The ionized and hot gas in M17 SW

Pérez-Beaupuits, J. P.; Wiesemeyer, H.; Ossenkopf, V.; Stutzki, J.; Guêsten, R.; Simon, R.; Huebers, Heinz-Wilhelm; Ricken, Oliver

doi:10.1051/0004-6361/201218929

Cited by 29 publications

(32 citation statements)

References 23 publications

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“…4.3.3, refer to a gas density of >10 5 cm −3 if they are compared to PDR models (Burton et al 1990). The high-density nature of M 17 SW is also evidenced by the molecular gas persisting just west of the IF (Pérez-Beaupuits et al 2012). This can be interpreted as the result of self-shielding of molecules in high-density PDR, which can move the transition regions for H i/H 2 close to the surface of the cloud (Burton et al 1990).…”

Section: Properties Of M 17 Swmentioning

confidence: 91%

VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 – IRS5 region

Chen

Nürnberger

Chini

et al. 2015

A&A

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Aims. We investigate the surroundings of the hypercompact H ii region M 17 UC1 to probe the physical properties of the associated young stellar objects and the environment of massive star formation. Methods. We use diffraction-limited near-IR (VLT/NACO) and mid-IR (VLT/VISIR) images to reveal the different morphologies at various wavelengths. Likewise, we investigate the stellar and nebular content of the region with VLT/SINFONI integral field spectroscopy with a resolution R ∼ 1500 at H + K bands. Results. Five of the seven point sources in this region show L-band excess emission. A geometric match is found between the H 2 emission and near-IR polarized light in the vicinity of IRS5A, and between the diffuse mid-IR emission and near-IR polarization north of UC1. The H 2 emission is typical for dense photodissociation regions (PDRs), which are initially far-ultraviolet pumped and repopulated by collisional de-excitation. The spectral types of IRS5A and B273A are B3−B7 V/III and G4−G5 III, respectively. The observed infrared luminosity L IR in the range 1−20 μm is derived for three objects; we obtain 2.0 × 10 3 L for IRS5A, 13 L for IRS5C, and 10 L for B273A. Conclusions. IRS5 might be a young quadruple system. Its primary star IRS5A is confirmed to be a high-mass protostellar object (∼9 M , ∼1 × 10 5 yrs); it might have terminated accretion due to the feedback from stellar activities (radiation pressure, outflow) and the expanding H ii region of M 17. The object UC1 might also have terminated accretion because of the expanding hypercompact H ii region, which it ionizes. The disk clearing process of the low-mass young stellar objects in this region might be accelerated by the expanding H ii region. The outflows driven by UC1 are running south-north with its northeastern side suppressed by the expanding ionization front of M 17; the blue-shifted outflow lobe of IRS5A is seen in two types of tracers along the same line of sight in the form of H 2 emission filament and mid-emission. The H 2 line ratios probe the properties of M 17 SW PDR, which is confirmed to have a clumpy structure with two temperature distributions: warm, dense molecular clumps with n H > 10 5 cm −3 and T ≈ 575 K and cooler atomic gas with n H ∼ 3.7 × 10 3 −1.5 × 10 4 cm −3 and T ∼ 50−200 K.

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Section: Properties Of M 17 Swmentioning

confidence: 91%

VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 – IRS5 region

Chen

Nürnberger

Chini

et al. 2015

A&A

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“…However, velocity resolved mapping observations of the [C ii] emission in Galactic regions have recently been made with the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel and are being made with the German REceiver for Astronomy at Terahertz Frequencies (GREAT) on board the Stratospheric Observatory for Infrared Astronomy (SOFIA), and they show complex line profiles of the [C ii] emission, typically substantially wider than expected from the [C i] and low-or mid-J CO emission profiles. The velocity information is thus essential in order to identify the origin of the [C ii] emission (Pérez-Beaupuits et al 2012;Carlhoff 2013), and the significant difference in the velocity profile of the [C ii] emission from the low-or mid-J CO emission indicates that a substantial fraction of the [C ii] emission is accelerated relative to the quiescent material, e.g., it undergoes ablation or is blown off (Dedes et al 2010;Mookerjea et al 2012;Okada et al 2012;Schneider et al 2012;Simon et al 2012;Pilleri et al 2012). These results emphasize the need of velocity resolved observations to distinguish different velocity components with their different physical conditions.…”

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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“…Recent SOFIA/GREAT observations of the velocityresolved [C II] spectra showed that a large fraction (>60%) of the [C II] emission, observed at the lower (<10 km s −1 ) and higher (>24 km s −1 ) velocity channels, is not associated with the starforming material (denser and colder gas) traced by species like CO and [C I], which has an average line width of 5 to 10 km s −1 centered at V LSR = 20 km s −1 (Pérez-Beaupuits et al 2012, 2013. Only the central narrow (1 km s −1 ) channel maps of the velocity-resolved [C II] spectra show a spatial association with other gas tracers (e.g., [C I] and 12 CO).…”

Section: Introductionmentioning

confidence: 99%

Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW

Pérez-Beaupuits

Stützki

Ossenkopf

et al. 2015

A&A

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Context. The [C II] 158 μm line is one of the dominant coolants of the ISM, and an important probe with which to study the star formation process. Recent Herschel/HIFI and SOFIA/GREAT observations showed that assuming the total velocity-integrated intensity of this line is directly associated with the star-forming material is inadequate. Aims. We probe the column densities and masses traced by the ionized and neutral atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [C I] and low-J CO lines toward the star-forming region M17 SW. A very large fraction of at least 64% of this mass is not associated with the star-forming material in M17 SW. We also found that about 36%, 17%, and 47% of the [C II] emission is associated with the H II, H I, and H 2 regimes, respectively. Comparisons with the H41α line shows an ionization region mixed with the neutral and part of the molecular gas, in agreement with the clumped structure and dynamical processes at play in M17 SW. These results are also relevant to extra-galactic studies in which [C II] is often used as a tracer of star-forming material.

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The ionized and hot gas in M17 SW

Cited by 29 publications

References 23 publications

VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 – IRS5 region

VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 – IRS5 region

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

Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW

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