scholarly journals Dust & Abundances of Metal-Poor Planetary Nebulae in the Galactic Anti-Center

2016 ◽  
Vol 12 (S323) ◽  
pp. 341-342
Author(s):  
George J. S. Pagomenos ◽  
Jeronimo Bernard-Salas ◽  
G. C. Sloan
Keyword(s):  
Galactic Center ◽  
A Priori ◽  
Dust Emission ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Good Opportunity ◽  
Abundance Gradient ◽  
Dust Composition ◽  
Solar Metallicity ◽  
Low Metallicity

AbstractMuch of the new dust in the local ISM is produced in the last phases of stellar evolution of low- and intermediate-mass stars on the Asymptotic Giant Branch (AGB). Despite its importance, our knowledge of how dust properties depend on metallicity is limited. Studies of planetary nebulae in irregular galaxies in the Local Group (mostly focused on the LMC and SMC) have revealed a diverse spectral zoo and shown that low metallicity favours carbon-rich dust production by AGB stars. However, at ~1/3 and ~1/5 times the solar metallicity respectively, they provide two snapshots of dust composition at low metallicity, emphasising the need to investigate a region with a range of metallicity values. With its abundance gradient, the Milky Way fits this criterion and provides a good opportunity to observe the dust composition over a large metallicity range. In particular the Galactic anti-center, which is largely unexplored beyond galactocentric distances of 10 kpc, allows us to study the AGB dust a priori assumed to be metal-poor as well as exploring the extent of the Galactic abundance gradient. We analyse a Spitzer spectroscopic sample of 23 planetary nebulae towards the anti-center in order to understand how the metallicity gradient extends beyond 10 kpc from the Galactic center and to observe the dust composition in this region of our Galaxy. We find that the abundance gradients of Ne, S and Ar continue to distances of around 20 kpc (albeit with a large scatter) and the dust emission shows a carbon-rich chemistry similar to that in the Magellanic Clouds.

scholarly journals WORKPLANS: Workshop on Planetary Nebula Observations

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 23 ◽  
Author(s):  
Isabel Aleman ◽  
Jeronimo Bernard-Salas ◽  
Joel H. Kastner ◽  
Toshiya Ueta ◽  
Eva Villaver
Keyword(s):  
Observational Data ◽  
Planetary Nebula ◽  
Dust Emission ◽  
Planetary Nebulae ◽  
Research Field ◽  
Theoretical Modeling ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Open Questions ◽  
Giant Branch Stars

This workshop is the second of the WORKPLANS series, which we started in 2016. The main goal of WORKPLANS is to build up a network of planetary nebulae (PNe) experts to address the main open questions in the field of PNe research. The specific aims of the WORKPLANS workshop series are (i) to discuss and prioritize the most important topics to be investigated by the PN community in the following years; (ii) to establish a network of excellent researchers with complementary expertise; (iii) to formulate ambitious observing proposals for the most advanced telescopes and instrumentation presently available (ALMA, SOFIA, VLT, GTC, HST, etc.), addressing those topics; and (iv) to develop strategies for major proposals to future observatories (JWST, ELT, SPICA, Athena, etc.). To achieve these goals, WORKPLANS II brought together experts in all key sub-areas of the PNe research field, namely: analysis and interpretation of PNe observational data; theoretical modeling of gas and dust emission; evolution from Asymptotic Giant Branch stars (PNe progenitors) to PNe; and the instrumentation and technical characteristics of the relevant observatories.

scholarly journals 7.6. Dust composition, energetics, and morphology of the Galactic center

1998 ◽  
Vol 184 ◽  
pp. 303-304
Author(s):  
Kin-Wing Chan ◽  
S. H. Moseley ◽  
S. Casey ◽  
J. P. Harrington ◽  
E. Dwek ◽  
...  
Keyword(s):  
Galactic Center ◽  
Broad Band ◽  
Dust Emission ◽  
Emission Feature ◽  
Elemental Abundances ◽  
Evolved Stars ◽  
The Galaxy ◽  
Dust Composition ◽  
Circumnuclear Disk ◽  
Theoretical Results

