Statistical properties of diffuse Lyα haloes around star-forming galaxies atz∼ 2

Abstract

We present statistical properties of diffuse Lyα halos (LAHs) around high-z starforming galaxies with large Subaru samples of Lyα emitters (LAEs) at z = 2.2. We make subsamples defined by the physical quantities of LAEs' central Lyα luminosities, UV magnitudes, Lyα equivalent widths, and UV slopes, and investigate LAHs' radial surface brightness (SB) profiles and scale lengths r n as a function of these physical quantities. We find that there exist prominent LAHs around LAEs with faint Lyα luminosities, bright UV luminosities, and small Lyα equivalent widths in cumulative radial Lyα SB profiles. We confirm this trend with the anti-correlation between r n and Lyα luminosities (equivalent widths) based on the Spearman's rank correlation coefficient that is ρ = −0.9 (−0.7) corresponding to the 96% (93%) confidence level, although the correlation between r n and UV magnitudes is not clearly found in the rank correlation coefficient. Our results suggest that LAEs with properties similar to typical Lyman-break galaxies (with faint Lyα luminosities and small equivalent widths) possess more prominent LAHs. We investigate scenarios for the major physical origins of LAHs with our results, and find that the cold stream scenario is not preferred, due to the relatively small equivalent widths up to 77Å in LAHs that include LAEs' central components. There remain two possible scenarios of Lyα scattering in circumgalactic medium and satellite galaxies that cannot be tested with our observational data.

A HIGH FRACTION OF Lyα EMITTERS AMONG GALAXIES WITH EXTREME EMISSION LINE RATIOS AT z ∼ 2*

“…They find that the total Lyα luminosity ranges from ∼ 2-4 times the luminosity within an aperture 1 in radius, and that the fraction in the extended halo depends on both Lyα luminosity and equivalent width, with lower luminosity galaxies with lower equivalent widths having a higher fraction of flux in the halo. Our extreme sample spans nearly the full range in Lyα luminosity and equivalent width considered by Momose et al (2016), but comparing our median luminosity and equivalent widths with their results suggest that the factor of 2-3 correction determined above is reasonable. Adjusting our escape fractions by this factor then results in a mean value of 0.16-0.24, somewhat lower than or roughly comparable to other samples of LAEs.…”

“…We can also estimate the size of this correction using the results of Momose et al (2016), who measure extended Lyα halos around a large sample of LAEs at z = 2.2. They find that the total Lyα luminosity ranges from ∼ 2-4 times the luminosity within an aperture 1 in radius, and that the fraction in the extended halo depends on both Lyα luminosity and equivalent width, with lower luminosity galaxies with lower equivalent widths having a higher fraction of flux in the halo.…”

Lyα EMITTER GALAXIES AT z ∼ 2.8 IN THE EXTENDED CHANDRA DEEP FIELD SOUTH. I. TRACING THE LARGE-SCALE STRUCTURE VIA Lyα IMAGING∗

“…A-1), and the different IGM absorption at the blue-end of Lyα line at z = 2-3. Recently Momose et al (2016) reported that faint LAEs tend to have prominent diffuse Lyα halos. Our multi-slit spectroscopic observation may miss the more extended Lyα emission, therefore it is not strange to see the trend of increasing F Phot (Lyα)/F Spec (Lyα) ratio with the decreasing F Spec (Lyα) line flux in Figure 7.…”

Small-scale Intensity Mapping: Extended Lyα, Hα, and Continuum Emission as a Probe of Halo Star Formation in High-redshift Galaxies

“…Nowadays, this faint emission is being proved to be nearly ubiquitousin galaxies at high redshift,   z 3 5, by means of stacking analyses Matsuda et al 2012;Feldmeier et al 2013;Momose et al 2014Momose et al , 2016anddue to the sensitivity and spatial resolution improvement of instruments such as MUSE (Bacon et al 2014). A clear understanding ofthe origin of these extended Lyα halos (LAHs; hereafter) is relevant because it yields information about the physical conditions of the circumgalactic medium (CGM) and, in turn, on the processes governing the formation and evolution of galaxies (Bahcall & Spitzer 1969).…”

“…The nonlinear clustering of objects derived from the hierarchical Cold Dark Matter model of structure formation predicts that a significant fraction of the faint sources likely reside around more massive, brighter galaxies. Therefore, starforming regions and galaxies surrounding the central galaxy (satellite sources) may provide additional contributions to the extended halos at large distances from the center,  r 30 pkpc, via the nebular radiation produced "in situ" in their ISM, and/ or inducing fluorescent emission in the CGM of the central galaxy (e.g., Shimizu & Umemura 2010;Matsuda et al 2012;Lake et al 2015;Momose et al 2016, see Maiolino et al 2017 for a recent detection of star formation within outflows). Although most of the satellites are probably too faint to be resolved individually, their overall collective emission may be detectable, similarlyto the method of intensity mapping on large scales (e.g., Chang et al 2010;Visbal & Loeb 2010;Carilli 2011;Gong et al 2011;Silva et al 2013;Doré et al 2014;Pullen et al 2014;Croft et al 2016;Li et al 2016).…”