The Large-Scale Bipolar Wind in the Galactic Center

By Joss Bland-Hawthorn, Marvin L. Cohen. 2002

247 citations recorded by the source corpus.

During a 9 month campaign (1996-1997), the Midcourse Space Experiment (MSX) satellite mapped the Galactic plane at mid-infrared wavelengths (4.3-21.3 μm). The much greater spatial resolution and sensitivity of the MSX 8.3 μm band, compared to IRAS at 12 μm, has revealed diffuse emission not seen before. Here we report evidence of a spectacular, limb-brightened, bipolar structure at the Galactic center extending more than a degree (170 pc at 8.0 kpc) on either side of the plane. The 8.3 μm filamentary emission appears confined to a dome-shaped shell, which extends perpendicular to the plane, and shows a tight correlation with the 3, 6, and 11 cm continuum emission over the same scales. The most likely scenario is that the extraplanar 8.3 μm emission arises from dust entrained in a large-scale, bipolar wind powered by a central starburst. The inferred energy injection at the source is ~1054/κ ergs, for which κ is the covering fraction of the dusty shell (κ ≲ 0.1). In accord with the stellar record in the Galactic center, we infer that a powerful nuclear starburst has taken place within the last several million years. The inferred energies require ≳104/ϵ supernovae, where ϵ is the thermalization efficiency of the supernova ejecta. There is observational evidence of a Galactic wind on much larger scales, presumably from the same central source that produced the bipolar shell seen by MSX. Sofue has long argued that the North Polar Spur—a thermal X-ray/radio loop that extends from the Galactic plane to b = +80°—was powered by a nuclear explosion [ × 1055 ergs] roughly 15 Myr ago, although his published models did not explain the projected loop structure. We demonstrate that an open-ended bipolar model, when viewed in projection in the near field, provides the most natural explanation for the observed loop structure. The ROSAT 1.5 keV diffuse X-ray map over the inner 45° provides compelling evidence for this interpretation. Since the faint bipolar emission would be very difficult to detect beyond the Galaxy, the phenomenon of large-scale galactic winds may be far more common than has been observed to date. The derived energetics for the bipolar wind are of the order of 1055 ergs, in line with the energy requirement of the MSX observations. We infer that the Galactic center is driving large-scale winds into the halo every ~10-15 Myr or so.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1a57d478ec29e67bffbad8b5fc18b843e5aa0bf4

