CO(J=6-5) Observations of the Quasar SDSS1044-0125 at z = 5.8

We present a result of the quasar CO(J=6-5) observations of SDSSp J104433.04-012502.2 at z = 5.8. Ten-days observations with the Nobeyama Millimeter Array yielded an rms noise level of ~ 2.1 mJy/beam in a frequency range from 101.28 GHz to 101.99 GHz at a velocity resolution of 120 km/s. No significant clear emission line was detected in the observed field and frequency range. Three sigma upper limit on the CO(J=6-5) luminosity of the object is 2.8 x 10^10 K km/s pc^2, corresponding to a molecular gas mass of 1.2 x 10^11 Solar Mass, if a conversion factor of 4.5 Solar Mass /(K km/s pc^2) is adopted. The obtained upper limit on CO luminosity is slightly smaller than those observed in quasars at z=4-5 toward which CO emissions are detected.Comment: 4 pages, 3 figures, LaTeX2e, to appear in Publication of Astronomical Society of Japan (PASJ), Postscript file available at ftp://ftp.kusastro.kyoto-u.ac.jp/pub/iwata/preprint/sdss1044/sdss.ps.g

Radio Observations of Infrared Luminous High Redshift QSOs

We present Very Large Array (VLA) observations at 1.4 GHz and 5 GHz of a sample of 12 Quasi-stellar Objects (QSOs) at z = 3.99 to 4.46. The sources were selected as the brightest sources at 250 GHz from the recent survey of Omont et al. (2001). We detect seven sources at 1.4 GHz with flux densities, S_{1.4} > 50 microJy. These centimeter (cm) wavelength observations imply that the millimeter (mm) emission is most likely thermal dust emission. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. For two sources the radio continuum luminosities and morphologies indicate steep spectrum, radio loud emission from a jet-driven radio source. For the remaining 10 sources the 1.4 GHz flux densities, or limits, are consistent with those expected for active star forming galaxies. If the radio emission is powered by star formation in these systems, then the implied star formation rates are of order 1e3 M_solar/year. We discuss the angular sizes and spatial distributions of the radio emitting regions, and we consider briefly these results in the context of co-eval black hole and stellar bulge formation in galaxies.Comment: to appear in the A

The ASCA spectrum of the z=4.72 blazar, GB 1428+4217

The X-ray luminous quasar GB 1428+4217 at redshift 4.72 has been observed with ASCA. The observed 0.5-10 keV flux is 3.2E-12 erg/s/cm2. We report here on the intrinsic 4-57 keV X-ray spectrum, which is very flat (photon index of 1.29). We find no evidence for flux variability within the ASCA dataset or between it and ROSAT data. We show that the overall spectral energy distribution of GB 1428+4217 is similar to that of lower redshift MeV blazars and present models which fit the available data. The Doppler beaming factor is likely to be at least 8. We speculate on the number density of such high redshift blazars, which must contain rapidly-formed massive black holes.Comment: 5 pages, 3 Postscript figures, to appear in MNRA

[OII] emitters in the GOODS field at z~1.85: a homogeneous measure of evolving star formation

