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Abstract The GAMA J0913−0107 system is a rare conjunction of a submillimeter galaxy (SMG) atz≈ 2.7 and two background QSOs with projected separations <200 kpc. Previous high-resolution QSO absorption-line spectroscopy has revealed high Hicolumn density, extremely metal-poor (∼1% solar) gas streams in the circumgalactic medium of the SMG. Here we present deep optical integral-field spectroscopy of the system with the Keck Cosmic Web Imager (KCWI). Reaching a 2σsurface brightness limit ≈10−19erg s−1cm−2arcsec−2with ∼2 hr of integration time, we detect a filamentary Lyαnebula stretching ∼180 kpc from the SMG intercepting both QSO sightlines. This Lyαfilament may correspond to the same cool gas stream penetrating through the hot halo seen in the absorption. In contrast to Lyαnebulae around QSOs, there is no obvious local source for photoionization due to the massive dust content. While uncertain, we consider the possibility that the nebula is ionized by shocks induced by the infall, obscured star formation, and/or a boosted UV background. The SMG–QSOs conjunction multiplied the efficiency of the KCWI observations, allowing a direct comparison of Lyαnebulae in two distinct environments. We find that the nebulae around the QSOs are much brighter and show steeper surface brightness profiles than the SMG nebula. This is consistent with the additional photoionization and Lyαscattering provided by the QSOs. While illustrating the challenges of detecting Lyαnebulae around SMGs, our work also demonstrates that important insights can be gained from comparative studies of high-zLyαnebulae.
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Empirical constraints on the turbulence in QSO host nebulae from velocity structure function measurements
ABSTRACT We present the first empirical constraints on the turbulent velocity field of the diffuse circumgalactic medium around four luminous quasi-stellar objects (QSOs) at z ≈ 0.5–1.1. Spatially extended nebulae of ≈50–100 physical kpc in diameter centred on the QSOs are revealed in [O ii] $$\lambda \lambda \, 3727,3729$$ and/or [O iii] $$\lambda \, 5008$$ emission lines in integral field spectroscopic observations obtained using Multi-Unit Spectroscopic Explorer on the Very Large Telescope. We measure the second- and third-order velocity structure functions (VSFs) over a range of scales, from ≲5 kpc to ≈20–50 kpc, to quantify the turbulent energy transfer between different scales in these nebulae. While no constraints on the energy injection and dissipation scales can be obtained from the current data, we show that robust constraints on the power-law slope of the VSFs can be determined after accounting for the effects of atmospheric seeing, spatial smoothing, and large-scale bulk flows. Out of the four QSO nebulae studied, one exhibits VSFs in spectacular agreement with the Kolmogorov law, expected for isotropic, homogeneous, and incompressible turbulent flows. The other three fields exhibit a shallower decline in the VSFs from large to small scales. However, with a limited dynamic range in the spatial scales in seeing-limited data, no constraints can be obtained for the VSF slopes of these three nebulae. For the QSO nebula consistent with the Kolmogorov law, we determine a turbulence energy cascade rate of ≈0.2 cm2 s−3. We discuss the implication of the observed VSFs in the context of QSO feeding and feedback in the circumgalactic medium.
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- Award ID(s):
- 1715692
- PAR ID:
- 10381879
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 518
- Issue:
- 2
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 2354-2372
- Size(s):
- p. 2354-2372
- Sponsoring Org:
- National Science Foundation
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