DENSE CLUMPS IN GIANT MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD: DENSITY AND TEMPERATURE DERIVED FROM<sup>13</sup>CO(<i>J</i>= 3-2) OBSERVATIONS

Minamidani, Tetsuhiro; Tanaka, Takanori; Mizuno, Yumiko; Mizuno, N.; Kawamura, Akiko; Onishi, Toshikazu; Hasegawa, Tetsuo; Tatematsu, Ken’ichi; Takekoshi, Tatsuya; Saito, Kazuo; Moribe, N.; Torii, Kazufumi; Sakai, Takeshi; Muraoka, Kazuyuki; Tanaka, K.; Ezawa, H.; Kohno, Kotaro; Kim, Sungeun; Rubio, M.; Fukui, Y.

doi:10.1088/0004-6256/141/3/73

Cited by 42 publications

(54 citation statements)

References 49 publications

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“…3, this condition is only valid for kinetic temperatures higher than 120 K for a volume density range between 3 × 10 3 −10 4 cm −3 . The intersection of the two CO line ratios constrains the CO column density per velocity interval to about 3 × 10 17 cm −2 /km s −1 at T kin 160 K. The derived kinetic temperature and H 2 density are consistent with previously published excitation analyzes based on CO observations Kim 2006;Minamidani et al 2008Minamidani et al , 2011. Figure 4 shows that the model-predicted clump-averaged absolute line intensity of the 13 CO J = 4 → 3 line, at the column 1 For an example of a typical temperature distribution and abundance structure of the main carbon species in PDRs, see e.g.…”

Section: Co-emissionsupporting

confidence: 89%

Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

Pineda

Mizuno

Röllig

et al. 2012

A&A

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Context. The 30 Dor region in the Large Magellanic Cloud (LMC) is the most vigorous star-forming region in the Local Group. Star formation in this region is taking place in low-metallicity molecular gas that is exposed to an extreme far-ultraviolet (FUV) radiation field powered by the massive compact star cluster R136. 30 Dor is therefore ideally suited to study the conditions in which stars formed at earlier cosmological times. Aims. Observations of (sub)mm and far-infrared (FIR) spectral lines of the main carbon-carrying species, CO, [C i] and [C ii], which originate in the surface layers of molecular clouds illuminated by the FUV radiation of young stars, can be used to constrain the physical and chemical state of the star-forming ISM. Methods. We used the NANTEN2 telescope to obtain high-angular resolution observations of the 12 CO J = 4 → 3, J = 7 → 6, and 13 CO J = 4 → 3 rotational lines and [C i] 3 P 1 − 3 P 0 and 3 P 2 − 3 P 1 fine-structure submillimeter transitions in 30 Dor-10, the brightest CO and FIR-emitting cloud at the center of the 30 Dor region. We derived the physical and chemical properties of the low-metallicity molecular gas using an excitation/radiative transfer code and found a self-consistent solution of the chemistry and thermal balance of the gas in the framework of a clumpy cloud PDR model. We compared the derived properties with those in the N159W region, which is exposed to a more moderate far-ultraviolet radiation field compared with 30 Dor-10, but has similar metallicity. We also combined our CO detections with previously observed low-J CO transitions to derive the CO spectral-line energy distribution in 30 Dor-10 and N159W. Results. The separate excitation analysis of the submm CO lines and the neutral carbon fine structure lines shows that the mid-J CO and [C i]-emitting gas in the 30 Dor-10 region has a temperature of about 160 K and a H 2 density of about 10 4 cm −3 . We find that the molecular gas in 30 Dor-10 is warmer and has a lower beam filling factor compared to that of N159W, which might be a result of the effect of a strong FUV radiation field heating and disrupting the low-metallicity molecular gas. We use a clumpy PDR model (including the [C ii] line intensity reported in the literature) to constrain the FUV intensity to about χ 0 ≈ 3100 and an average total H density of the clump ensemble of about 10 5 cm −3 in 30 Dor-10.