Spectra at 16 - 45 μm of several regions within the central 80″ of the Galaxy have been obtained at 20″ resolution using the Goddard Cryogenic Grating Spectrometer No. 2 on the Kuiper Airborne Observatory. A broad band of excess emission extending from 24 to 45 μm is present in the spectra at positions covering the “tongue” and the inner edge of the circumnuclear disk. A similar dust emission feature has been observed in some carbon-rich evolved stars and in a nitrogen-rich evolved massive star. The observations reported here are the first detection of this dust emission feature in the interstellar medium. After considering several possible candidates of the carrier for this 30 μm dust feature, we find that MgS is the best owing to its good fit to the observed spectra. The origin of this ~ 30 μm feature in the Galactic center is unknown. Based on the theoretical results of dust condensation and elemental abundances in a supernova, we find that the supernovae in the central 500 pc could provide the amount of MgS dust, which we proposed as the carrier of the 30 μm dust feature, observed in the central 3 pc.

scholarly journals Evolved massive stars at low metallicity

2020 ◽  
Vol 639 ◽  
pp. A116
Author(s):  
Ming Yang ◽  
Alceste Z. Bonanos ◽  
Bi-Wei Jiang ◽  
Jian Gao ◽  
Panagiotis Gavras ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Dust Emission ◽  
Evolutionary Model ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Near Ir ◽  
Low Metallicity ◽  
Bolometric Correction ◽  
Giant Branch Stars

We present the most comprehensive red supergiant (RSG) sample for the Small Magellanic Cloud (SMC) to date, including 1239 RSG candidates. The initial sample was derived based on a source catalog for the SMC with conservative ranking. Additional spectroscopic RSGs were retrieved from the literature, and RSG candidates were selected based on the inspection of Gaia and 2MASS color-magnitude diagrams (CMDs). We estimate that there are in total ∼1800 or more RSGs in the SMC. We purify the sample by studying the infrared CMDs and the variability of the objects, though there is still an ambiguity between asymptotic giant branch stars (AGBs) and RSGs at the red end of our sample. One heavily obscured target was identified based on multiple near-IR and mid-IR (MIR) CMDs. The investigation of color-color diagrams shows that there are fewer RSGs candidates (∼4%) showing PAH emission features compared to the Milky Way and LMC (∼15%). The MIR variability of RSG sample increases with luminosity. We separate the RSG sample into two subsamples (risky and safe), and identify one M5e AGB star in the risky subsample based on simultaneous inspection of variabilities, luminosities, and colors. The degeneracy of mass loss rate (MLR), variability, and luminosity of the RSG sample is discussed, indicating that most of the targets with high variability are also the bright ones with high MLR. Some targets show excessive dust emission, which may be related to previous episodic mass loss events. We also roughly estimate the total gas and dust budget produced by entire RSG population as ∼1.9−1.1+2.4 × 10−6 M⊙ yr−1 in the most conservative case, according to the derived MLR from IRAC1–IRAC4 color. Based on the MIST models, we derive a linear relation between Teff and observed J − KS color with reddening correction for the RSG sample. By using a constant bolometric correction and this relation, the Geneva evolutionary model is compared with our RSG sample, showing a good agreement and a lower initial mass limit of ∼7 M⊙ for the RSG population. Finally, we compare the RSG sample in the SMC and the LMC. Despite the incompleteness of LMC sample in the faint end, the result indicates that the LMC sample always shows redder color (except for the IRAC1–IRAC2 and WISE1–WISE2 colors due to CO absorption) and higher variability than the SMC sample, which is likely due to a positive relation between MLR, variability and the metallicity.

scholarly journals Heavy Element Abundances in Planetary Nebulae: A Theorist's Perspective

2010 ◽  
Vol 27 (2) ◽  
pp. 227-231 ◽  
Author(s):  
Amanda I. Karakas ◽  
Maria Lugaro
Keyword(s):  
Heavy Element ◽  
Asymptotic Giant Branch ◽  
Type I ◽  
Intermediate Mass ◽  
Element Abundances ◽  
Exciting Opportunity ◽  
Solar Metallicity ◽  
Low Metallicity ◽  
Low Mass

