Central molecular zones in galaxies:12CO-to-13CO ratios, carbon budget, andXfactors

Israel, F. P.

doi:10.1051/0004-6361/201834198

Cited by 47 publications

(48 citation statements)

References 212 publications

(112 reference statements)

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“…3. The central parts of normal star-forming galaxies show systematically higher R 21 (e.g., Braine & Combes 1992;Braine et al 1993;Leroy et al 2009Leroy et al , 2013bIsrael 2020;den Brok et al 2021;Yajima et al 2021), consistent with higher densities and hotter gas in the central parts of these galaxies (e.g., Mangum et al 2013;Sun et al 2020, among many others) and with observations showing high temperatures and densities in the center of our own Milky Way (e.g., Ao et al 2013;Ginsburg et al 2016;Krieger et al 2017).…”

supporting

confidence: 75%

Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA

Leroy,

Rosolowsky,

Usero

et al. 2021

Preprint

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We measure the low-J CO line ratio R 21 ≡ CO (2−1)/CO (1−0), R 32 ≡ CO (3−2)/CO (2−1), and R 31 ≡ CO (3−2)/CO (1−0) using whole-disk CO maps of nearby galaxies. We draw CO (2−1) from PHANGS-ALMA, HERACLES, and follow-up IRAM surveys; CO (1−0) from COMING and the Nobeyama CO Atlas of Nearby Spiral Galaxies; and CO (3−2) from the JCMT NGLS and APEX LASMA mapping. Altogether this yields 76, 47, and 29 maps of R 21 , R 32 , and R 31 at 20 ∼ 1.3 kpc resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high stellar mass, log(M /M ) = 10.25−11 and star formation rate, SFR = 1−5 M yr −1 , dominate the sample. We find galaxy-integrated mean values and 16%−84% range of R 21 = 0.65 (0.50−0.83), R 32 = 0.50 (0.23−0.59), and R 31 = 0.31 (0.20−0.42). We identify weak trends relating galaxy-integrated line ratios to properties expected to correlate with excitation, including SFR/M and SFR/L CO . Within galaxies, we measure central enhancements with respect to the galaxy-averaged value of ∼0.18 +0.09 −0.14 dex for R 21 , 0.27 +0.13 −0.15 dex for R 31 , and 0.08 +0.11 −0.09 dex for R 32 . All three line ratios anti-correlate with galactocentric radius and positively correlate with the local star formation rate surface density and specific star formation rate, and we provide approximate fits to these relations. The observed ratios can be reasonably reproduced by models with low temperature, moderate opacity, and moderate densities, in good agree-

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supporting

confidence: 75%

Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA

Leroy,

Rosolowsky,

Usero

et al. 2021

Preprint

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“…Thus far, the [C I](1-0) and CO(1-0) luminosity relation in galaxies has been determined by measurements of CO-bright sources, such as the galactic centers and (U)LIRGs. The relationship in the CO-bright region in the arm of M 83 follows the main relation (C ∼ 1), corresponding to the integrated intensity ratio, 5)), which is comparable to that for the central region of 30 nearby galaxies, R [C I]/CO = 0.16 ± 0.08 (Israel 2020). However, the data from the leading side of the arm (i.e., CO-dark region) is deviated from the main relation, i.e., [C I](1-0) enhancement to CO(1-0).…”

