Alejandro C. Raga

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[1] The most comprehensive search for organics in the Martian soil was performed by the Viking Landers. Martian soil was subjected to a thermal volatilization process to vaporize and break organic molecules, and the resultant gases and volatiles were analyzed by gas chromatography‐mass spectrometry. Only water at 0.1–1.0 wt% was detected, with traces of(More)
Energy released by a small fraction of the baryons in the universe, which condensed out while the IGM was cold, dark, and neutral, reheated and reionized it by redshift 6, exposing other baryons already condensed into dwarf-galaxy minihalos to the glare of ionizing radiation. We present the first gas dynamical simulations of the photoevaporation of(More)
We carry out a bibliometric study of the activity of astronomers in the field of Herbig-Haro (HH) objects. Through an appropriate choice of keywords, we recover the papers on HH objects from the ADS (Astrophysics Data Service) and ISI (“Web of Knowledge”) databases. From the two databases we recover number of papers and citations which differ by ∼10%. We(More)
The weak, R-type ionization fronts (I-fronts) which swept across the intergalactic medium (IGM) during the reionization of the universe often found their paths blocked by cosmological minihaloes (haloes with virial temperatures Tvir 6 10 4 K). When this happened, the neutral gas which filled each minihalo was photoevaporated; as the I-front burned its way(More)
We present an analytic model describing the ““ cluster wind ÏÏ Ñow that results from the multiple interaction of the stellar winds produced by the stars of a dense cluster of massive stars. The analytic solution (obtained by matching an inner and an outer solution at the radius of the stellar cluster) can have asymptotically subsonic or supersonic behavior,(More)
We present new results on the kinematics of the jet HH 110. New proper motion measurements have been calculated from [SII] CCD images obtained with a time baseline of nearly fifteen years. HH 110 proper motions show a strong asymmetry with respect to the outflow axis, with a general trend of pointing towards the west of the axis direction. Spatial(More)
We present [SII] images of the HH 30 and HL/XZ Tau region obtained at two epochs, as well as long-slit optical spectroscopy of the HH 30 jet. We measured proper motions of ∼100–300 km s for the HH 30 jet and counterjet, and of ∼120 km s for the HL Tau jet. Inclination angles with respect to the plane of the sky are 0–40 for the HH 30 jet and 60 for the HL(More)
The postcollapse structure of objects which form by gravitational condensation out of the expanding cosmological background universe is a key element in the theory of galaxy formation. Towards this end, we have reconsidered the outcome of the nonlinear growth of a uniform, spherical density perturbation in an unperturbed background universe – the(More)
We present the first gas dynamical simulations of the photoevaporation of cosmological minihalos overtaken by the ionization fronts which swept through the IGM during reionization in a ΛCDM universe, including the effects of radiative transfer. We demonstrate the phenomenon of I-front trapping inside minihalos, in which the weak, R-type fronts which(More)
We study the evolution of dense neutral clumps located in the outer parts of planetary nebulae. These clumps will be photo-ionized by the ionizing radiation from the central star and change their structure in the process. The main effect of the ionization process is the setting up of a photo-evaporation flow and a shock running through the clump. Once this(More)