Excited OH+, H2O+, and H3O+in NGC 4418 and Arp 220

González-Alfonso, E.; Fischer, J.; Bruderer, S.; Müller, H. S. P.; Graciá-Carpio, J.; Sturm, E.; Lutz, D.; Poglitsch, A.; Feuchtgruber, H.; Veilleux, Sylvain; Contursi, A.; Sternberg, A.; Hailey-Dunsheath, S.; Verma, Aprajita; Christopher, N.; Davies, R. I.; Genzel, R.; Tacconi, L. J.

doi:10.1051/0004-6361/201220466

Cited by 108 publications

(90 citation statements)

References 88 publications

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“…After subtracting this profile, the absorption lines appear to be centered on ∼−135 and 11 km s −1 with widths of 210 and 130 km s −1 , respectively. Our corrected blueshifted absorption agrees better with the average velocity centroid of −110 ± 10 km s −1 (relative to z = 0.018126) measured with several HCN IR absorption profiles (González-Alfonso et al 2013), which supports our result and thus the assumption of an underlying Gaussian emission profile.…”

Section: Absorption Systemssupporting

confidence: 91%

The unbearable opaqueness of Arp220

Martín

Aalto

Sakamoto

et al. 2016

A&A

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Context. The origin of the enormous luminosities of the two opaque nuclei of Arp 220, the prototypical ultra-luminous infrared galaxy, remains a mystery because we lack observational tools to explore the innermost regions around the nuclei. Aims. We explore the potential of imaging vibrationally excited molecular emission at high angular resolution to better understand the morphology and physical structure of the dense gas in Arp 220 and to gain insight into the nature of the nuclear powering sources. Methods. The Atacama Large Millimeter/submillimeter Array (ALMA) provided simultaneous observations of HCN, HCO + , and vibrationally excited HCN v 2 = 1 f emission. Their J = 4-3 and 3-2 transitions were observed at a matching resolution of ∼0.5 , which allows us to isolate the emission from the two nuclei. Results. The HCN and HCO + lines within the ground-vibrational state poorly describe the central ∼100 pc region around the nuclei because there are strong effects of cool absorbing gas in the foreground and severe line blending that is due to the prolific molecular emission of Arp 220. Vibrationally excited emission of HCN is detected in both nuclei with a very high ratio relative to the total L FIR , higher than in any other observed galaxy and well above what is observed in Galactic hot cores. HCN v 2 = 1 f is observed to be marginally resolved in ∼60 × 50 pc regions inside the dusty ∼100 pc sized nuclear cores. Its emission is centered on our derived individual nuclear velocities based on HCO + emission (V WN = 5342 ± 4 and V EN = 5454 ± 8 km s −1 , for the western and eastern nucleus, respectively). With virial masses within r ∼ 25-30 pc based on the HCN v 2 = 1 f line widths, we estimate gas surface densities (gas fraction f g = 0.1) of 3 ± 0.3 × 10 4 M pc −2 (WN) and 1.1 ± 0.1 × 10 4 M pc −2 (EN). The 4−3/3−2 flux density ratio could be consistent with optically thick emission, which would further constrain the size of the emitting region to >15 pc (EN) and >22 pc (WN). The absorption systems that may hide up to 70% of the HCN and HCO + emission are found at velocities of −50 km s −1 (EN) and 6, −140, and −575 km s −1 (WN) relative to velocities of the nuclei. Blueshifted absorptions are the evidence of outflowing motions from both nuclei. Conclusions. Although vibrationally excited molecular transitions could also be affected by opacity, they may be our best tool to peer into the central few tens of parsecs around compact obscured nuclei like those of Arp 220. The bright vibrational emission implies the existence of a hot dust region radiatively pumping these transitions. We find evidence of a strong temperature gradient that would be responsible for both the HCN v 2 pumping and the absorbed profiles from the vibrational ground state as a result of both continuum and self-absorption by cooler foreground gas.

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Section: Absorption Systemssupporting

confidence: 91%

The unbearable opaqueness of Arp220

Martín

Aalto

Sakamoto

et al. 2016

A&A

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“…Recently, PACS observations of excited OH + , H 2 O + and H 3 O + toward NGC 4418 and Arp. 220 have been discussed by González-Alfonso et al (2013). The Orion Bar is special in our Galaxy for its large column density of warm, mostly-atomic gas and its weak far-infrared continuum; we suspect that extragalactic nuclei where H n O + lines appear in emission have similar conditions.…”

