$ clouds follow consistent scaling relationships to the inner Milky Way clouds but with some departures. For instance, CO($3-2$) tends to be less turbulent and less luminous than the inner Milky Way clouds of similar sizes. Finally, we estimated a median virial-based CO($3-2$)-to-H$_2$ conversion factor of for the total sample.

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Three-dimensional geometry and dust/gas ratios in massive star-forming regions over the entire LMC as revealed by the IRSF/SIRIUS survey

Furuta

Kaneda

Kokusho

et al. 2022

Publications of the Astronomical Society of Japan

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We derive the entire dust extinction (AV) map for the Large Magellanic Cloud (LMC) estimated from the color excess at near-infrared wavelengths. Using the percentile method we recently adopted to evaluate AV distribution along the line of sight, we derive three-dimensional (3D) AV maps of the three massive star-forming regions of N44, N79, and N11 based on the IRSF/SIRIUS point source catalog. The 3D AV maps are compared with the hydrogen column densities N(H) of three different velocity components where one is of the LMC disk velocity and the other two are of velocities lower than the disk velocity. As a result, we obtain a 3D dust geometry suggesting that gas collision is ongoing between the different velocity components. We also find differences in the timing of the gas collision between the massive star-forming regions, which indicates that the gas collision in N44, N79, and N11 occurred later than that in 30 Doradus. In addition, a difference of a factor of two in AV/N(H) is found between the velocity components for N44, while a significant difference is not found for N79 and N11. From the 3D geometry and AV/N(H) in each star-forming region, we suggest that the massive star formation in N44 was induced by an external trigger of tidal interaction between the LMC and the Small Magellanic Cloud, while that in N79 and N11 is likely to have been induced by internal triggers such as gas converging from the galactic spiral arm and expansion of a supershell, although the possibility of tidal interaction cannot be ruled out.

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¹²CO and ¹³CO J = 3–2 observations toward N11 in the Large Magellanic Cloud

Cited by 5 publications

References 42 publications

Using CO line ratios to trace compressed areas in bubble N131

Using CO line ratios to trace compressed areas in bubble N131

SuperCAM CO(3–2) APEX survey at a 6 pc resolution in the Small Magellanic Clouds

Three-dimensional geometry and dust/gas ratios in massive star-forming regions over the entire LMC as revealed by the IRSF/SIRIUS survey

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