S[CLC]i[/CLC]O Emission from the Galactic Center Molecular Clouds

Martı́n-Pintado, J.; Vicente, P. de; Fuente, A.; Planesas, P.

doi:10.1086/310691

Cited by 151 publications

(158 citation statements)

References 23 publications

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“…6.2.1 suggest an enhancement of SiO abundances at the extreme velocities identified in the CND. A similar link between density waves and large-scale molecular shocks has been proposed to explain the enhancement of SiO in the circum-nuclear disks of our Galaxy (Martín-Pintado et al 1997;Hüttemeister et al 1998;Rodríguez-Fernández et al 2006) and of the starburst galaxies IC 342 and NGC 253 (Usero et al 2006;García-Burillo et al 2000). Usero et al (2006) analyzed the large-scale molecular shocks produced in the ILR region of IC 342.…”

Section: Tracers Of Shocks In Ngc 1068supporting

confidence: 52%

Molecular gas chemistry in AGN

García‐Burillo

Usero

Fuente

et al. 2010

A&A

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Context. This paper is part of a multi-species survey of line emission from the molecular gas in the circum-nuclear disk (CND) of the Seyfert 2 galaxy NGC 1068. Unlike in other active galaxies, the intensely star-forming regions in NGC 1068 and the CND can be resolved with current instrumentation. This makes this galaxy an optimal test-bed to probe the effects of AGN on the molecular medium at ∼100 pc scales. Aims. Single-dish observations have provided evidence that the abundance of silicon monoxide (SiO) in the CND of NGC 1068 is enhanced by 3-4 orders of magnitude with respect to the values typically measured in quiescent molecular gas in the Galaxy. We aim at unveiling the mechanism(s) underlying the SiO enhancement. Methods. We have imaged the emission of the SiO(2−1) (86.8 GHz) and CN(2−1) (226.8 GHz) lines in NGC 1068 at ∼150 pc and 60 pc spatial resolution with the IRAM Plateau de Bure interferometer (PdBI). We have also obtained complementary IRAM 30 m observations of HNCO and methanol (CH 3 OH) lines. These species are known as tracers of shocks in the Galaxy. Results. SiO is detected in a disk of ∼400 pc size around the AGN. SiO abundances in the CND of ∼(1−5)×10 −9 are about 1−2 orders of magnitude above those measured in the starburst ring. The overall abundance of CN in the CND is high: ∼(0.2−1) × 10 −7 . The abundances of SiO and CN are enhanced at the extreme velocities of gas associated with non-circular motions close to the AGN (r < 70 pc). On average, HNCO/SiO and CH 3 OH/SiO line ratios in the CND are similar to those measured in prototypical shocked regions in our Galaxy. Yet the strength and abundance of CN in NGC 1068 can be explained neither by shocks nor by photondominated region (PDR) chemistry. Abundances measured for CN and SiO and the correlation of CN/CO and SiO/CO ratios with hard X-ray irradiation suggest that the CND of NGC 1068 has become a giant X-ray-dominated region (XDR). Conclusions. The extreme properties of molecular gas in the circum-nuclear molecular disk of NGC 1068 result from the interplay between different processes directly linked to nuclear activity. The results presented here highlight in particular the footprint of shocks and X-ray irradiation on the properties of molecular gas in this Seyfert. Whereas XDR chemistry offers a simple explanation for CN and SiO in NGC 1068, the relevance of shocks deserves further scrutiny. The inclusion of dust grain chemistry would help solve the controversy regarding the abundances of other molecular species, like HCN, which are under-predicted by XDR models.

