arXiv subjects

José Alberto López

Publications and source records attributed to José Alberto López.

7 recordsLinked to original sources

arXiv2026

The ubiquity of turbulence in the expanding kinematics of the ionized shells of Galactic planetary nebulae

We present an analysis of the residual velocities from a sample of 105 Galactic planetary nebulae (PNe), the largest done to date on this subject. The analysis has been carried out with long-slit, high dispersion echelle spectra. The data were drawn from the San Pedro Mártir Kinematic Catalogue of Galactic Planetary Nebulae. The residual velocity is identified with turbulence in the plasma and is derived by decomposing the emission line profiles into their structural contributors. Turbulence seems pervasive throughout all the PNe in the sample. We find the values for the residual velocities in the sample to be either transonic or slightly supersonic in the ionized environment. When residual velocities of [N II], [O III] and He II in the same PNe are compared, there is a tendency for the residual velocities of the higher ionized ion to be larger by about 5-10 km s$^{-1}$, indicating that the turbulent structure is larger in the inner zones of the PN. We find in general no clear correlation between the residual velocities and other nebular parameters such as morphology, global expansion velocities, ionization degree and binary cores. The only exception is the case of PNe with H-poor ([WR]-type) central stars, where we confirm previous results that have consistently shown higher residual velocities for this group of PNe as compared to those with H-rich central star atmospheres. Turbulence seems to be a localised, random, dissipative process occurring in the inner sections of the shell and may affect its early evolution.

astro-ph.GA↗

arXiv2022

NGC 6153: Reality is complicated

We study the kinematics of emission lines that arise from many physical processes in NGC 6153 based upon deep, spatially-resolved, high resolution spectra acquired with the UVES spectrograph at the ESO VLT. Our most basic finding is that the plasma in NGC 6153 is complex, especially its temperature structure. The kinematics of most emission lines defines a classic expansion law, with the outer part expanding fastest (normal nebular plasma). However, the permitted lines of \ion{O}{1}, \ion{C}{2}, \ion{N}{2}, \ion{O}{2}, and \ion{Ne}{2} present a constant expansion velocity that defines a second kinematic component (additional plasma component). The physical conditions imply two plasma components, with the additional plasma component having lower temperature and higher density. The [\ion{O}{2}] density and the [\ion{N}{2}] temperature are anomalous, but may be understood considering the contribution of recombination to these forbidden lines. The two plasma components have very different temperatures. The normal nebular plasma appears to be have temperature fluctuations in part of its volume (main shell), but only small fluctuations elsewhere. The additional plasma component contains about half of the mass of the N$^{2+}$ and O$^{2+}$ ions, but only $3-5$\% of the mass of H$^+$ ions, so the two plasma components have very different chemical abundances. We estimate abundances of $12+\log(\mathrm O^{2+}/\mathrm H^+)\sim 9.2$\,dex and $\mathrm{He}/\mathrm H\sim 0.13$. Although they are all complications, multiple plasma components, temperature fluctuations, and the contributions of multiple physical processes to a given emission line are all part of the reality in NGC 6153, and should generally be taken into account.

astro-ph.GA↗

arXiv2017

The Kinematics of the Permitted C II $λ$ 6578 Line in a Large Sample of Planetary Nebulae

We present spectroscopic observations of the C II $λ$6578 permitted line for 83 lines of sight in 76 planetary nebulae at high spectral resolution, most of them obtained with the Manchester Echelle Spectrograph on the 2.1\,m telescope at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir. We study the kinematics of the C II $λ$6578 permitted line with respect to other permitted and collisionally-excited lines. Statistically, we find that the kinematics of the C II $λ$6578 line are not those expected if this line arises from the recombination of C$^{2+}$ ions or the fluorescence of C$^+$ ions in ionization equilibrium in a chemically-homogeneous nebular plasma, but instead its kinematics are those appropriate for a volume more internal than expected. The planetary nebulae in this sample have well-defined morphology and are restricted to a limited range in H$α$ line widths (no large values) compared to their counterparts in the Milky Way bulge, both of which could be interpreted as the result of young nebular shells, an inference that is also supported by nebular modeling. Concerning the long-standing discrepancy between chemical abundances inferred from permitted and collisionally-excited emission lines in photoionized nebulae, our results imply that multiple plasma components occur commonly in planetary nebulae.

