Papers by Walter Weidmann
We inform the preliminary results of the morphological and kinematic study of the members of the ... more We inform the preliminary results of the morphological and kinematic study of the members of the Compact Group of Galaxies, Hickson 63. This study is based on images and spectra obtained in Bosque Alegre as a part of a long time program destinated to the analysis of this kind of objects. Our spectra improve the determination of the radial velocities, setting the distance of the group at 126 Mpc (h=0.75). One of the most important results is that the galaxy Hcg 63A do not belongs to the group and it is about half the distance to it. We al so obtained the internal radial velocity curves of the objects, that enabled us to estimate their masses. We determine the objects luminosity and relative colour index, the bluer galaxies are those with smaller apparent diameter. All the nuclei present emission lines, the most intense ones are those of the galaxy D nucleus, the more compact one and of earlier morphological type. The morphology and the radial velocity curves, both show traces of inte...
We present the preliminary results of the morphological and kinematical study of the galaxies tha... more We present the preliminary results of the morphological and kinematical study of the galaxies that compose the Hickson 87 compact group, using HST-WFPC2 images and spectra obtained at Bosque Alegre Astrophysical Station. Our spectra yield a better radial velocity determination of the five galaxies that are nominally included in this group, and allowed the determination of the internal radial velocity amplitudes of the galaxies A, B, C and E. We made the surface photometry of the objects and estimated the mass/luminosity ratio of each object. The morphology of galaxy B presents perturbations at low luminosity levels, possibly due to the interaction with the spiral galaxy A, and shows a blue circumnuclear ring in the color map. The spectra of all the galaxies have emission lines, A and B would not harbour an AGN, in contradiction with previous, less detailed works. The most important result is that this would not be a completely physical group, because the galaxies HCG 87 D and E woul...
In this work we study the orientations of the orbital planes of visual binary stellar systems. Th... more In this work we study the orientations of the orbital planes of visual binary stellar systems. This analysis was carried out on a certain region of the sky, where we found a peculiar distribution of the position angles of elongated planetary nebulae. The distribution of the orientations of binary systems towards the galactic center shows some non-random characteristics, although the
In this work we analyzed the distribution of global expansion velocities of elongated Planetary N... more In this work we analyzed the distribution of global expansion velocities of elongated Planetary Nebulae (PN) as a function of the double peaked distribution of the orientations of such nebulae in the Milky Way. We found that some differences could exist in the intrinsic characteristics of the PN belonging to each peak. The difference between the average of the expansion
Un estudio detallado de las orientaciones diferenciales de nebulosas planetarias en todo el cielo... more Un estudio detallado de las orientaciones diferenciales de nebulosas planetarias en todo el cielo sugiere fuertemente una relación con la dirección de los campos magnéticos de origen galáctico, determinados en la polarización de estrellas de campo. Esto da consistencia a la hipótesis de que la orientación de las nebulosas planetarias ovaladas es inducida, al menos parcialmente, por el campo magnético
The circumnuclear regions of galaxies are frequent scenarios for starbursts and other extraordina... more The circumnuclear regions of galaxies are frequent scenarios for starbursts and other extraordinary events. Observations of the kinematics and physical properties of the ionized gas show that bars, resonances, gas flux and tidal forces play a very important role in their evolution. M 83, with its low inclination and proximity, presents one of the best opportunities for studying all these phenomena in one object. We performed two-dimensional spectroscopic observations with multi-pupils, a practically new technique for the observation of southern objects. The main preliminary results are the kinematical evidence of the presence of a secondary nucleus 3.2'' NW of the optical continuum center and the confirmation of the existence of an inner ring-like structure in the ionized gas.
We present some of the results obtained with the Gemini N and S telescopes, in the framework of o... more We present some of the results obtained with the Gemini N and S telescopes, in the framework of our research program about the central regions of galaxies with nuclear activity. In particular, we summarize our work about the circumnuclear perturbing patterns of the galaxy NGC 1241, which harbors a Seyfert nucleus and was observed with adaptive optics at the Gemini North telescope, in the bands J and K_s. We also present in advance the results obtained about the starburst nucleus in M 83, which was observed with 3D infrared spectroscopy techniques, at the Gemini South telescope.
