The recent discovery by Cantalupo et al. of the largest (∼500 kpc) luminous (L ≃ 1.43 1045 erg s-1) Lyα nebula associated with the quasar UM287 (z = 2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z ∼ 2 galaxies. Either an enormous reservoir of cool gas is required M ≃ 1012 Mo, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. However, observations of Lyα emission alone cannot distinguish between these two scenarios. We have obtained the deepest ever spectroscopic integrations in the He ii λ1640 and C iv λ1549 emission lines with the goal of detecting extended line emission, but detect neither line to a 3σ limiting SB ≃ 10-18 erg s-1 cm-2 arcsec-2. We construct simple models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. The non-detection of He ii implies that the nebular emission arises from a mass Mc ≲ 6.4 1010 Mo of cool gas on ∼200 kpc scales, distributed in a population of remarkably dense (nH γ 3 cm-3) and compact (R ≲ 20 pc) clouds, which would clearly be unresolved by current cosmological simulations. Given the large gas motions suggested by the Lyα line (v ≃ 500 km s-1), it is unclear how these clouds survive without being disrupted by hydrodynamic instabilities. Our work serves as a benchmark for future deep integrations with current and planned wide-field IFU spectrographs such as MUSE, KCWI, and KMOS. Our observations and models suggest that a ≃10 hr exposure would likely detect ∼10 rest-frame UV/optical emission lines, opening up the possibility of conducting detailed photoionization modeling to infer the physical state of gas in the circumgalactic medium.

Battaia, F., Hennawi, J., Prochaska, J., & Cantalupo, S. (2015). Deep he II and c IV spectroscopy of a giant lyα nebula: Dense compact gas clumps in the circumgalactic medium of a z ∼ 2 quasar. THE ASTROPHYSICAL JOURNAL, 809(2) [10.1088/0004-637X/809/2/163].

Deep he II and c IV spectroscopy of a giant lyα nebula: Dense compact gas clumps in the circumgalactic medium of a z ∼ 2 quasar

Cantalupo S.
2015

Abstract

The recent discovery by Cantalupo et al. of the largest (∼500 kpc) luminous (L ≃ 1.43 1045 erg s-1) Lyα nebula associated with the quasar UM287 (z = 2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z ∼ 2 galaxies. Either an enormous reservoir of cool gas is required M ≃ 1012 Mo, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. However, observations of Lyα emission alone cannot distinguish between these two scenarios. We have obtained the deepest ever spectroscopic integrations in the He ii λ1640 and C iv λ1549 emission lines with the goal of detecting extended line emission, but detect neither line to a 3σ limiting SB ≃ 10-18 erg s-1 cm-2 arcsec-2. We construct simple models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. The non-detection of He ii implies that the nebular emission arises from a mass Mc ≲ 6.4 1010 Mo of cool gas on ∼200 kpc scales, distributed in a population of remarkably dense (nH γ 3 cm-3) and compact (R ≲ 20 pc) clouds, which would clearly be unresolved by current cosmological simulations. Given the large gas motions suggested by the Lyα line (v ≃ 500 km s-1), it is unclear how these clouds survive without being disrupted by hydrodynamic instabilities. Our work serves as a benchmark for future deep integrations with current and planned wide-field IFU spectrographs such as MUSE, KCWI, and KMOS. Our observations and models suggest that a ≃10 hr exposure would likely detect ∼10 rest-frame UV/optical emission lines, opening up the possibility of conducting detailed photoionization modeling to infer the physical state of gas in the circumgalactic medium.
Articolo in rivista - Articolo scientifico
cosmology: observations; galaxies: formation; galaxies: halos; intergalactic medium; quasars: emission lines
English
Battaia, F., Hennawi, J., Prochaska, J., & Cantalupo, S. (2015). Deep he II and c IV spectroscopy of a giant lyα nebula: Dense compact gas clumps in the circumgalactic medium of a z ∼ 2 quasar. THE ASTROPHYSICAL JOURNAL, 809(2) [10.1088/0004-637X/809/2/163].
Battaia, F; Hennawi, J; Prochaska, J; Cantalupo, S
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/297347
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