Publications of the Astronomical Society of the Pacific
Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedb... more Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1–3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb...
We are entering our 5th year of AstroPAH! It makes us very happy to keep you up to date about our... more We are entering our 5th year of AstroPAH! It makes us very happy to keep you up to date about our community, and we hope to continue doing so for many years to come. Since our conception, the number of subscribers to AstroPAH has grown to more than 300 people, with roughly the same number of newsletter downloads each month. For our 4-year anniversary, we are changing things up and introducing a new monthly release date. AstroPAH will now be released on the 3rd or 4th Thursday of the month. The release date for an upcoming issue will continue to be published on our website and in the previous issue as usual. What better way to celebrate our anniversary than with a great Picture of the Month, sent by one of our subscribers-Martin Wendt. The picture shows the sub parsec variation of two Diffuse Interstellar Bands towards NGC 6397, as observed with the instrument MUSE installed on the VLT. This month, our In Focus dives into a subject that has been on the rise since the launch of AstroPAH: Aude Simon and Mathias Rapacioli take us on a journey through the modeling of dissociation and isomerisation of PAHs. Do not miss any of the interesting papers in our Abstract section, from calculations, to observational data analysis, to laboratory studies. We close this AstroPAH 4th anniversary issue with announcements of opportunities for Fellowships. AstroPAH will continue to help you promote your science. Please visit our webpage or contact us. Send us your contributions anytime or for publication in November, see the deadlines below. We thank you all for your contributions in these past 4 years and for the time to come.
Proceedings of the International Astronomical Union, 2018
We present the current status update of the Herschel Planetary Nebula Survey Plus project (HerPla... more We present the current status update of the Herschel Planetary Nebula Survey Plus project (HerPlaNS+) based on the original General Observer HerPlaNS survey program during the OT1 cycle and the follow-up exhaustive archival search of PN observations using the PACS and SPIRE instruments on-board the Herschel Space Observatory.
Monthly Notices of the Royal Astronomical Society, 2019
We present a detailed analysis of deep VLT/X-Shooter observations of the planetary nebula Tc 1. W... more We present a detailed analysis of deep VLT/X-Shooter observations of the planetary nebula Tc 1. We calculate gas temperature, density, extinction, and abundances for several species from the empirical analysis of the total line fluxes. In addition, a spatially resolved analysis of the most intense lines provides the distribution of such quantities across the nebula. The new data reveal that several lines exhibit a double peak spectral profile consistent with the blue- and red-shifted components of an expanding spherical shell. The study of such components allowed us to construct for the first time a three-dimensional morphological model, which reveals that Tc 1 is a slightly elongated spheroid with an equatorial density enhancement seen almost pole on. A few bright lines present extended wings (with velocities up to a few hundred km s−1), but the mechanism producing them is not clear. We constructed photoionization models for the main shell of Tc 1. The models predict the central st...
Monthly Notices of the Royal Astronomical Society, 2018
The bipolar nebula Menzel 3 (Mz 3) was observed as part of the Herschel Planetary Nebula Survey (... more The bipolar nebula Menzel 3 (Mz 3) was observed as part of the Herschel Planetary Nebula Survey (HerPlaNS), which used the PACS and SPIRE instruments aboard the Herschel Space Observatory to study a sample of planetary nebulae (PNe). In this paper, one of the series describing HerPlaNS results, we report the detection of H I recombination lines (HRLs) in the spectrum of Mz 3. Inspection of the spectrum reveals the presence of 12 HRLs in the 55-680 μm range covered by the PACS and SPIRE instruments (H11α to H21α and H14β). The presence of HRLs in this range is unusual for PNe and has not been reported in Mz 3 before. Our analysis indicates that the HRLs we observed are enhanced by laser effect occurring in the core of Mz 3. Our arguments for this are (i) the available Mz 3 optical to submillimetre HRL α line intensity ratios are not well reproduced by the spontaneous emission of optically thin ionized gas, as would be typical for nebular gas in PNe; (ii) the compact core of Mz 3 is responsible for a large fraction of the Herschel HRLs emission; (iii) the line intensity ratios for Mz 3 are very similar to those in the core emission of the well known star MWC 349A, where laser effect is responsible for the enhancement of HRLs in the Herschel wavelength range; (iv) the physical characteristics relevant to cause laser effect in the core of MWC 349A are very similar to those in the core of Mz 3.
