A survey of submillimeter C and CO lines in nearby galaxies

Bayet, E.; Gérin, M.; Phillips, T. G.; Contursi, A.

doi:10.1051/0004-6361:20053872

Cited by 72 publications

(146 citation statements)

References 72 publications

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“…Furthermore, Regions III are rather small as compared with the Regions I, but are likely responsible for feeding the star formation at high rates in these galaxies. On the other hand, CO arises in this galaxies from gas with densities in the range 10 3 − 10 4 cm −3 (Israel & Baas 2003;Bayet et al 2004Bayet et al , 2006Güsten et al 2006). The average clouds in these two galaxies resemble the Sgr B2 star forming region in the GC.…”

Section: Molecular Clouds In Galaxies Hosting Intermediate-age Starbumentioning

confidence: 86%

CS, HC₃N, and CH₃CCH multi-line analyses toward starburst galaxies

Aladro

Martı́n-Pintado

Martín

et al. 2010

A&A

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Aims. We aim to study the properties of the dense molecular gas towards the inner few 100 pc of four nearby starburst galaxies dominated both by photo dissociation regions (M 82) and large-scale shocks (NGC 253, IC 342 and Maffei 2), and to relate the chemical and physical properties of the molecular clouds with the evolutionary stage of the nuclear starbursts. Methods. We have carried out multi-transitional observations and analyses of three dense gas molecular tracers, CS, HC 3 N (cyanoacetylene) and CH 3 CCH (methyl acetylene), using Boltzmann diagrams in order to determine the rotational temperatures and column densities of the dense gas, and using a Large Velocity Gradients model to calculate the H 2 density structure in the molecular clouds.Results. The CS and HC 3 N data indicate the presence of density gradients in the molecular clouds. These two molecules show similar excitation conditions, suggesting that they arise from the same gas components. In M 82, CH 3 CCH has the highest fractional abundance determined in a extragalactic source (1.1 × 10 −8 ). Conclusions. The density and the chemical gradients we have found in all galaxies can be explained in the framework of the starburst evolution, which affects the chemistry and the structure of molecular clouds around the galactic nuclei. The young shock-dominated starburst galaxies, like presumably Maffei 2, show a cloud structure with a rather uniform density and chemical composition which suggests low star formation activity. Molecular clouds in galaxies with starburst in an intermediate stage of evolution, such as NGC 253 and IC 342, show clouds with a large density contrast (two orders of magnitude) between the denser regions (cores) and the less dense regions (halos) of the molecular clouds and relatively constant chemical abundance. Finally, the galaxy with the most evolved starburst, M 82, has clouds with a rather uniform density structure, large envelopes of atomic/molecular gas subjected to UV photodissociating radiation from young star clusters, and very different chemical abundances of HC 3 N and CH 3 CCH.

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Section: Molecular Clouds In Galaxies Hosting Intermediate-age Starbumentioning

confidence: 86%

CS, HC₃N, and CH₃CCH multi-line analyses toward starburst galaxies

Aladro

Martı́n-Pintado

Martín

et al. 2010

A&A

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“…The FS [C i] lines and low-J rotational lines of 13 CO are observed towards many galactic and extragalactic objects (Bayet et al 2006;Omont 2007). For our purpose we selected a few molecular clouds located at different galactocentric distances where the radial velocities of these species were measured with a sufficiently high precision (ε v ∼ 100 m s −1 ).…”

Section: The α 2 /μ Estimatementioning

confidence: 99%

Searching for spatial variations ofα²/μin the Milky Way

Levshakov

Molaro²,

Reimers

2010

A&A

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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.

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“…The variation of CO cooling intensities with rotational number, i.e. the peak of the CO cooling curve, reflects the star forming activity (Bayet et al 2006) and, possibly, also the underlying heating mechanisms. Several mechanisms have been proposed to explain the heating of the ISM in galactic nuclei and it is currently rather unclear which of these dominates in individual sources (e.g.…”

Section: Emission Of Co [C I] (And [C Ii]) Traces the Bulk Of Car-mentioning

confidence: 99%

$^\mathsf{{12}}$CO 4–3 and [CI] 1–0 at the centers of NGC 4945 and Circinus

Hitschfeld

Aravena²,

Krämer

et al. 2007

A&A

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Context. Studying molecular gas in the central regions of the star burst galaxies NGC 4945 and Circinus enables us to characterize the physical conditions and compare them to previous local and high-z studies. Aims. We estimate temperature, molecular density and column densities of CO and atomic carbon. Using model predictions we give a range of estimated CO/C abundance ratios. Methods. Using the new NANTEN2 4 m sub-millimeter telescope in Pampa La Bola, Chile, we observed for the first time CO 4-3 and [C i] 3 P 1 − 3 P 0 at the centers of both galaxies at linear scale of 682 pc and 732 pc respectively. We compute the cooling curves of 12 CO and 13 CO using radiative transfer models and estimate the physical conditions of CO and [CI].Results. 3 P 1 − 3 P 0 /CO 4-3 ratio of integrated intensities are large at 1.2 in NGC 4945 and 2.8 in Circinus. Combining previous CO J = 1−0, 2-1 and 3-2 and 13 CO J = 1−0, 2-1 studies with our new observations, the radiative transfer calculations give a range of densities, n(H 2 ) = 10 3 −3 × 10 4 cm −3 , and a wide range of kinetic temperatures, T kin = 20−100 K, depending on the density. To discuss the degeneracy in density and temperature, we study two representative solutions. In both galaxies the estimated total [CI] cooling intensity is stronger by factors of ∼1−3 compared to the total CO cooling intensity. The CO/C abundance ratios are 0.2−2, similar to values found in Galactic translucent clouds. Conclusions. Our new observations enable us to further constrain the excitation conditions and estimate the line emission of higher-J CO-and the upper [CI]-lines. For the first time we give estimates for the CO/C abundance ratio in the center regions of these galaxies. Future CO J = 7−6 and [CI] 2-1 observations will be important to resolve the ambiguity in the physical conditions and confirm the model predictions.

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A survey of submillimeter C and CO lines in nearby galaxies

Cited by 72 publications

References 72 publications

CS, HC₃N, and CH₃CCH multi-line analyses toward starburst galaxies

CS, HC₃N, and CH₃CCH multi-line analyses toward starburst galaxies

Searching for spatial variations ofα²/μin the Milky Way

$^\mathsf{{12}}$CO 4–3 and [CI] 1–0 at the centers of NGC 4945 and Circinus

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A survey of submillimeter C and CO lines in nearby galaxies

Cited by 72 publications

References 72 publications

CS, HC3N, and CH3CCH multi-line analyses toward starburst galaxies

CS, HC3N, and CH3CCH multi-line analyses toward starburst galaxies

Searching for spatial variations ofα2/μin the Milky Way

$^\mathsf{{12}}$CO 4–3 and [CI] 1–0 at the centers of NGC 4945 and Circinus

Contact Info

Product

Resources

About

CS, HC₃N, and CH₃CCH multi-line analyses toward starburst galaxies

CS, HC₃N, and CH₃CCH multi-line analyses toward starburst galaxies

Searching for spatial variations ofα²/μin the Milky Way