The stacked Lyα emission profile from the circum-galactic medium of z ∼ 2 quasars

Journal Article · Tue Sep 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/829/1/3· OSTI ID:22868694

Arrigoni Battaia, Fabrizio ^[1]; Hennawi, Joseph F. ^[2]; Cantalupo, Sebastiano ^[3]

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1. European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany)
2. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)
3. Institute for Astronomy, Department of Physics, ETH Zurich, CH-8093 Zurich (Switzerland)

In the context of the FLASHLIGHT survey, we obtained deep narrowband images of 15 z ∼ 2 quasars with the Gemini Multi-object Spectrograph on Gemini South in an effort to measure Lyα emission from circum- and intergalactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Lyα nebulae (SB ∼ 10{sup −17} erg s{sup −1} cm{sup −2} arcsec{sup −2} at distances >50 kpc) around any of our sources, although we routinely (≃47%) detect smaller-scale <50 kpc Lyα emission at this surface brightness level emerging from either the extended narrow emission line regions powered by the quasars or by star formation in their host galaxies. We stack our 15 deep images to study the average extended Lyα surface brightness profile around z ∼ 2 quasars, carefully PSF-subtracting the unresolved emission component and paying close attention to sources of systematic error. Our analysis, which achieves an unprecedented depth, reveals a surface brightness of SB{sub Lyα} ∼ 10{sup −19} erg s{sup −1} cm{sup −2} arcsec{sup −2} at ∼200 kpc, with a 2.3σ detection of Lyα emission at SB {sub Lyα}=(5.5±3.1)×10{sup −20} erg s{sup −1} cm{sup −2} arcsec{sup −2} within an annulus spanning 50 kpc < R < 500 kpc from the quasars. Assuming that this Lyα emission is powered by fluorescence from highly ionized gas illuminated by the bright central quasar, we deduce an average volume density of n {sub H} = 0.6 × 10{sup −2} cm{sup −3} on these large scales. Our results are in broad agreement with the densities suggested by cosmological hydrodynamical simulations of massive (M ≃ 10{sup 12.5} M {sub ⊙}) quasar hosts; however, they indicate that the typical quasars at these redshifts are surrounded by gas that is a factor of ∼100 times less dense than the (∼1 cm{sup −3}) gas responsible for the giant bright Lyα nebulae around quasars recently discovered by our group.

• OSTI ID: 22868694
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 829; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
COMPUTERIZED SIMULATION
DENSITY
DETECTION
DISTANCE
FLUORESCENCE
GALACTIC EVOLUTION
GALAXIES
NEBULAE
QUASARS
RED SHIFT
STARS