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J/ApJ/793/132   Perseus cloud sources Gaussian parameters  (Stanimirovic+, 2014)

Cold and warm atomic gas around the Perseus molecular cloud. I. Basic properties. Stanimirovic S.Z., Murray C.E., Lee M.-Y., Heiles C., Miller J. <Astrophys. J., 793, 132 (2014)> =2014ApJ...793..132S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Molecular clouds ; Interstellar medium ; Radio sources ; Spectroscopy ; Line Profiles ; H I data Keywords: ISM: clouds - ISM: structure - radio lines: ISM Abstract: Using the Arecibo Observatory, we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases, allowing us to estimate spin temperature (Ts) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual H I clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium (CNM and WNM), respectively) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium H I survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have, on average, a higher total H I column density and the CNM fraction, suggesting an enhanced amount of cold H I relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick H I. Only ∼15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with ≳85% of Planck's sky coverage. The observed CNM fraction is inversely proportional to the optical depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. (2014ApJ...786...64K). While the CNM fraction is, on average, higher around Perseus relative to a random interstellar field, it is generally low, between 10%-50%. This suggests that extended WNM envelopes around molecular clouds and/or significant mixing of CNM and WNM throughout molecular clouds are present and should be considered in the models of molecule and star formation. Our detailed comparison of H I absorption with CO emission spectra shows that only 3 of the 26 directions are clear candidates for probing the CO-dark gas as they have N(H I)>1021/cm2 yet no detectable CO emission. Description: We selected 27 radio continuum sources from the NVSS survey (Condon et al. 1998AJ....115.1693C, Cat. VIII/65), located over an area of roughly 500 deg2 centered on Perseus with flux densities at 1.4 GHz greater than 0.8 Jy. The observations were conducted with the Arecibo telescope. Using the L-wide receiver, we simultaneously recorded spectra centered at 1420 MHz and the two OH main lines (1665 and 1667 MHz), achieving a velocity resolution of 0.16 km/s. We sampled simultaneously two linearly polarized channels performing both auto- and cross-correlations with the Arecibo's three-level "interim" digital correlator. The Arecibo telescope has an angular resolution of 3.5' at these frequencies. As shown by Heiles & Troland (2003, J/ApJS/145/329) in their Millennium H I survey, Arecibo can accurately measure H I absorption lines for strong sources (flux density larger than ∼1 Jy). Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 03 35.0 +31 13 Perseus molecular cloud = NAME PMC ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 45 27 Source List table2.dat 81 182 Gaussian Parameters Associated with All CNM and WNM Components for Each Source from Erratum, 2015, ApJ, 799, 239
See also: VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998) J/ApJS/145/329 : Millennium Arecibo 21-cm Survey (Heiles+, 2003) J/ApJ/638/293 : 1.1mm sources in the Perseus Molecular Cloud (Enoch+, 2006) J/ApJ/646/1009 : Structures of dust in Perseus molecular cloud (Kirk+, 2006) J/ApJ/668/1042 : Dense cores in Perseus molecular cloud (Kirk+, 2007) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 9 A9 --- ID Source identifier 11- 12 I2 h RAh Hour of Right Ascension (J2000) 14- 15 I2 min RAm Minute of Right Ascension (J2000) 17- 21 F5.2 s RAs Second of Right Ascension (J2000) 23- 24 I2 deg DEd Degree of Declination (J2000) 26- 27 I2 arcmin DEm Arcminute of Declination (J2000) 29- 33 F5.2 arcsec DEs Arcsecond Declination (J2000) 35- 37 F3.1 Jy Tsrc NVSS flux density at 1.4GHz 39- 43 F5.3 K Tsky Sky temperature 45 A1 --- Note [a] Note on 4C+32.14 (1)
Note (1): a = One source that we exclude from analysis is 4C+32.14 which has a highly saturated absorption profile and therefore all fitted parameters are highly uncertain for this source.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 9 A9 --- ID Source identifier 11- 15 F5.2 K TB Brightness temperature (1) 17- 20 F4.2 K e_TB ? Uncertainty in TB 22- 27 F6.2 km/s VLSR Central velocity of fitted Gaussian function (2) 29- 32 F4.2 km/s e_VLSR ? Uncertainty in VLSR 34- 38 F5.2 km/s DelV FWHM of fitted Gaussian function (2) 40- 43 F4.2 km/s e_DelV ? Uncertainty in DelV 45- 49 F5.3 --- tau Peak optical depth (3) 51- 55 F5.3 --- e_tau ? Uncertainty in tau 57- 60 I4 K Ts Spin temperature (4) 62- 64 I3 K e_Ts ? Uncertainty in Ts 66- 71 I6 K Tkmax Maximum kinetic temperature (5) 73- 77 F5.2 10+20/cm2 NHI H I column density (6) 79- 81 F3.1 --- ForO [0/8] WNM or CNM code (7)
Note (1): For emission components: equal to fitted peak brightness temperature of each Gaussian function, with errors from the fit. For absorption components: equal to Ts*(1-e-tau), quoted without error. Note (2): To both emission and absorption spectra, with errors from the fits. Note (3): For absorption components: equal to the fitted peak optical depth of each Gaussian function, with error from the fit. For emission components: equal to the 1σ noise level in absorption at the central velocity of the emission component, quoted without error. Note (4): For absorption components: equal to the result from the total fit to the emission profile, with errors estimated from varying the possible order of CNM components along the line of sight (see Section 3). For emission components: equal to TB/tau, quoted without error. Note (5): Equal to 21.86*DelV2 (Heiles & Troland 2003ApJ...586.1067H), quoted without error. Note (6): For absorption components: equal to 1.064467*0.0183*Ts*tau*DelV. For emission components: equal to 1.064467*0.0183*TB*DelV. Note (7): WNM or CNM code as follows: F = fraction of each WNM component lying in front of CNM clouds (for emission components only, equal to 0.0, 0.5 or 1.0); O = order of CNM clouds along the line of sight (for absorption components only, equal to integer values).
History: From electronic version of the journal References: Lee et al., Paper II, 2015ApJ...809...56L
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 20-Apr-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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