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Brogan, C. L. & Troland, T. H., 2001, ApJ, 560, 821

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Pérez­Beaupuits, J.P., Spaans, M., Güsten, R., et al., 2010, A&A, 510, A87

Pérez­Beaupuits, J.P., Wiesemeyer, H., Ossenkopf, V., et al., 2012, A&A 542, L13

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Pérez­Beaupuits, J.P., Güsten R., Spaans M., et al., 2015b, A&A, accepted (arXiv:1508.06699)

(I) THz & sub-mm maps of the M17 SW nebula with SOFIA/GREAT and APEX/CHAMP(I) THz & sub-mm maps of the M17 SW nebula with SOFIA/GREAT and APEX/CHAMP++

Tracing the dense and warm molecular gasTracing the dense and warm molecular gas

Excitation conditions and energetics of the dense gas in M17 SW

J.P. Pérez-Beaupuits1,2, R. Güsten2, M. Spaans3, V. Ossenkopf4, K.M. Menten2,M.A. Requena-Torres2, J. Stutzki4, H. Wiesemeyer2, C. Guevara4, R. Simon4

1) European Southern Observatory, Santiago, Chile2) Max-Planck-Institut für Radioastronomie, Bonn, Germany

3) Kapteyn Astronomical Institute, Groningen, The Netherlands4) I. Physikalisches Institut der Universitaet zu Köln, Köln, Germany

e-mail:

jperezbe@eso.org

jp@mpifr.de

Figure 1 – Three-colour composite of M 17, a H II region excited by a cluster of young, hot stars. This image was obtained with the ISAAC near-infrared instrument at the 8.2-m VLT ANTU telescope at Paranal, Chile. The filters used were J (1.25 µm, shown in blue), H (1.6 µm, shown in green), and K (2.2 µm, shown in red).The central cluster of massive young stars whose intense radiation makes the surrounding hydrogen gas glow. To the lower right of the cluster is a huge cloud of molecular gas, the M17 SW. At visible wavelengths, dust grains in the cloud obscure the view, but by observing in far infrared light (THz) and sub-mm wavelengths, the molecular gas forming the cloud can be seen. A large silhouette disc has been found in the south-west cloud. Image credit: ESO/R. Chini.

Figure 4 - Velocity-integrated intensity map of 12CO J=3-2, convolved with a 25” beam to match the resolution of the 12CO J=11-10 map. The contour levels are the 10%, 25%, 50% (thick line), 75% and 90% of the peak emission (770 K km s-1 ). The ultracompact H II region M17-UC1 and the four H

2O

masers are marked by the filled circle and plus symbols, respectively. The positions of the peak intensities of HCN J=8-7 and 12CO J=16-15, as well as the offset positions at (−60”,−30”) and (−130”,+30”) analyzed by Pérez-Beaupuits et al. (2015b), are indicated with a triangle, a diamond, a pentagon and a star, respectively. The dashed circle of 200” diameter covers a spatial scale of 2 pc, which correspond to a region that would be resolved by ∼ALMA with the finest achievable angular resolution (0.03 with the capabilities available in Cycle 3) of the bands 6 (230 GHz) and 10 (870 GHz) towards a galaxy like NGC 1068 at a distance of 14.4 Mpc.∼

(II) Line Spectral Energy Distribution (LSED) in M17 SW(II) Line Spectral Energy Distribution (LSED) in M17 SWA synergy between SOFIA, APEX and IRAM 30mA synergy between SOFIA, APEX and IRAM 30m

(III) (III) Analysis of the energeticsAnalysis of the energetics

Table 4 – Energy terms of the virial equation of the cold and warm components at the four positions studied by Pérez-Beaupuits et al. (2015b).

Background image: Compose RGB color image of M17 or the Swan Nebula. Red (SII), green (Hα) and blue (OIII), obtained with the 300 mm telescope Dall-Kirkham Takahashi, Ibiza, Baleares. Credit & copy rights: Ignacio de la Cueva Torregrosa.

