158μm [CII] Mapping of the Galactic Center Molecular Clouds

We have made 55″ resolution maps of the 158 μm [CII] emission line in the region of the curved, thermal filaments and the +20 / +50 kms−1 molecular clouds in Sgr A. The [CII] emission is spatially well correlated with the radio continuum in the filaments. The large intensity of the [CII] radiation excludes shocks as the origin of the ionization and we conclude that the curved filaments are most likely photo-ionized HII regions at the surface of dense molecular clouds. Our [CII] maps of the +20 / +50 kms−1 clouds indicate that the +50 kms−1 cloud is close to (<10pc) Sgr A west while the more massive +20 kms−1 cloud is at a greater distance from the center (>30pc).

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Mid-Infrared Observations of the Galactic Center Arc and the Sgr A East HII Region

Symposium - International Astronomical Union ◽

10.1017/s0074180900186644 ◽

1989 ◽

Vol 136 ◽

pp. 287-292 ◽

Cited By ~ 1

Author(s):

F. Yusef-Zadeh ◽

C. M. Telesco ◽

R. Decher

Keyword(s):

Galactic Center ◽

Hii Regions ◽

Radio Continuum ◽

Radio Flux ◽

Ir Camera ◽

Hii Region ◽

Sgr A ◽

5 Ghz ◽

Almost All ◽

Ir Emission

We have used the 20-pixel IR camera to observe thermal IR emission from dust associated with the radio continuum Arc near the Galactic center and the cluster of HII regions in the immediate vicinity of Sgr A East. We detected strong 10μm emission from the eastern and western arched filaments (G0.1+0.08), from an unusual pistol-shaped structure known as G0.15–0.05 and from the brightest member of the Sgr A East HII region. Spatial maps of these features at 10μm with a resolution of 4.1″ × 4.2″ are presented and are compared with 5-GHz radio images. We find a general spatial correlation between the ionized gas and the dust distributions. The ratio of IR to radio flux densities is significantly different in the eastern and western arched filaments, which suggests that the source of heating has a softer spectrum along the eastern arched filaments. In addition, the ratio of IR to radio flux densities, which is typically ~10 in normal Galactic HII regions excited by O stars, is at least a factor of two higher than this value in almost all the sources we have observed. This suggests that additional mechanisms other than trapped Lymanαradiation should be present in heating the dust, e.g. stochastic heating of small dust grains by energetic particles associated with the nonthermal filaments.

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An X-ray survey of the central molecular zone: variability of the FeKα emission line

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000258 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 94-96

Author(s):

Simona Soldi ◽

Maïca Clavel ◽

Andrea Goldwurm ◽

Mark R. Morris ◽

Gabriele Ponti ◽

...

Keyword(s):

Emission Line ◽

Molecular Clouds ◽

Galactic Center ◽

X Ray ◽

Preliminary Results ◽

Sgr A ◽

Flux Increase ◽

C Complex ◽

First Time

AbstractThe bulk of the FeKα emission detected in the central molecular zone (CMZ) is thought to be associated with reflection by the central molecular clouds of enhanced past emission from an external X-ray source, most likely Sgr A*. In order to follow the propagation of the reflected emission through the Galactic center (GC), we analyzed all XMM-Newton observations carried out from 2000 to 2012. Preliminary results indicate that while most of the regions that were bright at 6.4 keV in 2000–2001 have a significantly lower flux in 2012, a few other experienced a flux increase. We report for the first time a significant decrease of the FeKα emission in the Sgr C complex, supporting the reflection origin of the 6.4 keV emission detected in this region.

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CO and OH in the Galactic Center Region

Symposium - International Astronomical Union ◽

10.1017/s0074180900072314 ◽

1980 ◽

Vol 87 ◽

pp. 111-112

Author(s):

Junji Inatani ◽

Nobuharu Ukita

Keyword(s):

Emission Line ◽

Intensity Ratio ◽

Molecular Clouds ◽

Galactic Center ◽

Point Of View ◽

The Other ◽

Kinetic Temperature ◽

Two Dimensional ◽

Center Region ◽

Dimensional Distribution

The two-dimensional distribution of molecular clouds in the galactic center region has been investigated in the CO 115 GHz line and in the OH 1665 and 1667 MHz lines. As the former is an emission line, we can find molecular clouds without the unavoidable bias to continuum sources which is inherent in a survey of OH absorption lines. Because the CO line is usually optically thick, the brightness temperature of the line is directly related to the kinetic temperature of the cloud. On the other hand, the real optical depth of the OH line can be obtained from the intensity ratio between 1665 and 1667 MHz lines (assuming LTE). From this point of view we have compared the CO and OH observational results.

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Radio Continuum Emission from the Nuclei of Normal Galaxies

Highlights of Astronomy ◽

10.1017/s1539299600003877 ◽

1980 ◽

Vol 5 ◽

pp. 177-184 ◽

Cited By ~ 2

Author(s):

J. M. van der Hulst

Keyword(s):