Proceedings of the International Astronomical Union, 2016
We performed a detailed spectroscopic analysis of the fullerene C60-containing planetary nebula (... more We performed a detailed spectroscopic analysis of the fullerene C60-containing planetary nebula (PN) Lin49 in the Small Magellanic Cloud (SMC). Lin49 is a C-rich and metal-deficient PN (Z~0.0006) and its nebular abundances are in agreement with the AGB model for the initially 1.25 M⊙ stars with the metallicity Z = 0.001. By stellar absorption fitting with TLUSTY, we derived stellar abundances, effective temperature, and surface gravity. We constructed the photoionization model with CLOUDY in order to investigate physical conditions of Lin49. The model with the 0.005-0.1 μm radius graphite and a constant hydrogen density shell could not fit the ~1-5 μm spectral energy distribution (SED) owing to the strong near-IR excess. We propose that the near-IR excess indicates (1) the presence of extremely small carbon molecules or (2) the presence of high-density structure surrounding the central star.
In the present work, we use a photoionisation code to study the H_2 emission of the Helix nebula ... more In the present work, we use a photoionisation code to study the H_2 emission of the Helix nebula (NGC 7293) cometary knots, particularly that produced in the interface H^+/H^0 of the knot, where a significant fraction of the H_2 1-0 S(1) emission seems to be produced. Our results show that the production of molecular hydrogen in such region may explain several characteristics of the observed emission, particularly the high excitation temperature of the H_2 infrared lines.
Context. Detections of molecular lines, mainly from H 2 and CO, reveal molecular material in plan... more Context. Detections of molecular lines, mainly from H 2 and CO, reveal molecular material in planetary nebulae. Observations of a variety of molecules suggest that the molecular composition in these objects differs from that found in interstellar clouds or in circumstellar envelopes. The success of the models, which are mostly devoted to explain molecular densities in specific planetary nebulae, is still partial however. Aims. The present study aims at identifying the influence of stellar and nebular properties on the molecular composition of planetary nebulae by means of chemical models. A comparison of theoretical results with those derived from the observations may provide clues to the conditions that favor the presence of a particular molecule. Methods. A self-consistent photoionization numerical code was adapted to simulate cold molecular regions beyond the ionized zone. The code was used to obtain a grid of models and the resulting column densities are compared with those inferred from observations. Results. Our models show that the inclusion of an incident flux of X-rays is required to explain the molecular composition derived for planetary nebulae. We also obtain a more accurate relation for the N(CO)/N(H 2) ratio in these objects. Molecular masses obtained by previous works in the literature were then recalculated, showing that these masses can be underestimated by up to three orders of magnitude. We conclude that the problem of the missing mass in planetary nebulae can be solved by a more accurate calculation of the molecular mass.
Monthly Notices of the Royal Astronomical Society, 2016
We performed a detailed spectroscopic analysis of the fullerene C 60-containing planetary nebula ... more We performed a detailed spectroscopic analysis of the fullerene C 60-containing planetary nebula (PN) Lin49 in the Small Magellanic Cloud (SMC) using XSHOOTER at the European Southern Observatory Very Large Telescope and the Spitzer/Infrared Spectrograph instruments. We derived nebular abundances for nine elements. We used TLUSTY to derive photospheric parameters for the central star. Lin49 is C-rich and metal-deficient PN (Z ∼ 0.0006). The nebular abundances are in good agreement with asymptotic giant branch nucleosynthesis models for stars with initial mass 1.25 M and metallicity Z = 0.001. Using the TLUSTY synthetic spectrum of the central star to define the heating and ionizing source, we constructed the photoionization model with CLOUDY that matches the observed spectral energy distribution (SED) and the line fluxes in the UV to far-IR wavelength ranges simultaneously. We could not fit the ∼1-5 µm SED using a model with 0.005-0.1-µm-sized graphite grains and a constant hydrogen density shell owing to the prominent near-IR excess, while at other wavelengths the model fits the observed values reasonably well. We argue that the near-IR excess might indicate either (1) the presence of very small particles in the form of small carbon clusters, small graphite sheets, or fullerene precursors, or (2) the presence of a high-density structure surrounding the central star. We found that SMC C 60 PNe show a near-IR excess component to lesser or greater degree. This suggests that these C 60 PNe might maintain a structure nearby their central star.
Proceedings of the International Astronomical Union, 2016
We observed the Planetary Nebula NGC 6720 with the Gemini Telescope and the Gemini Multi-Object S... more We observed the Planetary Nebula NGC 6720 with the Gemini Telescope and the Gemini Multi-Object Spectrographs. We obtained spatial maps of 36 emission-lines in the wavelength range between 3600 Å and 9400 Å. We derived maps of c(Hβ), electronic densities, electronic temperatures, ionic and elemental abundances, and Ionization Correction Factors (ICFs) in the source and investigated the mass-loss history of the progenitor. The elemental abundance results indicate the need for ICFs based on three-dimensional photoionization models.
