We present the first observations of foreground Lyman-$alpha$ forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with $zsim 2.3-2.8$ within a $5 times 15$ region of the COSMOS field. The transverse sightline sepa
ration is $sim 2,h^{-1}mathrm{Mpc}$ comoving, allowing us to create a tomographic reconstruction of the 3D Ly$alpha$ forest absorption field over the redshift range $2.20leq zleq 2.45$. The resulting map covers $6,h^{-1}mathrm{Mpc} times 14,h^{-1}mathrm{Mpc}$ in the transverse plane and $230,h^{-1}mathrm{Mpc}$ along the line-of-sight with a spatial resolution of $approx 3.5,h^{-1}mathrm{Mpc}$, and is the first high-fidelity map of large-scale structure on $simmathrm{Mpc}$ scales at $z>2$. Our map reveals significant structures with $gtrsim 10,h^{-1}mathrm{Mpc}$ extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. Simulated reconstructions with the same sightline sampling, spectral resolution, and signal-to-noise ratio recover the salient structures present in the underlying 3D absorption fields. Using data from other surveys, we identified 18 galaxies with known redshifts coeval with our map volume enabling a direct comparison to our tomographic map. This shows that galaxies preferentially occupy high-density regions, in qualitative agreement with the same comparison applied to simulations. Our results establishes the feasibility of the CLAMATO survey, which aims to obtain Ly$alpha$ forest spectra for $sim 1000$ SFGs over $sim 1 ,mathrm{deg}^2$ of the COSMOS field, in order to map out IGM large-scale structure at $langle z rangle sim 2.3$ over a large volume $(100,h^{-1}mathrm{Mpc})^3$.
The Ly$alpha$ forest transmission probability distribution function (PDF) is an established probe of the intergalactic medium (IGM) astrophysics, especially the temperature-density relationship of the IGM. We measure the transmission PDF from 3393 Ba
ryon Oscillations Spectroscopic Survey (BOSS) quasars from SDSS Data Release 9, and compare with mock spectra that include careful modeling of the noise, continuum, and astrophysical uncertainties. The BOSS transmission PDFs, measured at $langle z rangle = [2.3,2.6,3.0]$, are compared with PDFs created from mock spectra drawn from a suite of hydrodynamical simulations that sample the IGM temperature-density relationship, $gamma$, and temperature at mean-density, $T_0$, where $T(Delta) = T_0 Delta^{gamma-1}$. We find that a significant population of partial Lyman-limit systems with a column-density distribution slope of $beta_mathrm{pLLS} sim -2$ are required to explain the data at the low-transmission end of transmission PDF, while uncertainties in the mean Ly$alpha$ forest transmission affect the high-transmission end. After modelling the LLSs and marginalizing over mean-transmission uncertainties, we find that $gamma=1.6$ best describes the data over our entire redshift range, although constraints on $T_0$ are affected by systematic uncertainties. Within our model framework, isothermal or inverted temperature-density relationships ($gamma leq 1$) are disfavored at a significance of over 4$sigma$, although this could be somewhat weakened by cosmological and astrophysical uncertainties that we did not model.
We present the BOSS Lyman-alpha (Lya) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with zqso > 2.15 suitable for Lya forest analysis. This data set probes the intergalactic medium with absorption redshifts 2.0 < z_alpha <
5.7 over an area of 3275 square degrees, and encompasses an approximate comoving volume of 20 h^-3 Gpc^3. With each spectrum, we have included several products designed to aid in Lya forest analysis: improved sky masks that flag pixels where data may be unreliable, corrections for known biases in the pipeline estimated noise, masks for the cores of damped Lya systems and corrections for their wings, and estimates of the unabsorbed continua so that the observed flux can be converted to a fractional transmission. The continua are derived using a principal component fit to the quasar spectrum redwards of restframe Lya (lambda > 1216 Ang), extrapolated into the forest region and normalized by a linear function to fit the expected evolution of the Lya forest mean-flux. The estimated continuum errors are ~5% rms. We also discuss possible systematics arising from uncertain spectrophotometry and artifacts in the flux calibration; global corrections for the latter are provided. Our sample provides a convenient starting point for users to analyze clustering in BOSS Lya forest data, and it provides a fiducial data set that can be used to compare results from different analyses of baryon acoustic oscillations in the Lya forest. The full data set is available from the SDSS-III DR9 web site.
We have calculated the relativistic reflection component of the X-ray spectra of accretion disks in active galactic nuclei (AGN). Our calculations have shown that the spectra can be significantly modified by the motion of the accretion flow and the g
ravity and rotation of the central black hole. The absorption edges in the spectra suffer severe energy shifts and smearing, and the degree of distortion depends on the system parameters, in particular, the inner radius of the accretion disk and the disk viewing inclination angles. The effects are significant. Fluorescent X-ray emission lines from the inner accretion disk could be powerful diagnostic of space-time distortion and dynamical relativistic effects near the event horizons of accreting black holes. However, improper treatment of the reflection component in fitting the X-ray continuum could give rise to spurious line-like features. These features mimic the true fluorescent emission lines and may mask their relativistic signatures. Fully relativistic models for reflection continua together with the emission lines are needed in order to extract black-hole parameters from the AGN X-ray spectra.
