相关论文: Resonant temperature fluctuations in nebulae ioniz…

We create a photoionization model embedded in the turbulent ISM by using the state-of-the-art Messenger Monte-Carlo MAPPINGS~V code (M$^3$) in conjunction with the CMFGEN stellar atmosphere model. We show that the turbulent ISM causes the…

We present new deep imaging and high-resolution spectroscopy of the extreme-abundance-discrepancy planetary nebula Ou 5, together with photoionization modelling aimed at probing its unusual thermal and chemical structure. The nebula…

(abridged) Deep long-slit optical spectrophotometric observations are presented for 25 Galactic bulge planetary nebulae (GBPNe) and 6 Galactic disk planetary nebulae (GDPNe). The spectra, combined with archival ultraviolet spectra obtained…

The discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major unresolved problem in nebular astrophysics. We show here that the largest abundance discrepancies are…

The discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major, unresolved problem with significant implications for the determination of chemical abundances throughout…

We present an analysis of physical conditions in planetary nebulae (PNe) in terms of collisionally-excited line (CEL) and optical-recombination line (ORL) profiles. We aim to investigate whether line profiles could be used to study the…

The origin of the abundance discrepancy in nebulae is one of the key problems in the physics of photoionized nebulae. In this work we have analized a sample of Galactic and extragalactic H II regions where the abundance discrepancy have…

We present MUSE deep integral-field unit spectroscopy of three planetary nebulae(PNe) with high abundance discrepancy factors (ADF > 20): NGC 6778, M 1-42 and Hf 2-2. We have constructed flux maps for more than 40 emission lines, and use…

We re-examine the well-known discrepancy between ionic abundances determined via the analysis of recombination lines (RLs) and collisionally excited lines (CELs). We show that abundance variations can be mimicked in a {\it chemically…

The existence and origin of large spatial temperature fluctuations in HII regions and planetary nebulae are assumed to explain the differences between the heavy element abundances inferred from collisionally excited and recombination lines,…

Since the last IAU symposium on planetary nebulae (PNe), several deep spectroscopic surveys of the relatively faint optical recombination lines (ORLs) emitted by heavy element ions in PNe and H II regions have been completed. New diagnostic…

Here we present the spatially resolved study of six Galactic planetary nebulae (PNe), namely IC 4593, Hen 2-186, Hen 2-429, NGC 3918, NGC 6543 and NGC 6905, from intermediate-resolution spectra of the 2.5 m Isaac Newton Telescope and the…

The origin of the abundance discrepancy is one of the key problems in the physics of photoionized nebula. In this work, we analize and discuss data for a sample of Galactic and extragalactic HII regions where this abundance discrepancy has…

We investigate the electron temperature gradient in the galactic disk as measured by young HII regions on the basis of radio recombination lines and the corresponding gradient in planetary nebulae (PN) based on [OIII] electron temperatures.…

A hot central star illuminating the surrounding ionized H II region usually produces very rich atomic spectra resulting from basic atomic processes: photoionization, electron-ion recombination, bound-bound radiative transitions, and…

We carry out plasma diagnostic analyses for 123 planetary nebulae (PNe) and 42 H II regions using the N II and O II optical recombination lines (ORLs). New effective recombination coefficients for the N II and O II optical recombination…

A photoionized gas in thermal equilibrium can display a thermal instability, with 3 or more solutions in the multi-branch region of the S-shape curve giving the temperature versus the radiation-to-gas-pressure ratio. Many studies have been…

We present spectrophotometry of 12 Galactic and 3 Magellanic Cloud planetary nebulae (PNe). Nine of the Galactic PNe were observed by scanning the slit across the PN. We use the fluxes of collisionally excited lines (CELs) to derive…

(Abridged) The abundance discrepancy problem in planetary nebulae (PNe) has long puzzled astronomers. NGC6153, with its high Abundance Discrepancy Factor (ADF~10), provides an opportunity to understand the chemical structure and ionisation…

We present a linear analysis of acoustic and thermo-reactive instabilities in a diffuse gas, photoionized and heated by a radiation field, cooled by collisional excitation of hydrogen and metal lines. The hydrogen recombination reaction has…