arXiv subjects

M. G. Richer

Publications and source records attributed to M. G. Richer.

At least 37 records · Page 2Linked to original sources

arXiv2012

A Detailed Spatiokinematic Model of the Conical Outflow of the Multipolar Planetary Nebula, NGC 7026

We present an extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN), NGC 7026. We acquired ten spectra using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the 3-dimensional visualization and kinematic program, SHAPE, and using HST images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. NGC 7026 exhibits remarkable symmetry consisting of three lobe-pairs and four sets of knots, all symmetrical about the nucleus and displaying a conical outflow. Comparing the 3-D structure of this nebula to recent, XMM-Newton X-ray observations, we investigate the extended X-ray emission in relation to the nebular structure. We find that the X-ray emission, while confined to the closed, northern lobes of this PN, shows an abrupt termination in the middle of the SE lobe, which our long slit data shows to be open. This is where the shocked, fast wind seems to be escaping the interior of the nebula and the X-ray emission rapidly cools in this region.

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arXiv2012

Morpho-kinematic analysis of the point-symmetric, bipolar planetary nebulae Hb 5 and K 3-17, a pathway to poly-polarity

The kinematics of the bipolar planetary nebulae Hb~5 and K 3-17 are investigated in detail by means of a comprehensive set of spatially resolved high spectral resolution, long-slit spectra. Both objects share particularly interesting characteristics, such as a complex filamentary, rosette-type nucleus, axial point-symmetry and very fast bipolar outflows. The kinematic information of Hb~5 is combined with {\it HST} imagery to construct a detailed 3D model of the nebula using the code SHAPE. The model shows that the large scale lobes are growing in a non-homologous way. The filamentary loops in the core are proven to actually be secondary lobes emerging from what appears to be a randomly punctured, dense, gaseous core and the material that forms the point symmetric structure flows within the lobes with a distinct kinematic pattern and its interaction with the lobes has had a shaping effect on them. Hb~5 and K~3-17 may represent a class of fast evolving planetary nebulae that will develop poly-polar characteristics once the nebular core evolves and expands.

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arXiv2011

The San Pedro Mártir Kinematic Catalogue of Galactic Planetary Nebulae

The San Pedro Mártir kinematic catalogue of galactic planetary nebulae provides spatially resolved, long-slit Echelle spectra for about 600 planetary nebulae. The data are presented wavelength calibrated and corrected for heliocentric motion. For most objects multiple spectra have been acquired and images with accurate slit positions on the nebulae are also presented for each object. This is the most extensive and homogeneous single source of data concerning the internal kinematics of the ionized nebular material in planetary nebulae. Data can be retrieved for individual objects or selected by groups that share some common characteristics, such as by morphological classes, galactic population, binary cores, presence of fast outflows, etc. The catalogue is available through the world wide web at http://kincatpn.astrosen.unam.mx .

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arXiv2011

The Kinematics and Morphology of PNe with close binary nuclei

We have obtained images and long-slit, spatially resolved echelle spectra for twenty four planetary nebulae (PNe) that have confirmed close binary nuclei. The sample shows a variety of morphologies, however toroids or dense equatorial density enhancements are identified, both in the imagery and the spectra, as the common structural component. These toroids are thought to be the remnant fingerprints of the post common envelope phase. Based on the characteristics of the present sample we suggest a list of additional PNe that are likely to host close binary nuclei

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arXiv2010

The Evolution of the Kinematics of Nebular Shells in Planetary Nebulae in the Milky Way Bulge

We study the line widths in the [\ion{O}{3}]$λ$5007 and H$α$ lines for two groups of planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the Observatorio Astronómico Nacional in the Sierra San Pedro Mártir (OAN-SPM) using the Manchester Echelle Spectrograph. The first sample includes objects early in their evolution, having high H$β$ luminosities, but [\ion{O}{3}]$λ5007/\mathrm Hβ< 3$. The second sample comprises objects late in their evolution, with \ion{He}{2} $λ4686/\mathrm Hβ> 0.5$. These planetary nebulae represent evolutionary phases preceeding and following those of the objects studied by Richer et al. (2008). Our sample of planetary nebulae with weak [\ion{O}{3}]$λ$5007 has a line width distribution similar to that of the expansion velocities of the envelopes of AGB stars, and shifted to systematically lower values as compared to the less evolved objects studied by Richer et al. (2008). The sample with strong \ion{He}{2} $λ4686$ has a line width distribution indistinguishable from that of the more evolved objects from Richer et al. (2008), but a distribution in angular size that is systematically larger and so they are clearly more evolved. These data and those of Richer et al. (2008) form a homogeneous sample from a single Galactic population of planetary nebulae, from the earliest evolutionary stages until the cessation of nuclear burning in the central star. They confirm the long-standing predictions of hydrodynamical models of planetary nebulae, where the kinematics of the nebular shell are driven by the evolution of the central star.

