A computer program for fast non-LTE analysis of interstellar line spectra

Tak, F. F. S. van der; Black, J. H.; Schöier, F. L.; Jansen, D. J.; Dishoeck, E. F. van

doi:10.1051/0004-6361:20066820

Cited by 1,417 publications

(874 citation statements)

References 57 publications

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“…Simulations with the line escape probability program RADEX (van der Tak et al 2007), indicate that these observed CO(2-1)/CO(1-0) line ratios of order unity can be obtained for gas kinetic temperatures ranging from 20 to 500 K, for H 2 gas densities >10 2.5−3 cm −3 and N CO /ΔV > 10 15 cm −2 km s −1 (right panel of Fig. 2).…”

Section: Line Ratiosmentioning

confidence: 90%

A very extended molecular web around NGC 1275

Salomé

Combes

Revaz

et al. 2011

A&A

107

124

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We present the first detection of CO emission lines in the Hα filaments at distances as far as 50 kpc from the centre of the galaxy NGC 1275. This gas is probably dense (≥10 3 cm −3 ). However, it is not possible to accurately determine the density and the kinetic temperature of this relatively warm gas (T kin ∼ 20-500 K) with the current data alone. The amount of molecular gas in the filaments is large -10 9 M (assuming a Galactic N(H 2 )/I CO ratio). This is 10% of the total mass of molecular gas detected in this cD galaxy. This gas has large-scale velocities comparable to those seen in Hα. The origin of the filaments is still unclear, but their formation is very likely linked to the AGN positive feedback that regulates the cooling of the surrounding X-ray-emitting gas as suggested by numerical simulations. We also present high-resolution spectra of the galaxy core. The spatial characteristics of the double-peaked profile suggest that the molecular web of filaments and streamers penetrates down to radii of less than 2 kpc from the central AGN and eventually feeds the galaxy nucleus. The mass of gas inside the very central region is ∼10 9 M , and is similar to the mass of molecular gas found in the filaments.

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Section: Line Ratiosmentioning

confidence: 90%

A very extended molecular web around NGC 1275

Salomé

Combes

Revaz

et al. 2011

A&A

107

124

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“…The escape probability formalism used to treat this optically thick situation was first applied to molecular clouds by Scoville & Solomon (1974) and Goldreich & Kwan (1974) and is now routinely used to analyse interstellar molecule excitation (often called large velocity gradient [LVG], non-thermal equilibrium [non-LTE] analysis; see, e.g., van der Tak et al (2007) and their publicly available RADEX code) † . One of the biggest advantages of the LVG formalism is that it permits treatment of the coupled radiative transfer and molecular excitation as a local problem -a fact probably not fully appreciated by current routine users of these codes.…”

Section: Molecular Excitationmentioning

confidence: 99%

Evolution of star formation and gas

Scoville¹

2013

Secular Evolution of Galaxies

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In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to develop a physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material is drawn from early work in the field since much of the work was done two decades ago and this background is not generally available in the present literature. I also attempt to synthesise our welldeveloped understanding of star formation in low-redshift galaxies with constraints from theory and observations at high redshift to develop an intuitive model for the evolution of galaxy mass and luminosity functions in the early Universe.The overall goal of this contribution is to provide students with background helpful for analysis of far-infrared (FIR) observations from Herschel and millimetre/submillimetre (mm/submm) imaging with ALMA (the Atacama Large Millimetre/submillimetre Array).These two instruments will revolutionise our understanding of the interstellar medium (ISM) and associated star formation and galaxy evolution, both locally and in the distant Universe. To facilitate interpreting the FIR spectra of Galactic star-forming regions and high-redshift sources, I develop a model for the dust heating and radiative transfer in order to elucidate the observed infrared (IR) emissions. I do this because I am not aware of a similar coherent discussion in the literature. Star-forming molecular cloudsHere, I provide an overview of the observations and physics of star-forming molecular clouds in the Galaxy and nearby normal galaxies. The motivation is to develop the intuitive background for analysis of observations at high 1 arXiv:1210.6990v2 [astro-ph.CO] 1 Nov 2012

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“…To this end, we used the non-LTE excitation code RADEX with an escape probability formalism for the radiative transfer ( Van der Tak et al 2007) coupled with the LAMDA database . Methanol is the species detected in the largest number of lines.…”

Section: Physical Properties Along the B1 Bow Shockmentioning

confidence: 99%

The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1

Codella¹,

Leflóch

Ceccarelli

et al. 2010

A&A

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We present the first results of the unbiased survey of the L1157-B1 bow shock, obtained with HIFI in the framework of the key program Chemical HErschel Survey of Star forming regions (CHESS). The L1157 outflow is driven by a low-mass Class 0 protostar and is considered the prototype of the so-called chemically active outflows. The bright blue-shifted bow shock B1 is the ideal laboratory for studying the link between the hot (∼1000-2000 K) component traced by H 2 IR-emission and the cold (∼10-20 K) swept-up material. The main aim is to trace the warm gas chemically enriched by the passage of a shock and to infer the excitation conditions in L1157-B1. A total of 27 lines are identified in the 555-636 GHz region, down to an average 3σ level of 30 mK. The emission is dominated by CO(5-4) and H 2 O(1 10 -1 01 ) transitions, as discussed by Lefloch et al. in this volume. Here we report on the identification of lines from NH 3 , H 2 CO, CH 3 OH, CS, HCN, and HCO + . The comparison between the profiles produced by molecules released from dust mantles (NH 3 , H 2 CO, CH 3 OH) and that of H 2 O is consistent with a scenario in which water is also formed in the gas-phase in high-temperature regions where sputtering or grain-grain collisions are not efficient. The high excitation range of the observed tracers allows us to infer, for the first time for these species, the existence of a warm (≥200 K) gas component coexisting in the B1 bow structure with the cold and hot gas detected from ground.

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A computer program for fast non-LTE analysis of interstellar line spectra

Cited by 1,417 publications

References 57 publications

A very extended molecular web around NGC 1275

A very extended molecular web around NGC 1275

Evolution of star formation and gas

The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1

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