scholarly journals Utilization of MASH Planetary Nebula Catalogue of the Year 2006 for the Determination of the Milky-Way Plane

2009 ◽  
Vol 21 (2) ◽  
pp. 367-370
Author(s):  
A. Sendi
Keyword(s):  
Planetary Nebula ◽  
Milky Way

scholarly journals Milky Way Rotation Models from Neutral Hydrogen and Molecular Clouds: Galactic Constants, Common Details and Differences

2000 ◽  
Vol 174 ◽  
pp. 403-407
Author(s):  
Igor’ I. Nikiforov
Keyword(s):  
Milky Way ◽  
Galactic Center ◽  
Kinematic Model ◽  
Neutral Hydrogen ◽  
Galactic Rotation ◽  
Kinematic Data ◽  
Galactic Rotation Curve ◽  
The Common ◽  
Center Distance

Kinematic data from neutral hydrogen observations provide information to solve the interdependent problems of the determination of the main Galactic constants (the Solar-Galactic center distance R0, the Oort constant A and others) and the Galactic rotation curve (Nikiforov & Petrovskaya 1994, hereafter NP94, and references therein). However, in the standard method for finding R0 by comparing the rotations of HI clouds and some other objects (typically HII regions/CO clouds), the kinematic model, constructed typically solely from HI data, is considered to be the same for both galactic subsystems (e.g. Merrifield 1992). In practice a discrepancy between their rotation curves can produce strongly erroneous results (Merrifield 1992, NP94). Establishing the common rotation law from HI plus HII/CO data in NP94 is only a part of attacking the problem.

scholarly journals A comparison of the density gradients of main sequence stars obtained by two different methods in different galactic latitudes

1970 ◽  
Vol 38 ◽  
pp. 232-235
Author(s):  
W. Becker ◽  
R. Fenkart
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Absolute Magnitude ◽  
Galactic Centre ◽  
Density Gradients ◽  
The Sun ◽  
Main Sequence Stars

The Basel Observatory program of the determination of disc- and halo-density gradients for different intervals of absolute magnitude comprises in addition to Milky Way fields several directions, all pointing to Selected Areas near a plane perpendicular to the galactic equator and passing through the sun and the galactic centre. It was started with SA 51 (Becker, 1965) and continued with Sa 57, 54 and 141 (Fenkart, 1967, 1968, 1969).

Detection of the Angular Expansion Rate and Determination of the Distance of the Planetary Nebula NGC 6302

1993 ◽  
Vol 416 ◽  
pp. 620 ◽  
Author(s):  
Yolanda Gomez ◽  
Luis F. Rodriguez ◽  
James M. Moran
Keyword(s):  
Planetary Nebula ◽  
Expansion Rate ◽  
Angular Expansion

scholarly journals SpS5 - II. Stellar and wind parameters

2012 ◽  
Vol 10 (H16) ◽  
pp. 420-428
Author(s):  
F. Martins ◽  
M. Bergemann ◽  
J. M. Bestenlehner ◽  
P. A. Crowther ◽  
W. R. Hamann ◽  
...  
Keyword(s):  
Full Advantage ◽  
Milky Way ◽  
Massive Stars ◽  
Mid Infrared ◽  
Infrared Studies ◽  
Infrared Diagnostics

AbstractThe development of infrared observational facilities has revealed a number of massive stars in obscured environments throughout the Milky Way and beyond. The determination of their stellar and wind properties from infrared diagnostics is thus required to take full advantage of the wealth of observations available in the near and mid infrared. However, the task is challenging. This session addressed some of the problems encountered and showed the limitations and successes of infrared studies of massive stars.

scholarly journals Confronting expansion distances of planetary nebulae with Gaia DR2 measurements

2019 ◽  
Vol 625 ◽  
pp. A137 ◽  
Author(s):  
D. Schönberner ◽  
M. Steffen
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Precise Determination ◽  
Asymptotic Giant Branch ◽  
Correction Factors ◽  
Trigonometric Parallaxes ◽  
Formation And Evolution ◽  
Hydrodynamical Simulations ◽  
Good Agreement

Context. Individual distances to planetary nebulae are of the utmost relevance for our understanding of post-asymptotic giant-branch evolution because they allow a precise determination of stellar and nebular properties. Also, objects with individual distances serve as calibrators for the so-called statistical distances based on secondary nebular properties. Aims. With independently known distances, it is possible to check empirically our understanding of the formation and evolution of planetary nebulae as suggested by existing hydrodynamical simulations. Methods. We compared the expansion parallaxes that have recently been determined for a number of planetary nebulae with the trigonometric parallaxes provided by the Gaia Data Release 2. Results. Except for two out of 11 nebulae, we found good agreement between the expansion and the Gaia trigonometric parallaxes without any systematic trend with distance. Therefore, the Gaia measurements also prove that the correction factors necessary to convert proper motions of shocks into Doppler velocities cannot be ignored. Rather, the size of these correction factors and their evolution with time as predicted by 1D hydrodynamical models of planetary nebulae is basically validated. These correction factors are generally greater than unity and are different for the outer shell and the inner bright rim of a planetary nebula. The Gaia measurements also confirm earlier findings that spectroscopic methods often lead to an overestimation of the distance. They also show that even modelling of the entire system of star and nebula by means of sophisticated photoionisation modelling may not always provide reliable results. Conclusions. The Gaia measurements confirm the basic correctness of the present radiation-hydrodynamics models, which predict that both the shell and the rim of a planetary nebula are two independently expanding entities, created and driven by different physical processes, namely thermal pressure (shell) or wind interaction (rim), both of which vary differently with time.

