Mario Rodriguez-Martinez

Energy Distribution of Individual Quasars from Far-Ultraviolet to X-Rays. I. Intrinsic Ultraviolet Hardness and Dust Opacities

Using Chandra and HST archival data, we have studied the individual SED of 11 quasars at redshifts 0.3 < z < 1.8. All UV spectra show a spectral break around 1100 ?. Five X-ray spectra showed the presence of a soft excess, and seven spectra showed an intrinsic absorption. We found that for most quasars a simple extrapolation of the far-UV power law into the X-ray domain generally lies below the X-ray data and that the big blue bump and the soft X-ray excess do not share a common physical origin. We explore the issue of whether the observed SED might be dust absorbed in the far- and near-UV. We fit the UV break, assuming a power law that is absorbed by cubic nanodiamond dust grains. We then explore the possibility of a universal SED (with a unique spectral index) by including further absorption from SMC-like extinction. Using this approach, satisfactory fits to the spectra can be obtained. The hydrogen column densities required by either nanodiamonds or amorphous dust models are all consistent, except for one object, with the columns deduced by our X-ray analysis, provided that the C depletion is ~0.6. Because dust absorption implies a flux recovery in the EUV (<700 ?), our modeling opens the possibility that the intrinsic quasar SED is much harder and more luminous in the EUV than inferred from the near-UV data, as required by photoionization models of the broad emission line region. We conclude that the intrinsic UV SED must undergo a sharp turnover before the X-ray domain.

The wavelet transform function to analyze interplanetary scintillation observations

Interplanetary scintillation (IPS) observations are useful to remotely sense the inner heliosphere. We present a new technique to analyze IPS observations using a wavelet transform (WT) function. This technique allows us to derive, in a straightforward way, a simple method to obtain the scintillation index (m). We tested this WT technique to analyze IPS observations obtained by the Solar-Terrestrial Environment Laboratory (STEL) radio telescope. The analysis of the m index of the radio source 3C48 detected by STEL over the year 2012 shows the expected decrease with solar elongation reported in previous studies. The WT technique has a great potential for future solar wind studies using IPS observations from contemporary radio telescopes.

Technique for Detecting Warm-Hot Intergalactic Gas in Quasar Ultraviolet Spectra

The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution shortward of ~1200 ?. The change of the power-law index from approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being intrinsic to quasars. We consider the possibility that the steepening may result from a tenuous absorption component that is anticorrelated with large mass overdensities. UV-sensitive satellites, whose detectors can extend down to 1000 ?, can set a useful limit to such an absorption component through the search for a flux increase in the window 1050-1190 ? (observer frame) with respect to an extrapolation of the continuum above 1230 ?. Since the recent Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope Space Telescope Imaging Spectrograph data do not show any obvious discontinuity in this region, this effectively rules out the possibility that intergalactic H I absorption is very important, and we conclude that most if not all of the steepening is intrinsic to quasars. A smaller flux discontinuity of order 1% cannot, however, be ruled out yet and would still be consistent with the warm-hot intergalactic component if it amounts to 30% of the baryonic mass, as predicted by some models of large scale structure formation, provided its temperature lies around 105.3 K.