astro-ph.GA↗

arXiv2016

FRIDA: diffraction-limited imaging and integral-field spectroscopy for the GTC

FRIDA is a diffraction-limited imager and integral-field spectrometer that is being built for the adaptive-optics focus of the Gran Telescopio Canarias. In imaging mode FRIDA will provide scales of 0.010, 0.020 and 0.040 arcsec/pixel and in IFS mode spectral resolutions of 1500, 4000 and 30,000. FRIDA is starting systems integration and is scheduled to complete fully integrated system tests at the laboratory by the end of 2017 and to be delivered to GTC shortly thereafter. In this contribution we present a summary of its design, fabrication, current status and potential scientific applications.

astro-ph.IM↗

arXiv2016

The kinematics of the nebular shells around low mass progenitors of PNe with low metallicity

We analyze the internal kinematics of 26 Planetary Nebulae (PNe) with low metallicity that appear to derive from progenitor stars of the lowest masses, including the halo PN population. Based upon spatially-resolved, long-slit, echelle spectroscopy drawn from the San Pedro Mártir Kinematic Catalogue of PNe (López et al. 2012), we characterize the kinematics of these PNe measuring their global expansion velocities based upon the largest sample used to date for this purpose. We find kinematics that follow the trends observed and predicted in other studies, but also find that most of the PNe studied here tend to have expansion velocities less than 20 km/s in all of the emission lines considered. The low expansion velocities that we observe in this sample of low metallicity planetary nebulae with low mass progenitors are most likely a consequence of a weak central star wind driving the kinematics of the nebular shell. This study complements previous results (Pereyra et al. 2013, and references therein) that link the expansion velocities of the PN shells with the characteristics of the central star.

astro-ph.SR↗

arXiv2013

Spatio-kinematic modelling of Abell 65, a double-shelled planetary nebula with a binary central star

We present the first detailed spatio-kinematical analysis and modelling of the planetary nebula Abell 65, which is known to host a post-common envelope, binary, central star system. As such, this object is of great interest in studying the link between nebular morphology and central star binarity. [OIII]5007A and H-alpha+[NII]6584A longslit spectra and imagery of Abell 65 were obtained with the Manchester Echelle Spectrometer on the 2.1-m telescope at the San Pedro Martir Observatory (MES-SPM). Further [OIII]5007A longslit spectra were obtained with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope (VLT-UVES). These data were used to develop a spatio-kinematical model for the [OIII]5007A emission from Abell 65. A "best-fit" model was found by comparing synthetic spectra and images rendered from the model to the data. The model comprises an outer shell and an inner shell, with kinematical ages of 15000 +/- 5000 yr kpc^-1 and 8000 +/- 3000 yr kpc^-1, respectively. Both shells have peanut-shaped bipolar structures with symmetry axes at inclinations of 55 +/- 10 deg (to the line-of-sight) for the outer shell and 68 +/- 10 deg for the inner shell. The near-alignment between the nebular shells and the binary orbital inclination (of 68 +/- 2 deg) is strongly indicative that the binary is responsible for shaping the nebula. Abell 65 is one of a growing number of planetary nebulae (seven to date, including Abell 65 itself) for which observations and modelling support the shaping influence of a central binary.

astro-ph.SR↗

arXiv2013

The deceleration of nebular shells in evolved planetary nebulae

We have selected a group of 100 evolved planetary nebulae (PNe) and study their kinematics based upon spatially-resolved, long-slit, echelle spectroscopy. The data have been drawn from the San Pedro Mártir Kinematic Catalogue of PNe (López et al. 2012). The aim is to characterize in detail the global kinematics of PNe at advanced stages of evolution with the largest sample of homogenous data used to date for this purpose. The results reveal two groups that share kinematics, morphology, and photo-ionization characteristics of the nebular shell and central star luminosities at the different late stages under study.The typical flow velocities we measure are usually larger than seen in earlier evolutionary stages, with the largest velocities occurring in objects with very weak or absent [N II] λ6584 line emission, by all indications the least evolved objects in our sample. The most evolved objects expand more slowly. This apparent deceleration during the final stage of PNe evolution is predicted by hydrodynamical models, but other explanations are also possible. These results provide a template for comparison with the predictions of theoretical models.

astro-ph.SR↗