Probing planet formation and disk substructures in the inner disk of Herbig Ae stars with CO rovibrational emission

Context. CO rovibrational lines are efficient probes of warm molecular gas and can give unique insights into the inner 10 AU of proto-planetary disks, effectively complementing ALMA observations. Recent studies find a relation between the ratio of lines originating from the second and first vibrationally excited state, denoted as v2∕v1, and the Keplerian velocity or emitting radius of CO. Counterintuitively, in disks around Herbig Ae stars the vibrational excitation is low when CO lines come from close to the star, and high when lines only probe gas at large radii (more than 5 AU). The v2∕v1 ratio is also counterintuitively anti-correlated with the near-infrared (NIR) excess, which probes hot and warm dust in the inner disk. Aims. We aim to find explanations for the observed trends between CO vibrational ratio, emitting radii and NIR excess, and to identify their implications in terms of the physical and chemical structure of inner disks around Herbig stars. Methods. First, slab model explorations in local thermal equilibrium (LTE) and non-LTE are used to identify the essential parameter space regions that can produce the observed CO emission. Second, we explore a grid of thermo-chemical models using the DALI code, varying gas-to-dust ratio and inner disk radius. Line flux, line ratios, and emitting radii are extracted from the simulated lines in the same way as the observations and directly compared to the data. Results. Broad CO lines with low vibrational ratios are best explained by a warm (400–1300 K) inner disk surface with gas-to-dust ratios below 1000 (NCO < 1018 cm−2); no CO is detected within or at the inner dust rim, due to dissociation at high temperatures. In contrast, explaining the narrow lines with high vibrational ratios requires an inner cavity of a least 5 AU in both dust and gas, followed by a cool (100–300 K) molecular gas reservoir with gas-to-dust ratios greater than 10 000 (NCO > 1018 cm−2) at the cavity wall. In all cases, the CO gas must be close to thermalization with the dust (Tgas ~ Tdust). Conclusions. The high gas-to-dust ratios needed to explain high v2∕v1 in narrow CO lines for a subset of group I disks can be naturally interpreted as due to the dust traps that are proposed to explain millimeter dust cavities. The dust trap and the low gas surface density inside the cavity are consistent with the presence of one or more massive planets. The difference between group I disks with low and high NIR excess can be explained by gap opening mechanisms that do or do not create an efficient dust trap, respectively. The broad lines seen in most group II objects indicate a very flat disk in addition to inner disk substructures within 10 AU that can be related to the substructures recently observed with ALMA. We provide simulated ELT-METIS images to directly test these scenarios in the future.

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Central kiloparsec of NGC 1326 observed with SINFONI

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936451 ◽

2020 ◽

Vol 638 ◽

pp. A53

Author(s):

Nastaran Fazeli ◽

Gerold Busch ◽

Andreas Eckart ◽

Françoise Combes ◽

Persis Misquitta ◽

...

Keyword(s):

Black Hole ◽

Galaxy Evolution ◽

Near Infrared ◽

Velocity Fields ◽

Molecular Gas ◽

Nearby Galaxy ◽

Stellar Content ◽

Stellar Rotation ◽

Supermassive Black Hole ◽

Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

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Line identification in high-resolution, near-infrared CRIRES spectra of chemically peculiar and Herbig Ae stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201218968 ◽

2012 ◽

Vol 542 ◽

pp. A31 ◽

Cited By ~ 10

Author(s):

S. Hubrig ◽

F. Castelli ◽

J. F. González ◽

V. G. Elkin ◽

G. Mathys ◽

...

Keyword(s):

High Resolution ◽

Near Infrared ◽

Chemically Peculiar ◽

Line Identification ◽

Herbig Ae Stars

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Shocked Molecular Hydrogen from Star Forming Regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900095371 ◽

1987 ◽

Vol 115 ◽

pp. 181-181 ◽

Cited By ~ 2

Author(s):

Adair P. Lane ◽

John Bally

Keyword(s):

Shock Waves ◽

High Velocity ◽

Molecular Hydrogen ◽

Near Infrared ◽

Young Stars ◽

Emission Lines ◽

Molecular Gas ◽

Star Forming ◽

Star Forming Regions ◽

Post Shock

Near infrared (2 micron) emission lines from molecular hydrogen provide a powerful probe of the morphology and energetics of outflows associated with stellar birth. The H2 emission regions trace the location of shock waves formed when the high velocity outflow from young stars encounters dense quiescent gas. Since H2 is the dominant coolant of the hot post-shock molecular gas, the H2 lines provide a measure of the fraction of the total mechanical luminosity radiated away from the cloud.

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Precise Measurements of CH Maser Emission and Its Abundance in Translucent Clouds

The Astrophysical Journal Supplement Series ◽

10.3847/1538-4365/ac27a5 ◽

2021 ◽

Vol 257 (2) ◽

pp. 47

Author(s):

Ningyu Tang ◽

Di Li ◽

Gan Luo ◽

Carl Heiles ◽

Sheng-Li Qin ◽

...

