Spatially Resolved Chemistry in Nearby Galaxies. Ii. The Nuclear Bar in Maffei 2

Meier, David S.; Turner, Jean L.

doi:10.1088/0004-637x/755/2/104

Cited by 68 publications

(74 citation statements)

References 109 publications

(141 reference statements)

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“…9) toward the south-east CND region where the peak line emission is found for most species, with a significant but not too prominent (∼60%) relative abundance decrease toward the north-western part of the CND. In addition its abundance is also significant outside of the CND plane defined by HNCO, which might be linked to outflowing material similar to what is observed in Maffei 2 (Meier & Turner 2012). The differences observed might be due to temperature affecting its chemistry.…”

Section: Cs and Cchmentioning

confidence: 57%

“…On the other hand, the difference between their critical densities might suggest that HCO + is mostly concentrated toward the nuclear region where the densities are moderate ∼10 4.5 cm −3 , with a higher density region ranging 100−200 pc around the AGN. This scenario is equivalent to that discussed toward local starbursts (Meier & Turner 2012;Meier et al 2014), though the actual density structure and morphology is likely to differ in both galaxy types.…”

Section: The Hcn/hco + Gradientmentioning

confidence: 65%

“…As discussed above when comparing with the starburst ring, this gradient could be revealing the direct effect of the AGN imprinted in the molecular abundances on its immediate surroundings. However, it has been claimed that the variation of this ratio could be the result of a density gradient, or due to differences in the opacity of these species (Meier & Turner 2012;Meier et al 2014).…”

Section: The Hcn/hco + Gradientmentioning

confidence: 99%

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Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Martín

Kohno

Izumi

et al. 2015

A&A

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Context. The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory for exploring the molecular chemistry in the surroundings of an active galactic nucleus (AGN). Aims. Exploring the distribution of different molecular species allows us to understand the physical processes affecting the interstellar medium both in the AGN vicinity and in the outer star forming molecular ring. Methods. We carried out 3 mm ALMA observations that include seven different molecular species, namely HCN, HCO + , CCH, CS, HNCO, SiO, HC 3 N, and SO, as well as the 13 C isotopologues of the first two. Spectra were extracted from selected positions and all species were imaged over the central 2 kpc (∼30 ) of the galaxy at a resolution of ∼2.2 × 1.5 (150 pc × 100 pc). Results. HCO + and CS appear to be slightly enhanced in the star forming ring. CCH shows the largest variations across NGC 1097 and is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO, and HC 3 N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Conclusions. Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO + and HCN/CS differences observed between AGN-dominated and starburst (SB) galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally, we claim that lower HCN/CS is a combination of a small underabundance of CS in AGNs, together with excitation effects, where a high density gas component (∼10 6 cm −3 ) may be more prominent in SB galaxies. However, the most promising are the differences found among the dense gas tracers that, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well-shielded gas in the disk, surrounding the dense material moderately exposed to the X-ray radiation traced by HC 3 N. Finally SiO might be the innermost molecule in the disk structure.

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Section: Cs and Cchmentioning

confidence: 57%

Section: The Hcn/hco + Gradientmentioning

confidence: 65%

Section: The Hcn/hco + Gradientmentioning

confidence: 99%

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Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Martín

Kohno

Izumi

et al. 2015

A&A

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“…However, more recent chemical models find that the HCO + /HCN abundance ratio is a strong function of density and ionizing radiation, (e.g., Meijerink et al 2007), and that a low line ratio could be either caused by low-density (<10 5 cm −3 ) XDRs or dense (>10 5 cm −3 ) PDRs. In addition, given the different critical densities of the J = 1-0 transition of HCN and HCO + , localized variations in the ratios could be explained by variations in density (e.g., Meier & Turner 2012). …”

Section: Standard Line Ratios: Hcn Hnc and Hco +mentioning

confidence: 99%

Exploring the molecular chemistry and excitation in obscured luminous infrared galaxies