We present the preliminary results of a spectroscopy study of spiral galaxies with circumnuclear ... more We present the preliminary results of a spectroscopy study of spiral galaxies with circumnuclear rings. Each galaxy was observed in CASLEO in several position angles, in the red spectral range and with an approximate spectral resolution of 4000. We present the emission radial profiles of the ionized gas and the heliocentric radial velocity curves for these galaxies. The possible presence of noncircular motions are also studied. FULL TEXT IN SPANISH
The sample was extracted from the Catalogue of Galactic Planetary Nebulae updated version 2000 (K... more The sample was extracted from the Catalogue of Galactic Planetary Nebulae updated version 2000 (Kohoutek 2001; hereafter CGPN2000, Cat. IV/24) that includes 1510 true PNe and the MASH survey (Parker et al., 2006, Cat. V/127) with 903 objects; 578 of them are classified as true PN. (1 data file).
Vizier Online Data Catalog, Jun 1, 2008
The sample was extracted from the Catalogue of Galactic Planetary Nebulae updated version 2000 (K... more The sample was extracted from the Catalogue of Galactic Planetary Nebulae updated version 2000 (Kohoutek 2001; hereafter CGPN2000, Cat. IV/24) that includes 1510 true PNe and the MASH survey (Parker et al., 2006, Cat. V/127) with 903 objects; 578 of them are classified as true PN. (1 data file).
Astronomy and Astrophysics
Context. At least 492 central stars of Galactic planetary nebulae (CSPNs) have been assigned spec... more Context. At least 492 central stars of Galactic planetary nebulae (CSPNs) have been assigned spectral types. Since many CSPNs are faint, these classification efforts are frequently made at low spectral resolution. However, the stellar Balmer absorption lines are contaminated with nebular emission; therefore in many cases a low-resolution spectrum does not enable the determination of the H abundance in the CSPN photosphere. Whether or not the photosphere is H deficient is arguably the most important fact we should expect to extract from the CSPN spectrum, and should be the basis for an adequate spectral classification system. Aims. Our purpose is to provide accurate spectral classifications and contribute to the knowledge of central stars of planetary nebulae and stellar evolution. Methods. We have obtained and studied higher quality spectra of CSPNs described in the literature as weak emission-line star (WELS). We provide descriptions of 19 CSPN spectra. These stars had been previously classified at low spectral resolution. We used medium-resolution spectra taken with the Gemini Multi-Object Spectrograph (GMOS). We provide spectral types in the Morgan-Keenan (MK) system whenever possible. Results. Twelve stars in our sample appear to have normal H rich photospheric abundances, and five stars remain unclassified. The rest (two) are most probably H deficient. Of all central stars described by other authors as WELS, we find that at least 26% of them are, in fact, H rich O stars, and at least 3% are H deficient. This supports the suggestion that the denomination WELS should not be taken as a spectral type, because, as a WELS based on low-resolution spectra, it cannot provide enough information about the photospheric H abundance.
We observed 46 PNs using the 2.15m telescope at Casleo, Argentina, between 2005 November and 2008... more We observed 46 PNs using the 2.15m telescope at Casleo, Argentina, between 2005 November and 2008 December. (2 data files).
Context. About 2500 planetary nebulae are known in our Galaxy but only 224 have central stars wit... more Context. About 2500 planetary nebulae are known in our Galaxy but only 224 have central stars with reported spectral types in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker et al. 1992; Acker et al. 1996). Aims. We have started an observational program aiming to increase the number of PN central stars with spectral classification. Methods. By means of spectroscopy and high resolution imaging, we identify the position and true nature of the central star. We carried out low resolution spectroscopic observations at CASLEO telescope, complemented with medium resolution spectroscopy performed at Gemini South and Magellan telescopes. Results. As a first outcome of this survey, we present for the first time t he spectra of the central star of the PN Th 2-A. These spectra show emission lines of ionized C and O, typical in Wolf-Rayet stars. Conclusions. We identify the position of that central star, which is not th e brightest one of the visual central pair. We classify it...
