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

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

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

A Combined EIS-NVSS Survey Of Radio Sources (CENSORS) III: Spectroscopic observations

The Combined EIS-NVSS Survey Of Radio Sources (CENSORS) is a 1.4GHz radio survey selected from the NRAO VLA Sky Survey (NVSS) and complete to a flux-density of 7.2mJy. It targets the ESO Imaging Survey (EIS) Patch D, which is a 3 by 2 square degree field centred on 09 51 36.0, -21 00 00 (J2000). This paper presents the results of spectroscopic observations of 143 of the 150 CENSORS sources. The primary motivation for these observations is to achieve sufficient spectroscopic completeness so that the sample may be used to investigate the evolution of radio sources. The observations result in secure spectroscopic redshifts for 63% of the sample and likely redshifts (based on a single emission line, for example) for a further 8%. Following the identification of the quasars and star-forming galaxies in the CENSORS sample, estimated redshifts are calculated for the remainder of the sample via the K-z relation for radio galaxies. Comparison of the redshift distribution of the CENSORS radio sources to distributions predicted by the various radio luminosity function evolution models of Dunlop & Peacock 1990, results in no good match. This demonstrates that this sample can be used to expand upon previous work in that field.Comment: Accepted for publication in MNRAS. This version has some reduced resolution figures and 13 associated gif files. A version with all figures incorporated (at full resolution) is available at http://www.roe.ac.uk/~pnb/papers/censors_spectro.pd

The D/H ratio at z = 3.57 toward Q 1937-1009

Deuterium abundance re-measurements by Burles and Tytler (1998; hereafter BT) yielded D/H = (3.3 +/- 0.3) 10^{-5} and the robust upper limit D/H < 3.9 10^{-5} from the z_a = 3.572 system toward Q1937-1009. In this new analysis BT adopted multicomponent microturbulent models together with the possibility to vary freely the local continuum level around each HI line to improve the fit. The procedure failed, however, to fit adequately D Ly-beta without recourse to an additional H Ly-alpha contamination at the position of D Ly-beta. We show that this obstacle may be successfully overcome within the framework of the mesoturbulent model accounting (in contrast to the microturbulent approximation) for a correlated structure of the large scale velocity field. Using the same observational data and the original continuum as determined by Tytler et al. (1996), we obtained good fits. The one-component mesoturbulent models provide D/H in the range (3.2 - 4.8) 10^{-5} and the total hydrogen column density N(HI) = (5.6 - 7.0) 10^{17} cm^{-2}. This result is consistent with that found by us from the z_a = 2.504 and z_a = 0.701 systems toward Q1009+2956 and Q1718+4807, respectively. The range for D/H common to all three analyses is D/H = (4.1 - 4.6) 10^{-5}. This value is consistent with standard big bang nucleosynthesis [SBBN] if the baryon-to-photon ratio, \eta, is in the range 4.2 10^{-10} <= \eta <= 4.6 10^{-10}, implying 0.0155 <= \Omega_b h^2_{100} <= 0.0167.Comment: 8 pages, 2 Postscript figures, aaspp4.sty file, submit. ApJ Let

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

Near-Infrared Spectroscopy of Powerful Radio Galaxies at z=2.2-2.4

Near-infrared spectroscopy (rest-frame 3700-6800 Angstroms) of eight high redshift powerful radio galaxies (HzPRGs) at z = 2.2-2.6 is presented. Strong forbidden lines and H-alpha emission were detected in all sources; the data show evidence that the emission lines of the HzPRGs may contribute a substantial fraction (approx. 25-98%) of their total observed H - and/or K -band light. Diagnostic emission-line ratios for three of the eight HzPRGs are consistent with the presence of a Seyfert 2 nucleus; the [O III] 5007 / H-beta and [S II] 6716, 6731 / H-alpha ratios and/or limits of the remaining five galaxies are inconclusive. Furthermore, all six of the galaxies for which both H - and K -band spectra were obtained have observed [O III] 5007 / (H-alpha +[N II] 6548, 6583) ratios consistent with Seyfert 2 ionization...Comment: LaTex, 39 pages with 9 postscript figures and 2 gif figures, ApJ accepte

The final two redshifts for radio sources from the equatorial BRL sample

Best, Rottgering and Lehnert (1999, 2000a) defined a new sample of powerful radio sources from the Molonglo Reference Catalogue, for which redshifts were compiled or measured for 177 of the 178 objects. For the final object, MRC1059-010 (3C249), the host galaxy is here identified using near-infrared imaging, and the redshift is determined from VLT spectroscopy. For one other object in the sample, MRC0320+053 (4C05.14), the literature redshift has been questioned: new spectroscopic observations of this object are presented, deriving a corrected redshift. With these two results, the spectroscopic completeness of this sample is now 100%. New redshifts are also presented for PKS0742+10 from the Wall & Peacock 2.7 GHz catalogue, and PKS1336+003 from the Parkes Selected Regions. PKS0742+10 shows a strong neutral hydrogen absorption feature in its Lyman-alpha emission profile.Comment: 4 pages. LaTeX. Accepted for publication in MNRA