Figure 2 – Colour maps of the integrated intensity of the J=16-15 (1.841 THz), J=12-11 (1.381 THz) and J=11-10 (1.267 THz) transitions of 12CO, and the 13CO J = 13-12 line in M17 SW region depicted with a frame in Fig.1. Tese maps were obtained with the GREAT THz receiver on board of the SOFIA airborne telescope (see poster 39 for a brief description). The contour levels are the 10%, 25%, 50% (thick line), 75% and 90% of the peak emissions. The central position (∆α = 0,∆δ = 0), marked with a cross, corresponds to the star SAO 161357 at R.A(J2000)=18h 20m 27.6s and Dec(J2000)=−160 12' 00”.9. The ultracompact H II region M17-UC1 and four H

2O masers (Johnson et al. 1998) are marked by the circle and plus symbols, respectively.

The faint 13CO J=13-12 map was convolved with a 25” beam to match the resolution of the 12CO J=12-11 and to increase the S/N. All pixels with S/N< 3 (or an rms> 0.22 K) were blanked in the 13CO map. Note that the 13CO J=13-12 emission follows the distribution of the 12CO J=16-15 transition. All these maps are recently published in Pérez-Beaupuits et al. (2015b).

Figure 3 – Line intensity maps of the HCN J=8-7 (708.8 GHz) and HCO+ J=9-8 (802.4 GHz) transitions in the dense core of M17 SW, obtained simultaneously with the dual color receiver array CHAMP+ on the APEX telescope (see poster 39 for a brief description). The contour levels are the 10%, 25%, 50% (thick contour), 75% and 90% of the peak emission. The reference position (∆α = 0, ∆δ = 0) and other symbols are the same as in Fig. 2. The peak HCN and HCO+ emission is closer to one of the H

2O masers,

suggesting a warm and dense environment, while the 12CO J=16-15 emission of Fig.1 peaks closer to the M17-UC1 region, suggesting excitation by warmer gas (from Pérez-Beaupuits et al. 2015b).

Φx : beam area filling factor

Fx = F

x(n(H

2), T

K, N/∆V) ← RADEX (van der Tak et al. 2005)

Table 1 – Excitation conditions for the LSED of the 200” average spectra. Density n(H

2) and

column density N/∆V are in log10

scale.

Table 2 – Excitation conditions for the LSED of the CO-peak at offset position (-40”,+18”). Density n(H

2) and column density N/∆V are in log

10 scale.

Figure 5 – Top: Model fit of the LSEDs of CO, HCN and HCO+ for the 200” beam average spectra. Bottom: Model fit of the LSEDs of the spectra obtained at the position of the peak 12CO J=16-15 emission (CO-peak). The high-J CO lines obtained with SOFIA/GREAT are crucial to constrain the excitation conditions of the warm components of the models. The maps and spectra of all the lines used in the models were taken from Pérez-Beaupuits et al. (2010, 2012, 2015 and 2015b).

Table 3 – Sonic (ms) and Alfvénic (m

A) mach numbers, and the plasma

parameter (or the ratio of thermal to magnetic pressures) βp = 2(m

A/m

s)2 for the

cold and warm components at the four positions studied by Pérez-Beaupuits et al. (2015b).

MA ≤ 1 → Motions are Alfvén (or MHD) waves.

βp < 1 → Magnetic pressure dominates thermal pressure.

Virial equation:

External pressure

Gravitational energy

Static & Fluctuating magnetic energy

Kinetic energy (internal motions)

Using the magnetic field measured by Brogan & Troland (1999, 2001) and the densities and temperatures estimated from our LSEDs models, we conclude that the static magnetic energy dominates all the energy terms of the cold components in most of the selected positions, while the gravitational energy is between one and two orders of magnitude lower than M

S.

The static magnetic energy of the warm component is one or two orders of magnitude lower than W, meaning that the wave magnetic energy and internal motions support the cloudlets associated with the warm components.