Models of Clumpy Photodissociation Regions: Erratum

Meixner, M.; Tielens, A. G. G. M.

doi:10.1086/175848

Cited by 13 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To explain the observed correlation between the spatial distributions of C 0 and CO, inhomogeneous PDRs with clumping molecular gas were suggested. The revealed ubiquity of the [C i] transition 3 P 1 → 3 P 0 in molecular clouds is in agreement with clumpy PDR models (Meixner & Tielens 1995;Spaans et al 1997;Papadopoulos et al 2004).…”

Section: [C I] and Co Lines As Probes Of α 2 /µsupporting

confidence: 84%

“…An appropriate pair in our case is the atomic carbon FS transitions and rotational transitions of carbon monoxide 13 CO. The spatial distributions of 13 CO and [C i] are known to be well correlated (Keene et al 1985;Meixner & Tielens 1995;Spaans & van Dishoeck 1997;Ikeda et al 2002;Papadopoulos et al 2004). The carbon-bearing species C 0 , C + , and CO are observed in photodissociation regions (PDRs) -neutral regions where chemistry and heating are regulated by the far-UV photons (Hollenbach & Tielens 1999).…”

Section: [C I] and Co Lines As Probes Of α 2 /µmentioning

confidence: 99%

See 1 more Smart Citation

Searching for spatial variations ofα²/μin the Milky Way

Levshakov

Molaro²,

Reimers

2010

A&A

View full text Add to dashboard Cite

Aims. We probe the dependence of α 2 /μ on the ambient matter density by means of spectral observations in submm-and mm-wave bands. Methods. A procedure is suggested for exploring the value of F = α 2 /μ, where μ = m e /m p is the electron-to-proton mass ratio, and α = e 2 /( c) is the fine-structure constant. The fundamental physical constants, which are measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter are supposed to vary in chameleon-like scalar field models, which predict that both masses and coupling constant may depend on the local matter density. The parameter ΔF/F = (F obs − F lab )/F lab can be estimated from the radial velocity offset, ΔV = V rot − V fs , between the low-laying rotational transitions in carbon monoxide 13 CO and the fine-structure transitions in atomic carbon [C i]. A model-dependent constraint on Δα/α can be obtained from ΔF/F using Δμ/μ independently measured from the ammonia method. Results. Currently available radio astronomical datasets provide an upper limit on |ΔV| < 110 m s −1 (1σ). When interpreted in terms of the spatial variation of F, this gives |ΔF/F| < 3.7 × 10 −7 . An order of magnitude improvement in this limit will allow us to independently test a non-zero value of Δμ/μ = (2.2 ± 0.4 stat ± 0.3 sys ) × 10 −8 , recently found with the ammonia method. Considering that the ammonia method restricts the spatial variation of μ at the level of |Δμ/μ| ≤ 3 × 10 −8 and assuming that ΔF/F is the same in the entire interstellar medium, one obtains that the spatial variation of α does not exceed the value |Δα/α| < 2 × 10 −7 . Since extragalactic gas clouds have similar densities to those in the interstellar medium, the bound on Δα/α is also expected to be less than 2 × 10 −7 at high redshift if no significant temporal dependence of α is present.

show abstract

Section: [C I] and Co Lines As Probes Of α 2 /µsupporting

confidence: 84%

Section: [C I] and Co Lines As Probes Of α 2 /µmentioning

confidence: 99%

Searching for spatial variations ofα²/μin the Milky Way

Levshakov

Molaro²,

Reimers

2010

A&A

View full text Add to dashboard Cite

show abstract

“…This suggests that there is a chemical stratification of the PDR between the lines C + /C 0 /CO with increasing depth from the surface of the PDR. The observed correlation between the spatial distributions of C 0 and CO can be explained by clumpy PDR models (e.g., Meixner & Tielens 1995;Spaans & van Dishoeck 1997;Papadopoulos et al 2004). In the observed z = 5.2 galaxy, the derived excitation temperature of the higher-J CO lines, T ex = 40 K, and the gas density n H 2 = 3.5 × 10 3 cm −3 (CRR) just corresponds to the critical density of n cr ≈ 3 × 10 3 cm −3 required to excite collisionally the J = 2 level of the ground state triplet of C 0 (e.g., Levshakov et al 2010a).…”

