On the Origin of Lymanα\alpha Blobs at High Redshift: Submillimetric Evidence for a Hyperwind Galaxy at z=3.1

The most remarkable class of high-redshift objects observed so far is extended Ly$\alpha$ emission-line blobs found in an over-density region at redshift 3.1. They may be either a dust-enshrouded, extreme starburst galaxy with a large-scale galactic outflow (superwind) or cooling radiation from dark matter halos. Recently one of these Ly$\alpha$ blobs has been detected at submillimeter wavelengths (450 and 850 $\mu$m). Here we show that its rest-frame spectral energy distribution between optical and far-infrared is quite similar to that of Arp 220, which is a typical ultraluminous starburst/superwind galaxy in the local universe. This suggests strongly that the superwind model proposed by Taniguchi & Shioya is applicable to this Ly$\alpha$ blob. Since the blob is more luminous in the infrared by a factor of 30 than Arp 220, it comprises a new population of hyperwind galaxies at high redshift.Comment: 4 pages, 1 figure. ApJ (Letters), in pres

Absorbers and Globular Cluster Formation in Powerful High Redshift Radio Galaxies

A radiative hydrodynamic simulation for a typical, powerful high redshift radio galaxy is presented. The jet is injected at one third the speed of light into a 10000 times denser, homogeneous medium. In the beginning of the simulation, the bow shock consists of a spherical shell that is similar to a spherical blast wave. This shell cools radiatively down to approximately 10,000 K, providing after 6 Mio yrs a neutral column of 3.8 x 10^21 cm^-2 around the whole system. The shell starts to fragment and forms condensations. This absorbing screen will cover a smaller and smaller fraction of the radio source, and therefore the emission line region, and eventually form stars in typically 10,000 globular clusters of one million solar masses. Approximately 10^9 solar masses are entrained into the radio cocoon. This gas, cooling and illuminated from the radio source, could be the emission line gas observed in high redshifted radio galaxies and radio loud quasars. The neutral column behind the bow shock can account for the absorption found in almost all of the small sources. The globular cluster excess of approximately 10^4 systems found in present day brightest cluster galaxies (BCGs), which are believed to be the vestiges of these objects, is consistent with the presented scenario.Comment: A&A, accepted for publication. 4 pages, 2 figure

Radiative Transfer with Finite Elements II. Ly-alpha Line Transfer in Moving Media

A finite element method for solving the resonance line transfer problem in moving media is presented. The algorithm works in three spatial dimensions on unstructured grids which are adaptively refined by means of an a posteriori error indicator. Frequency discretization is implemented via a first-order Euler scheme. We discuss the resulting matrix structure for coherent isotropic scattering and complete redistribution. The solution is performed using an iterative procedure, where monochromatic radiative transfer problems are successively solved. The present implementation is applicable for arbitrary model configurations with an optical depth up to 10^(3-4). Results of Ly-alpha line transfer calculations for a spherically symmetric model, a disk-like configuration, and a halo containing three source regions are discussed. We find the characteristic double-peaked Ly-alpha line profile for all models with an optical depth > 1. In general, the blue peak of the profile is enhanced for models with infall motion and the red peak for models with outflow motion. Both velocity fields produce a triangular shape in the two-dimensional Ly-alpha spectra, whereas rotation creates a shear pattern. Frequency-resolved Ly-alpha images may help to find the number and position of multiple Ly-alpha sources located in a single halo. A qualitative comparison with observations of extended Ly-alpha halos associated with high redshift galaxies shows that even models with lower hydrogen column densities than required from profile fitting yield results which reproduce many features in the observed line profiles and two-dimensional spectra.Comment: 13 pages, accepted for publication in A&

A Radio Galaxy at z=5.19

We report the discovery of the most distant known AGN, the radio galaxy TN J0924-2201 at z = 5.19. The radio source was selected from a new sample of ultra-steep spectrum (USS) sources, has an extreme radio spectral index alpha_365MHz^1.4GHz = -1.63, and is identified at near-IR wavelengths with a very faint, K = 21.3 +- 0.3 object. Spectroscopic observations show a single emission line at lambda ~ 7530A, which we identify as Ly-alpha. The K-band image, sampling rest frame U-band, shows a multi-component, radio-aligned morphology, typical of lower-redshift radio galaxies. TN J0924-2201 extends the near-IR Hubble, or K-z, relation for powerful radio galaxies to z > 5, and is consistent with models of massive galaxies forming at even higher redshifts.Comment: 11 Pages, including 3 PostScript figures. Accepted for publication in the Astrophysical Journal Letter

