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J/ApJ/814/133     Herschel Galactic plane survey of [NII]     (Goldsmith+, 2015)

Herschel Galactic plane survey of [NII] fine structure emission. Goldsmith P.F., Yildiz U.A., Langer W.D., Pineda J.L. <Astrophys. J., 814, 133 (2015)> =2015ApJ...814..133G (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Interstellar medium ; Spectroscopy Keywords: ISM: general; ISM: structure Abstract: We present the first large-scale high angular resolution survey of ionized nitrogen in the Galactic Plane through emission of its two fine structure transitions ([N II]) at 122 and 205 µm. The observations were largely obtained with the PACS instrument onboard the Herschel Space Observatory. The lines of sight were in the Galactic plane, following those of the Herschel OTKP project GOT C+. Both lines are reliably detected at the 10-8-10-7 W/m2/sr level over the range -60°≤l≤60°. The rms of the intensity among the 25 PACS spaxels of a given pointing is typically less than one third of the mean intensity, showing that the emission is extended. [N II] is produced in gas in which hydrogen is ionized, and collisional excitation is by electrons. The ratio of the two fine structure transitions provides a direct measurement of the electron density, yielding n(e) largely in the range 10-50 cm-3 with an average value of 29 cm-3 and N+ column densities 1016-1017 cm-2. [N II] emission is highly correlated with that of [C II], and we calculate that between 1/3 and 1/2 of the [C II] emission is associated with the ionized gas. The relatively high electron densities indicate that the source of the [N II] emission is not the warm ionized medium (WIM), which has electron densities more than 100 times smaller. Possible origins of the observed [N II] include the ionized surfaces of dense atomic and molecular clouds, the extended low-density envelopes of H II regions, and low-filling factor high-density fluctuations of the WIM. Description: Observations of both fine structure transitions of [N II], at 121.898 µm (2459.371 GHz) and 205.178 µm (1461.134 GHz) (Brown et al. 1994ApJ...428L..37B), were carried out with the PACS spectrometer (Poglitsch et al. 2010A&A...518L...2P) on Herschel (Pilbratt et al. 2010A&A...518L...1P). At 10 selected positions, the lower frequency transition was also observed with the high spectral resolution Heterodyne Instrument for the Far-Infrared (HIFI; de Graauw et al. 2010A&A...518L...6D). Based on the expected relative intensities of the [N II] and [C II] lines (Bennett et al. 1994ApJ...434..587B), observations were largely restricted to the inner galaxy, with both lines detected only in the range -60°=<l=<60°. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 91 70 Observed PACS Integrated Intensities for [N II] 122 and 205 µm Transitions are Tabulated Together with the Inferred Electron Volume Densities and N+ Column Densities table3.dat 91 79 PACS Results
See also: VI/139 : Herschel Observation Log (Herschel Science Centre, 2013) J/ApJ/829/93 : CO, [CI] and [NII] lines from Herschel spectra (Kamenetzky+, 2016) Byte-by-byte Description of file: table2.dat table3.dat
Bytes Format Units Label Explanations
1- 10 A10 --- ID Line of sight (LOS) label (GLLL.l+B.b) 12- 19 F8.4 deg GLON Galactic longitude 21- 23 F3.1 deg GLAT Galactic latitude 25- 34 I10 --- OBSID Herschel OBSID 36 I1 --- R [0/3]? Detection status (1) 38 A1 --- l_NII122 [<] Limit flag on NII122 39- 43 F5.2 10-8W/m2/sr NII122 ? [N II] 122 µm intensity averaged over the 25 PACS spaxels 45- 49 F5.3 10-8W/m2/sr e_NII122 ? Uncertainty in NII122 51- 55 F5.2 10-8 RMS ? RMS variation among the 25 spaxels at 122 µm wavelength 57 I1 --- R1 [0/3]? Detection status (1) 59 A1 --- l_NII205 [<] Limit flag on NII205 60- 64 F5.2 10-8W/m2/sr NII205 ? [N II] 205 µm intensity averaged over the 25 PACS spaxels 66- 70 F5.3 10-8W/m2/sr e_NII205 ? Uncertainty in NII205 72- 76 F5.1 cm-3 n(e) ? Electron density 78- 81 F4.1 cm-3 e_n(e) ? Uncertainty in n(e) 83- 86 F4.1 10+16cm-2 N(N+) ? N+ column density 88- 91 F4.2 10+16cm-2 e_N(N+) ? Uncertainty in N(N+)
Note (1): Detection status as follows: 0 = Not observed; 1 = Non-detection; 2 = Detection in individual spaxel or spaxels; 3 = Only the average of all spaxels provides a detection. For the non-detections, we give the 3σ upper limits on the intensities.
History: From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 17-Oct-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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