The MUSE Extremely Deep Field: The cosmic web in emission at high redshift

Abstract

We report the discovery of diffuse extended Lyα emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5−4 cMpc. These structures have been observed in overdensities of Lyα emitters in the MUSE Extremely Deep Field, a 140 h deep MUSE observation located in the Hubble Ultra-Deep Field. Among the 22 overdense regions identified, five are likely to harbor very extended Lyα emission at high significance with an average surface brightness of 5 × 10−20 erg s−1 cm−2 arcsec−2. Remarkably, 70% of the total Lyα luminosity from these filaments comes from beyond the circumgalactic medium of any identified Lyα emitter. Fluorescent Lyα emission powered by the cosmic UV background can only account for less than 34% of this emission at z ≈ 3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Lyα emission of a large population of ultra low-luminosity Lyα emitters (< 1040 erg s−1), provided that the faint end of the Lyα luminosity function is steep (α ⪅ −1.8), it extends down to luminosities lower than 1038 − 1037 erg s−1, and the clustering of these Lyα emitters is significant (filling factor < 1/6). If these Lyα emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates < 10−4 M⊙ yr−1. These observations provide the first detection of the cosmic web in Lyα emission in typical filamentary environments and the first observational clue indicating the existence of a large population of ultra low-luminosity Lyα emitters at high redshift.

Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at 1.5 <z< 6.4

“…The updated release of the UDF mosaic and UDF10 catalogs by Bacon et al (in prep. ) merges the independent LSDCat and ORIGIN emission line source detections performed on the improved reductions of the MUSE-Deep data complemented by even deeper MUSE data in the HUDF from the MUSE eXtremely Deep Field (MXDF; see Bacon et al 2021). Bacon et al (in prep.…”

The MUSE eXtremely Deep Field: Individual detections of Lyα haloes around rest-frame UV-selected galaxies at z~2.9-4.4

“…The MXDF data were obtained as a part of the MUSE guaranteed time observations (GTO) program (PI: R. Bacon). The survey design of MXDF is presented in Bacon et al in prep. (see also Bacon et al 2021). The field has a circular shape, centered at R.A.=53.…”

“…The MXDF is the deepest MUSE survey with AO, reaching up to 140 hours at r 29 arcsec and 100 hours out to r = 31 arcsec, while the outer edge has a 10-hour integration (r 41 arcsec). In this paper we use the very deep area with 100-to 140-hour integration, located inside a radius of 31 arcsec from the center of the field (0.84 arcmin 2 , see Figure 1 in Bacon et al 2021), which we used in this paper. The corresponding survey volume in this work is 4.0 × 10 3 cMpc 3 (z = 2.86-4.44, excluding an AO gap, see below for more details).…”

“…Meanwhile, the HST neighbor of RID=4838 (RID=6666 at z s = 3.06) has a velocity offset of ∆V = −25.4 km s −1 from RID=4838, which indeed contaminates the Lyα NB used in the halo test (see Figures 3 and A .3). They belong to a group of galaxies within the cosmic web detected with Lyα emission in Bacon et al (2021), see Appendix A.4 for more details. Since both RID=7876 and 9944 are assigned to counterparts of MID=103 at z s = 2.09, they are interpreted to share Lyα emission in their Lyα NBs.…”

Super

“…Originally expected to be in a rarefied, highly ionised diffuse phase at T ∼ 10 6 K claudia.cicone@astro.uio.no (the 'Galactic corona'), the CGM has been studied mostly in absorption (Tumlinson et al 2017;Chen 2017). However, there is now overwhelming evidence that the CGM of both normal and active galaxies, at any redshift, also embeds much colder and denser gas clouds, which allow it to be detected in emission using several tracers: Lyα (Arrigoni Battaia et al 2019;Cai et al 2019;Bacon et al 2021), CIV and HeII (Travascio et al 2020;Guo et al 2020), [OII] (Rupke et al 2019), MgII (Burchett et al 2021), and Hα (Fossati et al 2019). Nevertheless, the total mass of (multi-phase) gas stored on CGM scales remains unconstrained.…”