Planetary nebulae (PNe), the ejected envelopes of red giant stars, provide us with a history of t... more Planetary nebulae (PNe), the ejected envelopes of red giant stars, provide us with a history of the last, mass-losing phases of 90% of stars initially more massive than the Sun. Here, we analyse James Webb Space Telescope (JWST) Early Release Observation (ERO) images of the PN NGC 3132. A structured, extended H 2 halo surrounding an ionised central bubble is imprinted with spiral structures, likely shaped by a low-mass companion orbiting the central star at ∼40-60 AU. The images also reveal a mid-IR excess at the central star interpreted as a dusty disk, indicative of an interaction with another, closer companion. Including the previously known, A-type visual companion, the progenitor of the NGC 3132 PN must have been at least a stellar quartet. The JWST images allow us to generate a model of the illumination, ionisation and hydrodynamics of the molecular halo, demonstrating the power of JWST to investigate complex stellar outflows. Further, new measurements of the A-type visual companion allow us to derive the value for Springer Nature 2021 L A T E X template 6 JWST PN the mass of the progenitor of a central star to date with excellent precision: 2.86 ± 0.06 M. These results serve as pathfinders for future JWST observations of PNe providing unique insight into fundamental astrophysical processes including colliding winds, and binary star interactions, with implications for supernovae and gravitational wave systems.
The young and well-studied planetary nebula (PN) NGC 7027 harbors significant molecular gas that ... more The young and well-studied planetary nebula (PN) NGC 7027 harbors significant molecular gas that is irradiated by luminous, pointlike UV (central star) and diffuse (shocked nebular) X-ray emission. This nebula represents an excellent subject to investigate the molecular chemistry and physical conditions within photon- and X-ray-dominated regions (PDRs and XDRs). As yet, the exact formation routes of CO+ and HCO+ in PN environments remain uncertain. Here we present ∼2″ resolution maps of NGC 7027 in the irradiation tracers CO+ and HCO+ obtained with the IRAM NOEMA interferometer, along with SMA CO and HST 2.12 μm H2 data for context. The CO+ map constitutes the first interferometric map of this molecular ion in any PN. Comparison of CO+ and HCO+ maps reveals strikingly different emission morphologies, as well as a systematic spatial displacement between the two molecules; the regions of brightest HCO+, found along the central waist of the nebula, are radially offset by ∼1″ (∼900 au) ...
The young and well-studied planetary nebula NGC 7027 harbors significant molecular gas that is ir... more The young and well-studied planetary nebula NGC 7027 harbors significant molecular gas that is irradiated by luminous, point-like UV (central star) and diffuse (shocked nebular) X-ray emission. This nebula represents an excellent subject to investigate the molecular chemistry and physical conditions within photon-and X-ray-dominated regions (PDRs and XDRs). As yet, the exact formation routes of CO + and HCO + in PN environments remain uncertain. Here, we present ∼2 resolution maps of NGC 7027 in the irradiation tracers CO + and HCO + , obtained with the IRAM NOEMA interferometer, along with SMA CO and HST 2.12 µm H 2 data for context. The CO + map constitutes the first interferometric map of this molecular ion in any PN. Comparison of CO + and HCO + maps reveal strikingly different emission morphologies, as well as a systematic spatial displacement between the two molecules; the regions of brightest HCO + , found along the central waist of the nebula, are radially offset by ∼1 (∼900 au) outside the corresponding CO + emission peaks. The CO + emission furthermore precisely traces the inner boundaries of the nebula's PDR (as delineated by near-IR H 2 emission), suggesting that central star UV emission drives CO + formation. The displacement of HCO + radially outward with respect to CO + is indicative that dust-penetrating soft X-rays are responsible for enhancing the HCO + abundance in the surrounding molecular envelope, forming an XDR. These interferometric CO + and HCO + observations of NGC 7027 thus clearly establish the spatial distinction between the PDR and XDR formed (respectively) by intense UV and X-ray irradiation of molecular gas.
This workshop is the second of the WORKPLANS series, which we started in 2016. The main goal of W... more 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 emissio...