Costagliola

Sakamoto

Müller

et al. 2015

A&A

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Context. Extragalactic observations allow the study of molecular chemistry and excitation under physical conditions which may differ greatly from those found in the Milky Way. The compact, obscured nuclei (CON) of luminous infrared galaxies (LIRG) combine large molecular columns with intense infrared (IR), ultra-violet (UV), and X-radiation and represent ideal laboratories for the study of the chemistry of the interstellar medium (ISM) under extreme conditions. Aims. Our aim was to obtain for the first time a multi-band spectral scan of a LIRG, and to derive molecular abundances and excitation to be compared to other Galactic and extragalactic environments. Methods. We obtained an ALMA Cycle 0 spectral scan of the dusty LIRG NGC 4418, spanning a total of 70.7 GHz in bands 3, 6, and 7. We use a combined local thermal equilibrium (LTE) and non-LTE (NLTE) fit of the spectrum in order to identify the molecular species and to derive column densities and excitation temperatures. We derive molecular abundances and compare them with other Galactic and extragalactic sources by means of a principal component analysis. Results. We detect 317 emission lines from a total of 45 molecular species, including 15 isotopic substitutions and 6 vibrationally excited variants. Our LTE/NLTE fit find kinetic temperatures from 20 to 350 K, and densities between 10 5 and 10 7 cm −3 . The spectrum is dominated by vibrationally excited HC 3 N, HCN, and HNC, with vibrational temperatures from 300 to 450 K. We find that the chemistry of NCG 4418 is characterized by high abundances of HC 3 N, SiO, H 2 S, and c-HCCCH but a low CH 3 OH abundance. A principal component analysis shows that NGC 4418 and Arp 220 share very similar molecular abundances and excitation, which clearly set them apart from other Galactic and extragalactic environments. Conclusions. Our spectral scan confirms that the chemical complexity in the nucleus of NGC 4418 is one of the highest ever observed outside our Galaxy. The similar molecular abundances observed toward NCG 4418 and Arp 220 are consistent with a hot gas-phase chemistry, with the relative abundances of SiO and CH 3 OH being regulated by shocks and X-ray driven dissociation. The bright emission from vibrationally excited species confirms the presence of a compact IR source, with an effective diameter smaller than 5 pc and brightness temperatures higher than 350 K. The molecular abundances and the vibrationally excited spectrum are consistent with a young AGN/starburst system. We suggest that NGC 4418 may be a template for a new kind of chemistry and excitation, typical of CON. Because of the narrow line widths and bright molecular emission, NGC 4418 is the ideal target for further studies of the chemistry in CONs.

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“…With molecular lines of different species and their different transitions, not only can the chemical composition of the interstellar medium be investigated, but other important physical parameters, such as temperature, pressure, density, and non-collisional pumping mechanisms can be derived as well (e.g., Henkel et al 1991;Evans 1999;Fukui & Kawamura 2010;Meier & Turner 2012;Meier et al 2014). New facilities providing wide band and highly sensitive instruments are making weak line surveys and multi-species analyses feasible, and the detections and measurements of a variety of species are helping us to reveal the gas components of galaxies, and how their abundances, densities, and ratios reflect their radiative properties.…”

Section: Introductionmentioning

confidence: 99%

HC₃N observations of nearby galaxies

Jiang

Wang

Gao

et al. 2017

A&A

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Aims. We aim to systematically study the properties of the different transitions of the dense molecular gas tracer HC 3 N in galaxies. Methods. We have conducted single-dish observations of HC 3 N emission lines towards a sample of nearby gas-rich galaxies. HC 3 N(J = 2−1) was observed in 20 galaxies with the Effelsberg 100-m telescope. HC 3 N(J = 24−23) was observed in nine galaxies with the 10-m Submillimeter Telescope (SMT). Results. HC 3 N 2−1 is detected in three galaxies: IC 342, M 66, and NGC 660 (>3σ). HC 3 N 24−23 is detected in three galaxies: IC 342, NGC 1068, and IC 694. These are the first measurements of HC 3 N 2−1 in a relatively large sample of external galaxies, although the detection rate is low. For the HC 3 N 2−1 non-detections, upper limits (2σ) are derived for each galaxy, and stacking the non-detections is attempted to recover the weak signal of HC 3 N. The stacked spectrum, however, does not show any significant signs of HC 3 N 2−1 emission. The results are also compared with other transitions of HC 3 N observed in galaxies. Conclusions. The low detection rate of both transitions suggests low abundance of HC 3 N in galaxies, which is consistent with other observational studies. The comparison between HC 3 N and HCN or HCO + shows a large diversity in the ratios between HC 3 N and HCN or HCO + . More observations are needed to interpret the behavior of HC 3 N in different types of galaxies.

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Spatially Resolved Chemistry in Nearby Galaxies. Ii. The Nuclear Bar in Maffei 2

Cited by 68 publications

References 109 publications

Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Exploring the molecular chemistry and excitation in obscured luminous infrared galaxies

HC₃N observations of nearby galaxies

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Spatially Resolved Chemistry in Nearby Galaxies. Ii. The Nuclear Bar in Maffei 2

Cited by 68 publications

References 109 publications

Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097

Exploring the molecular chemistry and excitation in obscured luminous infrared galaxies

HC3N observations of nearby galaxies

Contact Info

Product

Resources

About

HC₃N observations of nearby galaxies