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Section: Tracers Of Shocks In Ngc 1068supporting

confidence: 52%

Molecular gas chemistry in AGN

García‐Burillo

Usero

Fuente

et al. 2010

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126

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“…First, we have targeted mIR sources. The bulk of the interstellar SiO emission in the Galactic centre is not associated with mIR radiation (Martin-Pintado et al 1997). Furthermore, our SiO maser lines are generally narrower than the 10-50 km s −1 found for shocked and energetic outflows associated with young stars.…”

Section: Confusion With Interstellar Sio Emissioncontrasting

confidence: 44%

“…However, a second ISOGAL source, ISOGAL−PJ174232.9−294124, happened to fall inside the beam, at 15.6 from the position we targeted. Martin-Pintado et al 1997). The SiO emission in #94 may not be associated with the circumstellar envelope close to the star as in all other cases, as its profile may be more typical to that of bipolar molecular outflows.…”

Section: Comments On Individual Objectsmentioning

confidence: 88%

86 GHz SiO maser survey of late-type stars in the Inner Galaxy

Messineo¹,

Habing²,

Sjouwerman³

et al. 2002

A&A

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Abstract. We present 86 GHz (v = 1, J = 2 → 1) SiO maser line observations with the IRAM 30-m telescope of a sample of 441 late-type stars in the Inner Galaxy (−4 • < l < +30 • ). These stars were selected on the basis of their infrared magnitudes and colours from the ISOGAL and MSX catalogues. SiO maser emission was detected in 271 sources, and their line-of-sight velocities indicate that the stars are located in the Inner Galaxy. These new detections double the number of line-of-sight velocities available from previous SiO and OH maser observations in the area covered by our survey and are, together with other samples of e.g. OH/IR stars, useful for kinematic studies of the central parts of the Galaxy.

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“…For the lower longitudes in the CMZ, the heating could be explained by interactions with SNRs close to Sgr A and also with nonthermal filaments in the radio arc, and cloud-cloud collisions, and expanding bubbles in the vicinity of Sgr B (Martín-Pintado et al 1997). Cloud-cloud collisions were also proposed in the GC region (Wilson et al 1982), which is favored by the large linewidth typical of the GC clouds.…”

Section: The Heating Of the Gas In The Gcmentioning

confidence: 99%

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

Riquelme

Amo-Baladrón

Martı́n-Pintado

et al. 2012

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Context. It is well known that the kinetic temperatures, T kin , of the molecular clouds in the Galactic center region are higher than in typical disk clouds. However, the T kin of the molecular complexes found at higher latitudes towards the giant molecular loops in the central region of the Galaxy is so far unknown. The gas of these high-latitude molecular clouds (hereafter referred to as "halo clouds") is located in a region where the gas in the disk may interact with the gas in the halo in the Galactic center region. Aims. To derive T kin in the molecular clouds at high latitude and understand the physical process responsible for the heating of the molecular gas both in the central molecular zone (the concentration of molecular gas in the inner ∼500 pc) and in the giant molecular loops. Methods. We measured the metastable inversion transitions of NH 3 from (J, K) = (1, 1) to (6, 6) toward six positions selected throughout the Galactic central disk and halo. We used rotational diagrams and large velocity gradient (LVG) modeling to estimate the kinetic temperatures toward all the sources. We also observed other molecules like SiO, HNCO, CS, C 34 S, C 18 O, and 13 CO, to derive the densities and to trace different physical processes (shocks, photodissociation, dense gas) expected to dominate the heating of the molecular gas. Results. We derive for the first time T kin of the high-latitude clouds interacting with the disk in the Galactic center region. We find high rotational temperatures in all the observed positions. We derive two kinetic temperature components (∼150 K and ∼40 K) for the positions in the central molecular zone, and only the warm kinetic temperature component for the clouds toward the giant molecular loops. The fractional abundances derived from the different molecules suggest that shocks provide the main heating mechanism throughout the Galactic center, also at high latitudes.

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S[CLC]i[/CLC]O Emission from the Galactic Center Molecular Clouds

Cited by 151 publications

References 23 publications

Molecular gas chemistry in AGN

Molecular gas chemistry in AGN

86 GHz SiO maser survey of late-type stars in the Inner Galaxy

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region

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