Dense Molecular Clouds in the Galactic Center Region. I. Observations and Data

Tsuboi, Masamichi; Handa, Toshihiro; Ukita, Nobuharu

doi:10.1086/313165

Cited by 238 publications

(339 citation statements)

References 22 publications

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“…An area empty of SiO sources is seen at the middle-velocity range in the central part of Figure 6a (l \ [0¡ .4È1¡ .0, V lsr \ 20È150 km s~1). This artifact is possibly caused by undersampling of sources in the central nuclear disk by IRAS PSC, because Figure 6a reveals the strongest CO and CS emission at this location Oka et al 1998 ;Tsuboi et al 1999). In fact, Shiki, Ohishi, & Deguchi (1997) found six new SiO sources toward Sgr B2 (l \ four of them fall at this missing velocity range of 0¡ .25È1¡ .0) ; 20È150 km s~1.…”

Section: Elocity Distributionmentioning

confidence: 95%

SiO Maser Survey of the Galactic Disk IRAS Sources. II. | l | ≤ 3o and | b | ≤ 3o, the Galactic Center Area

Deguchi

Fujii

Izumiura

et al. 2000

ASTROPHYS J SUPPL S

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A survey has been made in the SiO J \ 1È0, v \ 1 and 2 transitions (D43 GHz) for color-selected IRAS sources in the Galactic-center region of o l o ¹ 3¡ and o b o ¹ 3¡ using the Nobeyama 45 m telescope. We have detected 86 of 176 observed sources in the SiO masers. Distances to the sources are deduced from IRAS 12 and 25 km Ñux densities and range approximately from 5 to 12 kpc. Radial velocities of the detected sources spread between [300 and 310 km s~1. The longitude-velocity (l-v) diagram exhibits an empty region of sources at and km s~1, which is interpreted as an underl \ [0¡ .4È1¡ .0 V lsr \ 20È150 sampling e †ect of sources in the IRAS catalog at the Galactic central disk. The rotation rate, velocity dispersion, tilt angle of the rotation axis, and velocity shift at l \ 0¡ are derived by Ðtting the velocities of the sources with a straight line as a function of Galactic longitude. These quantities are compatible with those obtained from previous observations of bulge stars with o b o [ 3¡. The average radial velocity of subsamples of stars tends to increase with distance, suggesting the presence streaming motion of stars in a barlike bulge. We conclude that most of the IRAS sources in the sample belong to the bulge.

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Section: Elocity Distributionmentioning

confidence: 95%

SiO Maser Survey of the Galactic Disk IRAS Sources. II. | l | ≤ 3o and | b | ≤ 3o, the Galactic Center Area

Deguchi

Fujii

Izumiura

et al. 2000

ASTROPHYS J SUPPL S

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“…Observations of the atomic and molecular interstellar medium in the inner Milky Way exhibit large noncircular motion of the gas (Rougoor & Oort 1960;Scoville 1972;Liszt & Burton 1978;Bally et al 1987;Oka et al 1998;Tsuboi, Handa & Ukita 1999;Sawada et al 2004;Oka et al 2005;Takeuchi et al 2010). Among various possible explanations for the noncircular motion, de Vaucouleurs (1964) raised a possibility that the gas responds to a stellar bar potential of the Milky Way.…”

Section: Introductionmentioning

confidence: 99%

Stochastic non-circular motion and outflows driven by magnetic activity in the Galactic bulge region

Suzuki

Fukui

Torii

et al. 2015

Mon. Not. R. Astron. Soc.

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By performing a global magneto-hydrodynamical simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic center region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches > ∼ 0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. In addition, the magnetic pressuregradient force also drives radial flows in a similar manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the intermittency of the magnetic turbulence; the present model provides a viable alternative to the bar-potential-driven model for the parallelogram-shape of the central molecular zone. This is a natural extension into the central few 100 pc of the magnetic activity, which is observed as molecular loops at radii from a few 100 pc to 1 kpc. Furthermore, the time-averaged net gas flow is directed outward, whereas the flows are highly time-dependent, which we discuss from a viewpoint of the outflow from the bulge.

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“…In Figs. 1 and 2 we show the SiO J=2→1 and CS J=1→0 [5] emission maps as contour levels for three different negative and positive radial velocities, respectively, superimposed on the image of the EW of the Fe o line emission [2]. This line is only associated with a subset of the molecular clouds located along any given line of sight, which can be identified by their radial velocities [4].…”

Section: Observations and Resultsmentioning

confidence: 99%

“…In this paper, we present maps of the Sgr A molecular cloud complex in the GC in the SiO(2-1) line with a higher spatial resolution (∼40"), and compare our SiO(2-1) data cube with that of CS(1-0) emission of [5]. We find a correlation between the SiO(2-1)/CS(1-0) intensity ratio and the Equivalent Width (EW) of the Fe o line.…”

Section: Introductionmentioning

confidence: 99%

Correlation between SiO and X-ray emission in the galactic center

Amo-Baladrón

Martı́n-Pintado

Morris

et al. 2008

J. Phys.: Conf. Ser.

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Abstract. We present emission maps (spatial resolution ∼40") of the Sgr A molecular cloud complex at the Galactic Center (GC) in the J=2→1 SiO line, observed with the IRAM-30m telescope at Pico Veleta. We have compared our SiO(2-1) data cube with CS(1-0) maps, and we have found a correlation between the SiO/CS intensity ratio and the equivalent width of the X-ray Fe line at 6.4 keV. We discuss the SiO abundance enhancement in the two most plausible scenarios for the origin of the Fe line, which is, at the moment, under debate: fluorescence in an X-ray Reflection Nebula (XRN), or impact by Low-Energy Cosmic Rays (LECRs) followed by electronic relaxation. Both could explain the enhancement in the SiO/CS intensity ratio with the intensity of the Fe line, but both scenarios present difficulties: the first one requires a population of very small grains to produce the enhancement in the SiO/CS intensity ratio, and the second needs higher column densities than the ones derived from observations in the region.

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Dense Molecular Clouds in the Galactic Center Region. I. Observations and Data

Cited by 238 publications

References 22 publications

SiO Maser Survey of the Galactic Disk IRAS Sources. II. | l | ≤ 3o and | b | ≤ 3o, the Galactic Center Area

SiO Maser Survey of the Galactic Disk IRAS Sources. II. | l | ≤ 3o and | b | ≤ 3o, the Galactic Center Area

Stochastic non-circular motion and outflows driven by magnetic activity in the Galactic bulge region

Correlation between SiO and X-ray emission in the galactic center

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