Tracing the Milky Way’s Vestigial Nuclear Jet

Abstract MeerKAT radio continuum and XMM-Newton X-ray images have recently revealed a spectacular bipolar channel at the Galactic Center that spans several degrees (∼0.5 kpc). An intermittent jet likely formed this channel and is consistent with earlier evidence of a sustained, Seyfert-level outburst fueled by black hole accretion onto Sgr A* several Myr ago. Therefore, to trace a now weak jet that perhaps penetrated, deflected, and percolated along multiple paths through the interstellar medium, relevant interactions are identified and quantified in archival X-ray images, Hubble Space Telescope Paschen α images and Atacama Large Millimeter/submillimeter Array millimeter-wave spectra, and new SOAR telescope IR spectra. Hydrodynamical simulations are used to show how a nuclear jet can explain these structures and inflate the ROSAT/eROSITA X-ray and Fermi γ-ray bubbles that extend ± 75° from the Galactic plane. Thus, our Galactic outflow has features in common with energetic, jet-driven structures in the prototypical Seyfert galaxy NGC 1068.

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First results from the NuSTAR “mini-survey” of the Galactic center region

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314001094 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 439-443

Author(s):

Charles J. Hailey ◽

Keyword(s):

Galactic Center ◽

Galactic Plane ◽

Pulsar Wind Nebulae ◽

Telescope Array ◽

X Ray ◽

Center Region ◽

First Results ◽

Pulsar Wind ◽

Sgr A

AbstractOne of the major science objectives of the Nuclear Spectroscopic Telescope Array (NuSTAR) observatory is to perform the first sub-arcminute, hard X-ray survey of several square degrees of the Galactic plane, centered on a region near the Galactic center. As a prelude to the full survey, which began in July 2013, NuSTAR conducted a ∼500 ks, 0.3 × 0.4° “mini-survey” focused on Sgr A* and its environs. We present analysis of several candidate pulsar wind nebulae and filaments, which are revealed to be intense sources of X-ray emission at >10 keV.

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The Nucleus of Our Home Galaxy: A Remnant of an Active or a Starburst Galaxy?

Symposium - International Astronomical Union ◽

10.1017/s0074180900175527 ◽

1994 ◽

Vol 159 ◽

pp. 351-354

Author(s):

Leonid M. Ozernoy

Keyword(s):

Black Hole ◽

Galactic Center ◽

Radiation Spectrum ◽

Seyfert Galaxy ◽

Star Formation History ◽

Starburst Galaxy ◽

Formation History ◽

History Of ◽

Sgr A ◽

Radio Band

To resolve the above dilemma, two essentially different approaches are undertaken: First, a new, detailed analysis of the entire radiation spectrum of Sgr A∗, from radio band up to gamma-rays, is reviewed, which enables us to put substantial constraints on the mass of a putative black hole. The derived upper limit turns out to be too small to allow the black hole to serve as an ‘engine’ for a Seyfert galaxy. Second, analyses of recent data on the 10 KeV gas in the central 200 pc and on star formation history at the Galactic center both make a star burst the likely episode in a recent past. Taken together, the two approaches seem to indicate that the history of the central part of our Galaxy can be better described as that of a starburst, rather than a Seyfert, galaxy.

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7.13. The Sgr A East HII complex and associated features

Symposium - International Astronomical Union ◽

10.1017/s0074180900085090 ◽

1998 ◽

Vol 184 ◽

pp. 317-318 ◽

Cited By ~ 4

Author(s):

Keven I. Uchida ◽

Mark R. Morris ◽

Gene Serabyn ◽

David Fong ◽

Thomas Meseroll

Keyword(s):

Star Formation ◽

Massive Star ◽

Galactic Center ◽

Galactic Plane ◽

Alternative Hypothesis ◽

Rapid Expansion ◽

H Ii Regions ◽

Expansion Time ◽

Sgr A ◽

Relativistic Particles

The Sgr A East H ii complex consists of 4 compact H ii regions situated just east of and following, in an arc pattern, the edge of the Sgr A East nonthermal shell. Located between the arc of H ii regions and the nonthermal shell is a dense molecular ridge – presumably compressed – known as the “50 km/s cloud”. The hypothesis that these H ii regions delineate massive star formation provoked by the rapid expansion of Sgr A East into the molecular cloud is problematical because of the mismatch of the shell expansion and star formation time scales. We therefore examine the alternative hypothesis that Sgr A East is a quasi-static or slowly expanding structure fed from within by the release of relativistic particles from sources at or near the nucleus. The elongation of SgrA East along the Galactic plane is ascribed to the shear inherent in the velocity field this close to the Galactic center (GC). In this proceeding we discuss our ongoing efforts to model the effects of shear in detail, using the elongation of Sgr A East to constrain its expansion time scale.

