Mapping the Nuclear Outflow of the Milky Way: Studying the Kinematics and Spatial Extent of the Northern Fermi Bubble

Bordoloi, Rongmon; Fox, Andrew; Lockman, Felix J.; Wakker, Bart P.; Jenkins, Edward B.; Savage, Blair D.; Hernández, Svea; Tumlinson, Jason; Bland-Hawthorn, Joss; Kim, Tae-Sun

doi:10.3847/1538-4357/834/2/191

Cited by 104 publications

(149 citation statements)

References 91 publications

(128 reference statements)

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“…The C II observations for LS 4825 are consistent with the outflow velocity versus galactic latitude trend established by the five lines of sight through the northern Fermi Bubble displayed in Figure 3 of Bordoloi et al (2017).…”

Section: The Kinematical Signature Of An Outflow In Multiple Gas Phasessupporting

confidence: 81%

“…In a subsequent paper Bordoloi et al (2017) studied the UV absorption toward five lines of sight passing through the northern Fermi Bubble and found that all five exhibited blue shifted high velocity components while only 9 of 42 lines of sight outside the Fermi Bubble exhibited blue shifted high velocity components. The blue shifted Galactic standard of rest (GSR) velocities for the high velocity absorbers in directions inside the Fermi Bubble change from v GSR = -265 to -91 km s -1 from Galactic latitude b = 11° to b = 50°.…”

Section: Introductionmentioning

confidence: 99%

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Probing the Outflowing Multiphase Gas ∼1 kpc below the Galactic Center

Savage¹,

Kim²,

Fox³

et al. 2017

ApJS

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Comparison of ISM absorption in the UV spectrum of LS 4825, a B1 Ib-II star d=21±5 kpc from the Sun toward l = 1.67° and b = -6.63°, with ISM absorption toward an aligned foreground star at d < 7.0±1.7 kpc, allows us to isolate and study gas associated with the Milky Way nuclear wind. Spectra from the Space Telescope Imaging Spectrograph (STIS) show low ion absorption out to d < 7 kpc ( e.g., O I, C II, Mg II, Si II, Fe II, S II) only between 0 and 40 km s -1 , while absorption at d > 7 kpc, ~1 kpc below the galactic plane, is complex and spans -290 to + 94 km s -1 . The intermediate and high ions Si III, C IV, Si IV and N V show extremely strong absorption with multiple components from -283 to 107 km s -1 implying that the ISM ~1 kpc below the galactic center has a substantial reservoir of plasma, and more gas containing C IV and N V than in the Carina OB1 association at z = 0 kpc. Abundances and physical conditions are presented for many absorption components. The high ion absorption traces cooling transition temperature plasma probably driven by the outflowing hot gas, while the extraordinary large thermal pressure, p/k ~ 10 5 cm -3 K -1 in an absorption component at -114 km s -1 probably arises from the ram pressure of the outflowing hot gas. The observations are consistent with a flow whose ionization structure in the high ions can be understood through a combination of non-equilibrium radiative cooling and turbulent mixing.

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Section: The Kinematical Signature Of An Outflow In Multiple Gas Phasessupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Probing the Outflowing Multiphase Gas ∼1 kpc below the Galactic Center

Savage¹,

Kim²,

Fox³

et al. 2017

ApJS

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“…This is achieved by cross-matching the R17 sample with the Fox et al (2014) catalog of Stream absorbers, which covers sightlines within 30 • of the 21 cm emission from the Stream, and then removing matched sightlines from the sample. We also remove several sightlines passing through the Fermi Bubbles (Bordoloi et al 2017;Karim et al 2018), since the HVCs in these directions are thought to trace a nuclear wind and so are distinct from the general HVC population.…”

Section: Derivation Of Hvc Mass and Mass Flow Ratementioning

confidence: 99%

“…Finally, the HVC mass flow rates presented here do not include (by design) the Magellanic Stream and Leading Arm or the Fermi Bubbles, since these structures are physically unrelated to the remaining HVC population. The Stream represents an a much larger inflow rate of ≈3-7 M yr −1 (Fox et al 2014, R17) and the Fermi Bubbles have an outflow rate of 0.2-0.3 M yr −1 in cool gas (Bordoloi et al 2017).…”

