The eROSITA Final Equatorial Depth Survey (eFEDS) X-ray emission around star-forming and quiescent galaxies at 0.05 < z < 0.3

Johan Comparat, Nhut Truong, Andrea Merloni, Annalisa Pillepich, Gabriele Ponti, Simon Driver, Sabine Bellstedt, Joe Liske, James Aird, Marcus Brueggen, Esra Bulbul, Luke Davies, Justo Antonio Gonzalez Villalba, Antonis Georgakakis, Frank Haberl, Teng Liu, Chandreyee Maitra, Kirpal Nandra, Paola Popesso, Peter PredehlAaron Robotham, Mara Salvato, Jessica E. Thorne, Yi Zhang

Research output: Contribution to journalArticlepeer-review

1 Citation (Web of Science)


Aims. The circumgalactic medium (CGM) plays an important role in galaxy evolution as the main interface between the star-forming body of galaxies and the surrounding cosmic network of in- and out-flowing matter. In this work, we aim to characterize the hot phase of the CGM in a large sample of galaxies using recent soft-X-ray observations made by SRG/eROSITA.

Methods. We stack X-ray events from the 'eROSITA Final Equatorial Depth Survey' (eFEDS) around central galaxies in the 9hr field of the 'GAlaxy and Mass Assembly' (GAMA) survey to construct radially projected X-ray luminosity profiles in the 0.5-2 keV rest frame energy band as a function of their stellar mass and specific star formation rate. We consider samples of quiescent (star-forming) galaxies in the stellar mass range 2 x 10(10)-10(12) M-circle dot (3 x 10(9)-6 x 10(11) M-circle dot).

Results. For quiescent galaxies, the X-ray profiles are clearly extended throughout the available mass range; however, the measured profile is likely biased high because of projection effects, as these galaxies tend to live in dense and hot environments. For the most massive star-forming samples (>= 10(11) M-circle dot), there is a hint of detection of extended emission. On the other hand, for star-forming galaxies with 10(11) M-circle dot) star-forming or quiescent galaxies follow the expected scaling of virialized hot haloes, while lower mass star-forming galaxies show a less prominent luminosity and a weaker dependence on stellar mass consistent with empirical models of the population of weak AGN. When comparing our results with state-of-the-art numerical simulations (IllustrisTNG and EAGLE), we find overall consistency on the average emission on large (>80 kpc) scales at masses >= 10(11) M-circle dot, but disagreement on the small scales, where brighter-than-observed compact cores are predicted. The simulations also do not predict the clear differentiation that we observe between quiescent and star-forming galaxies in our samples.

Conclusions. This is a stepping stone towards a more profound understanding of the hot phase of the CGM, which holds a key role in the regulation of star formation. Future analysis using eROSITA all-sky survey data, combined with future generation galaxy evolution surveys, shall provide much enhanced quantitative measurements and mapping of the CGM and its hot phase(s).

Original languageEnglish
Article number156
Number of pages23
JournalAstronomy & Astrophysics
Publication statusPublished - 20 Oct 2022


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