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Detailed distributions of the CO J = (2 − 1)/J = (1 − 0) intensity ratios toward a large area of the central molecular zone

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000295 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 106-108

Author(s):

Kazufumi Torii ◽

Rei Enokiya ◽

Yasuo Fukui ◽

Hiroaki Yamamoto ◽

Akiko Kawamura ◽

...

Keyword(s):

Angular Resolution ◽

Galactic Center ◽

Galactic Plane ◽

Area Coverage ◽

High Angular Resolution ◽

Molecular Gas ◽

Large Area ◽

First Results ◽

Intensity Ratios ◽

Sgr A

AbstractWe present the first results of the new CO J = (2 − 1) observations toward the central molecular zone (CMZ) using the NANTEN2 telescope at an angular resolution of 100″. Large area coverage of 4° × 2° in l and b and a high angular resolution of 100″ enable us to investigate detailed structures of the molecular gas in the CMZ including peculiar molecular filaments perpendicularly to the Galactic plane to b > |0.5°|. The major components of the CMZ, e.g., Sgr A, Sgr B and Sgr C cloud complexes, show high CO J = (2 − 1)/J = (1 − 0) ratios around 0.9, indicating highly excited conditions of the molecular gas, while the local foreground components show less than 0.4. The molecular filaments show the typical ratios of 0.6–0.7 indicate that they are indeed located in the Galactic center.

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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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An X-ray image of the Seyfert galaxy NGC 1068

The Astrophysical Journal ◽

10.1086/186402 ◽

1992 ◽

Vol 391 ◽

pp. L75 ◽

Cited By ~ 39

Author(s):

A. S. Wilson ◽

M. Elvis ◽

A. Lawrence ◽

J. Bland-Hawthorn

Keyword(s):

Seyfert Galaxy ◽

X Ray ◽

Ngc 1068

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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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Nonthermal filamentary radio features within 20 pc of the Galactic center

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000933 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 369-373 ◽

Cited By ~ 2

Author(s):

M. R. Morris ◽

J.-H. Zhao ◽

W. M. Goss

Keyword(s):

Galactic Center ◽

Galactic Plane ◽

Pulsar Wind Nebulae ◽

Flux Tubes ◽

Deep Imaging ◽

Point Reflection ◽

Predominant Orientation ◽

Magnetic Flux Tubes ◽

Field Lines ◽

Sgr A

AbstractDeep imaging of the Sgr A complex at 6 cm wavelength with the B and C configurations of the Karl G. Jansky VLA† has revealed a new population of faint radio filaments. Like their brighter counterparts that have been observed throughout the Galactic center on larger scales, these filaments can extend up to ∼10 parsecs, and in most cases are strikingly uniform in brightness and curvature. Comparison with a survey of Paschen-α emission reveals that some of the filaments are emitting thermally, but most of these structures are nonthermal: local magnetic flux tubes illuminated by synchrotron emission. The new image reveals considerable filamentary substructure in previously known nonthermal filaments (NTFs). Unlike NTFs previously observed on larger scales, which tend to show a predominant orientation roughly perpendicular to the Galactic plane, the NTFs in the vicinity of the Sgr A complex are relatively randomly oriented. Two well-known radio sources to the south of Sgr A – sources E and F – consist of numerous quasi-parallel filaments that now appear to be particularly bright portions of a much larger, strongly curved, continuous, nonthermal radio structure that we refer to as the “Southern Curl”. It is therefore unlikely that sources E and F are Hii regions or pulsar wind nebulae. The Southern Curl has a smaller counterpart on the opposite side of the Galactic center – the Northern Curl – that, except for its smaller scale and smaller distance from the center, is roughly point-reflection symmetric with respect to the Southern Curl. The curl features indicate that some field lines are strongly distorted, presumably by mass flows. The point symmetry about the center then suggests that the flows originate near the center and are somewhat collimated.

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