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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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Circumgalactic Ly α emission around submillimeter-bright galaxies with different quasar contributions
We present VLT/MUSE observations targeting the extended Lyman-α(Lyα) emission of five high-redshift (z ∼ 3-4) submillimeter galaxies (SMGs) with increasing quasi-stellar object (QSO) radiation: two SMGs; two SMGs that host a QSO; and one SMG that hosts a QSO with an SMG companion (QSO+SMG). These sources are predicted to be located in dark matter halos of comparable masses (average mass ofMDM ∼ 1012.2 M⊙). We quantified the luminosity and extent of the Lyαemission, together with its kinematics, and examined four Lyαpowering mechanisms: photoionization from QSOs or star formation, shocks by galactic and/or QSO outflows, gravitational cooling radiation, and Lyαphoton resonant scattering. We find a variety of Lyαluminosities and extents, with the QSO+SMG system displaying the most extended and bright nebula, followed by the SMGs hosting a QSO, and finally the undetected circumgalactic medium of SMGs. This diversity implies that gravitational cooling is unlikely to be the main powering mechanism. We show that photoionization from the QSO and QSO outflows can contribute to power the emission for average densitiesnH > 0.5 cm−3. Moreover, the observed Lyαluminosities scale with the QSO’s budget of Lyαphotons modulo the dust content in each galaxy, highlighting a possible contribution from resonant scattering of QSO radiation in powering the nebulae. We find larger Lyαlinewidths (FWHM ≳ 1200 km s−1) than usually reported around radio-quiet systems, pointing to large-scale outflows. A statistical survey targeting similar high-redshift massive systems with known host properties is needed to confirm our findings.
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- Award ID(s):
- 2103251
- PAR ID:
- 10539221
- Publisher / Repository:
- A&A
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 679
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A41
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1051/0004-6361/202346879
