相关论文: The Composite Spectrum of Strong Lyman-alpha Fores…

We present composite spectra constructed from a sample of 242,150 Lyman-alpha (Lya) forest absorbers at redshifts 2.4<z<3.1 identified in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of…

We investigate the metal species associated with the Ly$\alpha$ forest in the eBOSS quasar spectra. Metal absorption lines are revealed in the stacked spectra from cross-correlating the selected Ly$\alpha$ absorbers in the forest and the…

We present high S/N echelle spectra of the recently discovered ultraluminous QSO APM 08279+5255 and use these data to re-examine the abundance of Carbon in Ly alpha forest clouds. In agreement with previous work, we find that approximately…

We examine the Ly-alpha absorber population at z<0.3 detected in spectra of the QSOs PG0953+415 and H1821+643 taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. We compare their statistical properties to…

We present high signal-to-noise, 5 A resolution (FWHM) spectra of 66 z \ga 4 bright quasars obtained with the 4 m Cerro Tololo Inter-American Observatory and 4.2 m William Hershel telescopes. The primary goal of these observations was to…

We present an ultraviolet spectroscopic survey of strong H I absorbers in the intergalactic medium, probing their evolution over the last 6-7 Gyr at redshifts $0.24 \leq z \leq 0.84$. We measure column densities $N_{\rm HI} \,( {\rm…

We analyzed the absorption line spectra of all quasars observed with the high resolution gratings of the Faint Object Spectrograph on board the Hubble Space Telescope. We examined 788 spectra for 334 quasars, and present line lists and…

The low-redshift Ly-alpha forest of absorption lines provides a probe of large-scale baryonic structures in the intergalactic medium, some of which may be remnants of physical conditions set up during the epoch of galaxy formation. We…

With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We search 149 moderate resolution background quasar spectra, from Gemini, Keck, the MMT,…

We present the first science results from our Hubble Space Telescope Survey for Lyman limit absorption systems (LLS) using the low dispersion spectroscopic modes of the Advanced Camera for Surveys and the Wide Field Camera 3. Through an…

We search for OVI absorption in a Keck HIRES spectrum of the z=3.62 quasar Q1422+231. Comparison of CIV measurements to cosmological simulations shows that \lya forest absorbers with N_HI > 10^{14.5} have [C/H]~=-2.5, for the UV background…

We measure the amount of absorption in the Lyman-alpha forest at 0 < z < 1.6 in HST FOS spectra of 74 QSOs. At 0 < z < 1.6 we find that 79% of the absorption is from the low density intergalactic medium, 12% from metals and 9% from the…

The APM multicolor survey for bright z > 4 objects, covering 2500 deg^2 of sky to m(R)~19, resulted in the discovery of thirty-one quasars with z > 4. High signal-to-noise optical spectrophotometry at 5A resolution has been obtained for the…

We create stacked composite absorption spectra from Hubble Space Telescope Faint Object Spectrograph data from four quasi-stellar objects to search for absorption lines in the extreme ultraviolet wavelength region associated with LyA forest…

We present a high signal-to-noise high resolution spectrum of the radio-quiet QSO HS1700+6416 (z = 2.72). Analysis of the absorption line systems with metals yields the following results. (1) The dense cluster of C IV doublets at 2.432 <…

We study of the properties of a new class of circumgalactic medium absorbers identified in the Lyman-$\alpha$ forest: "Strong, Blended Lyman-$\alpha$" (or SBLA) absorption systems. We study SBLAs at $2.4<z<3.1$ in SDSS-IV/eBOSS spectra by…

We study the galaxy number density (smoothed on a 5h^{-1} Mpc scale) around 18 low-redshift Lyman-alpha absorbers previously observed with HST. The absorbers lie in the foregrounds of Mrk 335, Mrk 421, Mrk 501, I Zw 1, and 3C 273, all…

We present intermediate resolution ($\sim3$ \AA ) spectra of the Ly$\alpha$ emission from 15 high redshift radio galaxies ($z>2$). Together with previously published spectra we analyze data for a sample of 18 objects. In 11 of the 18 radio…

We present a detailed analysis of the intergalactic metal-line absorption systems in the archival HST/STIS and FUSE ultraviolet spectra of the low-redshift quasar PKS1302-102 (z_QSO = 0.2784). We supplement the archive data with CLOUDY…

We present the results of a large survey of HI, OVI, and CIII absorption lines in the low-redshift (z<0.3) intergalactic medium (IGM). We begin with 171 strong Lyalpha absorption lines (W>80 mA) in 31 AGN sight lines studied with the Hubble…