The Hot Interstellar Medium of the Galactic Center: Observations with Chandra

AbstractObservations of interstellar Na I in the spectra of 93 stars within 315 pc from the Sun show that it lies in a tunnel of gas moving away from Scorpio-Centaurus and is surrounded by gas moving toward the Galactic center.Gas approaches the Sun from Scorpio-Centaurus expanding from (r, l, b)=(160 pc, 313°7, +28°2) with LSR velocity 15.3 km s−1. The radius of this shell is 153 pc.We identify these clouds:D: velocity vector (υd, ld, bd)=(+7.2 km s−1, 305°1, −13°5), above and below the Galactic plane (GP) in the range of Galactic longitudes 357°–55°.C: velocity vector (υc, lc, bc)=(+11.5 km s−1, 349°0, −35°2), above and below the GP in the range 30°≤l≤110°.M: velocity vector (υm, lm, bm)=(+21.9 km s−1, 34°2, +1°5), above and below the GP in the range 100°≤l≤130°.P: velocity vector (υp, lp, bp)=(+13.8 km s−1, 244°9, +5°4), above and below the GP from l~120° to the limit of our data at l~210°.E: velocity vector (υe, le, be)=(+16.8 km s−1, 208°4, +6°2) in the range 160°≤l≤185° and −10°≤b≤–35°.A: velocity vector (υa, la, ba)=(+12.9 km s−1, 73°6, −5°6) towards the Galactic anti-center, below the GP.I: velocity vector (υi, li, bi)=(+37.7 km s−1, 132°8, −64°3) towards the Galactic anti-center, above the GP.

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Galactic Center Extinction: Evidence of Metallic Needles in the General Interstellar Medium

The Astrophysical Journal ◽

10.1086/423893 ◽

2004 ◽

Vol 611 (2) ◽

pp. L109-L112 ◽

Cited By ~ 21

Author(s):

Eli Dwek

Keyword(s):

Interstellar Medium ◽

Galactic Center

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The Galactic center: not an active galactic nucleus

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000131 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 54-58

Author(s):

Deokkeun An ◽

Solange V. Ramírez ◽

Kris Sellgren

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Active Galactic Nuclei ◽

Active Galactic Nucleus ◽

Galactic Center ◽

Galactic Nuclei ◽

Extensive Area ◽

Star Forming ◽

Nearby Galaxies

AbstractWe present 10 μm – 35μm Spitzer spectra of the interstellar medium in the central molecular zone (CMZ), the central 210 pc × 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and H2 emission, covering a more extensive area than earlier spectroscopic surveys in this region. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from low-ionization nuclear emission-line regions (LINERs) and active galactic nuclei (AGNs). Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

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7.4. The 3.4 micron absorption in the Galactic center sources

Symposium - International Astronomical Union ◽

10.1017/s0074180900085004 ◽

1998 ◽

Vol 184 ◽

pp. 299-300

Author(s):

T. Nagata

Keyword(s):

Interstellar Medium ◽

Near Infrared ◽

Galactic Center ◽

Absorption Feature ◽

Visual Extinction ◽

Stretching Vibrations ◽

Central Parsec ◽

Infrared Sources

The 3.4μm absorption feature, first detected in the Galactic center source IRS7 (Soifer et al., 1976), has been observed in other Galactic center sources IRS3, IRS12 (McFadzean et al., 1989), and IRS6E (Pendleton et al., 1994). This feature is regarded as characteristic of dust in the diffuse interstellar medium, and attributed to C-H stretching vibrations. Several objects in the lines of sight other than the Galactic center is now known to have the feature (Sandford et al. 1995 and references therein; Imanishi et al. 1996). The absorption depths per unit visual extinction τ3.4/AV for these sources are compared with those for the Galactic center sources, and they are thought to increase near the Galactic center. However, the “Galactic center” sources are all in the central parsec cluster, and the features observed in them may be only representative of interstellar medium local to the central parsec, not the general diffuse interstellar medium of the inner Galaxy. In this paper, we report the 3.4μm absorption feature detected in near-infrared sources within 1° of the Galactic center.

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The Mid‐Infrared Colors of the Interstellar Medium and Extended Sources at the Galactic Center

The Astrophysical Journal ◽

10.1086/589635 ◽

2008 ◽

Vol 682 (1) ◽

pp. 384-399 ◽

Cited By ~ 17

Author(s):

R. G. Arendt ◽

S. R. Stolovy ◽

S. V. Ramírez ◽

K. Sellgren ◽

A. S. Cotera ◽

...

Keyword(s):

Interstellar Medium ◽

Galactic Center ◽

Mid Infrared ◽

Extended Sources

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Herschel/HIFI Discoveryof a Far-Infrared DIB Analog

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313015846 ◽

2013 ◽

Vol 9 (S297) ◽

pp. 197-202

Author(s):

H. S. P. Müller ◽

P. Schilke ◽

M. Gerin ◽

D. C. Lis ◽

E. A. Bergin ◽

...

Keyword(s):

Interstellar Medium ◽

Molecular Clouds ◽

Galactic Center ◽

Galactic Disk ◽

Far Infrared ◽

Line Of Sight ◽

Absorption Feature ◽

Substantial Part ◽

Star Forming ◽

Star Forming Regions

AbstractThe Herschel Space Observatory carried out observations at far-infrared wavelengths, which significantly increased our knowledge of the interstellar medium and the star-formation process in the Milky Way and external galaxies, as well as our understanding of astrochemistry.Absorption features, known, e.g., from observations at millimeter wavelengths, are more commonly observed in the far-infrared, in particular toward strong dust continuum sources. The lowest energy transitions are not only observed at LSR-velocities related to the source, but often also at velocities associated with diffuse molecular clouds along the line of sight toward the background source.Unbiased spectral line surveys of the massive and very luminous Galactic Center sources Sagittarius B2(M) and (N) were carried out across the entire frequency range of the high-resolution Heterodyne Instrument for Far-Infrared Astronomy (HIFI). An absorption feature was detected toward both sources at about 617.531 GHz, corresponding to 20.599 cm−1, 485.47 μm, or 2.5539 meV. This feature is unique in its appearance at all velocity components associated with diffuse foreground molecular clouds, together with its conspicuous absence at velocities related to the sources themselves. The carriers of at least a substantial part of the DIBs are thought to reside in the diffuse interstellar medium. Therefore, we consider this absorption feature to be a far-infrared DIB analog.Subsequent dedicated observations confirmed that the line is present only in the foreground clouds on the line of sight toward other massive star-forming regions in the Galactic disk. There is indication that the feature has substructure, possibly of fine or hyperfine nature. Attempts to assign the feature to atomic or molecular species have been unsuccessful so far.

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