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Title: H i Lyα Emission from a Metal-poor Cool Stream Fueling an Early Dusty Starburst
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.  more » « less
Award ID(s):
2103251
PAR ID:
10539217
Author(s) / Creator(s):
;
Publisher / Repository:
IOP
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
969
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
39
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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