We studied the geometrical parameters of all known planetary nebulae in a sky sector that include... more We studied the geometrical parameters of all known planetary nebulae in a sky sector that includes the Milky Way plane (-40o
We have carried out an spectroscopy study of the Planetary Nebula Ap 2-1, obtaing for the first t... more We have carried out an spectroscopy study of the Planetary Nebula Ap 2-1, obtaing for the first time its radial and expansion velocity, we have also analysed the spatial variation of the electronic density, and we have detected a growth toward the centre. Finally we discuss its physical nature, which have been questioned since some years ago; there are arguments in favour/against of HII Regions-Planetary Nebulae. FULL TEXT IN SPANISH
Context. There are more than 3000 confirmed and probable known Galactic planetary nebulae, but ce... more Context. There are more than 3000 confirmed and probable known Galactic planetary nebulae, but central star spectroscopic information is available for only 13% of them. Aims. We undertook a spectroscopic survey of central stars of PNe to identify their spectral types. Methods. We performed spectroscopic observations, at low resolution, with the 2-m telescope at CASLEO, Argentina. Results. We present the spectra of 46 central stars of PNe, most of them are OB-type and emission-line stars.
We have carried out a spectroscopy study of the planetary nebulae H1-3 (PN G 342.7+00.7) with the... more We have carried out a spectroscopy study of the planetary nebulae H1-3 (PN G 342.7+00.7) with the spectrograph REOSC at the 2.15-m telescope at CASLEO, Argentina. The measured wavelength of the strong line H alpha indicate a systematic velocity V_{LSR} = 8+/-10 km s^{-1}, the expansion velocity of the nebula is estimated in V_{exp} = 25km s^{-1}. The emission lines
Based on observations carried out with the REOSC spectrograph on the 2.15 m telescope at CASLEO, ... more Based on observations carried out with the REOSC spectrograph on the 2.15 m telescope at CASLEO, Argentina, with a spectral resolution of 2000, we have discovered that the spectrum of the central star of the planetary nebula Th 2-A (PN G 306.4-00.6) shows Wolf-Rayet type emission lines of CIV and OVI. We classify this spectrum as of type WO. This
Be objects are stars of B spectral type showing lines of the Balmer series in emission. The prese... more Be objects are stars of B spectral type showing lines of the Balmer series in emission. The presence of these lines is attributed to the existence of an extended envelope, disk type, around them. Some stars are observed in both the Be and normal B-type spectroscopic states and they are known as transient Be stars. In this paper we show the analysis carried out on a new possible transient Be star, labelled HD 112999, using spectroscopic optical observations and photometric data.
Publications of the Astronomical Society of the Pacific, 2008
We analyze the spatial orientation of a homogenous sample of 440 elongated Planetary Nebulae (PNe... more We analyze the spatial orientation of a homogenous sample of 440 elongated Planetary Nebulae (PNe) in order to determine the orientation of their apparent major axis respect to the Milky Way plane. We present some important geometrical and statistical considerations that have been overlooked by the previous works on the subject. The global distribution of galactic position angles (GPA) of PNe is quantitatively not very different from a random distribution of orientations in the Galaxy. Nevertheless we find that there is at least one region on the sky, toward the galactic center, where a weak correlation may exist between the orientation of the major axis of some PNe and the Galactic equator, with an excess of axes with GPA∼ 100 • . Therefore, we confirm that "extrinsic" phenomena (i.e., global galactic magnetic fields, shell compression from motion relative to the Interstellar Medium) do not determine the morphology of PNe on most of the sky, with a possible exception towards the galactic center.
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Papers by Walter Weidmann