The REQUIEM Survey. I. A Search for Extended Lyα Nebular Emission Around 31 z > 5.7 Quasars

Abstract

The discovery of quasars a few hundred megayears after the Big Bang represents a major challenge to our understanding of black holes as well as galaxy formation and evolution. Quasarsʼ luminosity is produced by extreme gas accretion onto black holes, which have already reached masses of M BH >10 9 M e by z∼6. Simultaneously, their host galaxies form hundreds of stars per year, using up gas in the process. To understand which environments are able to sustain the rapid formation of these extreme sources, we started a Very Large Telescope/Multi-Unit Spectroscopic Explorer (MUSE) effort aimed at characterizing the surroundings of a sample of 5.7<z<6.6 quasars, which we have dubbed the Reionization Epoch QUasar InvEstigation with MUSE (REQUIEM) survey. We here present results of our searches for extended Lyα halos around the first 31 targets observed as part of this program. Reaching 5σ surface brightness limits of 0.1-1.1×10 −17 erg s −1 cm −2 arcsec −2 over a 1 arcsec 2 aperture, we were able to unveil the presence of 12 Lyα nebulae, eight of which are newly discovered. The detected nebulae show a variety of emission properties and morphologies with luminosities ranging from 8×10 42 to 2×10 44 erg s −1 , FWHMs between 300 and 1700 km s −1 , sizes <30 pkpc, and redshifts consistent with those of the quasar host galaxies. As the first statistical and homogeneous investigation of the circumgalactic medium of massive galaxies at the end of the reionization epoch, the REQUIEM survey enables the study of the evolution of the cool gas surrounding quasars in the first 3 Gyr of the universe. A comparison with the extended Lyα emission observed around bright (M 1450 −25 mag) quasars at intermediate redshift indicates little variations on the properties of the cool gas from z∼6 to z∼3, followed by a decline in the average surface brightness down to z∼2.

Into the Ly α jungle: exploring the circumgalactic medium of galaxies at z ∼ 4−5 with MUSE

“…Once corrected for the cosmological surface brightness dimming, the nebula around SDSS J074749.17+115352.4 is found to be broadly consistent with the ranges measured for such nebulae at z > 3, but with somewhat enhanced surface brightnesses at scales of r 80 comoving kpc. The surface brightness profile of SDSS J074749.17+115352.4 is also comparable to the profiles reported around z ≈ 6 quasars in Drake et al (2019) and Farina et al (2019).…”

“…Further Díaz et al (2020) also report a preference for the galaxies in the proximity of C iv absorption to be towards the faint end of the Lyα luminosity function, something that we do not observe in our own sample. Goto et al 2009;Cantalupo et al 2014;Martin et al 2014;Hennawi et al 2015;Fumagalli et al 2016b;Borisova et al 2016;Arrigoni Battaia et al 2019;Farina et al 2019). Whilst the LAEs and LBGs predominantly probe halo masses of ∼ 10 11 M (e.g.…”

“…In Fig. 19, we compare the nebula's surface brightness profile (extracted from a narrow-band image of 25Å in width and centred at the peak line emission of the nebula) with the average profiles of other nebulae detected with MUSE at z > 3 (Borisova et al 2016;Arrigoni Battaia et al 2019;Farina et al 2019) and with the Keck Cosmic Web Imager (KCWI) at z ∼ 2 (Cai et al 2019). Once corrected for the cosmological surface brightness dimming, the nebula around SDSS J074749.17+115352.4 is found to be broadly consistent with the ranges measured for such nebulae at z > 3, but with somewhat enhanced surface brightnesses at scales of r 80 comoving kpc.…”

Three Lyα Emitting Galaxies within a Quasar Proximity Zone at z ∼ 5.8

“…smaller separations from fainter quasars. Over 30 (and growing) fields around > z 5.7 quasars have been observed with integral field spectroscopy by the MUSE instrument (Farina et al 2019). Finding additional proximate LAEs offers a clear path to refining the results presented in this paper.…”

A search for dust and molecular gas in enormous Lyαnebulae atz≈ 2

“…Diffuse nebulae of hydrogen Lyman-α (Lyα), extending over 50−100 kpc, have been observed around star forming galaxies (e.g., Steidel et al 2000;Matsuda et al 2004;Dey et al 2005;Yang et al 2009;Wisotzki et al 2016Wisotzki et al , 2018Li et al 2019;Herenz et al 2020), high-z radio galaxies (e.g., Keel et al 1999;Venemans et al 2002;Miley et al 2006;Marques-Chaves et al 2019), and quasars (e.g., Husband et al 2015;Borisova et al 2016;Arrigoni-Battaia et al 2016Ginolfi et al 2018;Farina et al 2019;Lusso et al 2019;Drake et al 2020;Travascio et al 2020) up to z ∼ 6.5. These large reservoirs of cool (T ∼ 10 4 K) gas extend well into the circum-galactic medium.…”