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

Abstract

Hydrogen Lyα haloes (LAHs) are commonly used as a tracer of the circumgalactic medium (CGM) at high redshifts. In this work, we aim to explore the existence of Lyα haloes around individual UV-selected galaxies, rather than around Lyα emitters (LAEs), at high redshifts. Our sample was continuum-selected with F775W ≤ 27.5, and spectroscopic redshifts were assigned or constrained for all the sources thanks to the deepest (100-to 140-hour) existing Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) data with adaptive optics. The final sample includes 21 galaxies that are purely F775W-magnitude selected within the redshift range z ≈ 2.9-4.4 and within a UV magnitude range −20 ≤ M 1500 ≤ −18, thus avoiding any bias toward LAEs. We tested whether galaxy's Lyα emission is significantly more extended than the MUSE PSF-convolved continuum component. We find 17 LAHs and four non-LAHs. We report the first individual detections of extended Lyα emission around non-LAEs. The Lyα halo fraction is thus as high as 81.0 +10.3 −11.2 %, which is close to that for LAEs at z = 3-6 in the literature. This implies that UV-selected galaxies generally have a large amount of hydrogen in their CGM. We derived the mean surface brightness (SB) profile for our LAHs with cosmic dimming corrections and find that Lyα emission extends to 5.4 arcsec ( 40 physical kpc at the midpoint redshift z = 3.6) above the typical 1σ SB limit. The incidence rate of surrounding gas detected in Lyα per one-dimensional line of sight per unit redshift, dn/dz, is estimated to be 0.76 +0.09 −0.09 for galaxies with M 1500 ≤ −18 mag at z 3.7. Assuming that Lyα emission and absorption arise in the same gas, this suggests, based on abundance matching, that LAHs trace the same gas as damped Lyα systems (DLAs) and sub-DLAs.

Surface Brightness Profile of Lyman-α Halos out to 320 kpc in HETDEX

“…Most individual high-redshift star-forming galaxies such as LAEs and Lymanbreak galaxies (LBGs) are surrounded by smaller, 1-10 kpc size Lyα halos (Hayashino et al 2004;Swinbank et al 2007;Rauch et al 2008;Ouchi et al 2009;Patrício et al 2016;Wisotzki et al 2016;Leclercq et al 2017;Smit et al 2017;Erb et al 2018;Claeyssens et al 2019Claeyssens et al , 2022. Kusakabe et al (2022) detected Lyα halos with sizes between 10 and 50 kpc in 17 out of 21 continuum-selected galaxies. While Bond et al (2010), Feldmeier et al (2013), and Jiang et al (2013) report a lack of evidence for spatially extended Lyα emission around LAEs and LBGs, the ubiquitous presence of extended Lyα halos around high-redshift star-forming galaxies has been confirmed by stacking analyses (Møller & Warren 1998;Steidel et al 2011;Matsuda et al 2012;Momose et al 2014Momose et al , 2016Xue et al 2017;Wisotzki et al 2018;Wu et al 2020;Huang et al 2021).…”

Probing the Diffuse Lyman-alpha Emission on Cosmological Scales: Lyα Emission Intensity Mapping Using the Complete SDSS-IV eBOSS Survey

“…Our estimates based on the empirical model of Dijkstra & Wyithe (2012) and the observed UV LFs of star-forming galaxies are able to match the Lyα luminosity density inferred from our cross-correlation measurements. The picture is supported by stacked analysis from NB surveys (e.g., Steidel et al 2011) and by the IFU observations of Lyα emission associated with UVselected galaxies (e.g., Kusakabe et al 2022).…”

“…A large portion of LBGs exhibit Lyα emission, though their rest-frame equivalent width (REW) might not satisfy the criteria for LAE selections (Shapley et al 2003;de La Vieuville et al 2020) if measured with a typical aperture of 2 in diameter in NB surveys. It is also detected in deep stacks of luminous and massive LBGs (Steidel et al 2011) and in individual UV-selected galaxies in recent MUSE eXtremely Deep Field (MXDF) observations (Kusakabe et al 2022).…”

“…As discussed before, many previous works have reported detections of extended Lyα emission around high-redshift galaxies, either by discoveries of Lyα halos/blobs around bright individual star-forming galaxies through ultradeep exposures (Steidel et al 2000;Matsuda et al 2004Matsuda et al , 2011Wisotzki et al 2016;Leclercq et al 2017;Kusakabe et al 2022), or by employing stacking analyses on large samples (Steidel et al 2011;Matsuda et al 2012;Momose et al 2014Momose et al , 2016Xue et al 2017). Most extended Lyα-emitting halos are discovered around LAEs (Wisotzki et al 2016;Leclercq et al 2017); they are also prevalent around non-LAEs, e.g., UV-selected galaxies, due to a significant amount of cool/warm gas in their CGM (Steidel et al 2011;Kusakabe et al 2022).…”

“…Large amounts of individual Lyα halos around strong Lyα emitters (LAEs), have been detected thanks to these state-ofthe-art instruments (e.g., Wisotzki et al 2016;Leclercq et al 2017). Moreover, a recent discovery unveiled that star-forming galaxies generally have Lyα halos by investigating Lyα emission around UV-selected galaxies (Kusakabe et al 2022).…”