The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way

Sarkar, Kartick C.

doi:10.1007/s00159-024-00152-1

Cited by 10 publications

(2 citation statements)

References 417 publications

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“…Alternatively, they could be a local structure at a 100 pc scale (e.g., Das et al 2020;West et al 2021), based on various pieces of evidence against the distant GC-blown model, including the alignment of polarization between the NPS and nearby dust (e.g., Panopoulou et al 2021), the association of the NPS with nearby magnetic field (e.g., Santos et al 2011) and nearby neutral hydrogen (e.g., Welsh & Shelton 2009), and the nondetection of Faraday rotation associated with the NPS (e.g., Hutschenreuter et al 2022). See Lallement et al 2022 andSarkar 2024 for extended reviews of the NPS and the eROSITA bubbles.…”

Section: Introductionmentioning

confidence: 99%

Morphological Evidence for the eROSITA Bubbles Being Giant and Distant Structures

Liu 刘,

Merloni,

Sanders

et al. 2024

ApJL

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There are two contradictory views of the eROSITA bubbles: either a 104 pc scale pair of giant bubbles blown by the Galactic center (GC), or a 102 pc scale local structure coincidentally located in the direction of GC. A key element of this controversy is the distance to the bubbles. Based on the 3D dust distribution in the Galactic plane, we found three isolated, distant (500–800 pc) clouds at intermediate Galactic latitudes. Their projected morphologies perfectly match the X-ray shadows on the defining features of the north eROSITA bubble, i.e., the North Polar Spur (NPS) and the Lotus Petal Cloud (LPC), indicating that both the NPS and LPC are distant, with a distance lower limit of nearly 1 kpc. In the X-ray-dark region between the NPS and LPC, we found a few polarized radio arcs and attributed them to the bubble’s shock front. These arcs match up perfectly with the outer border of the NPS and LPC and provide a way to define the bubble’s border. The border defined in this way can be well described by the line-of-sight tangent of a 3D skewed cup model rooted in the GC. We conclude that, instead of being two independent, distant features, the NPS and LPC compose a single, giant bubble, which therefore is most plausibly a 10 kpc scale bubble rooted at the GC.

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Section: Introductionmentioning

confidence: 99%

Morphological Evidence for the eROSITA Bubbles Being Giant and Distant Structures

Liu 刘,

Merloni,

Sanders

et al. 2024

ApJL

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“…Benefiting from large-scale surveys in multiwavelength, many exciting discoveries have been made in observational and theoretical studies. One of the most important findings is the revelation of the existence of the Fermi bubbles (FBs; i.e., Su et al 2010) that are directly related to the Galactic nuclear winds (e.g., Sofue & Handa 1984;Bland-Hawthorn & Cohen 2003;Dobler et al 2010;Heywood et al 2019;Ponti et al 2019;Predehl et al 2020;Ponti et al 2021;Sarkar 2024). The FBs, together with the combined features in multiwavelengths and multiple spatial scales, are believed to be associated with past energetic events (e.g., nuclear activities and intense processes of massive star formation) near the Galactic center (GC).…”

Section: Introductionmentioning

confidence: 99%

Revealing Gas Inflows Toward the Galactic Central Molecular Zone

Su,

Zhang,

Sun

et al. 2024

ApJL

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We study the gas inflows toward the Galactic Central Molecular Zone (CMZ) based on the gas morphological and kinematic features from the Milky Way Imaging Scroll Painting in the region of l = 1.°2–19.°0 and ∣b∣ ≲ 3.°0. We find that the near dust lane appears to extend to l ∼ 15°, in which the end of the large-scale gas structure intersects with the 3 kpc ring at a distance of ∼5 kpc. Intriguingly, many filamentary molecular clouds (MCs), together with the bow-like/ballistic-like clouds and continuous CO features with notable velocity gradient, are finely outlined along the long structure. These MCs also have relatively large velocity dispersions, indicating the shocked gas generated by local continuous accretion and thus the enhanced turbulence along the entire gas structure. We suggest that the ∼3.1–3.6 kpc-long CO structure originates from the accretion molecular gas driven by the Galactic bar. The gas near the bar end at the 3 kpc ring region becomes an important reservoir for the large-scale accreting flows inward to the CMZ through the bar channel. The inclination angle of the bar is estimated to be ϕ bar = 23° ± 3°, while the pattern speed of the bar is Ωbar ≲ 32.5 ± 2.5 km s−1 kpc−1. The total mass of the whole near gas lane is about 1.3 ± 0.4 × 107 M ⊙ according to the calculated X CO ∼ 1.0 ± 0.4 × 1020 cm−2(K km s−1)−1 from the large-scale 12CO and 13CO data and the complementary H i data. We revisit the gas inflow rate as a mean value of 1.1 ± 0.3 M ⊙ yr−1, which seems to be comparable to the outflow's rate of the Galactic nuclear winds after applying the updated lower X-factor above.

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eROSITA narrowband maps at the energies of soft X-ray emission lines

Zheng,

Ponti,

Locatelli

et al. 2024

A&A

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Hot plasma plays a crucial role in regulating the baryon cycle within the Milky Way, flowing from the energetic sources in the Galactic center and plane, to the corona and the halo. This hot plasma represents an important fraction of the Galactic baryons, plays a key role in galactic outflows and is an important ingredient in galaxy evolution models. Taking advantage of the Spectrum-Roentgen-Gamma (SRG first all-sky survey (eRASS1), in this work our aim is to provide a panoramic view of the hot circumgalactic medium (CGM) of the Milky Way. Compared to the previous all-sky X-ray survey performed by ROSAT, the improved energy resolution of enabled us to map, for the first time, the sky within the narrow energy bands characteristic of soft X-ray emission lines. These lines provide essential information on the physical properties of the hot plasma. Here we present the eRASS1\ half sky maps in narrow energy bands corresponding to the most prominent soft X-ray lines and which allowed us to constrain the distribution of the hot plasma within and surrounding the Milky Way. We corrected the maps by removing the expected contribution associated with the cosmic X-ray background, the time-variable solar wind charge exchange, and the local hot bubble. We applied corrections to mitigate the effect of absorption, therefore highlighting the emission from the CGM of the Milky Way. We used the line ratio of the oxygen lines as a proxy to constrain the temperature of the warm-hot CGM, and we defined a pseudo-temperature $ T $ map. The map highlights how different regions are dominated by different thermal components. Toward the outer halo, the temperature distribution of the CGM on angular scales of 2--20 deg is consistent with being constant $ T T 4<!PCT!>$ with a marginal detection of $ T T = 2.7 <!PCT!> 0.2<!PCT!>$ (statistical) $ 0.6<!PCT!>$ (systematic) in the southern hemisphere. Instead significant variations of $ 12<!PCT!>$ are observed on scales of many tens of degrees when comparing the northern and southern hemispheres. The pseudo-temperature map shows significant variations across the borders of the bubbles, suggesting temperature variations, possibly linked to shocks, between the interior of the Galactic outflow and the unperturbed CGM. In particular, a shell characterized by a lower line ratio appears close to the edge of the bubbles.

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The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way

Cited by 10 publications

References 417 publications

Morphological Evidence for the eROSITA Bubbles Being Giant and Distant Structures

Morphological Evidence for the eROSITA Bubbles Being Giant and Distant Structures

Revealing Gas Inflows Toward the Galactic Central Molecular Zone

eROSITA narrowband maps at the energies of soft X-ray emission lines

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