Section: Velocity Limit Ionization and Saturation Effectsmentioning

confidence: 99%

The Mass Inflow and Outflow Rates of the Milky Way

Richter

Ashley

Heckman

et al. 2019

ApJ

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We present new calculations of the mass inflow and outflow rates around the Milky Way (MW), derived from a catalog of ultraviolet metal-line high velocity clouds (HVCs). These calculations are conducted by transforming the HVC velocities into the Galactic Standard of Rest (GSR) reference frame, identifying inflowing (v GSR < 0 km s −1 ) and outflowing (v GSR > 0 km s −1 ) populations, and using observational constraints on the distance, metallicity, dust content, covering fractions, and total silicon column density of each population. After removing HVCs associated with the Magellanic Stream and the Fermi Bubbles, we find inflow and outflow rates in cool (T ∼ 10 4 K) ionized gas of dM in /dt (0.53± 0.23) (d/12 kpc)(Z/0.2Z ) −1 M yr −1 and dM out /dt (0.16 ± 0.07) (d/12 kpc)(Z/0.5Z ) −1 M yr −1 . The apparent excess of inflowing over outflowing gas suggests that the MW is currently in an inflowdominated phase, but the presence of substantial mass flux in both directions supports a Galactic fountain model, in which gas is constantly recycled between the disk and the halo. We also find that the metal flux in both directions (in and out) is indistinguishable. By comparing the outflow rate to the Galactic star formation rate, we present the first estimate of the mass loading factor (η HVC ) of the disk-wide MW wind, finding η HVC (0.10±0.06) (d/12 kpc)(Z/0.5Z ) −1 . Including the contributions from low-and intermediate-velocity clouds and from hot gas would increase these inflow and outflow estimates.

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“…The canonical threshold surface density for driving galactic outflows, Σ SFR > 0.1 M yr −1 kpc −2 , is based on local starburst galaxies (Heckman 2002). However, both recent integral field spectroscopy results from local main sequence galaxies (Ho et al 2016) and evidence of galactic outflows within the Milky Way Fermi Bub- bles (Fox et al 2015;Bordoloi et al 2017) suggest that galaxies with lower Σ SFR values (Σ SFR ≈ 10 −3 − 10 −1.5 M yr −1 kpc −2 ) can drive outflows. The threshold surface density may evolve with redshift (Sharma et al 2016) and may also depend on the galaxy properties, especially the gas fraction (Newman et al 2012).…”

Section: 4mentioning

confidence: 99%

The MUSEHubbleUltra Deep Field Survey

Finley

Bouché

Contini

et al. 2017

A&A

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Non-resonant Fe ii* (λ2365, λ2396, λ2612, λ2626) emission can potentially trace galactic winds in emission and provide useful constraints to wind models. From the 3.15 × 3.15 mosaic of the Hubble Ultra Deep Field (UDF) obtained with the VLT/MUSE integral field spectrograph, we identify a statistical sample of 40 Fe ii* emitters and 50 Mg ii (λλ2796, 2803) emitters from a sample of 271 [O ii]λλ3726, 3729 emitters with reliable redshifts from z = 0.85 − 1.50 down to 2 × 10 −18 (3 σ) ergs s, covering the M range from 10 8 − 10 11 M . The Fe ii* and Mg ii emitters follow the galaxy main sequence, but with a clear dichotomy. Galaxies with masses below 10 9 M and star formation rates (SFRs) of 1 M yr −1 have Mg ii emission without accompanying Fe ii* emission, whereas galaxies with masses above 10 10 M and SFRs 10 M yr −1 have Fe ii* emission without accompanying Mg ii emission. Between these two regimes, galaxies have both Mg ii and Fe ii* emission, typically with Mg ii P-Cygni profiles. Indeed, the Mg ii profile shows a progression along the main sequence from pure emission to P-Cygni profiles to strong absorption, due to resonant trapping. Combining the deep MUSE data with HST ancillary information, we find that galaxies with pure Mg ii emission profiles have lower star formation rate surface densities than those with either Mg ii P-Cygni profiles or Fe ii* emission. These spectral signatures produced through continuum scattering and fluorescence, Mg ii P-Cygni profiles and Fe ii* emission, are better candidates for tracing galactic outflows than pure Mg ii emission, which may originate from H ii regions. We compare the absorption and emission rest-frame equivalent widths for pairs of Fe ii transitions to predictions from outflow models and find that the observations consistently have less total re-emission than absorption, suggesting either dust extinction or non-isotropic outflow geometries.

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Mapping the Nuclear Outflow of the Milky Way: Studying the Kinematics and Spatial Extent of the Northern Fermi Bubble

Cited by 104 publications

References 91 publications

Probing the Outflowing Multiphase Gas ∼1 kpc below the Galactic Center

Probing the Outflowing Multiphase Gas ∼1 kpc below the Galactic Center

The Mass Inflow and Outflow Rates of the Milky Way

The MUSEHubbleUltra Deep Field Survey

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