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Section: Co-emissionsupporting

confidence: 89%

Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

Pineda

Mizuno

Röllig

et al. 2012

A&A

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“…The critical densities of CO(3-2) and CO(6-5) are (3-4)×10 4 cm −3 and 3 × 10 5 cm −3 , respectively, for 10-100 K (calculated using Flower 2001; Goorvitch 1994). Minamidani et al (2011) derived n(H 2 ) of (4-5)×10 3 cm −3 for N159 W and E, and Pineda et al (2008) discuss the result of PDR modeling with an average density of the clump ensemble of about 10 5 cm −3 . These densities are consistent with the assumption that the CO(6-5) emission does not reach LTE, in contrast to with the RADEX radiative transfer program show that the CO(3-2)/CO(6-5) intensity ratio at 30-100 K changes by more than a factor of 2 between 10 4 -10 5 cm −3 (van der Tak et al 2007), which can explain the CO(6-5) discrepancy in Fig.…”

Section: Column Densities Of C + C and Comentioning

confidence: 99%

“…When we estimate T ex at N159 W and E in the same spatial resolution, η = 0.3-0.4 gives the same temperature for T ex as their dust temperature. Minamidani et al (2011) derive the kinetic temperature from a LVG analysis with 45 ′′ resolution to be 40-82 K and 65-151 K in N159 W and E, respectively. If we assume that T ex equals their kinetic temperature, it requires a value for η of < 0.3.…”

Section: Column Densities Of C + C and Comentioning

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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“…We use the CO J = 1-0 transition observed References. (a) SAGE (Meixner et al 2006); (b) HERITAGE (Meixner et al 2013) with Mopra (Wong et al 2011) and CO J = 3-2 observed with the Atacama Submillimeter Telescope Experiment (ASTE; Minamidani et al 2011;see Fig. 2).…”

Section: Ground-based Observationsmentioning

confidence: 99%

A milestone toward understanding PDR properties in the extreme environment of LMC-30 Doradus

Chevance

Madden

Lebouteiller

et al. 2016

A&A

103

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Context. More complete knowledge of galaxy evolution requires understanding the process of star formation and the interaction between the interstellar radiation field and interstellar medium (ISM) in galactic environments traversing a wide range of physical parameter space. We focus on the impact of massive star formation on the surrounding low metallicity ISM in 30 Doradus in the Large Magellanic Cloud (LMC). A low metal abundance, which can characterizes some galaxies of the early Universe, results in less ultraviolet (UV) shielding for the formation of the molecular gas necessary for star formation to proceed. The half-solar metallicity gas in this region is strongly irradiated by the super star cluster R136, making it an ideal laboratory to study the structure of the ISM in an extreme environment. Aims. Our goal is to construct a comprehensive, self-consistent picture of the density, radiation field, and ISM structure in the most active star-forming region in the LMC, 30 Doradus. Our spatially resolved study investigates the gas heating and cooling mechanisms, particularly in the photodissociation regions (PDR) where the chemistry and thermal balance are regulated by far-UV photons (6 eV < hν < 13.6 eV). Methods. We present Herschel observations of far-infrared (FIR) fine-structure lines obtained with PACS and SPIRE/FTS. We combined atomic fine-structure lines from Herschel and Spitzer observations with ground-based CO data to provide diagnostics on the properties and structure of the gas by modeling it with the Meudon PDR code. For each tracer we estimate the possible contamination from the ionized gas to isolate the PDR component. We derive the spatial distribution of the radiation field, the pressure, the size, and the filling factor of the photodissociated gas and molecular clouds. Results. We find a range of pressure of ∼10 5 −1.7×10 6 cm −3 K and a range of incident radiation field G UV ∼ 10 2 −2.5×10 4 through PDR modeling. Assuming a plane-parallel geometry and a uniform medium, we find a total extinction A max V of 1-3 mag, which corresponds to a PDR cloud size of 0.2 to 3pc with small CO depth scale of 0.06 to 0.5 pc. At least 90% of the [C ii] originates in PDRs in this region, while a significant fraction of the L FIR (up to 70% in some places) can be associated with an ionized gas component. Theratio (2 to 60) throughout the observed map, correlated with the filling factor, reveals the porosity of the ISM in this region, which is traversed by hard UV photons surrounding small PDR clumps. We also determine the three-dimensional structure of the gas, showing that the clouds are distributed 20 to 80 pc away from the main ionizing cluster, R136.

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DENSE CLUMPS IN GIANT MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD: DENSITY AND TEMPERATURE DERIVED FROM¹³CO(J= 3-2) OBSERVATIONS

Cited by 42 publications

References 49 publications

Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

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

A milestone toward understanding PDR properties in the extreme environment of LMC-30 Doradus

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DENSE CLUMPS IN GIANT MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD: DENSITY AND TEMPERATURE DERIVED FROM13CO(J= 3-2) OBSERVATIONS

Cited by 42 publications

References 49 publications

Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

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

A milestone toward understanding PDR properties in the extreme environment of LMC-30 Doradus

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DENSE CLUMPS IN GIANT MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD: DENSITY AND TEMPERATURE DERIVED FROM¹³CO(J= 3-2) OBSERVATIONS