21/07/2004

Research with OSIRIS:

My scientific interests are connected to the research with OSIRIS onboard the Rosetta orbiter.

Earliest stages of star formation:

During my Ph.D studies ( TLS Tautenburg, Germany) I studied the earliest stages of star formation (Class 0/I sources). During these phases, the deeply embedded prestellar objects radiate thermal energy, which emerges mostly at far-infrared and sub-mm-wavelengths (in the optical and near-infrared they are completely obscured). Here my interest is focused on far-infrared, sub-mm, and mm studies.

Left picture: an example of a birthplace of stars. The stars actually form from the cores of the molecular clouds.

Why are Class 0 sources so difficult to study? They are highly obscured by extended dusty envelopes (thousands of Astronomical Units), and spend only a short time in this evolutionary phase (10⁴ yr) that their detection is quite difficult. Hence constraining physical properties of Class 0 sources is an extremely difficult task.

   Schematic structure of a Class 0 source: a central protostellar object surrounded by an infallling dusty envelope, with a flattened accretion disk, and ejecting a bipolar molecular outflow.

During my Ph.D. research (under the supervision of Dr. J. Eisl\"offel, TLS Tautenburg, Germany), I studied the physical structure and kinematics of the components of Class 0 sources and their physics. I have experience of data reduction of continuum sub-mm data taken with SCUBA (at JCMT on Mauna Kea, Hawaii), and continuum and spectral line sub-mm observations with the MPIfR 37-Channel Bolometer and the heterodyne receivers (at IRAM 30-m, Pico Veleta, Spain), and the SEST Heterodyne Receivers (at SEST, La Silla, Chile). I work also with radiative transfer codes to analyze the data.
 

Age of Globular Clusters:

Globular Cluster NGC 1261
H-band
 

During my M.Sc. studies (under the supervision of Dr. G. Bruzual, CIDA, Venezuela), I was dealing with the problem of  the determination of the age of Globular Clusters (GCs) by likelihood procedures. Up to now, determining a reliable age of GCs has proven to be rather difficult. This is not only because of errors introduced by the observations, but also because of the rather subjective way in which the stellar evolutionary models have been selected in some conventional procedures. Here then I got background on the determination of the age of GCs applying modern approaches. This work involved a combination of cosmology, statistics, and stellar evolution.
 

  Outline of technical/observational experience

I have participated in several observing runs at the 1-m Schmidt telescope at the Venezuelan National Astronomical Observatory, using a large-area CCD Camera (the camera is optimized for drift-scan photometry and objective-prism spectroscopy). There, I had the opportunity of being a member of the QUEST project (Quasar Equatorial Survey Team, a collaboration between groups from Yale University, Indiana University, CIDA and Universidad de Los Andes (Mérida, Venezuela)). Several results had been obtained, for example the discovery of the optical transient of GRB 990308 (Bradley et. al 1999), a variability survey in the Orion OB Association (Briceno et al. 1999) and then the discovery of the trans-Neptunian object 2000 EB₁₇₃ (Ferrin et al. 2001), among other results. Furthermore, I have carried up an observing run on the 2.2-m telescope on Calar Alto, Spain, during two weeks in December 1998, where we have done imaging of pre-sequence stars. Also I have observed with the 2-m Schmidt telescope at the Thueringer Landessternwarte Tautenburg using the Coudé spectrograph.

During my participation in the Eurolab Course in the IRAM Summer school 2001 ''mm Observing Techniques and applications'', I was observing with the 30-m telescope (IRAM, Spain) using the MAMBO bolometer and the heterodyne receivers. Then I became a member of the observing team on the 30-m telescope during several observing runs in April 2002. There, I was conducting the observations with bolometer and heterodyne modes for different projects of the astronomical community.

During my Ph.D. work I have reduced and analyzed continuum sub-mm data obtained with SCUBA at the 15-m JMCT on Mauna Kea, Hawaii, partly performed using SURF, the SCUBA User Reduction Facility Software package. From the sub-mm imaging of the deeply embedded sources in the Orion and Perseus star forming regions, we have derived physical parameters (Rengel et al., 2004, in preparation; Rengel, Ph.D. Thesis) and testing models of their structures. I was observing in January 2003 at the Swedish-ESO Submillimetre Telescope (SEST) at La Silla, Chile, using heterodyne receivers to study the kinematics of deeply embedded sources.