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arXiv2010

The San Pedro Mártir Planetary Nebula Kinematic Catalogue: Extragalactic Planetary Nebulae

We present kinematic data for 211 bright planetary nebulae in eleven Local Group galaxies: M31 (137 PNe), M32 (13), M33 (33), Fornax (1), Sagittarius (3), NGC 147 (2), NGC 185 (5), NGC 205 (9), NGC 6822 (5), Leo A (1), and Sextans A (1). The data were acquired at the Observatorio Astronómico Nacional in the Sierra de San Pedro Mártir using the 2.1m telescope and the Manchester Echelle Spectrometer in the light of [\ion{O}{3}]$λ$5007 at a resolution of 11 km/s. A few objects were observed in H$α$. The internal kinematics of bright planetary nebulae do not depend strongly upon the metallicity or age of their progenitor stellar populations, though small systematic differences exist. The nebular kinematics and H$β$ luminosity require that the nebular shells be accelerated during the early evolution of their central stars. Thus, kinematics provides an additional argument favoring similar stellar progenitors for bright planetary nebulae in all galaxies.

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arXiv2009

The chemical composition of TS 01, the most oxygen-deficient planetary nebula. AGB nucleosynthesis in a metal-poor binary star

The planetary nebula TS 01 (also called PN G 135.9+55.9 or SBS 1150+599A), with its record-holding low oxygen abundance and its double degenerate close binary core (period 3.9 h), is an exceptional object located in the Galactic halo. We have secured observational data in a complete wavelength range in order to pin down the abundances of half a dozen elements in the nebula. The abundances are obtained via detailed photoionization modelling taking into account all the observational constraints (including geometry and aperture effects) using the pseudo-3D photoionization code Cloudy_3D. The spectral energy distribution of the ionizing radiation is taken from appropriate model atmospheres. Both stellar components contribute to the ionization: the ``cool'' one provides the bulk of hydrogen ionization, and the ``hot'' one is responsible for the presence of the most highly charged ions, which explains why previous attempts to model the nebula experienced difficulties. The nebular abundances of C, N, O, and Ne are found to be respectively, 1/3.5, 1/4.2, 1/70, and 1/11 of the Solar value, with uncertainties of a factor 2. Thus the extreme O deficiency of this object is confirmed. The abundances of S and Ar are less than 1/30 of Solar. Standard models of stellar evolution and nucleosynthesis cannot explain the abundance pattern observed in the nebula. To obtain an extreme oxygen deficiency in a star whose progenitor has an initial mass of about 1 msun requires an additional mixing process, which can be induced by stellar rotation and/or by the presence of the close companion. We have computed a stellar model with initial mass of 1 msun, appropriate metallicity, and initial rotation of 100 kms, and find that rotation greatly improves the agreement between the predicted and observed abundances.

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arXiv2009

The Expanding Nebular Remnant of the Recurrent Nova RS Ophiuchi (2006): II. Modeling of Combined Hubble Space Telescope Imaging and Ground-based Spectroscopy