Keyword(s):

Thermal Equilibrium ◽

Column Density ◽

High Sensitivity ◽

Local Thermal Equilibrium ◽

Molecular Gas ◽

Excitation Temperature ◽

Hyperfine Transitions ◽

Visible Wavelengths ◽

Log Normal ◽

Log Normal Distribution

Abstract We present high-sensitivity CH 9 cm ON/OFF observations toward 18 extragalactic continuum sources that have been detected with OH 18 cm absorption in the Millennium survey with the Arecibo telescope. CH emission was detected toward 6 of the 18 sources. The excitation temperature of CH has been derived directly through analyzing all detected ON and OFF velocity components. The excitation temperature of CH 3335 MHz transition ranges from −54.5 to −0.4 K and roughly follows a log-normal distribution peaking within [−5, 0] K, which implies overestimation by 20% to more than 10 times during calculating CH column density by assuming the conventional value of −60 or −10 K. Furthermore, the column density of CH would be underestimated by a factor of 1.32 ± 0.03 when adopting local thermal equilibrium assumption instead of using the CH three hyperfine transitions. We found a correlation between the column density of CH and OH following log N(CH) = (1.80 ± 0.49) and log N(OH −11.59 ± 6.87. The linear correlation between the column density of CH and H2 is consistent with that derived from visible wavelengths studies, confirming that CH is one of the best tracers of H2 components in diffuse molecular gas.

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Radiant Interchange Between Circular Disks Having Arbitrarily Different Temperatures

Journal of Heat Transfer ◽

10.1115/1.3683676 ◽

1961 ◽

Vol 83 (4) ◽

pp. 494-502 ◽

Cited By ~ 7

Author(s):

E. M. Sparrow ◽

J. L. Gregg

Keyword(s):

Heat Transfer ◽

Numerical Solutions ◽

Local Heat Transfer ◽

Disk Surface ◽

Radiant Heat ◽

Local Heat ◽

Radiant Heat Transfer ◽

Disk Radius ◽

Integral Equation Formulation ◽

Different Temperatures

The problem of radiant heat transfer between parallel disks has been analyzed by generalizing the standard gray-body enclosure theory. In particular, the assumption that the radiant flux leaving a surface and the local heat flux are uniformly distributed over the surface has been lifted by an integral equation formulation. It has been shown that the general problem of disks at arbitrarily different temperatures can be conveniently broken down into two subproblems, each of which can be solved independently of the temperature level. Numerical solutions of the governing integral equations have been carried out for spacing ratios h/R (h = spacing, R = disk radius) ranging from 5.0 to 0.05 and for emissivities ranging from 0.1 to 0.9. Local heat-transfer results have been presented which, depending on spacing and emissivity, display marked variations over the disk surface. Over-all heat-transfer results have been calculated and compared with the predictions of the standard simplified enclosure theory. These predictions of the simplified theory were found to be unexpectedly good, especially in view of the large surface variations of the local heat transfer.

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Feeding Versus Feedback in AGNs from Near-Infrared IFU Observations: The Case of Mrk 1066

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310006897 ◽

2009 ◽

Vol 5 (S267) ◽

pp. 405-405

Author(s):

Rogemar A. Riffel ◽

Thaisa Storchi-Bergmann

Keyword(s):

Spatial Resolution ◽

Central Region ◽

Near Infrared ◽

Galactic Plane ◽

Seyfert Galaxy ◽

Active Galaxies ◽

Molecular Gas ◽

Field Observations ◽

Ionized Gas ◽

Integral Field

Previous studies of the central region of active galaxies show that the molecular and ionized gas have distinct kinematics and flux distributions, with the former dominated by quiescent kinematics characteristic of rotation in the galactic plane and the latter with more disturbed kinematics and apparently extending to larger galactic latitudes. These results suggest that the molecular gas can be a tracer of the feeding of the AGN and the ionized gas a tracer of its feedback (e.g., Riffel et al. 2009, 2008, 2006; Storchi-Bergmann et al. 2009a, b). In the present study we use Gemini NIFS integral field observations of the inner 700×700 pc2 of the Seyfert galaxy Mrk 1066 at a spatial resolution of ~ 35 pc to investigate if the above scenario is also valid for this galaxy.

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Surface Modification and Ablation of Insulators Using a Tunable, Picosecond Mid-Infrared Laser

MRS Proceedings ◽

10.1557/proc-526-3 ◽

1998 ◽

Vol 526 ◽

Cited By ~ 2

Author(s):

R. F. Haglund ◽

D. R. Ermer ◽

A. H. Lines ◽

M. R. Papantonakis ◽

H. K. Park ◽

...

