Radio continuum and radio recombination line observations of Sagittarius B2

Mehringer, David M.; Palmer, Patrick; Goss, W. M.; Yusef‐Zadeh, F.

doi:10.1086/172954

Cited by 89 publications

(124 citation statements)

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“…We use a two-step approach. In the first step we account for observed early-type highmass stars by including the known Hii regions (Mehringer et al 1993;Gaume et al 1995;De Pree et al 1998, see Table B.1 for a complete list of all parameters). Due to a revised distance of the Galactic center we estimated the corresponding parameters, see Sect.…”

Section: Heating Sourcesmentioning

confidence: 99%

“…as a fully ionized, spherical regions of uniform electron density with no dust. There are more than 70 Hii regions known in Sgr B2 (Mehringer et al 1993;Gaume et al 1995;De Pree et al 1998).…”

Section: H II Regionsmentioning

confidence: 99%

“…The Hii regions detected by Mehringer et al (1993) were included according to the parameters stated therein. However, Mehringer et al (1993) assumed a source distance of 7.5 kpc.…”

Section: H II Regionsmentioning

confidence: 99%

“…More than 70 Hii regions have been detected in the whole Sgr B2 cloud complex (see Fig. A.1;Mehringer et al 1993;Gaume et al 1995;De Pree et al 1998). …”

Section: Introductionmentioning

confidence: 99%

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The physical and chemical structure of Sagittarius B2

Schmiedeke

Schilke

Möller

et al. 2016

A&A

143

189

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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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Section: Heating Sourcesmentioning

confidence: 99%

Section: H II Regionsmentioning

confidence: 99%

“…The Hii regions detected by Mehringer et al (1993) were included according to the parameters stated therein. However, Mehringer et al (1993) assumed a source distance of 7.5 kpc.…”

Section: H II Regionsmentioning

confidence: 99%

“…More than 70 Hii regions have been detected in the whole Sgr B2 cloud complex (see Fig. A.1;Mehringer et al 1993;Gaume et al 1995;De Pree et al 1998). …”

Section: Introductionmentioning

confidence: 99%

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The physical and chemical structure of Sagittarius B2

Schmiedeke

Schilke

Möller

et al. 2016

A&A

143

189

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“…Ferrière et al 2007). For example, Mezger & Pauls (1979) used thermal radio continuum radio observations to derive a central n(e) ∼26 cm −3 while Mehringer et al (1992Mehringer et al ( , 1993 derive even higher electron densities outside compact HII regions near Sgr B1 and B2 and derive an average electron density of ∼60 and 80 cm −3 over two regions ∼700 and 170 pc 2 , respectively. The conditions encountered in the most energetic region of the CMZ is likely to prevail over a much larger volume in AGNs.…”

Section: Agn Representative Model Of [C Ii] Emissionmentioning

confidence: 99%

[C ii] emission from galactic nuclei in the presence of X-rays

Langer

Pineda

2015

A&A

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Context. The luminosity of [C ii] is used as a probe of the star formation rate in galaxies, but the correlation breaks down in some active galactic nuclei (AGNs). Models of the [C ii] emission from galactic nuclei do not include the influence of X-rays on the carbon ionization balance, which may be a factor in reducing the [C ii] luminosity.Aims. We aim to determine the properties of the ionized carbon and its distribution among highly ionized states in the interstellar gas in galactic nuclei under the influence of X-ray sources. We calculate the [C ii] luminosity in galactic nuclei under the influence of bright sources of soft X-rays. Methods. We solve the balance equation of the ionization states of carbon as a function of X-ray flux, electron, atomic hydrogen, and molecular hydrogen density. These are input to models of [C ii] emission from the interstellar medium (ISM) in galactic nuclei representing conditions in the Galactic central molecular zone and a higher density AGN model. The behavior of the [C ii] luminosity is calculated as a function of the X-ray luminosity. We also solve the distribution of the ionization states of oxygen and nitrogen in highly ionized regions. Results. We find that the dense warm ionized medium (WIM) and dense photon dominated regions (PDRs) dominate the [C ii]emission when no X-rays are present. The X-rays in galactic nuclei can affect strongly the C + abundance in the WIM, converting some fraction to C 2+ and higher ionization states and thus reducing its [C ii] luminosity. For an X-ray luminosity L(X-ray) 10 43 erg s −1 the [C ii] luminosity can be suppressed by a factor of a few, and for very strong sources, L(X-ray) >10 44 erg s −1 such as found for many AGNs, the [C ii] luminosity is significantly depressed. Comparison of the model with several extragalactic sources shows that the [C ii] to far-infrared ratio declines for L(X-ray) 10 43 erg s −1 , in reasonable agreement with our model. Conclusions. We conclude that X-rays can suppress the C + abundance and, therefore, the [C ii] luminosity of the ISM in active galactic nuclei with a large X-ray flux. The X-ray flux can arise from a central massive accreting black hole and/or from many smaller discrete sources distributed throughout the nuclei. We also find that the lower ionization states of nitrogen and oxygen are also suppressed at high X-ray fluxes in warm ionized gas.

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Large‐scale distribution of interstellar matter in the central region of our Galaxy

Ferrière¹

2008

Astron Nachr

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International audienceIn this paper, we review the present observational knowledge on the physical properties and the large-scale spatial distribution of interstellar matter in the central region of our Galaxy, out to a distance of 3 kpc from the Galactic center. We mainly focus on the interstellar gas, which contains ˜98 % of the total interstellar mass, leaving the remaining ˜2% to interstellar dust. In a second step, we present a global model of the interstellar gas distribution, which incorporates the relevant results of a vast number of observational studies as well as those of numerical simulations of gas flows in the gravitational potential of a barred galaxy

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Radio continuum and radio recombination line observations of Sagittarius B2

Cited by 89 publications

References 0 publications

The physical and chemical structure of Sagittarius B2

The physical and chemical structure of Sagittarius B2

[C ii] emission from galactic nuclei in the presence of X-rays

Large‐scale distribution of interstellar matter in the central region of our Galaxy

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