Fast outflow of neutral hydrogen in the radio galaxy 3C293

We report the detection of very broad HI absorption against the central regions of the radio galaxy 3C293. The absorption profile, obtained with the Westerbork Synthesis Radio Telescope, has a full width at zero intensity of about 1400 km/s and most of this broad absorption (~1000 km/s) is blueshifted relative to the systemic velocity. This absorption represents a fast outflow of neutral gas from the central regions of this AGN. Possible causes for such an outflow are discussed. We favour the idea that the interaction between the radio jet and the rich ISM produces this outflow. Some of the implications of this scenario are considered.Comment: 11 pages, 4 Figures To be published in: Astrophysical Journal Letter

Lyman Alpha Imaging of a Proto-Cluster Region at <z>=3.09

We present very deep imaging observations, through a narrow-band filter tuned to Lyman alpha at , of a volume containing a significant over-density of galaxies at this redshift previously discovered in our survey for continuum-selected Lyman break galaxies (LBGs). The new observations are used in conjunction with our spectroscopic results on LBGs to compare the effectiveness of continuum and emission line searches for star forming galaxies at high redshift, and to extend the search for members of the structure at = 3.09 to much fainter continuum luminosities. We find that only 20-25 percent of all galaxies at a given UV continuum luminosity would be flagged as narrow-band excess objects subject to the typical limits W_Lya > 80 Angstroms in the observed frame. The density enhancement of strong Lyman alpha emitters in this field is consistent with that inferred from the analysis of the spectroscopic Lyman break galaxy sample in the same region (6+/-1), but extends to continuum luminosities up to 2 magnitudes fainter. There is no evidence for a significantly higher fraction of large Lyman alpha line equivalent widths at faint continuum luminosities. By combining the 24 spectroscopic members of the z=3.09 ``spike'' with the narrow-band candidates, we are able to produce a sample of 162 objects which are either known or likely members of this large structure. We have also discovered two extremely large and diffuse Lyman alpha emitting ``blobs'', which have physical extents >100/h kpc and Lyman alpha line fluxes 20-40 times larger than the typical line emitters at the same redshifts in the field. The possible nature of the ``blobs'' is discussed. (abstract abridged)Comment: To appear in the ApJ, 31 pages, aaste

Giant Lya nebulae associated with high redshift radio galaxies

We report deep Keck narrow-band Lya images of the luminous z > 3 radio galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100-200 kpc scale emission line nebulae, centered on these galaxies, which exhibit a wealth of morphological structure, including extended low surface brightness emission in the outer regions, radially directed filaments, cone-shaped structures and (indirect) evidence for extended Lya absorption. We discuss these features within a general scenario where the nebular gas cools gravitationally in large Cold Dark Matter (CDM) halos, forming stars and multiple stellar systems. Merging of these ``building'' blocks triggers large scale starbursts, forming the stellar bulges of massive radio galaxy hosts, and feeds super-massive black holes which produce the powerful radio jets and lobes. The radio sources, starburst superwinds and AGN radiation then disrupt the accretion process limiting galaxy and black hole growth, and imprint the observed filamentary and cone-shaped structures of the Lya nebulae.Comment: 36 Pages, including 8 Postscript figures. Accepted for publication in the Astrophysical Journa

Radio galaxies at z~2.5: results from Keck spectropolarimetry

In classifying the ensemble of powerful extragalactic radio sources, considerable evidence has accumulated that radio galaxies and quasars are orientation-dependent manifestations of the same parent population: massive spheroidal galaxies containing correspondingly massive black holes. [...] In this study, we exploit the opportunity to eliminate the quasar glare by performing sensitive spectropolarimetry with the Keck II telescope of a sample of radio galaxies with redshifts around 2.5. [...] We show that dust-reflected quasar light generally dominates the restframe ultraviolet continuum of these sources and that a highly clumped scattering medium results in almost grey scattering of the active galactic nucleus photons. The observations, however, do not exclude a substantial star formation rate averaged over a Gyr of evolution. The sub-mm reradiation from the scattering dust is likely to represent only a small fraction (~10%) of the total far infrared luminosity. An analysis of the emission lines excited in the interstellar medium of the host galaxy by the hard quasar radiation field reveals evidence of a dramatic chemical evolution within the spheroid during this epoch. Secondary nitrogen production in intermediate mass stars produces a characteristic signature in the NV/CIV and NV/HeII line ratios which has been seen previously in the broad line region of quasars at similar redshifts. We find intriguing correlations between the strengths of the Ly alpha and NV emission lines and the degree of ultraviolet continuum polarization which may represent the dispersal of dust associated with the chemical enrichment of the spheroid.Comment: 24 pages, 12 figures, accepted for publication in Astronomy & Astrophysics. Properly formatted for A4 and Letter paper formats ps files available at http://www.eso.org/~jvernet/research.htm