The Sagittarius B2 star-forming region - Subarcsecond radio spectral line and continuum observations

Gaume, R. A.; Claussen, M. J.

doi:10.1086/168492

Cited by 65 publications

(66 citation statements)

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“…The total mass of the core is: M d = 2300 M . This mass is lower than the total masses determined by Qin et al (2011): ∼3300 M , and higher than the mass calculated by Gaume & Claussen (1990): ∼1050 M . The derived physical quantities indicate that the corrected spectrum is generally in agreement with results obtained in previous studies of Sgr B2(M).…”

Section: Sgr B2contrasting

confidence: 61%

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Polehampton

Etxaluze

et al. 2013

A&A

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The Spectral and Photometric Imaging Receiver (SPIRE) on the European Space Agency's Herschel Space Observatory utilizes a pioneering design for its imaging spectrometer in the form of a Fourier Transform Spectrometer (FTS). The standard FTS data reduction and calibration schemes are aimed at objects with either a spatial extent that is much larger than the beam size or a source that can be approximated as a point source within the beam. However, when sources are of intermediate spatial extent, neither of these calibrations schemes is appropriate and both the spatial response of the instrument and the source's light profile must be taken into account and the coupling between them explicitly derived. To that end, we derive the necessary corrections using an observed spectrum of a fully extended source with the beam profile and considering the source's light profile. We apply the derived correction to several observations of planets and compare the corrected spectra with their spectral models to study the beam coupling efficiency of the instrument in the case of partially extended sources. We find that we can apply these correction factors for sources with angular sizes up to θ D ∼ 17 . We demonstrate how the angular size of an extended source can be estimated using the difference between the subspectra observed at the overlap bandwidth of the two frequency channels in the spectrometer, at 959 < ν < 989 GHz. Using this technique on an observation of Saturn, we estimate a size of 17.2 , which is 3% larger than its true size on the day of observation. Finally, we show the results of the correction applied on observations of a nearby galaxy, M82, and the compact core of a Galactic molecular cloud, Sgr B2.

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Section: Sgr B2contrasting

confidence: 61%

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Polehampton

Etxaluze

et al. 2013

A&A

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“…SgrB2 Main contains a large number of UCHii regions (Gaume & Claussen 1990), and molecular gas of very high temperature is present (e.g. Wilson et al 2006;Comito et al 2003).…”

Section: Sgrb2(m)mentioning

confidence: 99%

Structure of evolved cluster-forming regions

Rolffs

Schilke

Wyrowski

et al. 2011

A&A

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Context. An approach towards understanding the formation of massive stars and star clusters is to study the structure of their hot core phase, an evolutionary stage where dust has been heated, but molecules have not yet been destroyed by ultraviolet radiation. These hot molecular cores are very line-rich, but the interpretation of line surveys is also hampered by poor knowledge of the physical and chemical structure. Aims. To constrain the radial structure of high-mass star-forming regions containing hot cores, we attempt to reproduce by radiative transfer modeling both the intensity and shape of a variety of molecular lines. Methods. We observed 12 hot cores with the Atacama Pathfinder EXperiment (APEX) in lines of HCN, HCO + , CO, and their isotopologues, including high-J lines and vibrationally excited HCN. We investigate how well the sources can be modeled as centrally heated spheres with a power-law density gradient, making use of the radiative transfer code RATRAN and the radial profile of the submm continuum emission, taken from the APEX Telescope Large Area Survey of the GALaxy (ATLASGAL). Results. Most of the observed lines have complicated shapes that incorporate self-absorption, asymmetries, and line wings. Vibrationally excited HCN is detected in all sources, and vibrationally excited H 13 CN in half of the sources. We are able to successfully model most features seen in the APEX data, such as the ratio of the isotopologue lines (very high optical depths), self-absorption (temperature gradient), blue asymmetries (moderate infall), vibrationally excited HCN (high inner temperatures), and H 13 CN (high HCN abundance under dense and hot conditions). Other features could not be reproduced, such as an occasional lack of self-absorption, the emission from high-J lines in the outer pixels of the CHAMP+ receiver (15 −20 from the center), the outflow wings, and the red asymmetric profiles. Conclusions. The amount of molecular gas, in particular of HCN, at very high temperatures is larger than previously thought. A complex interplay between infall and outflow motions is present. Our basic model assumptions of pure central heating and a power-law radial density distribution can serve as approximations for most sources, but are too simple to explain all observed lines. In particular, taking into account clumpiness, multiplicity of heating sources and a more complex velocity field seems to be necessary to more closely match model calculations to observations. This would require three-dimensional radiative transfer modeling of high-resolution interferometric data.

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“…The contours indicate the location of the 111,507.27 and the 111,548.53 MHz CH 3 COOH emission. In addition, we have labeled the positions of the ultracompact H ii regions K1-K3 and K5 as given by Gaume & Claussen (1990). The CH 3 COOH emission peaks given by Mehringer et al (1997) are seen as large crosses with error bars.…”

Section: Bima Array Observations Of W51e2mentioning

confidence: 99%

Acetic Acid in the Hot Cores of Sagitarrius B2(N) and W51

Remijan

Snyder

Liu

et al. 2002

ApJ

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We have detected interstellar acetic acid (CH 3 COOH) toward the hot core source W51e2. This is the first new source of interstellar CH 3 COOH since its discovery by Mehringer et al. toward the hot core source Sgr B2(N-LMH). In this paper, we report CH 3 COOH observations at two new frequencies toward Sgr B2(N-LMH) with the OVRO array and at 10 frequencies toward W51e2 with the Berkeley-Illinois-Maryland Association array. Toward Sgr B2(N-LMH) the agreement in positions, intensities, and velocities between the two lines from the previous study and the two new lines strongly indicates that all four CH 3 COOH lines are coming from a common source. Using all four detected transitions, we find an average column density of 6:1ð6Þ Â 10 15 cm À2 , a fractional abundance of ð0:8 6Þ Â 10 À10 relative to H 2 and ð3 6Þ Â 10 À2 relative to its isomer methyl formate (HCOOCH 3 ). Toward W51e2, we find a CH 3 COOH column density of 1:7ð5Þ Â 10 16 cm À2 with a fractional abundance of 1:7 Â 10 À9 relative to H 2 and ð1 6Þ Â 10 À2 relative to HCOOCH 3 . Furthermore, we find the distribution of CH 3 COOH toward W51e2 is coincident with HCOOCH 3 , thus suggesting a similar formation mechanism.

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The Sagittarius B2 star-forming region - Subarcsecond radio spectral line and continuum observations

Cited by 65 publications

References 0 publications

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Structure of evolved cluster-forming regions

Acetic Acid in the Hot Cores of Sagitarrius B2(N) and W51

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