Section: Discussionmentioning

confidence: 99%

An upper limit to the variation in the fundamental constants at redshiftz= 5.2

Levshakov

Combes

Boone

et al. 2012

A&A

View full text Add to dashboard Cite

Aims. We constrain a hypothetical variation in the fundamental physical constants over the course of cosmic time. Methods. We use unique observations of the CO(7-6) rotational line and the [C i] 3 P 2 − 3 P 1 fine-structure line towards a lensed galaxy at redshift z = 5.2 to constrain temporal variations in the constant F = α 2 /μ, where μ is the electron-to-proton mass ratio and α is the fine-structure constant. The relative change in F between z = 0 and z = 5.2, ΔF/F = (F obs − F lab )/F lab , is estimated from the radial velocity offset, ΔV = V rot − V fs , between the rotational transitions in carbon monoxide and the fine-structure transition in atomic carbon. Results. We find a conservative value ΔV = (1±5) km s −1 (1σ C.L.), which when interpreted in terms of ΔF/F gives ΔF/F < 2×10 −5 . Independent methods restrict the μ-variations at the level of Δμ/μ < 1 × 10 −7 at z = 0.7 (look-back time t z0.7 = 6.4 Gyr). Assuming that temporal variations in μ, if any, are linear, this leads to an upper limit on Δμ/μ < 2 × 10 −7 at z = 5.2 (t z5.2 = 12.9 Gyr). From both constraints on ΔF/F and Δμ/μ , one obtains for the relative change in α the estimate Δα/α < 8 × 10 −6 , which is at present the tightest limit on Δα/α at early cosmological epochs.

show abstract

“…An illustration of a clumpy photodissociation region (Meixner and Tielens, 1995). The far-ultraviolet photons scatter and penetrate through the interclump material and reach points deeper in the regions than if the material were uniformly spread throughout the region.…”

Section: Figmentioning

confidence: 99%

Photodissociation regions in the interstellar medium of galaxies

Hollenbach

Tielens²

1999

Rev. Mod. Phys.

Self Cite

754

712

View full text Add to dashboard Cite

The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eVϽh Ͻ13.6 eV) photons from massive stars dominate the heating and influence the chemistry of the neutral atomic gas and much of the molecular gas in galaxies. Predominantly neutral regions of the interstellar medium in which the heating and chemistry are regulated by far ultraviolet photons are termed PhotoDissociation Regions (PDRs). These regions are the origin of most of the non-stellar infrared (IR) and the millimeter and submillimeter CO emission from galaxies. The importance of PDRs has become increasingly apparent with advances in IR and submillimeter astronomy. The IR emission from PDRs includes fine structure lines of C, C ϩ , and O; rovibrational lines of H 2 ; rotational lines of CO; broad mid-IR features of polycyclic aromatic hydrocarbons; and a luminous underlying IR continuum from interstellar dust. The transition of H to H 2 and C ϩ to CO occurs within PDRs. Comparison of observations with theoretical models of PDRs enables one to determine the density and temperature structure, the elemental abundances, the level of ionization, and the radiation field. PDR models have been applied to interstellar clouds near massive stars, planetary nebulae, red giant outflows, photoevaporating planetary disks around newly formed stars, diffuse clouds, the neutral intercloud medium, and molecular clouds in the interstellar radiation field-in summary, much of the interstellar medium in galaxies. Theoretical PDR models explain the observed correlations of the [CII] 158 m with the CO Jϭ1 -0 emission, the CO Jϭ1 -0 luminosity with the interstellar molecular mass, and the [CII] 158 m plus [OI] 63 m luminosity with the IR continuum luminosity. On a more global scale, PDR models predict the existence of two stable neutral phases of the interstellar medium, elucidate the formation and destruction of star-forming molecular clouds, and suggest radiation-induced feedback mechanisms that may regulate star formation rates and the column density of gas through giant molecular clouds. [S0034-6861(99)01001-6] CONTENTS

show abstract

Models of Clumpy Photodissociation Regions: Erratum

Cited by 13 publications

References 0 publications

Searching for spatial variations ofα²/μin the Milky Way

Searching for spatial variations ofα²/μin the Milky Way

An upper limit to the variation in the fundamental constants at redshiftz= 5.2

Photodissociation regions in the interstellar medium of galaxies

Contact Info

Product

Resources

About

Models of Clumpy Photodissociation Regions: Erratum

Cited by 13 publications

References 0 publications

Searching for spatial variations ofα2/μin the Milky Way

Searching for spatial variations ofα2/μin the Milky Way

An upper limit to the variation in the fundamental constants at redshiftz= 5.2

Photodissociation regions in the interstellar medium of galaxies

Contact Info

Product

Resources

About

Searching for spatial variations ofα²/μin the Milky Way

Searching for spatial variations ofα²/μin the Milky Way