Submillimeter continuum observations of Sagittarius B2 at subarcsecond spatial resolution

Qin, Sheng-Li; Schilke, P.; Rolffs, R.; Comito, C.; Lis, D. C.; Zhang, Qizhou

doi:10.1051/0004-6361/201116928

Cited by 74 publications

(151 citation statements)

References 20 publications

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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: 60%

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: 60%

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Polehampton

Etxaluze

et al. 2013

A&A

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“…The phase tracking centers were α J2000 = 17 h 47 m 19.883 s , δ J2000 = −28 • 22 18.4 for Sgr B2(N) and α J2000 = 17 h 47 m 20.158 s , δ J2000 = −28 • 23 5.0 for Sgr B2(M). The data reduction and results are described in detail in Qin et al (2011). The absolute flux scale is estimated to be accurate to within 20%.…”

Section: Submillimeter Array (Sma)mentioning

confidence: 99%

“…Following Qin et al (2011), we use a modified Plummerlike profile to model the SMA dust density cores as well as the large-scale envelopes. For a subset of our models, we find it useful to introduce elongated density structures (see Sect.…”

Section: Dust Density Distributionmentioning

confidence: 99%

The physical and chemical structure of Sagittarius B2

Schmiedeke

Schilke

Möller

et al. 2016

A&A

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Context. We model the dust and free-free continuum emission in the high-mass star-forming region Sagittarius B2. Aims. We want to reconstruct the 3D density and dust temperature distribution, as a crucial input to follow-up studies of the gas velocity field and molecular abundances. Methods. We employ the 3D radiative transfer program RADMC-3D to calculate the dust temperature self-consistently, providing a given initial density distribution. This density distribution of the entire cloud complex is then recursively reconstructed, based on available continuum maps, including both single-dish and high-resolution interferometric maps that cover a wide frequency range (ν = 40 GHz−4 THz). The model covers spatial scales from 45 pc down to 100 au, i.e., a spatial dynamic range of 10 5 . Results. We find that the density distribution of Sagittarius B2 can be reasonably well fitted by applying a superposition of spherical cores with Plummer-like density profiles. To reproduce the spectral energy distribution, we position Sgr B2(N) along the line of sight behind the plane containing Sgr B2(M). We find that the entire cloud complex comprises a total gas mass of 8.0 × 10 6 M within a diameter of 45 pc. This corresponds to an averaged gas density of 170 M pc −3 . We estimate stellar masses of 2400 M and 20 700 M and luminosities of 1.8 × 10 6 L and 1.2 × 10 7 L for Sgr B2(N) and Sgr B2(M), respectively. We report H 2 column densities of 2.9 × 10 24 cm −2 for Sgr B2(N) and 2.5 × 10 24 cm −2 for Sgr B2(M) in a 40 beam. For Sgr B2(S), we derive a stellar mass of 1100 M , a luminosity of 6.6 × 10 5 L , and an H 2 column density of 2.2 × 10 24 cm −2 in a 40 beam. We calculate a star formation efficiency of 5% for Sgr B2(N) and 50% for Sgr B2(M). This indicates that most of the gas content in Sgr B2(M) has already been converted to stars or dispersed.

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“…Sgr B2(N) has a greater variety of complex organic molecules than Sgr B2(M). It contains two dense, compact hot cores that are separated by Supplementary text files S1.dat, S2.dat, and S3.dat are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A93 about 5 in the north-south direction Qin et al 2011). The more prominent hot core is Sgr B2(N1), also known as the Large Molecule Heimat, and Sgr B2(N2) is to the north of it.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic study and astronomical detection of doubly¹³C-substituted ethyl cyanide

Margulès

Беллоче

Müller

et al. 2016

A&A

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Context. We have performed a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1. Line intensities of the main isotopic species of ethyl cyanide and its singly 13 C-substituted isotopomers observed toward the hot molecular core Sagittarius B2(N2) suggest that the doubly 13 C-substituted isotopomers should also be detectable. Aims. We want to determine the spectroscopic parameters of all three doubly 13 C-substituted isotopologues of ethyl cyanide to search for them in our ALMA data. Methods. We investigated the laboratory rotational spectra of the three species between 150 GHz and 990 GHz. We searched for emission lines produced by these species in the ALMA spectrum of Sagittarius B2(N2). We modeled their emission and the emission of the 12 C and singly 13 C-substituted isotopologues assuming local thermodynamic equilibrium. Results. We identified more than 5000 rotational transitions, pertaining to more than 3500 different transition frequencies, in the laboratory for each of the three doubly 13 C-substituted isotopomers. The quantum numbers reach J ≈ 115 and K a ≈ 35, resulting in accurate spectroscopic parameters and accurate rest frequency calculations beyond 1000 GHz for strong to moderately weak transitions of either isotopomer. All three species are unambiguously detected in our ALMA data. The 12 C/ 13 C column density ratio of the isotopomers with one 13 C atom to those with two 13 C atoms is about 25. Conclusions. Ethyl cyanide is the second molecule after methyl cyanide for which isotopologues containing two 13 C atoms have been securely detected in the interstellar medium. The model of our ethyl cyanide data suggests that we should be able to detect vibrational satellites of the main species up to at least 19 = 1 at ∼1130 K and up to 13 + 21 = 2 at ∼600 K for the isotopologues with one 13 C atom in our present ALMA data. Such satellites may be too weak to be identified unambiguously for isotopologues with two 13 C atoms.

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Submillimeter continuum observations of Sagittarius B2 at subarcsecond spatial resolution

Cited by 74 publications

References 20 publications

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

The physical and chemical structure of Sagittarius B2

Spectroscopic study and astronomical detection of doubly¹³C-substituted ethyl cyanide

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Submillimeter continuum observations of Sagittarius B2 at subarcsecond spatial resolution

Cited by 74 publications

References 20 publications

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

Observing extended sources with theHerschelSPIRE Fourier Transform Spectrometer

The physical and chemical structure of Sagittarius B2

Spectroscopic study and astronomical detection of doubly13C-substituted ethyl cyanide

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Product

Resources

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Spectroscopic study and astronomical detection of doubly¹³C-substituted ethyl cyanide