Monthly Notices of the Royal Astronomical Society, 2020
We present a new approach to study planetary nebulae using integral field spectroscopy. VLT@VIMOS... more We present a new approach to study planetary nebulae using integral field spectroscopy. VLT@VIMOS datacube of the planetary nebula Abell 14 is analysed in three different ways by extracting: (i) the integrated spectrum, (ii) one-dimensional simulated long-slit spectra for different position angles, and (iii) spaxel-by-spaxel spectra. These data are used to build emission-line diagnostic diagrams and explore the ionization structure and excitation mechanisms combining data from one- and three-dimensional photoionization models. The integrated and 1D simulated spectra are suitable for developing diagnostic diagrams, while the spaxel spectra can lead to misinterpretation of the observations. We find that the emission-line ratios of Abell 14 are consistent with UV photoionised emission; however, there are some pieces of evidence of an additional thermal mechanism. The chemical abundances confirm its previous classification as a Type I planetary nebula, without spatial variation. We find...
Proceedings of the International Astronomical Union
The excitation mechanism of the narrow line region (NLR) of AGNs is still an open question. Excit... more The excitation mechanism of the narrow line region (NLR) of AGNs is still an open question. Excitation by UV radiation from O and B stars, x-rays from the central black hole, shock from supernovae or jets, or a combination of these mechanisms have been suggested. In the present work, we use photoionization models to study the excitation mechanisms of the H_2 infrared emission lines in the NLR. In the literature, analyzes of the H_2 emission have been done assuming that the molecules is present only in neutral regions (photodissociation regions, x-ray-dominated regions, or shocks; Veilleux et al. 1997, Krabbe et al. 2000, Rigopoulou et al. 2002, Rodriguez-Ardila et al. 2004, 2005, and Davies et al. 2005). However, they are not conclusive. In previous work (Aleman & Gruenwald 2004, 2011), we show that the H_2 emission from the ionized region of PNe can be significant for planetary nebulae (PNe) with hot central stars (T* > 150000 K). Such stars produce copious amounts of high energ...
Publications of the Astronomical Society of the Pacific
Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedb... more Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1–3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb...
We are entering our 5th year of AstroPAH! It makes us very happy to keep you up to date about our... more We are entering our 5th year of AstroPAH! It makes us very happy to keep you up to date about our community, and we hope to continue doing so for many years to come. Since our conception, the number of subscribers to AstroPAH has grown to more than 300 people, with roughly the same number of newsletter downloads each month. For our 4-year anniversary, we are changing things up and introducing a new monthly release date. AstroPAH will now be released on the 3rd or 4th Thursday of the month. The release date for an upcoming issue will continue to be published on our website and in the previous issue as usual. What better way to celebrate our anniversary than with a great Picture of the Month, sent by one of our subscribers-Martin Wendt. The picture shows the sub parsec variation of two Diffuse Interstellar Bands towards NGC 6397, as observed with the instrument MUSE installed on the VLT. This month, our In Focus dives into a subject that has been on the rise since the launch of AstroPAH: Aude Simon and Mathias Rapacioli take us on a journey through the modeling of dissociation and isomerisation of PAHs. Do not miss any of the interesting papers in our Abstract section, from calculations, to observational data analysis, to laboratory studies. We close this AstroPAH 4th anniversary issue with announcements of opportunities for Fellowships. AstroPAH will continue to help you promote your science. Please visit our webpage or contact us. Send us your contributions anytime or for publication in November, see the deadlines below. We thank you all for your contributions in these past 4 years and for the time to come.
Proceedings of the International Astronomical Union, 2018
We present the current status update of the Herschel Planetary Nebula Survey Plus project (HerPla... more We present the current status update of the Herschel Planetary Nebula Survey Plus project (HerPlaNS+) based on the original General Observer HerPlaNS survey program during the OT1 cycle and the follow-up exhaustive archival search of PN observations using the PACS and SPIRE instruments on-board the Herschel Space Observatory.
Monthly Notices of the Royal Astronomical Society, 2019
We present a detailed analysis of deep VLT/X-Shooter observations of the planetary nebula Tc 1. W... more We present a detailed analysis of deep VLT/X-Shooter observations of the planetary nebula Tc 1. We calculate gas temperature, density, extinction, and abundances for several species from the empirical analysis of the total line fluxes. In addition, a spatially resolved analysis of the most intense lines provides the distribution of such quantities across the nebula. The new data reveal that several lines exhibit a double peak spectral profile consistent with the blue- and red-shifted components of an expanding spherical shell. The study of such components allowed us to construct for the first time a three-dimensional morphological model, which reveals that Tc 1 is a slightly elongated spheroid with an equatorial density enhancement seen almost pole on. A few bright lines present extended wings (with velocities up to a few hundred km s−1), but the mechanism producing them is not clear. We constructed photoionization models for the main shell of Tc 1. The models predict the central st...