Section: Comparison With Extragalactic Systemsmentioning

confidence: 85%

Spatially extended OH⁺emission from the Orion Bar and Ridge

Tak

Nagy

Ossenkopf

et al. 2013

A&A

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ContextWe analyze these HIFI data with non-local thermodynamic equilibrium radiative transfer and PDR chemical models, using newly calculated inelastic collision data for the e-OH + system. Results. Line emission is detected over ∼1 (0.12 pc), tracing the Bar itself as well as a perpendicular feature identified as the southern tip of the Orion Ridge, which borders the Orion Nebula on its western side. The line width of ≈4 km s −1 suggests an origin of the OH + emission close to the PDR surface, at a depth of A V ∼ 0.3-0.5 into the cloud where most hydrogen is in atomic form. Steadystate collisional and radiative excitation models for OH + require unrealistically high column densities to match the observed line intensity, indicating that the formation of OH + in the Bar is rapid enough to influence its excitation. Our best-fit OH + column density of ∼1.0 × 10 14 cm −2 is similar to that in previous absorption line studies, while our limits on the ratios of OH + /H 2 O + ( > ∼ 40) and OH + /H 3 O + ( > ∼ 15) are somewhat higher than seen before. Conclusions. The column density of OH + is consistent with estimates from a thermo-chemical model for parameters applicable to the Orion Bar, given the current uncertainties in the local gas pressure and the spectral shape of the ionizing radiation field. The unusually high OH + /H 2 O + and OH + /H 3 O + ratios are probably due to the high UV radiation field and electron density in this object. In the Bar, photodissociation and electron recombination are more effective destroyers of OH + than the reaction with H 2 , which limits the production of H 2 O + . The appearance of the OH + lines in emission is the result of the high density of electrons and H atoms in the Orion Bar, since for these species, inelastic collisions with OH + are faster than reactive ones. In addition, chemical pumping, far-infrared pumping by local dust, and near-UV pumping by Trapezium starlight contribute to the OH + excitation. Similar conditions may apply to extragalactic nuclei where H n O + lines are seen in emission.

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“…Observations with PACS for the 43 ULIRGs were split between the HERUS program Spoon et al 2013) and the SHINING program Sturm et al 2011;Hailey-Dunsheath et al 2012a;González-Alfonso et al 2013;Mashian et al 2015). A similar study of the intermediate redshift ULIRG population (0.21<z<0.88) was presented by Rigopoulou et al (2014) and Magdis et al (2014).…”

Section: Observationsmentioning

confidence: 97%

HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

Pearson¹,

Rigopoulou²,

Hurley³

et al. 2016

ApJS

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We present the Herschel SPIRE Fourier Transform Spectroscopy (FTS) atlas for a complete flux-limited sample of local ultraluminous infrared galaxies (ULIRGs) as part of the HERschel Ultra Luminous InfraRed Galaxy Survey (HERUS). The data reduction is described in detail and was optimized for faint FTS sources ,with particular care being taken for the subtraction of the background, which dominates the continuum shape of the spectra. To improve the final spectra, special treatment in the data reduction has been given to any observation suffering from artifacts in the data caused by anomalous instrumental effects. Complete spectra are shown covering 200-671 μm, with photometry in the SPIRE bands at 250, 350, and 500 μm. The spectra include near complete CO ladders for over half of our sample, as well as fine structure lines from [C I] 370 μm, [C I] 609 μm, and [N II] 205 μm. We also detect H 2 O lines in several objects. We construct CO spectral line energy distributions (SLEDs) for the sample, and compare their slopes with the far-infrared (FIR) colors and luminosities. We show that the CO SLEDs of ULIRGs can be broadly grouped into three classes based on their excitation. We find that the mid-J (5<J<8) lines are better correlated with the total FIR luminosity, suggesting that the warm gas component is closely linked to recent star formation. The higher J transitions do not linearly correlate with the FIR luminosity, consistent with them originating in hotter, denser gas that is unconnected to the current star formation. We conclude that in most cases more than one temperature component is required to model the CO SLEDs.

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Excited OH⁺, H₂O⁺, and H₃O⁺in NGC 4418 and Arp 220

Cited by 108 publications

References 88 publications

The unbearable opaqueness of Arp220

The unbearable opaqueness of Arp220

Spatially extended OH⁺emission from the Orion Bar and Ridge

HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

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Excited OH+, H2O+, and H3O+in NGC 4418 and Arp 220

Cited by 108 publications

References 88 publications

The unbearable opaqueness of Arp220

The unbearable opaqueness of Arp220

Spatially extended OH+emission from the Orion Bar and Ridge

HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

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Product

Resources

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Excited OH⁺, H₂O⁺, and H₃O⁺in NGC 4418 and Arp 220

Spatially extended OH⁺emission from the Orion Bar and Ridge