We report Hubble Space Telescope imaging, obtained 155 and 449 days after the 2006 outburst of the recurrent nova RS Ophiuchi, together with ground-based spectroscopic observations, obtained from the Observatorio Astronómico Nacional en San Pedro Mártir, Baja California, México and at the Observatorio Astrofísico Guillermo Haro, at Cananea, Sonora, México. The observations at the first epoch were used as inputs to model the geometry and kinematic structure of the evolving RS Oph nebular remnant. We find that the modeled remnant comprises two distinct co-aligned bipolar components; a low-velocity, high-density innermost (hour glass) region and a more extended, high-velocity (dumbbell) structure. This overall structure is in agreement with that deduced from radio observations and optical interferometry at earlier epochs. We find that the asymmetry observed in the west lobe is an instrumental effect caused by the profile of the HST filter and hence demonstrate that this lobe is approaching the observer. We then conclude that the system has an inclination to the line of sight of 39$^{+1}_{-10}$ degrees. This is in agreement with the inclination of the binary orbit and lends support to the proposal that this morphology is due to the interaction of the outburst ejecta with either an accretion disk around the central white dwarf and/or a pre-existing red giant wind that is significantly denser in the equatorial regions of the binary than at the poles. The second epoch HST observation was also modeled. However, as no spectra were taken at this epoch, it is more difficult to constrain any model. Nevertheless, we demonstrate that between the two HST epochs the outer dumbbell structure seems to have expanded linearly.

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arXiv2009

What can we learn about the kinematics of bright extragalactic planetary nebulae

We present high resolution spectroscopy in the [\ion{O}{3}]$λ$5007 and H$α$ lines of bright planetary nebulae in the Milky Way bulge and the dwarf galaxies M32, Fornax, Sagittarius, and NGC 6822 obtained at the Observatorio Astronomico Nacional in the Sierra San Pedro Martir using the Manchester Echelle Spectrograph. We use the high signal-to-noise (S/N) observations of Milky Way bulge planetary nebulae to explore what kinematic information can be determined reliably when observing extragalactic planetary nebulae in the [\ion{O}{3}]$λ$5007 line at modest S/N. We find that the intrinsic line widths measured in [\ion{O}{3}]$λ$5007 and H$α$ are very similar. Over the range of S/N available in this sample, the line width we measure is independent of the S/N. Finally, deviations from a Gaussian line shape are small. Thus, the line width of the [\ion{O}{3}]$λ$5007 line in bright extragalactic planetary nebulae should reflect the kinematics of most of the mass in the ionized nebular shell.

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arXiv2009

The outflows and 3D structure of NGC 6337, a planetary nebula with a close binary nucleus

NGC 6337 is a member of the rare group of planetary nebulae where a close binary nucleus has been identified. The nebula's morphology and emission line profiles are both unusual, particularly the latter. We present a thorough mapping of spatially resolved, long-slit echelle spectra obtained over the nebula that allows a detailed characterization of its complex kinematics. This information, together with narrow band imagery is used to produce a three dimensional model of the nebula using the code SHAPE. The 3-D model yields a slowly expanding toroid with large density fluctuations in its periphery that are observed as cometary knots. A system of bipolar expanding caps of low ionization are located outside the toroid. In addition, an extended high velocity and tenuous bipolar collimated outflow is found emerging from the core and sharply bending in opposite directions, a behavior that cannot be accounted for by pure magnetic launching and collimation unless the source of the outflow is precessing or rotating, as could be expected from a close binary nucleus.

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arXiv2008

NLTE Model of NGC 6543's Central Star and its Relation with the Surrounding Planetary Nebula

We analyze the chemical composition of the central star of the planetary nebula NGC 6543 based upon a detailed NLTE model of its stellar wind. The logarithmic abundances by number are H=12.00, He=11.00, C=9.03, N=8.36, O=9.02, Si=8.19, P=5.53, S=7.57 and Fe=7.24. Compared with the solar abundances, most of the elements have solar composition with respect to hydrogen except C which is overabundant by 0.28 dex and Fe which is depleted by $\sim 0.2$ dex. Contrary to most previous work, we find that the star is not H-poor and has a normal He composition. These abundances are compared with those found in the diffuse X-ray plasma and the nebular gas. Compared to the plasma emitting in diffuse X-rays, the stellar wind is much less depleted in iron. Since the iron depletions in the nebular gas and X-ray plasma are similar, we conclude that the plasma emitting diffuse X-rays is derived from the nebular gas rather than the stellar wind. Excellent agreement is obtained between the abundances in the stellar wind and the nebular recombination line abundances for He, C, and O relative to H. On the other hand, the derived stellar N abundance is smaller than the nebular N abundance derived from recombination lines and agrees with the abundance found from collisionally-excited lines. The mean temperature variation determined by five different methods indicates that the difference in the nebular abundances between the recombination lines and collisionally excited lines can be explained as due to the temperature variations in a chemically homogeneous medium.