Radio Emission ◽

Galactic Center ◽

Galactic Nuclei ◽

Radio Continuum ◽

Continuum Emission ◽

Thermal Source ◽

Very Large Array ◽

Normal Galaxies ◽

The Galaxy ◽

Sgr A

During the last few years detailed and sensitive observations of the radio emission from the nuclei of many normal spiral galaxies has become available. Observations from the Very Large Array (VLA) of the National Radio Astronomy Observatory (NRAO1), in particular, enable us to distinguish details on a scale of ≤100 pc for galaxies at distances less than 21 Mpc. The best studied nucleus, however, still is the center of our own Galaxy (see Oort 1977 and references therein). Its radio structure is complex. It consists of an extended non-thermal component 200 × 70 pc in size, with embedded therein several giant HII regions and the central source Sgr A (˜9 pc in size). Sgr A itself consists of a thermal source, Sgr A West, located at the center of the Galaxy, and a weaker, non-thermal source, Sgr A East. Sgr A West moreover contains a weak, extremely compact (≤10 AU) source. The radio morphology of several other galactic nuclei is quite similar to that of the Galactic Center, as will be discussed in section 2. Recent reviews of the radio properties of the nuclei of normal galaxies have been given by Ekers (1978a,b) and De Bruyn (1978). The latter author, however, concentrates on galaxies with either active nuclei or an unusual radio morphology. In this paper I will describe recent results from the Westerbork Synthesis Radio Telescope (WSRT, Hummel 1979), the NRAO 3-element interferometer (Carlson, 1977; Condon and Dressel 1978), and the VLA (Heckman et al., 1979; Van der Hulst et al., 1979). I will discuss the nuclear radio morphology in section 2, the luminosities in section 3, and the spectra in section 4. In section 5 I will briefly comment upon the possible implications for the physical processes in the nuclei that are responsible for the radio emission.

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RADIO CONTINUUM OBSERVATIONS OF THE GALACTIC CENTER: PHOTOEVAPORATIVE PROPLYD-LIKE OBJECTS NEAR SGR A*

The Astrophysical Journal ◽

10.1088/2041-8205/801/2/l26 ◽

2015 ◽

Vol 801 (2) ◽

pp. L26 ◽

Cited By ~ 22

Author(s):

F. Yusef-Zadeh ◽

D. A. Roberts ◽

M. Wardle ◽

W. Cotton ◽

R. Schödel ◽

...

Keyword(s):

Galactic Center ◽

Radio Continuum ◽

Sgr A

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A Survey of Radio Recombination Line Emission From the Galactic Center Region

Symposium - International Astronomical Union ◽

10.1017/s0074180900186474 ◽

1989 ◽

Vol 136 ◽

pp. 159-166 ◽

Cited By ~ 6

Author(s):

K. R. Anantharamaiah ◽

Farhad Yusef-Zadeh

Keyword(s):

Galactic Center ◽

Line Emission ◽

Radio Continuum ◽

Strong Line ◽

Line Profiles ◽

Ionized Gas ◽

Center Region ◽

Radio Recombination Line ◽

Nonthermal Emission ◽

Sgr A

Preliminary results of a systematic survey of H78α, H91α and H98β emission from the inner 40′ of the Galactic center region are presented. This region consists of two prominent continuum features, the Sgr A complex and the radio continuum Arc. In spite of much nonthermal emission arising from these two features, we detected strong line emission with large line widths in more than half of the observed 130 positions. Many of the detections are new, in particular −50 km s−1 ionized gas linking the Sgr A complex and the Arc, β line emission from GO.1+0.08 (the arched filaments), and α line emission from the loop-like structures which surround the non-thermal filaments near G0.2−0.05. We find that much of the detected lines are probably associated with the −50 km s−1 and the 20 km s−1 molecular clouds, known to lie near the Galactic center. We present line profiles of a number of Galactic center sources including Sgr B1, Sgr C and Sgr D.

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Oxygen isotope ratio studies in the Galactic center region

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000350 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 123-125

Author(s):

JiangShui Zhang ◽

Lulu Sun ◽

Jianjie Qiu ◽

Dengrong Lu ◽

Min Wang

Keyword(s):

Oxygen Isotope ◽

Intensity Ratio ◽

Isotope Ratio ◽

Molecular Clouds ◽

Galactic Center ◽

Metal Enrichment ◽

Oxygen Isotope Ratio ◽

Integrated Intensity ◽

Sgr A ◽

Nuclear Processing

AbstractUsing the Delingha 13.7 m telescope with a 9-beam SIS superconducting receiver installed, we carried out mapping of C18O and C17O J = (1 − 0) toward molecular clouds in the central molecular zone (CMZ) and in the halo of our galaxy. From the integrated intensity ratio of C18O to C17O, the isotope ratio 18O/17O ratio can be estimated, which is considered to be one of the most useful tracers of nuclear processing and metal enrichment. Here preliminary results are presented toward Sgr A, Sgr B2, Sgr C, Sgr D, and the 1.°3 complex in the CMZ and M+5.3–0.3 in the halo.

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Mini-spiral as source of material for Sgr A* in bright state

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312019606 ◽

2012 ◽

Vol 8 (S290) ◽

pp. 199-200 ◽

Cited By ~ 1

Author(s):

Bozena Czerny ◽

Vladimír Karas ◽

Devaky Kunneriath ◽

Tapas K. Das

Keyword(s):

Black Hole ◽

Angular Momentum ◽

Molecular Clouds ◽

Galactic Center ◽

Supermassive Black Hole ◽

The Past ◽

Accretion Process ◽

Ring Mode ◽

Sgr A ◽

Bright Phase

AbstractThe question of the origin of the gas supplying the accretion process is pertinent especially in the context of enhanced activity of Galactic Center during the past few hundred years, seen now as echo from the surrounding molecular clouds, and the currently observed new cloud approaching Sgr A*. We discuss the so-called Galactic Center mini-spiral as a possible source of material feeding the supermassive black hole on a 0.1 parsec scale. The collisions between individual clumps reduce their angular momentum. and set some of the clumps on a plunging trajectory.We conclude that the amount of material contained in the mini-spiral is sufficient to sustain the luminosity of Sgr A* at the required level. The accretion episodes of relatively dense gas from the mini-spiral passing through a transient ring mode at ~ 104 Rg provide a viable scenario for the bright phase of Galactic Center.

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