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

Abstract

[abridged] 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 disc, 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))/eROSITA first all-sky survey (eRASS1), in this work, we aim to provide a panoramic view of the hot circumgalactic medium (CGM) of the Milky Way. Here we present the eROSITA eRASS1 half sky maps in narrow energy bands corresponding to the most prominent soft X-ray lines: OVII and OVIII, which allow 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 use the line ratio of the oxygen lines as a proxy to constrain the temperature of the warm-hot CGM, and we define a pseudo-temperature $\mathcal{T}$ map. The map highlights how different regions are dominated by different thermal components. Towards the outer halo, the temperature distribution of the CGM on angular scales of 2-20 deg is consistent with being constant $\Delta \mathcal{T}/⟨\mathcal{T}⟩\le 4\%$, with a marginal detection of $\Delta \mathcal{T}/⟨\mathcal{T}⟩=2.7\%\pm 0.2\%$ (statistical) $\pm 0.6\%$ (systematic) in the southern hemisphere. Instead, significant variations $\sim 12\%$ are observed on many tens of degrees scales when comparing the northern and southern hemispheres.

15 pages, 14 figures, 1 table, A&A in press

References in corpus (18)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The eROSITA X-ray telescope on SRG
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• The SRG X-ray orbital observatory, its telescopes and first scientific results
• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• The eROSITA Final Equatorial Depth Survey (eFEDS): The X-ray catalog
• Constraining the Milky Way's Hot Gas Halo with OVII and OVII Emission Lines
• Detection of large-scale X-ray bubbles in the Milky Way halo
• Polarised radio filaments outside the Galactic plane
• The Structure of the Local Hot Bubble
• Abundance and temperature of the outer hot circum-Galactic medium: The SRG/eROSITA view of the soft X-ray background in the eFEDS field
• The warm-hot circumgalactic medium of the Milky Way as seen by eROSITA
• Thermal and chemical properties of the eROSITA bubbles from Suzaku observations
• SRG/eROSITA X-ray shadowing study of giant molecular clouds
• disnht: modeling X-ray absorption from distributed column densities
• On the patchy appearance of the circum-Galactic medium and the influence of foreground absorption
• Discovery of the Goat Horn complex: a $\sim 1000$ deg${}^2$ diffuse X-ray source connected to radio loop XII

Cited by in corpus (5)

• Quantifying Observational Projection Effects with a Simulation-based hot CGM model
• Cross-correlation between soft X-rays and galaxies A new benchmark for galaxy evolution models
• The SRG/eROSITA All-Sky Survey: Large-scale view of the Centaurus cluster
• Discovery of the Goat Horn complex: a $\sim 1000$ deg${}^2$ diffuse X-ray source connected to radio loop XII
• Retrieving the hot circumgalactic medium physics from the X-ray radial profile from eROSITA with an IlustrisTNG-based forward model