We present the results of a deep, near-infrared, narrow band imaging survey at a central wavelength of 1.062 microns (FWHM=0.01 microns) in the GOODS-South field using the ESO VLT instrument, HAWK-I. The data are used to carry out the highest redshift search for [OII]3727 emission line galaxies to date. The images reach an emission line flux limit (5 sigma) of 1.5 x 10^-17 erg cm^-2 s^-1, additionally making the survey the deepest of its kind at high redshift. In this paper we identify a sample of [OII]3727 emission line objects at redshift z~1.85 in a co-moving volume of ~4100 Mpc^3. Objects are selected using an observed equivalent width (EW_obs) threshold of EW_obs = 50 angstroms. The sample is used to derive the space density and constrain the luminosity function of [OII] emitters at z=1.85. We find that the space density of objects with observed [OII] luminosities in the range log(L_[OII]) > 41.74 erg s^-1 is log(rho)=-2.45+/-0.14 Mpc^-3, a factor of 2 greater than the observed space density of [OII] emitters reported at z~1.4. After accounting for completeness and assuming an internal extinction correction of A_Halpha=1 mag (equivalent to A_[OII]=1.87), we report a star formation rate density of rho* ~0.38+/-0.06 Msun yr^-1 Mpc^-3. We independently derive the dust extinction of the sample using 24 micron fluxes and find a mean extinction of A_[OII]=0.98+/-0.11 magnitudes (A_Halpha=0.52). This is significantly lower than the A_Halpha=1 (A[OII]=1.86) mag value widely used in the literature. Finally we incorporate this improved extinction correction into the star formation rate density measurement and report rho*~0.24+/-0.06 Msun yr^-1 Mpc^-3.Comment: 11 pages, 10 figures, accepted for publication in MNRA

PMN J0525-3343: soft X-ray spectral flattening in a blazar at z=4.4

We report optical, radio and X-ray observations of a new distant blazar, PMN J0525-3343, at a redshift of 4.4. The X-ray spectrum measured from ASCA and BeppoSAX flattens below a few keV, in a manner similar to the spectra of two other z>4 blazars, GB 1428+4217 (z=4.72) reported by Boller et al and RXJ 1028.6-0844 (z=4.28) by Yuan et al. The spectrum is well fitted by a power-law continuum which is either absorbed or breaks at a few keV. An intrinsic column density corresponding to 2 x 10^23 H-atoms cm-2 at solar abundance is required by the absorption model. This is however a million times greater than the neutral hydrogen, or dust, column density implied by the optical spectrum, which covers the rest-frame UV emission of the blazar nucleus. We discuss the problems raised and suggest that, unless there is intrinsic flattening in the spectral distribution of the particles/seed photons producing X-rays via inverse Compton scattering, the most plausible solution is a warm absorber close to the active nucleus.Comment: 7 pages, 7 figures; MNRAS, in pres

Revealing Cosmic Rotation

Cosmological Birefringence (CB), a rotation of the polarization plane of radiation coming to us from distant astrophysical sources, may reveal parity violation in either the electromagnetic or gravitational sectors of the fundamental interactions in nature. Until only recently this phenomenon could be probed with only radio observations or observations at UV wavelengths. Recently, there is a substantial effort to constrain such non-standard models using observations of the rotation of the polarization plane of cosmic microwave background (CMB) radiation. This can be done via measurements of the $B$-modes of the CMB or by measuring its TB and EB correlations which vanish in the standard model. In this paper we show that $EB$ correlations-based estimator is the best for upcoming polarization experiments. The $EB$ based estimator surpasses other estimators because it has the smallest noise and of all the estimators is least affected by systematics. Current polarimeters are optimized for the detection of $B$-mode polarization from either primordial gravitational waves or by large scale structure via gravitational lensing. In the paper we also study optimization of CMB experiments for the detection of cosmological birefringence, in the presence of instrumental systematics, which by themselves are capable of producing $EB$ correlations; potentially mimicking CB.Comment: 10 pages, 3 figures, 2 table

The SCUBA Bright Quasar Survey II: unveiling the quasar epoch at submillimetre wavelengths

We present results of the first systematic search for submillimetre continuum emission from z=2, radio-quiet, optically-luminous quasars, using the SCUBA/JCMT. We have observed a homogeneous sample of 57 quasars in the redshift range 1.54) redshift. The target sensitivity of the survey (3sigma=10mJy at 850um) was chosen to enable efficient identification of bright submm sources, suitable for detailed follow-up. 9 targets are detected, with fluxes in the range 7-17mJy. Although there is a suggestion of variation of submm detectability between z=2 and z=4, this is consistent with the K-correction of a characteristic far-infrared spectrum. Additionally, the weighted mean fluxes of non-detections at z=2 and z>4 are comparable