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Cited by 29Astrophysical Phenomena and ObservationsAstrophysics and Star Formation StudiesGalaxies: Formation, Evolution, Phenomena

Dense, Ionized, and Neutral Gas Surrounding Sagittarius A*

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Shukla, Hemant, Yun, Min S., Scoville, N. Z.·2004·The Astrophysical Journal
DOI 10.1086/424868
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Abstract

We present high-resolution H41α hydrogen recombination line observations of the 1 2 (3 pc) region surrounding Sagittarius A* (Sgr A*) at 92 GHz using the Millimeter Array at the Owens Valley Radio Observatory (OVRO) with an angular resolution of 7'' × 3'' and velocity resolution of 13 km s -1 . New observations of H31α, H35α, H41α, and H44α lines were obtained using the NRAO 12 m telescope, and their relative line strengths are interpreted in terms of various possible emission mechanisms. These NRAO 12 m measurements are the most extensive recombination line survey of this region to date. These OVRO data also represent the highest angular resolution and the highest sensitivity observations of Sgr A West in hydrogen recombination line and continuum emission at millimeter wavelengths. Observations of HCO + ( J = 1 → 0) transition at 89 GHz are obtained simultaneously with a 40% improved angular resolution and 4-15 times improved sensitivity over the previously published results, and the distribution and kinematics of the dense molecular gas in the circumnuclear disk (CND) are mapped and compared with those of the ionized gas. The line brightness ratios of the hydrogen recombination lines are consistent with purely spontaneous emission from T e ~ 7000 K gas with n e ~ 2 × 10 4 cm -3 near LTE condition. A virial analysis suggests that the most prominent molecular gas clumps in the CND have mean densities on the order of 10 7 cm -3 , sufficient to withstand the tidal shear in the Galactic center region. Therefore, these clumps may survive over several dynamical times, and the CND may be a dynamically stable structure. We estimate a total gas mass of about 3 × 10 5 M ☉ for the CND. Our combined analysis of the new high-resolution H41α and HCO + images and our kinematic model demonstrates a widely spread physical and dynamical link between the molecular gas in the CND and the ionized gas, including along the eastern rim of the CND where a gap was previously suggested.

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47 of 47 references verified0 citation errors · 0 not checkable

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  • Most of the CND clumps are compact enough to overcome the tidal force from Sgr A* and may either remain in rough equilibrium or form stars.

    “Most of these clumps are compact enough to overcome the tidal force from Sgr A ∗ and may either remain in rough equilibrium or form stars. (Shukla et al. 2004; Christopher et al. 2005; Hsieh et al. 2021).”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Shukla et al. 2004

    Section 4.1 (page unavailable) concludes that, if self-gravitating, the CND clumps have densities close to or above the threshold for surviving tidal shear; it also says the CND may persist for several dynamical times. Our copy does not say that most clumps meet that threshold or that they may form stars. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

  • The central 1-1.5 pc radius can be described as the 'ionized cavity' (T~5-7×10^3 K) that is affected by UV radiation either from Sgr A* or from the nuclear starcluster.

    “The central 1 -1 . 5 pc radius can be described as the 'ionized cavity' ( T ∼ 5 -7 × 10 3 K) that is affected by the UV radiation either from Sgr A ∗ or from the nuclear starcluster (Becklin et al. 1982; Guesten et al. 1987; Shukla et al. 2004; Christopher et al. 2005).”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Shukla et al. 2004

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Cites

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Research works printed but not linked: 4

  1. Genzel, R., & Eckart, A. 1999, in ASP Conf. Ser. 186, The Galactic Center Black Hole, ed. H. Falcke et al. (San Francisco: ASP), 3
  2. Pearson, T. J., Shepherd, M. C., Taylor, G. B., & Myers, S. T. 1994, BAAS, 185.0808
  3. Yun, M. S., Scoville, N. Z., & Shukla, H. 2004, in ASP Conf. Ser. 320, The Neutral ISM in Starburst Galaxies, ed. S. Aalto, S. Huttenmeister, & A. Pedlar (San Francisco: ASP), in press
  4. Zhao, J., & Goss, W. M. 1999, in ASP Conf. Ser. 186, The Central Parsecs of the Galaxy, ed. H. Falcke et al. (San Francisco: ASP), 224

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Authors
Shukla, H., Yun, M. S., & Scoville, N. Z.
Affiliations
  • California Institute of Technology (US)
  • University of Massachusetts Amherst (US)
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2004-11-20
Volume
616
Issue
1
Pages
231-246
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1086/424868
OpenAlex
W2010884536
Cited by
29
References
47
Citations by year
2024: 1 · 2022: 2 · 2021: 3 · 2019: 1 · 2018: 2 · 2016: 1 · 2013: 1 · 2012: 2
FWCI
1.18
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • ScholarWorks@UMassAmherst (University of Massachusetts Amherst) (submittedVersion)
  • CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • National Science Foundation
  • National Radio Astronomy Observatory
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
Keywords
Sgr A*, circumnuclear disk, dense gas, ionized gas, hydrogen recombination lines, HCO+ emission, gas kinematics, virial analysis, gas clumps, Galactic Center, Sgr A West, millimeter-wave emission, gas mass

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