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
2015
809
2
163
none
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].
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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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