J/A+A/604/A135 Dynamics of ionized and neutral gas in M8 (Damiani+, 2017)
The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M8). Damiani F., Bonito R., Prisinzano L., Zwitter T., Bayo A., Kalari V., Jimenez-Esteban F. M., Costado M. T., Jofre P., Randich S., Flaccomio E., Lanzafame A. C., Lardo C., Morbidelli L., Zaggia S. <Astron. Astrophys. 604, A135 (2017)> =2017A&A...604A.135D (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Interstellar medium ; Nebulae Keywords: ISM: individual objects: Lagoon nebula - ISM: general - HII regions Abstract: We present a spectroscopic study of the dynamics of the ionized and neutral gas throughout the Lagoon nebula (M8), using VLT/FLAMES data from the Gaia-ESO Survey. We explore the connections between the nebular gas and the stellar population of the associated star cluster NGC6530. We characterize through spectral fitting emission lines of Hα, [NII] and [SII] doublets, [OIII], and absorption lines of sodium D doublet, using data from the FLAMES/Giraffe and UVES spectrographs, on more than 1000 sightlines towards the entire face of the Lagoon nebula. Gas temperatures are derived from line-width comparisons, densities from the [SII] doublet ratio, and ionization parameter from Hα/[NII] ratio. Although doubly-peaked emission profiles are rarely found, line asymmetries often imply multiple velocity components along the same line of sight. This is especially true for the sodium absorption, and for the [OIII] lines. Spatial maps for density and ionization are derived, and compared to other known properties of the nebula and of its massive stars 9 Sgr, Herschel 36 and HD 165052 which are confirmed to provide most of the ionizing flux. The detailed velocity fields across the nebula show several expanding shells, related to the cluster NGC6530, the O stars 9 Sgr and Herschel 36, and the massive protostar M8East-IR. The origins of kinematical expansion and ionization of the NGC6530 shell appear to be different. We are able to put constrains on the line-of-sight (relative or absolute) distances between some of these objects and the molecular cloud. The large obscuring band running through the middle of the nebula is being compressed by both sides, which might explain its enhanced density. We also find an unexplained large-scale velocity gradient across the entire nebula. At larger distances, the transition from ionized to neutral gas is studied using the sodium lines. Description: We report in Table 2 best-fit parameters for four emission lines from ionized gas in the Lagoon nebula M8, using single-Gaussian models. Table 3 reports best-fit parameters for sodium-doublet absorption lines, using multi-Gaussian models. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 129 1177 Best-fit parameters for Halpha, [NII], [SII] table3.dat 118 53 Multi-Gaussian best fits to NaI lines
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 20 A20 --- Id Sky-position identifier (1) 22- 29 F8.4 deg RAdeg Right Ascension (J2000) 31- 39 F9.5 deg DEdeg Declination (J2000) 41- 46 F6.2 km/s RVHalpha ? Radial velocity of H-alpha line 48- 52 F5.2 km/s sigHalpha ? Gaussian width of H-alpha line 54- 62 F9.2 km/s/min NormHalpha ? Intensity of H-alpha line (in ADU*km/s/min) 64- 69 F6.2 km/s RV[NII]6584 ? Radial velocity of [NII] 6584 71- 75 F5.2 km/s sig[NII]6584 ? Gaussian width of [NII] 6584 77- 85 F9.2 km/s/min Norm[NII]6584 ? Intensity of [NII] 6584 (in ADU*km/s/min) 87- 92 F6.2 km/s RV[SII]6717 ? Radial velocity of [SII] 6717 94- 98 F5.2 km/s sig[SII]6717 ? Gaussian width of [SII] 6717 100-107 F8.2 km/s/min Norm[SII]6717 ? Intensity of [SII] 6717 (in ADU*km/s/min) 109-114 F6.2 km/s RV[SII]6731 ? Radial velocity of [SII] 6731 116-120 F5.2 km/s sig[SII]6731 ? Gaussian width of [SII] 6731 122-129 F8.2 km/s/min Norm[SII]6731 ? Intensity of [SII] 6731 (in ADU*km/s/min)
Note (1): Identifier from J2000 coordinates of sky/star position, SKY_HHMMSSss+DDMMSSs or HHMMSSss+DDMMSSs. Id's starting with 'SKY' are measurements from pure-sky fibers, all others are from faint-star fibers.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 6 A6 --- StarId Identifier from UVES setup/star Id (2) 8- 23 A16 --- Name Star identifier from J2000 coordinates (HHMMSSss+DDMMSSs) 25- 29 F5.2 km/s RVComp1 Radial velocity of component #1 31- 34 F4.2 km/s sigComp1 Gaussian width of component #1 36- 42 F7.2 km/s NormComp1 Intensity of component #1 44- 49 F6.2 km/s RVComp2 ? Radial velocity of component #2 51- 55 F5.2 km/s sigComp2 ? Gaussian width of component #2 57- 63 F7.2 km/s NormComp2 ? Intensity of component #2 65- 70 F6.2 km/s RVComp3 ? Radial velocity of component #3 72- 75 F4.2 km/s sigComp3 ? Gaussian width of component #3 77- 83 F7.2 km/s NormComp3 ? Intensity of component #3 85- 90 F6.2 km/s RVComp4 ? Radial velocity of component #4 92- 95 F4.2 km/s sigComp4 ? Gaussian width of component #4 97-101 F5.2 km/s NormComp4 ? Intensity of component #4 103-108 F6.2 km/s RVComp5 ? Radial velocity of component #5 110-113 F4.2 km/s sigComp5 ? Gaussian width of component #5 115-118 F4.2 km/s NormComp5 ? Intensity of component #5
Note (2): Form of identifier is UUU-NN. UVES setup UUU is either 520 or 580nm; star number NN is sequential within the same UVES setup.
Acknowledgements: Francesco Damiani, damiani(at)astropa.inaf.it
(End) Francesco Damiani [INAF-OAPA, Italy], Patricia Vannier [CDS] 02-Jun-2017
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