Keyword(s):

Surface Modification ◽

Near Infrared ◽

Energy Content ◽

Laser Energy ◽

Vibrational Excitation ◽

Average Power ◽

Surface Modifications ◽

Fused Silica ◽

Laser Source ◽

Near Ultraviolet

AbstractUltrashort-pulse lasers with fundamental wavelengths ranging from near-infrared to near-ultraviolet are increasingly being used for laser-induced surface modification of non-metallic solids. The relaxation of the initial electronic excitation into vibrational relaxation modes can produce efficient ablation and other desirable surface modifications with little collateral damage because the laser energy is deposited on a time scale much shorter than thermal diffusion times. Little is known, however, about how ultrashort pulses interact with insulators at wavelengths in the vibrational infrared. This paper describes surface modifications achieved by picosecond laser irradiation in the 2-10 lim range. The laser source was a tunable, free-electron laser (FEL) with I-ps micro-pulses spaced 350 ps apart in a macropulse lasting up to 4 μs, with an average power of up to 3 W. This unusual pulse structure makes possible novel tests of the influences vs fluence and intensity, as well as the effects of resonant vibrational excitation. As model materials systems, we studied calcium carbonate, its isoelectronic cousin sodium nitrate, and fused silica. Particularly intriguing are surface modifications achieved by tuning the laser into vibrational resonances and overtones of the target materials, or by tailoring the energy content of the pulse. The mechanisms underlying these effects, and their implications for materials-modification strategies, are discussed.

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Near infrared spectroscopy of protostars

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1981.0217 ◽

1981 ◽

Vol 303 (1480) ◽

pp. 487-496

Keyword(s):

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Gas Dynamics ◽

Near Infrared ◽

Molecular Gas ◽

Orion Nebula ◽

Ionized Gas ◽

Physical Conditions ◽

Vibrational Bands ◽

Optical Wavelengths

Observational study of protostars and their immediate environs has recently become possible as a result of advances in infrared spectroscopy, especially in the near infrared (A = 2—5 pm). Although such stars are totally obscured at optical wavelengths by the enshrouding dust and gas from which they formed, the near infrared spectroscopy has yielded detection of emission lines from both ionized gas and high excitation molecular gas ( T >2000 K) probably within a few astronomical units of several such sources (e.g. the BN object in the Orion nebula). The former lines provide the first constraints on the spectral type and temperature of the protostar; the latter reveal the physical conditions (density and temperature) and gas dynamics in the immediate protostellar nebula. . Data on the BN object covering the CO, 13 CO, and H 2 vibrational bands and the H II lines are presented as an illustration of these techniques.

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Near-infrared observations of star formation and gas flows in the NUGA galaxy NGC 1365

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834255 ◽

2019 ◽

Vol 622 ◽

pp. A128 ◽

Cited By ~ 8

Author(s):

Nastaran Fazeli ◽

Gerold Busch ◽

Mónica Valencia-S. ◽

Andreas Eckart ◽

Michal Zajaček ◽

...

Keyword(s):

Star Formation ◽

Emission Line ◽

Galaxy Evolution ◽

Large Scale ◽

Near Infrared ◽

Molecular Gas ◽

Nuclear Region ◽

Stellar Kinematics ◽

Hydrogen Recombination ◽

Ngc 1365

In the framework of understanding the gas and stellar kinematics and their relations to AGNs and galaxy evolution scenarios, we present spatially resolved distributions and kinematics of the stars and gas in the central ∼800 pc radius of the nearby Seyfert galaxy NGC 1365. We obtained H + K- and K-band near-infrared (NIR) integral-field observations from VLT/SINFONI. Our results reveal strong broad and narrow emission-line components of ionized gas (hydrogen recombination lines Paα and Brγ) in the nuclear region, as well as hot dust with a temperature of ∼1300 K, both typical for type-1 AGNs. From MBH − σ* and the broad components of hydrogen recombination lines, we find a black-hole mass of (5 − 10)×106 M⊙. In the central ∼800 pc, we find a hot molecular gas mass of ∼615 M⊙, which corresponds to a cold molecular gas reservoir of (2 − 8)×108 M⊙. However, there is a molecular gas deficiency in the nuclear region. The gas and stellar-velocity maps both show rotation patterns consistent with the large-scale rotation of the galaxy. However, the gaseous and stellar kinematics show deviations from pure disk rotation, which suggest streaming motions in the central < 200 pc and a velocity twist at the location of the ring which indicates deviations in disk and ring rotation velocities in accordance with published CO kinematics. We detect a blueshifted emission line split in Paα, associated with the nuclear region only. We investigate the star-formation properties of the hot spots in the circumnuclear ring which have starburst ages of ≲10 Myr and find indications for an age gradient on the western side of the ring. In addition, our high-resolution data reveal further substructure within this ring which also shows enhanced star forming activity close to the nucleus.

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