A sample of [C II] clouds tracing dense clouds in weak FUV fields observed by<i>Herschel</i>

Pineda, J. L.; Velusamy, T.; Langer, W. D.; Goldsmith, Paul F.; Li, Di; Yorke, H. W.

doi:10.1051/0004-6361/201015089

Cited by 38 publications

(37 citation statements)

References 23 publications

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“…In a preliminary study of [C ii], 12 CO, and 13 CO velocity components on 16 GOT C+ LOSs, Pineda et al (2010b) used PDR model calculations to constrain the strength of the FUV field to be mostly χ 0 = 1−10, over a wide range of H 2 volume densities, thus suggesting that most of the observed [C ii] emission associated with 12 CO and 13 CO is exposed to weak FUV radiation fields. A similar result, was obtained from PDR modeling of the [C ii] emission observed by COBE by Cubick et al (2008), suggesting that most of the [C ii] in our Galaxy originates in a clumpy medium exposed to an FUV field of χ 0 60.…”

Section: The Fuv Radiation Field Distribution In the Milky Waymentioning

confidence: 99%

“…Kaufman et al (1999) showed that the ratio of [C ii] to CO is a good tracer of the strength of the FUV field in the galaxy. Using this line ratio in a sample of 16 LOSs, Pineda et al (2010b) found that most of the dense PDRs have FUV fields lower than 100 times the interstellar FUV field. With the complete GOT C+ survey, we can use the [C ii]/CO ratio to trace the strength of the FUV radiation field over the entire Galactic disk.…”

Section: Introductionmentioning

confidence: 99%

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AHerschel[C ii] Galactic plane survey

Pineda

Langer

Velusamy

et al. 2013

A&A

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Context. The [C ii] 158 μm line is an important tool for understanding the life cycle of interstellar matter. Ionized carbon is present in a variety of phases of the interstellar medium (ISM), including the diffuse ionized medium, warm and cold atomic clouds, clouds in transition from atomic to molecular, and dense and warm photon dominated regions.Aims. Velocity-resolved observations of [C ii] are the most powerful technique available to disentangle the emission produced by these components. These observations can also be used to trace CO-dark H 2 gas and determine the total mass of the ISM.Methods. The Galactic Observations of Terahertz C+ (GOT C+) project surveys the [C ii] 158 μm line over the entire Galactic disk with velocity-resolved observations using the Herschel/HIFI instrument. We present the first longitude-velocity maps of the [C ii] emission for Galactic latitudes b = 0• , ±0.5• , and ±1.0• . We combine these maps with those of H i, 12 CO, and 13 CO to separate the different phases of the ISM and study their properties and distribution in the Galactic plane.Results. [C ii] emission is mostly associated with spiral arms, mainly emerging from Galactocentric distances between 4 and 10 kpc.It traces the envelopes of evolved clouds as well as clouds that are in the transition between atomic and molecular. We estimate that most of the observed [C ii] emission is produced by dense photon dominated regions (∼47%), with smaller contributions from COdark H 2 gas (∼28%), cold atomic gas (∼21%), and ionized gas (∼4%). Atomic gas inside the Solar radius is mostly in the form of cold neutral medium (CNM), while the warm neutral medium gas dominates the outer galaxy. The average fraction of CNM relative to total atomic gas is ∼43%. We find that the warm and diffuse CO-dark H 2 is distributed over a larger range of Galactocentric distances (4−11 kpc) than the cold and dense H 2 gas traced by 12 CO and 13 CO (4−8 kpc). The fraction of CO-dark H 2 to total H 2 increases with Galactocentric distance, ranging from ∼20% at 4 kpc to ∼80% at 10 kpc. On average, CO-dark H 2 accounts for ∼30% of the molecular mass of the Milky Way. When the CO-dark H 2 component is included, the radial distribution of the CO-to-H 2 conversion factor is steeper than that when only molecular gas traced by CO is considered. Most of the observed [C ii] emission emerging from dense photon dominated regions is associated with modest far-ultraviolet fields in the range χ 0 1−30.