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Citations in the corpus

DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA (2016, result): “In Casandjian (2015a), we noted that those catenary curves also correctly reproduce the structures observed close to the GC in the ROSAT X-ray observations (Bland-Hawthorn & Cohen 2003).”
A 20 Centimeter Survey of the Galactic Center Region. I. Detection of Numerous Linear Filaments (2004, background): “It is possible the winds from clustered star formation in a star burst environment are responsible for the origin of the filaments as well as the lobes (Bland-Hawthorn and Cohen 2003; Law et al. 2004).”
THE FERMI BUBBLES. I. POSSIBLE EVIDENCE FOR RECENT AGN JET ACTIVITY IN THE GALAXY (2011, methodology): “The shocked gas near the shock front has higher densities (ne ∼ 1 - 4 × 10−3 cm−3) and temperatures (T ∼ 3 - 7 keV), potentially explaining the dumbbellshaped X-ray shell features detected by the ROSAT X-ray telescope (Sofue 2000; Bland-Hawthorn & Cohen 2003).”
GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND? (2010, background): “Reflection of the shocks increases the density and temperature of the post-shocked gas, which has been suggested to have T ≈ 5×106 K and n ≈ 0.1 cm−3 at 2 kpc above the plane (Bland-Hawthorn & Cohen 2003b).”
Cool outflows in galaxies and their implications (2020, background): “5-keV ROSAT all-sky maps (Fig. 9d; Bland-Hawthorn and Cohen 2003) are indicative of a large (± 3 kpc) bipolar outflow of warm-hot plasma centered on the GC.”
Chemical evolution with radial mixing (2008, background): “Indeed, in addition to gas that flows out in the Galactic wind (Bland-Hawthorn & Cohen 2003), Type Ia SNe in dwarf spheroidal galaxies will have contributed their Fe to the local IGM, and if the Magellanic Stream C© 2009 The Authors.”
EVIDENCE FOR UBIQUITOUS COLLIMATED GALACTIC-SCALE OUTFLOWS ALONG THE STAR-FORMING SEQUENCE AT z ∼ 0.5 (2013, methodology): “These include the detection of dust emission with a bipolar structure at the Galactic center (Bland-Hawthorn & Cohen 2003) and the presence of high-velocity clouds of metal-enriched gas directly above and below the Galactic center (Keeney et al. 2006).”
Hierarchical formation of bulgeless galaxies – II. Redistribution of angular momentum via galactic fountains (2011, background): “The bipolar structure at the Galactic centre (Bland-Hawthorn & Cohen 2003; Su et al. 2010) lends support for galactic scale outflows from the central regions, even locally.”
The physics of galactic winds driven by active galactic nuclei (2012, background): “…cooling (T ∝ ρ2/3) would then imply that the bubble would now have an interior temperature ∼ 107 K. Thermal free free emission from gas at this temperature is consistent with 1.5 keV soft X-ray features coincident with the Fermi bubbles previously detected by ROSAT 10 (Bland-Hawthorn & Cohen 2003).”
THREE-DIMENSIONAL INTEGRAL FIELD OBSERVATIONS OF 10 GALACTIC WINDS. I. EXTENDED PHASE (≳10 Myr) OF MASS/ENERGY INJECTION BEFORE THE WIND BLOWS (2010, background): “Secondly, there is now strong evidence for large-scale outflows in the Galaxy across the electromagnetic spectrum (Bland-Hawthorn & Cohen 2003; Fox et al. 2005; Keeney et al. 2006).”
A NEW ELECTRON-DENSITY MODEL FOR ESTIMATION OF PULSAR AND FRB DISTANCES (2016, background): “Although not universally accepted (see, e.g., Bland-Hawthorn & Cohen 2003; Puspitarini et al. 2014), we adopt the view that the North Polar Spur is associated with Loop I and that Loop I is relatively local, probably associated with outflow from the Scorpio–Centaurus OB association (see, e.g.,…”
Multiphase High-Velocity Clouds toward HE 0226–4110 and PG 0953+414 (2005, methodology): “HVCs regulate the rate of star formation in our ownGalaxy, by providing gaseous material from which new stars are born.”
Dynamics for galactic archaeology (2013, background): “This is a region of intense star formation as is evidenced by the plethora of SN remnants seen in radio continuum maps (Kassim et al., 1999) and the X-ray emitting wind that emanates from this region (Bland-Hawthorn & Cohen, 2003).”
CONSTRAINING THE MILKY WAY'S HOT GAS HALO WITH O vii AND O viii EMISSION LINES (2014, background): “It is unclear how the bubbles have impacted the Milky Way’s hot gas halo, but there are signatures of the bubbles in X-ray spectra (Bland-Hawthorn & Cohen 2003; Kataoka et al. 2013).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “But it remains uncertain how much of the gas lies close to the Galactic Plane, and how much of it extends into the halo (Bland-Hawthorn & Cohen 2003).”
Gaseous Galaxy Halos (2012, background): “4) There is a low-density bipolar structure of unknown distance detected in x-ray (Bland-Hawthorn & Cohen, 2003) and gamma-ray maps (Su et al., 2010) that is consistent with hot gas being sent into the extended halo.”
Three-Dimensional Simulations of a Starburst-driven Galactic Wind (2008, background): “The center of the biconical region could also have been swept clear by a previous wind, powered by an earlier burst of star formation (e.g., Bland-Hawthorn & Cohen 2003; Förster Schreiber et al. 2003).”
Observational Signatures of Particle Acceleration in Supernova Remnants (2012, background): “The estimated energy content of the bubbles is of the order of 1055 erg (Bland-Hawthorn and Cohen, 2003; Su et al., 2010).”
Variations in the Galactic star formation rate and density thresholds for star formation (2012, background): “Evidence exists of episodic SF events in the CMZ (Sofue & Handa 1984; Yusef-Zadeh et al. 2009; Su et al. 2010; Bland-Hawthorn & Cohen 2003) and mechanisms exist to explain how such episodic SF can occur.”