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arXiv2008

The planetary nebula NGC 1360, a test case of magnetic collimation and evolution after the fast wind

The central star of this nebula has an observed intense magnetic field and the fast wind is no longer present, indicating that a back flow process has probably developed. Long-slit, spatially resolved echelle spectra have been obtained across the main body of NGC 1360 and over its system of bipolar jets. Deep images of the knotty structures of the jets have also been obtained. The data allow a detailed study of the structure and kinematics of this object and the results are modeled considering the effects of a magnetic collimation process in the development of the nebula and then switching off the fast stellar wind to follow its evolution to its current state. The model is able to successfully reproduce many of the key features of NGC 1360 under these premises.

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arXiv2007

Optical line profiles of the Helix planetary nebula (NGC 7293) to large radii

New, very long (25'), cuts of spatially resolved profiles of the Halpha and [N II] optical emission lines have been obtained over the face of the Helix planetary nebula, NGC 7293. These directions were chosen to supplement previous similar, though shorter, cuts as well as crossing interesting phenomena in this nebular envelope. In particular one new cut crosses the extremes of the proposed CO J=2-1 emitting outer "torus" shown by Huggins and his co-workers to be nearly orthogonal to its inner counterpart. The second new cut crosses the extensive outer filamentary arcs on either side of the bright nebular core. It is shown that NGC 7293 is composed of multiple bipolar outflows along different axes. Hubble-type outflows over a dynamical timescale of 11,000 years are shown to be occurring for all the phenomena from the smallest He II emitting core out to the largest outer filamentary structure. All must then have been ejected over a short timescale but with a range of ejection velocities

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arXiv2007

The enigma of the oldest `nova': the central star and nebula of CK Vul

CK Vul is classified as, amongst others, the slowest known nova, a hibernating nova, or a very late thermal pulse object. Following its eruption in AD 1670, the star remained visible for 2 years. A 15-arcsec nebula was discovered in the 1980's, but the star itself has not been detected since the eruption. We here present radio images which reveal an 0.1-arcsec radio source with a flux of 1.5 mJy at 5 GHz. Deep Halpha images show a bipolar nebula with a longest extension of 70 arcsec, with the previously known compact nebula at its waist. The emission-line ratios show that the gas is shock-ionized, at velocities >100 km/s. Dust emission yields an envelope mass of ~0.05 Msun. Echelle spectra indicate outflow velocities up to 360 km/s. From a comparison of images obtained in 1991 and 2004 we find evidence for expansion of the nebula, consistent with an origin in the 1670 explosion; the measured expansion is centred on the radio source. No optical or infrared counterpart is found at the position of the radio source. The radio emission is interpreted as thermal free-free emission from gas with Tel ~ 10000 K. The radio source may be due to a remnant circumbinary disk, similar to those seen in some binary post-AGB stars. We discuss possible classifications of this unique outburst, including that of a sub-Chandrasekhar mass supernova, a nova eruption on a cool, low-mass white dwarf, or a thermal pulse induced by accretion from a circumbinary disk.

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arXiv2007

Chemical Properties of Star Forming Dwarf Galaxies

Recent studies of the near-infrared (NIR) properties of dwarf irregular galaxies (dIs) and blue compact dwarfs (BCDs) have provided improved estimates for the NIR luminosity of old stellar populations in these galaxies. These can be used to derive gas fractions, and thereby to evaluate how BCDs have evolved with respect to dIs. Oxygen abundances have been derived for four BCDs in the Virgo Cluster from a run at Gemini-North in 2003. Combining these new abundances with published values, we study the correlations among the metallicity, Ks luminosity, gas mass, baryonic mass, and gas fraction. Within errors, the two types of dwarfs appear to share a common relation between the oxygen abundance and the luminosity in Ks. The correlation between metallicity and the gas fraction is the same for BCDs as for dIs, indicating that BCD evolution has been similar to dIs. Since dIs appear to have evolved as isolated systems, the BCD bursts are unlikely to be a consequence of gas infall or merging.

