arXiv subjects

S. Savaglio

Publications and source records attributed to S. Savaglio.

96 records · Page 6Linked to original sources

arXiv1995

CLUSTERING PROPERTIES OF THE LY$α$ CLOUDS

The spectra of the QSOs PKS2126-158 ($z_{em}=3.27$) and Q0055-269 ($z_{em}=3.66$) have been observed at high resolution ($2.2 - 2.7 \times 10^4$). Significant clustering, with $ξ\simeq 1$ at $Δv=100$ km s$^{-1}$, is detected in both cases for lines with $\log N_{HI} \geq 13.8$. A similar result is obtained analysing the data available in the literature for Q0014+81. An anticlustering signal is also detected on scales $Δv \sim 600$ km s$^{-1}$. Two voids of size $\sim 2000$ km s$^{-1}$ are found in the spectrum of Q0055-269 with a probability of $2\times 10^{-4}$.

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arXiv1995

New results on the Gunn-Peterson Effect at High Redshift

Attempts to measure the optical depth due to a diffuse intergalactic medium (IGM) in the spectra of high redshift quasars (GP test) within the ESO key program on the intergalactic medium are reviewed. It is shown that there is no evidence for any Gunn-Peterson effect up to the highest redshifts observable in quasar spectra. The Ly$α$ line statistics consistent with this limit is not able to explain the strong absorption observed at the HeII forest in one QSO, leaving room for a true HeII GP effect. The HI/HeII GP ratio implies a steep ionizing UV background at $z\sim 5$ and ionizing sources of stellar origin.

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arXiv1995

Intrinsic Interstellar Absorption in two Radio Galaxies at z=0.8

We have found a strong absorption feature at 2598Å~ in the spectra of two distant radio galaxies, which we interpret as due to interstellar FeII. We discuss this interpretation and the possibility of obtaining important information on the evolution of the ISM in galaxies, to be compared with the results of the study of intervening and associated absorptions in quasars.

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arXiv1995

Clustering of the Lyman Alpha Clouds in the Line of Sight to the Z=3.66 QSO 0055-269

The spectrum of the Q0055-269 ($z=3.66$) has been observed at the resolution of 14 km s$^{-1}$ in the wavelength interval 4750--6300 Å. The statistical distribution of the Doppler parameter for the Ly$_α$ lines is peaked at $b\simeq 23$ km s$^{-1}$. The column density distribution is described by a power-law with a break at $\log N_{HI} \simeq 14.5$. Significant clustering, with $ξ\simeq 1$ at $Δv=100$ km s$^{-1}$, is detected for lines with $\log N_{HI} \geq 13.8$. Two voids of size $\sim 2000$ km s$^{-1}$ are found in the spectrum with a probability of $2\times 10^{-4}$.

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arXiv1994

The Space Distribution of the Lyman Alpha Clouds in the Line of Sight to the Z=3.66 QSO 0055-269

The spectrum of the quasar Q0055-269 ($z=3.66$) has been observed at the resolution of 14 km s$^{-1}$ in the wavelength interval 4750--6300 Å. We give a list of Lyman$-α$ lines and metal-line systems for which column densities and Doppler widths have been derived by a fitting procedure. The statistical distribution of the Doppler parameter for the Lyman$-α$ lines is peaked at $b\simeq 23$ km s$^{-1}$, with 13\% of lines with $15\leq b\leq 20$ km s$^{-1}$. The column density distribution of the Lyman$-α$ lines is described by a power-law with a break or cutoff at $\log N_{HI} \simeq 14.5$. A featureless power-law distribution is rejected with a probability of $99.94$\%. Significant clustering, with $ξ\simeq 1$ at $Δv=100$ km s$^{-1}$, is detected only for lines with $\log N_{HI}\magcir 13.8$. In addition, two voids of size $\sim 2000$ km s$^{-1}$ are found in the spectrum with a random probability of $2\times 10^{-4}$. {}From the proximity effect for lines in the interval $\log N_{HI}=13.3-14.2$ it is possible to infer an UV ionizing background $J=5\times 10^{-22}$ ergs s$^{-1}$ cm$^{-2}$ Hz$^{-1}$ sr$^{-1}$, within a factor of two from the integrated quasar contribution.

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arXiv1994

The Gunn-Peterson Effect in the Spectrum of the Z=4.7 QSO 1202-0725: The Intergalactic Medium at Very High Redshift

A measure of the average depression between Lyman absorption lines in the spectrum of the faint quasar BR1202-0725 ($z_{em}=4.695$) is presented. The relatively high resolution of the spectrum ($\sim 40$ km s$^{-1}$) allows the selection of regions free of strong absorption lines in the Lyman alpha forest. A reliable evaluation of the continuum shape is based on the careful flux calibration and on the large wavelength interval covered (5000--9300 ~Å). A best estimate of $τ_{_{GP}}\leq 0.02\pm 0.03$ has been found for the Gunn-Peterson optical depth at the highest absorption redshift observed at this resolution, $z \simeq 4.3$. The derived baryon density of the intergalactic medium is $Ω_{IGM}\mincir 0.01$ if the observed quasars are the major contributor to the ionizing UV background flux. This limit, when compared with the total baryon density deduced from the nucleosynthesis, could imply that most of the baryons are already in bound systems at $z\sim 5$.

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