Cold and warm atomic gas around the Perseus molecular cloud I: Basic Properties

Abstract

(Abridged) 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 (T_s) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual HI clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium, CNM and WNM) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium HI 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 HI column density and the CNM fraction, suggesting an enhanced amount of cold HI 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 HI. 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. While the CNM fraction is on average higher around Perseus relative to a random interstellar field, it is generally low, 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.

23 pages; accepted for publication in ApJ

References in corpus (35)

• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The Milky Way in Molecular Clouds: A New Complete CO Survey
• The Star Formation Law in Nearby Galaxies on Sub-Kpc Scales
• On the Star Formation Rates in Molecular Clouds
• The Dark Molecular Gas
• The Relationship Between Gas Content and Star Formation in Molecule-Rich Spiral Galaxies
• The Millennium Arecibo 21-CM Absorption Line Survey. II. Properties of the Warm and Cold Neutral Media
• A Molecular Star Formation Law in the Atomic Gas Dominated Regime in Nearby Galaxies
• IRIS: A new generation of IRAS maps
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• Thermal condensation in a turbulent atomic hydrogen flow
• A Herschel [CII] Galactic plane survey I: the global distribution of ISM gas components
• CO Isotopologues in the Perseus Molecular Cloud Complex: the X-Factor and Regional Variations
• The COMPLETE Survey of Star-Forming Regions: Phase I Data
• The Role of Pressure in GMC Formation
• The GALFA-HI Survey: Data Release 1
• CO-dark gas and molecular filaments in Milky Way type galaxies
• Formation of Structure in Molecular Clouds: A Case Study
• The Millennium Arecibo 21-cm Absorption Line Survey. I. Techniques and Gaussian Fits
• HI Narrow Line Absorption in Dark Clouds
• HI Narrow Self-Absorption in Dark Clouds: Correlations with Molecular Gas and Implications for Cloud Evolution and Star Formation
• Formation of Spiral-Arm Spurs and Bound Clouds in Vertically Stratified Galactic Gas Disks
• How long does it take to form a molecular cloud?
• The Global Evolution of Giant Molecular Clouds II: The Role of Accretion
• A High Resolution Study of the HI-H2 Transition across the Perseus Molecular Cloud
• The Outer Disk of the Milky Way Seen in 21-cm Absorption
• Molecular and Atomic Gas in the Large Magellanic Cloud II. Three-dimensional Correlation between CO and HI
• First results from the Arecibo Galactic HI Survey: the disk/halo interface region in the outer Galaxy
• Imaging diffuse clouds: Bright and dark gas mapped in CO
• Three Dimensional Hydrodynamic Simulations of Multiphase Galactic Disks with Star Formation Feedback: II. Synthetic HI 21 cm Line Observations
• The CO-to-H2 Conversion Factor across the Perseus Molecular Cloud
• Indications of a sub-linear and non-universal Kennicutt-Schmidt relationship
• The thinnest cold HI clouds in the diffuse interstellar medium?
• Can WNM survive inside Molecular Clouds ?
• The Chemical Composition of Cernis 52 (BD+31 640)

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