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arXiv2007

A catalog of planetary nebula candidates and HII regions in NGC 3109

Images obtained with the ESO VLT and FORS1 in [O III] 5007 on- and off-band as well as r_Gunn filters are analyzed to search for Planetary Nebula (PN) candidates in the dwarf irregular NGC 3109. In the continuum-subtracted [O III] 5007 on-band images, a large number of emission-line regions were detected. We describe the criteria employed in order to distinguish PN candidates from compact HII regions, finding that the sizes and the properties of the ionizing stars are the most unambiguous discriminators for separating the two classes. Based upon these criteria, we have found 20 PN candidates for which we present coordinates, nebular [O III] fluxes, and stellar magnitudes. The cumulative luminosity function for these PNe is discussed. A catalog of HII regions listing coordinates, nebular [O III] fluxes, stellar magnitudes and other characteristics is also presented. We find that HII regions are rather concentrated towards the disk of the galaxy, while PNe are found also above and below this structure, consistent with their belonging to an older stellar population.

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arXiv2006

The X-ray binary 2S0114+650=LSI+65 010:A slow pulsar or tidally-induced pulsations?

The X-ray source 2S0114+650=LSI+65 010 is a binary system containing a B-type primary and a low mass companion believed to be a neutron star. The system has three reported periodicities: the orbital period, P{orb}~11.6 d, X-ray flaring with P{flare}~2.7 hr, and a "superorbital" X-ray periodicity P{super}~30.7 d. The objective of this paper is to show that the puzzling periodicities in the system may be explained in the context of scenarios in which tidal interactions drive oscillations in the B-supergiant star. We calculate the solution of the equations of motion for one layer of small surface elements distributed along the equator of the star, as they respond to the forces due to gas pressure, centrifugal, coriolis, viscous forces, and the gravitational forces of both stars. This calculation provides variability timescales that can be compared with the observations. In addition, we use observational data obtained at the Observatorio Astronómico Nacional en San Pedro Mártir (OAN/SPM) between 1993-2004 to determine which of the periodicities may be present in the optical region. We suggest that the tidal oscillations lead to a structured stellar wind which, when fed to the neutron star, produces the X-ray modulations. The connection between the stellar oscillations and the modulation of the mass ejection may lie in the shear energy dissipation generated by the tangential motions that are produced by the tidal interaction, particularly in the tidal bulge region. The tidal oscillation scenario weakens the case for 2S0114+650 containing a magnetar descendent.

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arXiv2005

Infrared Properties of Star Forming Dwarf Galaxies: Blue Compact Dwarfs in the Virgo Cluster

A sample of 16 blue compact dwarf galaxies (BCDs) in the Virgo Cluster has been imaged in the near-infrared (NIR) in $J$ and $K_s$ on the 2.1m telescope at OAN-SPM in Mexico. Isophotes as faint as $μ_J$ = 24 mag arcsec$^{-2}$ and $μ_{K_s}$ = 23 mag arcsec$^{-2}$ have been reached in most of the targets. Surface brightness profiles can be fitted across the whole range of radii by the sum of two components: a hyperbolic secant (sech) function, which is known to fit the light profiles of dIs, and a Gaussian component, which quantifies the starburst near the centre. Isophotal and total fitted NIR magnitudes have been calculated, along with semimajor axes at $μ_J$ = 23 mag arcsec$^{-2}$ and $μ_{K_s}$ = 22 mag arcsec$^{-2}$. The diffuse underlying component and the young starburst have been quantified using the profile fitting. Most color profiles show a constant color, between $J-K_s$=0.7 to 0.9 mag. The diffuse component represents the overwhelming majority of the NIR light for most BCDs, the starburst enhancing the flux by less than about 0.3 mag. Linear correlations were found between the sech scale length and the sech magnitude, and between the sech semimajor axis and the sech magnitude. Overall, galaxies with more luminous diffuse components are larger and brighter in the centre. The central burst correlates with the diffuse component, with brighter BCDs having stronger star-bursts, suggesting that more massive objects are forming stars more efficiently. BCDs lie on the ``fundamental plane'' defined by dwarf irregulars (dISs) in Paper I, following the same relation between sech absolute magnitude, sech central surface brightness, and the hydrogen line-width $W_{20}$, although the scatter is larger than for the dIs. [one sentence cut]

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