AbstractThe determination of heavy element abundances from planetary nebula (PN) spectra provides an exciting opportunity to study the nucleosynthesis occurring in the progenitor asymptotic giant branch (AGB) star. We perform post-processing calculations on AGB models of a large range of mass and metallicity to obtain predictions for the production of neutron-capture elements up to the first s-process peak at strontium. We find that solar metallicity intermediate-mass AGB models provide a reasonable match to the heavy element composition of Type I PNe. Likewise, many of the Se and Kr enriched PNe are well fitted by lower mass models with solar or close-to-solar metallicities. However, those objects most enriched in Krand those PN with sub-solar Se/O ratios are difficult to explain with AGB-nucleosynthesis models. Furthermore, we compute s-process abundance predictions for low-mass AGB models of very low metallicity ([Fe/H]≈−2.3) using both scaled solar and an α-enhanced initial composition. For these models, O is dredged to the surface, which means that abundance ratios measured relative to this element (e.g. X/O) do not provide a reliable measure of initial abundance ratios, or of production within the star owing to internal nucleosynthesis.

scholarly journals The s-Process in the Yellow Symbiotic AG Draconis

2000 ◽  
Vol 177 ◽  
pp. 103-104
Author(s):  
Katia Cunha ◽  
Verne V. Smith ◽  
Alain Jorissen
Keyword(s):  
Mass Loss ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Element Abundance ◽  
Neutron Density ◽  
Symbiotic Stars ◽  
Solar Metallicity ◽  
Low Metallicity ◽  
K Giants

An abundance analysis of the yellow symbiotic system AG Draconis reveals it to be a metal-poor K giant ([Fe/H] = −1.3) which is enriched in the heavy s-process elements. This star thus provides a link between the symbiotic stars and the binary barium and CH stars which are also s-process enriched. These binary systems, which exhibit overabundances of the heavy elements, owe their abundance peculiarities to mass transfer from thermally-pulsing asymptotic giant branch stars, which have since evolved to become white-dwarf companions of the cool stars we now view as the chemically peculiar primaries. A comparison of the heavy-element abundance distribution in AG Dra with theoretical nucleosynthesis calculations shows that the s-process is defined by a relatively large neutron exposure (τ = 1.3 mb−1), while an analysis of the rubidium abundance suggests that the s-process occurred at a neutron density of about 2 × 108 cm−3. The derived spectroscopic orbit of AG Dra is similar to the orbits of barium and CH stars. Because the luminosity function of low-metallicity K giants is skewed towards higher luminosities by about 2 magnitudes relative to solar-metallicity giants, it is argued that the lower metallicity K giants have larger mass-loss rates. It is this larger mass-loss rate that drives the symbiotic phenomena in AG Dra and we suggest that the other yellow symbiotic stars are probably low-metallicity objects as well.

scholarly journals The Galactic deuterium gradient

2009 ◽  
Vol 5 (S268) ◽  
pp. 179-180
Author(s):  
Donald Lubowich ◽  
Jay M. Pasachoff
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
The Sun ◽  
Abundance Gradient ◽  
The Galaxy ◽  
Low Metallicity ◽  
Galactic Sources

AbstractThe Galactic deuterium abundance gradient has been determined from observations of DCN in Galactic molecular clouds. This is the only way to observe D throughout the Galaxy because the molecular clouds are not limited to the 2 kpc region around the Sun observed with FUSE and from DI. We used an astrochemistry model and the DCN/HCN ratios to estimate the underlying D/H ratios in 16 molecular clouds including five in the Galactic Center. The resulting positive Galactic D gradient and reduced Galactic Center D/H ratio imply that there are no significant Galactic sources of D, there is continuous infall of low-metallicity gas into the Galaxy, and that deuterium is cosmological.

