Title:	Clues to the origin of Fermi bubbles from O viii/O vii line ratio
Authors:	Sarkar, Kartick Chandra Nath, Biman B. Sharma, Prateek
Keywords:	ISM bubbles star formation
Issue Date:	Jun-2017
Publisher:	Oxford University Press for the Royal Astronomical Society
Citation:	Monthly Notices of the Royal Astronomical Society, 2017, Vol. 467, p3544-3555
Abstract:	We constrain the origin of Fermi bubbles using 2D hydrodynamical simulations of both star formation-driven and black hole accretion-driven wind models. We compare our results with recent observations of O viii to O vii line ratio within and near Fermi bubbles. Our results suggest that independent of the driving mechanisms, a low-luminosity ( L∼0.7--1×1041 erg s−1) energy injection best reproduces the observed line ratio for which the shock temperature is ≈3 × 106 K. Assuming the Galactic halo temperature to be 2 × 106 K, we estimate the shock velocity to be ∼300 km s−1 for a weak shock. The corresponding estimated age of the Fermi bubbles is ∼15–25 Myr. Such an event can be produced either by a star formation rate of ∼0.5 M⊙ yr−1 at the Galactic Centre or a very low-luminosity jet/accretion wind arising from the central black hole. Our analysis rules out any activity that generates an average mechanical luminosity ≳1041 erg s−1 as a possible origin of the Fermi bubbles.
Description:	Open access
URI:	http://hdl.handle.net/2289/6921
ISSN:	0035-8711 1365-2966 (Online)
Alternative Location:	http://adsabs.harvard.edu/abs/2017MNRAS.467.3544S https://arxiv.org/abs/1610.00719 http://dx.doi.org/10.1093/mnras/stx314
Copyright:	2017 The authors & the Royal Astronomical Society
Appears in Collections:	Research Papers (A&A)

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