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Section: The Fuv Radiation Field Distribution In the Milky Waymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

AHerschel[C ii] Galactic plane survey

Pineda

Langer

Velusamy

et al. 2013

A&A

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338

497

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“…In this paper we use the [C ii] and CO data for 354 lines of sight Pineda et al (2010Pineda et al ( , 2013 toward the inner Galaxy in the longitude range l = 270…”

Section: Got C+ Survey Datamentioning

confidence: 99%

Origin andz-distribution of Galactic diffuse [C II] emission

Velusamy

Langer

2014

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Context. The [C ii] emission is an important probe of star formation in the Galaxy and in external galaxies. The GOT C+ survey and its follow up observations of spectrally resolved 1.9 THz [C ii] emission using Herschel HIFI provides the data needed to quantify the Galactic interstellar [C ii] gas components as tracers of star formation. Aims. We determine the source of the diffuse [C ii] emission by studying its spatial (radial and vertical)

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“…Our sample is made of relatively metal-rich spiral galaxies for which CO should be a more reliable tracer of the total molecular content. Still, some dark gas can also be found in the Milky Way (Grenier et al 2005;Langer et al 2010;Pineda et al 2010;Velusamy et al 2010;Planck Collaboration 2011). However, theoretical models suggest that for a given mean attenuation, the fraction of dark gas remains constant (Wolfire et al 2010).…”

Section: Dark Gasmentioning

confidence: 99%

Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales

Boquien

Boselli

Buat

et al. 2013

A&A

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Context. Understanding the relation between the attenuation and the gas is fundamental for interpreting the appearance of galaxies. This can now be done down to a local scale in the local Universe, thanks to the high spatial resolution achievable from the farultraviolet (FUV) to the far-infrared (FIR). More importantly, this relation is also crucial for predicting the emission of galaxies. This is essential in semi-analytic models that link dark matter from large cosmological simulations, to the baryonic matter which we can observe directly. Aims. The aim of the present paper is to provide new and more detailed relations at the kpc scale between the gas surface density and the face-on optical depth directly calibrated on galaxies, in order to compute the attenuation not only for semi-analytic models, but also for observational models as new and upcoming radio observatories are able to trace gas ever farther away in the Universe. Methods. We have selected a sample of 4 nearby resolved galaxies and a sample of 27 unresolved galaxies from the Herschel Reference Survey and the Very Nearby Galaxies Survey, for which we have a large set of multi-wavelength data from the FUV to the FIR including metallicity gradients for resolved galaxies, along with radio HI and CO observations. For each pixel in resolved galaxies and for each galaxy in the unresolved sample, we compute the face-on optical depth from the attenuation determined with the CIGALE spectral energy distribution fitting code and an assumed geometry. We determine the gas surface density from HI and CO observations with a metallicity-dependent X CO factor. Results. We provide new, simple-to-use relations to determine the face-on optical depth from the gas surface density, taking the metallicity into account, which proves to be crucial for a proper estimate. The method used to determine the gas surface density or the face-on optical depth has little impact on the relations except for galaxies that have an inclination over 50• . Finally, we provide detailed instructions on how to efficiently compute the attenuation from the gas surface density taking into account possible information on the metallicity. Conclusions. Examination of the influence of these new relations on simulated FUV and IR luminosity functions shows a clear impact compared to older, more-frequently used relations, which in turn could affect the conclusions drawn from studies based on large-scale cosmological simulations.

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A sample of [C II] clouds tracing dense clouds in weak FUV fields observed byHerschel

Cited by 38 publications

References 23 publications

AHerschel[C ii] Galactic plane survey

AHerschel[C ii] Galactic plane survey

Origin andz-distribution of Galactic diffuse [C II] emission

Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales

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