2017/10/25 by Floriane Leclercq, Roland Bacon, L. Wisotzki +25 · 72 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Emission spectrum #Equivalent width #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Hubble Deep Field #Hubble Ultra-Deep Field #Physics #Redshift #Spectral line #Star formation #Virial theorem #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/201731480
published in Leiden Repository (Leiden University) 608, A8 (Leiden University) · 24 pages, 18 figures, 1 table, accepted for publication in A&A
arxiv created 2017/10/27 · openalex publication_date 2017/12/01 · arxiv updated 2017/12/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We report the detection of extended Ly<i>α<i/> haloes around 145 individual star-forming galaxies at redshifts 3 ≤ <i>z<i/> ≤ 6 in the <i>Hubble <i/>Ultra Deep Field observed with the Multi-Unit Spectroscopic Explorer (MUSE) at ESO-VLT. Our sample consists of continuum-faint (− 15 ≥ <i>M<i/><sub>UV<sub/> ≥ −22) Ly<i>α<i/> emitters (LAEs). Using a 2D, two-component (continuum-like and halo) decomposition of Ly<i>α<i/> emission assuming circular exponential distributions, we measure scale lengths and luminosities of Ly<i>α<i/> haloes. We find that 80% of our objects having reliable Ly<i>α<i/> halo measurements show Ly<i>α<i/> emission that is significantly more extended than the UV continuum detected by HST (by a factor ≈4 to >20). The median exponential scale length of the Ly<i>α<i/> haloes in our sample is ≈4.5 kpc with a few haloes exceeding 10 kpc. By comparing the maximal detected extent of the Ly<i>α<i/> emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Ly<i>α<i/> emission of our selected sample of Ly<i>α<i/> emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). This result therefore shows that there must be significant HI reservoirs in the circum-galactic medium and reinforces the idea that Ly<i>α<i/> haloes are ubiquitous around high-redshift Ly<i>α<i/> emitting galaxies. Our characterization of the Ly<i>α<i/> haloes indicates that the majority of the Ly<i>α<i/> flux comes from the halo (≈65%) and that their scale lengths seem to be linked to the UV properties of the galaxies (sizes and magnitudes). We do not observe a significant Ly<i>α<i/> halo size evolution with redshift, although our sample for <i>z<i/>> 5 is very small. We also explore the diversity of the Ly<i>α<i/> line profiles in our sample and we find that the Ly<i>α<i/> lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km s<sup>-1<sup/>. While the FWHM does not seem to be correlated to the Ly<i>α<i/> scale length, most compact Ly<i>α<i/> haloes and those that are not detected with high significance tend to have narrower Ly<i>α<i/> profiles (<350 km s<sup>-1<sup/>). Finally, we investigate the origin of the extended Ly<i>α<i/> emission but we conclude that our data do not allow us to disentangle the possible processes, i.e. scattering from star-forming regions, fluorescence, cooling radiation from cold gas accretion, and emission from satellite galaxies.