Luis Salas

Destruction of the Environment of the BN-KL Nebula

Resumen en: We present the velocity structure of the 2.12 micron H2 emission in Orion, obtained with an IR Fabry-Perot interferometer with a spectral resolution of 2...

Kinematics of the Molecular Hydrogen from the Planetary Nebula NGC 2346

We present scanning Fabry-Perot observations of the planetary nebula NGC 2346 at the near-infrared vibrationally excited line H2 S(1) 1–0 at 2.122 μm. The kinematics matches a model of two ellipsoids with an outflow velocity proportional to the distance of the gas from the central star and moving radially outward. The stronger emission is located in an equatorial torus expanding at 16 km s-1. It is likely that a shock between 6 and 16 km s-1, depending on the assumed velocity of the red giant envelope (0 to 10 km s-1), excites the molecular gas. Depending on those limiting values for the shock velocity, the density of the preshock gas falls in the range (0.3–1.7) × 104 cm-3, and consequently the mass of the molecular gas in the nebula is estimated to be between 0.34 and 1.85 M⊙, much larger than the mass of the ionized gas, and marginally in agreement with the estimate coming from CO observations alone.

Molecular Hydrogen Kinematics in Cepheus A

We present the radial velocity structure of the molecular hydrogen outflows associated with the star-forming region Cepheus A. This structure is derived from the Doppler shift of the H2 v = 1–0 S(1) emission line obtained by Fabry-Perot spectroscopy. The east and west regions of emission, called Cep A (E) and Cep A (W), show radial velocities in the range of -20 to 0 km s-1 with respect to the molecular cloud. Cep A (W) shows an increasing velocity with position offset from the core, indicating the existence of a possible accelerating mechanism. Cep A (E) has an almost constant mean radial velocity of -18 km s-1 along the region, although with a large dispersion in velocity, indicating the possibility of a turbulent outflow. A detailed analysis of the Cep A (E) region shows evidence for the presence of a Mach disk on that outflow. In addition, we argue that the presence of a velocity gradient in Cep A (W) is indicative of a C-shock in this region. Following Riera and coworkers, we analyzed the data using wavelet analysis to study the line width and central radial velocity distributions. We found that both outflows have complex spatial and velocity structure characteristic of a turbulent flow.

Correlation Algorithm to recover the phase of a test surface using Phase-Shifting Interferometry

A correlation algorithm to recover the phase in phase-shifting interferometry is presented. We make numerical simulations to test the proposed algorithm and apply it to real interferograms with satisfactory results.

Deterministic convergence in iterative phase shifting

Previous implementations of the iterative phase shifting method, in which the phase of a test object is computed from measurements using a phase shifting interferometer with unknown positions of the reference, do not provide an accurate way of knowing when convergence has been attained. We present a new approach to this method that allows us to deterministically identify convergence. The method is tested with a home-built Fizeau interferometer that measures optical surfaces polished to lambda/100 using the Hydra tool. The intrinsic quality of the measurements is better than 0.5 nm. Other possible applications for this technique include fringe projection or any problem where phase shifting is involved.

Flux-Velocity Relation for H2 Outflows*

We present an analysis of velocity-resolved near-IR molecular hydrogen observations of a variety of protostellar outflows with very different energetics, degrees of collimation, and morphologies. Observations in the 2.12 μm line of H2 were obtained using an IR Fabry-Perot interferometer with a spectral resolution of 23 km s-1. The integrated flux-velocity diagrams for each outflow show a flat spectrum for low velocities followed by a decreasing power law dF/dv ∝ vγ, with γ between -1.8 and -2.6, for velocities higher than a clearly defined break velocity at 2-17 km s-1. Contrary to shock model predictions, it is shown that the H2 intensity is constant with velocity. We argue that the flux-velocity relation can then be interpreted as a mass-velocity relation, in striking similarity to the power-law mass spectra observed in CO outflows. By comparing H2 and CO mass-velocity spectra, it is shown that there is a velocity regime in which both molecules coexist and produce similar γ-values. Evolution effects in outflows appear as a correlation between outflow length and γ; as outflows age, the spectra becomes steeper. Our results support a common physical origin for both CO and H2 emission and a strong association between the molecular outflows traced in each molecule.

VARIABLE SEPARATION IN CURVATURE SENSING : FAST METHOD FOR SOLVING THE IRRADIANCE TRANSPORT EQUATION IN THE CONTEXT OF OPTICAL TELESCOPES

A method to evaluate wave-front aberrations in optical telescopes that is based on the method of curvature sensing but that solves the irradiance transport equation by variable separation is presented. This technique is simpler for processing than are previously released techniques and can perform more efficiently, as is required by active and adaptive optics. Testing for consistency of the method by evaluation of several sets of out-of-focus images obtained with the 2-m telescope at the Universidad Nacional Autónoma de México was carried out, and a stability of 10% for the derived values of Zernike coefficients was found.

Geometric method to measure astigmatism aberration at astronomical telescopes

A simple geometrical method to measure the aberration of astigmatism present in the wavefront that emerges from a telescope is presented. The method is based on the analysis of the external contour of the image of a slightly defocused star. An expression elliptical edge is obtained, which links the rms value of Z22 to the geometric parameters of the ellipse. This expression is tested as a function of introduced defocus and astigmatism aberration in telescopes of the San Pedro Martir Observatory. It is shown that the method gives comparable results to wavefront tests, being capable of measuring astigmatism values of approximately 60 nm and larger without the need for auxiliary optics.

Surface roughness results using a hydrodynamic polishing tool (HyDra)

HyDRa is a hydrodynamic radial polishing tool ideal for the corrective lapping and fine polishing of diverse materials by means of an accelerated abrasive flux. The roughness of an optical surface is analysed for a continuous manufacturing process, beginning with the basic generation steps up to a finished optical surface. These results were obtained using a Linnik interferometer.

Ronchi test can detect piston by means of the defocusing term

We present simulated results on piston detection applying the classical Ronchi test to a segmented surface. We have found that a piston error in a test segment, induces a change in the transversal aberration, that can be analyzed by mutually comparing the fringes frequency in each segment. We propose that the piston term of the segmented surface can be recovered by geometrically relating the change in transversal aberration with the piston term. To test this, we have simulated some ronchigrams for a known piston error, and we have been able to recover this term for a dynamic range comprised among 57nm and 550 microm. For piston errors > 550 microm a change in the transversal aberration can be appreciated and measured in the ronchigrams although these large pistons are now classical defocusings. Thus we have demonstrated that the Ronchi test can be an alternative method for the piston detection with a large dynamic range.