scholarly journals The Pristine Inner Galaxy Survey (PIGS) II: Uncovering the most metal-poor populations in the inner Milky Way

2020 ◽  
Vol 496 (4) ◽  
pp. 4964-4978 ◽  
Author(s):  
Anke Arentsen ◽  
Else Starkenburg ◽  
Nicolas F Martin ◽  
David S Aguado ◽  
Daniel B Zucker ◽  
...  
Keyword(s):  
Milky Way ◽  
Dynamical Evolution ◽  
Spectral Library ◽  
Data Set ◽  
Unique Data ◽  
Horizontal Branch Stars ◽  
History Of ◽  
Low Metallicity

ABSTRACT Metal-poor stars are important tools for tracing the early history of the Milky Way, and for learning about the first generations of stars. Simulations suggest that the oldest metal-poor stars are to be found in the inner Galaxy. Typical bulge surveys, however, lack low metallicity ($\rm {[Fe/H]} \lt -1.0$) stars because the inner Galaxy is predominantly metal-rich. The aim of the Pristine Inner Galaxy Survey (PIGS) is to study the metal-poor and very metal-poor (VMP, $\rm {[Fe/H]} \lt -2.0$) stars in this region. In PIGS, metal-poor targets for spectroscopic follow-up are selected from metallicity-sensitive CaHK photometry from the CFHT. This work presents the ∼250 deg2 photometric survey as well as intermediate-resolution spectroscopic follow-up observations for ∼8000 stars using AAOmega on the AAT. The spectra are analysed using two independent tools: ULySS with an empirical spectral library, and FERRE with a library of synthetic spectra. The comparison between the two methods enables a robust determination of the stellar parameters and their uncertainties. We present a sample of 1300 VMP stars – the largest sample of VMP stars in the inner Galaxy to date. Additionally, our spectroscopic data set includes ∼1700 horizontal branch stars, which are useful metal-poor standard candles. We furthermore show that PIGS photometry selects VMP stars with unprecedented efficiency: 86 per cent/80 per cent (lower/higher extinction) of the best candidates satisfy $\rm {[Fe/H]} \lt -2.0$, as do 80 per cent/63 per cent of a larger, less strictly selected sample. We discuss future applications of this unique data set that will further our understanding of the chemical and dynamical evolution of the innermost regions of our Galaxy.

scholarly journals Density Distribution and Chemical Abundances in NGC 7027

1978 ◽  
Vol 76 ◽  
pp. 357-358
Author(s):  
Andrea Preite-Martinez ◽  
Nino Panagiat
Keyword(s):  
Density Distribution ◽  
Planetary Nebula ◽  
Constant Density ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Ngc 7027

The data available on permitted and forbidden line intensities of the planetary nebula NGC 7027 have been analyzed in terms of non-constant density models. The significance of the derived density distribution is discussed. Some implications to the determination of the chemical abundances are also discussed.

scholarly journals Neon, sulphur, and argon abundances of planetary nebulae in the sub-solar metallicity Galactic anti-centre

2018 ◽  
Vol 615 ◽  
pp. A29 ◽  
Author(s):  
G. J. S. Pagomenos ◽  
J. Bernard-Salas ◽  
S. R. Pottasch
Keyword(s):  
Planetary Nebula ◽  
Milky Way ◽  
Planetary Nebulae ◽  
Ionic Species ◽  
Infrared Emission ◽  
Emission Lines ◽  
Solar Neighbourhood ◽  
Radial Dependence ◽  
Galactic Centre ◽  
H Ii Regions

Context. Spectra of planetary nebulae show numerous fine structure emission lines from ionic species, enabling us to study the overall abundances of the nebular material that is ejected into the interstellar medium. The abundances derived from planetary nebula emission show the presence of a metallicity gradient within the disk of the Milky Way up to Galactocentric distances of ~10 kpc, which are consistent with findings from studies of different types of sources, including H II regions and young B-type stars. The radial dependence of these abundances further from the Galactic centre is in dispute. Aims. We aim to derive the abundances of neon, sulphur and argon from a sample of planetary nebulae towards the Galactic anti-centre, which represent the abundances of the clouds from which they were formed, as they remain unchanged throughout the course of stellar evolution. We then aim to compare these values with similarly analysed data from elsewhere in the Milky Way in order to observe whether the abundance gradient continues in the outskirts of our Galaxy. Methods. We have observed 23 planetary nebulae at Galactocentric distances of 8–21 kpc with Spitzer IRS. The abundances were calculated from infrared emission lines, for which we observed the main ionisation states of neon, sulphur, and argon, which are little affected by extinction and uncertainties in temperature measurements or fluctuations within the planetary nebula. We have complemented these observations with others from optical studies in the literature, in order to reduce or avoid the need for ionisation correction factors in abundance calculations. Results. The overall abundances of our sample of planetary nebulae in the Galactic anti-centre are lower than those in the solar neighbourhood. The abundances of neon, sulphur, and argon from these stars are consistent with a metallicity gradient from the solar neighbourhood up to Galactocentric distances of ~20 kpc, albeit with varying degrees of dispersion within the data.

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