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

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

The [OIII] Emission-line Nebula of the z=3.594 Radio Galaxy 4C +19.71

We have imaged the z=3.594 radio galaxy 4C +19.71 in the light of the redshifted [OIII] 5007 angstrom emission line, using a narrow-band filter centered at 2.3 microns with the Near Infrared Camera on the Keck Telescope. The [OIII] nebula of 4C +19.71 has a size of 74 x 9 kpc, and a luminosity of 3 x 10^37 W. The rest frame equivalent width of the 5007 line, averaged over the entire nebula, is 560 angstroms. The length of the major axis of the [OIII] emission is nearly identical to the separation of the radio lobes seen at 1465 MHz (Rottgering, et al. 1994), and the position angle of the nebula is the same as that of the two radio lobes. In addition, 4C +19.71 follows the optical emission line vs. radio power correlation seen in other powerful radio galaxies. The [OIII] and Lyman alpha emission line luminosities suggest that the ionized gas mass lies in the range of 2 x 10^8 - 10^9 solar masses. The O/H ratio in the nebula is at least a few tenths solar, and may be as high as a factor of three above solar, indicating a previous phase of star formation in 4C +19.71. Thirty five percent of the total K-band flux is contributed by the 5007 angstrom emission line, and the continuum of 4C +19.71 has a K=19.6 mag. This places 4C +19.71 along the K-z relation found for other radio galaxies and radio loud quasars. If the continuum is dominated by starlight, the host galaxy has a rest frame visual luminosity of about 40L*. There are no candidate emission-line objects at the redshift of 4C +19.71 having [OIII] rest frame equivalent widths of more than about 2% that of the radio galaxy itself within a volume of 212 cubic Mpc.Comment: plain LaTex with 3 postscript figures. ApJ accepte

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

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

Subaru Spectroscopy of the Giant Lyα\alpha Nebula Associated with the High-zz Powerful Radio Galaxy 1243+036

We report results of our new spatially-resolved, optical spectroscopy of the giant Ly$\alpha$ nebula around a powerful radio galaxy 1243+036 (4C+03.24) at $z=3.57$. The nebula is extended over $\sim 30$ kpc from the nucleus, and forms a pair of cones or elongated bubbles. The high-velocity ($\sim -1000$ km s$^{-1}$; blueshifted with respect to the systemic velocity) Ly$\alpha$-emitting components are detected at both sides of the nucleus along its major axis. The northwestern nebula is more spectacular in its velocity shift (blueshifted by -1000 km s$^{-1}$ to -1400 km s$^{-1}$) and in its width ($\simeq 1900$ km s$^{-1}$ FWHM) over $\simeq 30$ kpc scale. We discuss possible origin of the nebula; 1) the shock-heated expanding bubble or outflowing cone associated with the superwind activity of the host galaxy, 2) halo gas photoionized by the anisotropic radiation from the active galactic nuclei (AGN), and 3) the jet-induced star-formation or shock. The last possibility may not be likely because Ly$\alpha$ emission is distributed out of the narrow channel of the radio jet. We show that the superwind model is most plausible since it can explain both the characteristics of the morphology (size and shape) and the kinematical structures (velocity shift and line width) of the nebula although the photoionization by AGN may contribute to the excitation to some extent.Comment: 12 pages, 2 figures, accepted for publication in A

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