Section: [C I] -Co Correlationsupporting

confidence: 66%

Atomic Carbon [CI]$(^3P_1-^3P_0)$ Mapping of the Nearby Galaxy M83

Miyamoto,

Yasuda,

Watanabe

et al. 2021

Preprint

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Atomic carbon (C I) has been proposed to be a global tracer of the molecular gas as a substitute for CO, however, its utility remains unproven. To evaluate the suitability of C I as the tracer, we performed [C I]( 3 P 1 − 3 P 0 ) (hereinafter [C I](1-0)) mapping observations of the northern part of the nearby spiral galaxy M83 with the ASTE telescope and compared the distributions of [C I](1-0) with CO lines (CO(1-0), CO(3-2), and 13 CO(1-0)), H I, and infrared (IR) emission (70, 160, and 250 µm). The [C I](1-0) distribution in the central region is similar to that of the CO lines, whereas [C I](1-0) in the arm region is distributed outside the CO. We examined the dust temperature, T dust , and dust mass surface density, Σ dust , by fitting the IR continuumspectrum distribution with a single temperature modified blackbody. The distribution of Σ dust shows a much better consistency with the integrated intensity of CO(1-0) than with that of [C I](1-0), indicating that CO(1-0) is a good tracer of the cold molecular gas. The spatial distribution of the [C I] excitation temperature, T ex , was examined using the intensity ratio of the two [C I] transitions. An appropriate T ex at the central, bar, arm, and inter-arm regions yields a constant [C]/[H 2 ] abundance ratio of ∼ 7 × 10 −5 within a range of 0.1 dex in all regions. We successfully detected weak [C I](1-0) emission, even in the inter-arm region, in addition to the central, arm, and bar regions, using spectral stacking analysis. The stacked intensity of [C I](1-0) is found to be strongly correlated with T dust . Our results indicate that the atomic carbon is a photodissociation product of CO, and consequently, compared to CO(1-0), [C I](1-0) is less reliable in tracing the bulk of "cold" molecular gas in the galactic disk.

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“…For example, Crocker et al (2019) modeled the [C I] and CO line emission using large-velocity gradient models and demonstrated that α [CI] = 7.3 M (K km s −1 pc 2 ) −1 and α CO = 0.9 M (K km s −1 pc 2 ) −1 using the Herschel SPIRE results. In the case of Israel (2020), the [C I] to H 2 conversion factor at the central molecular zone in galaxies is calculated as X([C I]) = (9 ± 2) × 10 19 cm −2 /K km s −1 , which corresponds to α [CI] ∼ 2 M (K km s −1 pc 2 ) −1 (they also calculate CO (1-0) to H 2 conversion factor X(CO) = (1.9 ± 0.2) × 10 19 cm −2 /K km s −1 , which is a factor of ten below the standard solar neighborhood Milky Way factor of ∼ 2 × 10 20 cm −2 /K km s −1 ). Conversely, a relatively higher value of α [CI] ∼ 18.8 M (K km s −1 pc 2 ) −1 and α CO ∼ 3.0 M (K km s −1 pc 2 ) −1 was calculated by Dunne et al (2021).…”

Section: Iras F22491-1808mentioning

confidence: 99%

An ACA Survey of [CI] $^3P_1-^3P_0$, CO $J=4-3$, and Dust Continuum in Nearby U/LIRG

Michiyama,

Saito,

Tadaki

et al. 2021

Preprint

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We present the results of surveying [C I] 3 P 1 -3 P 0 , 12 CO J=4-3, and 630 µm dust continuum emission for 36 nearby ultra/luminous infrared galaxies (U/LIRGs) using the Band 8 receiver mounted on the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array. We describe the survey, observations, data reduction, and results; the main results are as follows. (i) We confirmed that [C I] 3 P 1 -3 P 0 has a linear relationship with both the 12 CO J=4-3 and 630 µm continuum. (ii) In NGC 6052 and NGC 7679, 12 CO J=4-3 was detected but [C I] 3 P 1 -3 P 0 was not detected with a [C I] 3 P 1 -3 P 0 / 12 CO J=4-3 ratio of 0.08. Two possible scenarios of weak [C I] 3 P 1 -3 P 0 emission are C 0 -poor/CO-rich environments or an environment with an extremely large [C I] 3 P 1 -3 P 0 missing flux. (iii) There is no clear evidence showing that galaxy mergers, AGNs, and dust temperatures control the ratios of [C I] 3 P 1 -3 P 0 / 12 CO J=4-3 and L [CI](1−0) /L 630µm . (iv) We compare our nearby U/LIRGs with high-z galaxies, such as galaxies on the star formation main sequence (MS) at z∼ 1 and submillimeter galaxies (SMGs) at z = 2 − 4. We found that the mean value for the [C I] 3 P 1 -3 P 0 / 12 CO J=4-3 ratio of U/LIRGs is similar to that of SMGs but smaller than that of galaxies on the MS.

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Central molecular zones in galaxies:¹²CO-to-¹³CO ratios, carbon budget, andXfactors

Cited by 47 publications

References 212 publications

Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA

Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA

Atomic Carbon [CI]$(^3P_1-^3P_0)$ Mapping of the Nearby Galaxy M83

An ACA Survey of [CI] $^3P_1-^3P_0$, CO $J=4-3$, and Dust Continuum in Nearby U/LIRG

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