Observations of High Rotational CO Lines in Post–Asymptotic Giant Branch Stars and Planetary Nebulae

1997 ◽  
Vol 476 (1) ◽  
pp. 319-326 ◽  
Author(s):  
K. Justtanont ◽  
A. G. G. M. Tielens ◽  
C. J. Skinner ◽  
Michael R. Haas
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Giant Branch Stars

scholarly journals Molecular Envelopes of Planetary Nebulae and Proto-Planetary Nebulae

1994 ◽  
Vol 140 ◽  
pp. 152-153
Author(s):  
Sun Kwok
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
High Rate ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
Cool Component ◽  
Dust Envelope ◽  
Peak Energy

As stars evolve up the asymptotic giant branch (AGB), they begin to lose mass at a high rate, and in the process they create extended circumstellar molecular envelopes. Since the transition from AGB to planetary nebula stages is of the order of 1000 yr, the remnant of such molecular envelopes should still be observable in pro to-planetary nebulae (PPN) and planetary nebulae (PN). Recent ground-based survey of cool IRAS sources have discovered ~30 candidates of PPN (Kwok 1992). These sources show the characteristic “double-peak” energy distribution. The cool component is due to the remnant of the AGB dust envelope, and the hot component represents the reddened photosphere. The fact that the two components are clearly separated suggests that the dust envelope is well detached from the photosphere. Radiative transfer model fits to the spectral energy distributions of PPN suggest a typical separation of ~1 arc sec between the dust envelope and the photosphere, and such “hole-in-the-middle” structure can be mapped by millimeter interferometry in CO.

scholarly journals Carbon- and Oxygen-Rich Progenitors of Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 243-250 ◽  
Author(s):  
H.J. Habing ◽  
J.A.D.L. Blommaert
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Spectral Class ◽  
Class C

This review concerns stars on the Asymptotic Giant Branch that are about to develop into planetary nebulae (=PNe). They are still termed “stars”, and properly so, and yet they have already, in statu nascendi, the structure of a PN. There are two different kinds: oxygen-rich stars (spectral class: M) and carbon-rich stars (spectral class: C).

scholarly journals Evolved massive stars at low-metallicity

2019 ◽  
Vol 629 ◽  
pp. A91 ◽  
Author(s):  
Ming Yang ◽  
Alceste Z. Bonanos ◽  
Bi-Wei Jiang ◽  
Jian Gao ◽  
Panagiotis Gavras ◽  
...  
Keyword(s):  
Massive Star ◽  
Far Infrared ◽  
Asymptotic Giant Branch ◽  
Initial Mass ◽  
Agb Stars ◽  
Proper Motions ◽  
Future Studies ◽  
Low Metallicity ◽  
Different Color ◽  
Yellow Supergiant

We present a clean, magnitude-limited (IRAC1 or WISE1 ≤ 15.0 mag) multiwavelength source catalog for the Small Magellanic Cloud (SMC) with 45 466 targets in total, with the purpose of building an anchor for future studies, especially for the massive star populations at low-metallicity. The catalog contains data in 50 different bands including 21 optical and 29 infrared bands, retrieved from SEIP, VMC, IRSF, AKARI, HERITAGE, Gaia, SkyMapper, NSC, Massey (2002, ApJS, 141, 81), and GALEX, ranging from the ultraviolet to the far-infrared. Additionally, radial velocities and spectral classifications were collected from the literature, and infrared and optical variability statistics were retrieved from WISE, SAGE-Var, VMC, IRSF, Gaia, NSC, and OGLE. The catalog was essentially built upon a 1″ crossmatching and a 3″ deblending between the Spitzer Enhanced Imaging Products (SEIP) source list and Gaia Data Release 2 (DR2) photometric data. Further constraints on the proper motions and parallaxes from Gaia DR2 allowed us to remove the foreground contamination. We estimate that about 99.5% of the targets in our catalog are most likely genuine members of the SMC. Using the evolutionary tracks and synthetic photometry from MESA Isochrones & Stellar Tracks and the theoretical J − KS color cuts, we identified 1405 red supergiant (RSG), 217 yellow supergiant, and 1369 blue supergiant candidates in the SMC in five different color-magnitude diagrams (CMDs), where attention should also be paid to the incompleteness of our sample. We ranked the candidates based on the intersection of different CMDs. A comparison between the models and observational data shows that the lower limit of initial mass for the RSG population may be as low as 7 or even 6 M⊙ and that the RSG is well separated from the asymptotic giant branch (AGB) population even at faint magnitude, making RSGs a unique population connecting the evolved massive and intermediate stars, since stars with initial mass around 6 to 8 M⊙ are thought to go through a second dredge-up to become AGB stars. We encourage the interested reader to further exploit the potential of our catalog.

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