Ryosuke Yamauchi

Diffuse Lyα haloes around Lyα emitters at z = 3: do dark matter distributions determine the Lyα spatial extents?

Using stacks of Ly-a images of 2128 Ly-a emitters (LAEs) and 24 protocluster UV-selected galaxies (LBGs) at z=3.1, we examine the surface brightness profiles of Ly-a haloes around high-z galaxies as a function of environment and UV luminosity. We find that the slopes of the Ly-a radial profiles become flatter as the Mpc-scale LAE surface densities increase, but they are almost independent of the central UV luminosities. The characteristic exponential scale lengths of the Ly-a haloes appear to be proportional to the square of the LAE surface densities (r(Lya) \propto Sigma(LAE)^2). Including the diffuse, extended Ly-a haloes, the rest-frame Ly-a equivalent width of the LAEs in the densest regions approaches EW_0(Lya) ~ 200 A, the maximum value expected for young (< 10^7 yr) galaxies. This suggests that Ly-a photons formed via shock compression by gas outflows or cooling radiation by gravitational gas inflows may partly contribute to illuminate the Ly-a haloes; however, most of their Ly-a luminosity can be explained by photo-ionisation by ionising photons or scattering of Ly-a photons produced in HII regions in and around the central galaxies. Regardless of the source of Ly-a photons, if the Ly-a haloes trace the overall gaseous structure following the dark matter distributions, it is not surprising that the Ly-a spatial extents depend more strongly on the surrounding Mpc-scale environment than on the activities of the central galaxies.

Diffuse Lyman Alpha Haloes around Lyman Alpha Emitters at z=3: Do Dark Matter Distributions Determine the Lyman Alpha Spatial Extents?

Using stacks of Ly-a images of 2128 Ly-a emitters (LAEs) and 24 protocluster UV-selected galaxies (LBGs) at z=3.1, we examine the surface brightness profiles of Ly-a haloes around high-z galaxies as a function of environment and UV luminosity. We find that the slopes of the Ly-a radial profiles become flatter as the Mpc-scale LAE surface densities increase, but they are almost independent of the central UV luminosities. The characteristic exponential scale lengths of the Ly-a haloes appear to be proportional to the square of the LAE surface densities (r(Lya) \propto Sigma(LAE)^2). Including the diffuse, extended Ly-a haloes, the rest-frame Ly-a equivalent width of the LAEs in the densest regions approaches EW_0(Lya) ~ 200 A, the maximum value expected for young (< 10^7 yr) galaxies. This suggests that Ly-a photons formed via shock compression by gas outflows or cooling radiation by gravitational gas inflows may partly contribute to illuminate the Ly-a haloes; however, most of their Ly-a luminosity can be explained by photo-ionisation by ionising photons or scattering of Ly-a photons produced in HII regions in and around the central galaxies. Regardless of the source of Ly-a photons, if the Ly-a haloes trace the overall gaseous structure following the dark matter distributions, it is not surprising that the Ly-a spatial extents depend more strongly on the surrounding Mpc-scale environment than on the activities of the central galaxies.

A Keck/DEIMOS Spectroscopy of Lyα Blobs at Redshift z = 3.1* **

We present the results of intermediate-resolution (~2 ?) spectroscopy of a sample of 37 candidate Ly? blobs and emitters at redshift z = 3.1 using the DEIMOS spectrograph on the 10 m Keck telescope. The emission lines are detected for all 37 objects and show variety in their line profiles. The Ly? velocity widths (FWHM) of the 28 objects with higher quality spectra, measured by fitting a single Gaussian profile, are in the range of 150-1700 km s-1 and correlate with the Ly? spatial extents. All 12 Ly? blobs (?16 arcsec2) have large velocity widths of 500 km s-1. While there are several possible physical interpretations of the Ly? velocity widths (the motion of gravitationally bound gas clouds, inflows, the merging of clumps, or outflows from superwinds), the large velocity widths of the Ly? blobs suggest that they are the sites of massive galaxy formation. If we assume gravitationally bound gas clouds, the dynamical masses of the Ly? blobs are estimated to be ~1012-1013 M?. Even for the case of outflows, the outflow velocities are likely to be comparable to the rotation velocities as inferred from the observational evidence for local starburst galaxies.

Subaru/MOIRCS Near-Infrared Imaging in the Proto-Cluster Region at z = 3.1

We present the results of deep near-infrared imaging observations of the z = 3:1 proto-cluster region in the SSA 22a field taken by MOIRCS mounted on the Subaru Telescope. We observed a 21.7 arcmin field to depths of J = 24.5, H = 24.3, and K = 23.9 (5 ). We examined the distribution of the K-selected galaxies at z 3 by using a simple color cut for distant red galaxies (DRGs) as well as a photometric-redshift selection technique. The marginal density excess of DRGs and the photo-z selected objects were found around the two most luminous Ly blobs (LABs). We investigated the correlation between the K-selected objects and the LABs, and found that several galaxies with stellar mass, M = 10–10Mˇ, exist in the vicinity of LABs, especially around the two most luminous ones. We also found that 7 of the 8 LABs in the field have plausible Ks-band counterparts, and the sum of the stellar mass possibly associated with LABs correlates with their luminosity and surface brightness, which implies that the origin of Ly emission may be closely correlated with their previous star-formation phenomena.