Monthly Notices of the Royal Astronomical Society, 2018
The bipolar nebula Menzel 3 (Mz 3) was observed as part of the Herschel Planetary Nebula Survey (... more The bipolar nebula Menzel 3 (Mz 3) was observed as part of the Herschel Planetary Nebula Survey (HerPlaNS), which used the PACS and SPIRE instruments aboard the Herschel Space Observatory to study a sample of planetary nebulae (PNe). In this paper, one of the series describing HerPlaNS results, we report the detection of H I recombination lines (HRLs) in the spectrum of Mz 3. Inspection of the spectrum reveals the presence of 12 HRLs in the 55-680 μm range covered by the PACS and SPIRE instruments (H11α to H21α and H14β). The presence of HRLs in this range is unusual for PNe and has not been reported in Mz 3 before. Our analysis indicates that the HRLs we observed are enhanced by laser effect occurring in the core of Mz 3. Our arguments for this are (i) the available Mz 3 optical to submillimetre HRL α line intensity ratios are not well reproduced by the spontaneous emission of optically thin ionized gas, as would be typical for nebular gas in PNe; (ii) the compact core of Mz 3 is responsible for a large fraction of the Herschel HRLs emission; (iii) the line intensity ratios for Mz 3 are very similar to those in the core emission of the well known star MWC 349A, where laser effect is responsible for the enhancement of HRLs in the Herschel wavelength range; (iv) the physical characteristics relevant to cause laser effect in the core of MWC 349A are very similar to those in the core of Mz 3.
Proceedings of the International Astronomical Union, 2016
We performed a detailed spectroscopic analysis of the fullerene C60-containing planetary nebula (... more We performed a detailed spectroscopic analysis of the fullerene C60-containing planetary nebula (PN) Lin49 in the Small Magellanic Cloud (SMC). Lin49 is a C-rich and metal-deficient PN (Z~0.0006) and its nebular abundances are in agreement with the AGB model for the initially 1.25 M⊙ stars with the metallicity Z = 0.001. By stellar absorption fitting with TLUSTY, we derived stellar abundances, effective temperature, and surface gravity. We constructed the photoionization model with CLOUDY in order to investigate physical conditions of Lin49. The model with the 0.005-0.1 μm radius graphite and a constant hydrogen density shell could not fit the ~1-5 μm spectral energy distribution (SED) owing to the strong near-IR excess. We propose that the near-IR excess indicates (1) the presence of extremely small carbon molecules or (2) the presence of high-density structure surrounding the central star.
In the present work, we use a photoionisation code to study the H_2 emission of the Helix nebula ... more In the present work, we use a photoionisation code to study the H_2 emission of the Helix nebula (NGC 7293) cometary knots, particularly that produced in the interface H^+/H^0 of the knot, where a significant fraction of the H_2 1-0 S(1) emission seems to be produced. Our results show that the production of molecular hydrogen in such region may explain several characteristics of the observed emission, particularly the high excitation temperature of the H_2 infrared lines.
Context. Detections of molecular lines, mainly from H 2 and CO, reveal molecular material in plan... more Context. Detections of molecular lines, mainly from H 2 and CO, reveal molecular material in planetary nebulae. Observations of a variety of molecules suggest that the molecular composition in these objects differs from that found in interstellar clouds or in circumstellar envelopes. The success of the models, which are mostly devoted to explain molecular densities in specific planetary nebulae, is still partial however. Aims. The present study aims at identifying the influence of stellar and nebular properties on the molecular composition of planetary nebulae by means of chemical models. A comparison of theoretical results with those derived from the observations may provide clues to the conditions that favor the presence of a particular molecule. Methods. A self-consistent photoionization numerical code was adapted to simulate cold molecular regions beyond the ionized zone. The code was used to obtain a grid of models and the resulting column densities are compared with those inferred from observations. Results. Our models show that the inclusion of an incident flux of X-rays is required to explain the molecular composition derived for planetary nebulae. We also obtain a more accurate relation for the N(CO)/N(H 2) ratio in these objects. Molecular masses obtained by previous works in the literature were then recalculated, showing that these masses can be underestimated by up to three orders of magnitude. We conclude that the problem of the missing mass in planetary nebulae can be solved by a more accurate calculation of the molecular mass.
Monthly Notices of the Royal Astronomical Society, 2016
We performed a detailed spectroscopic analysis of the fullerene C 60-containing planetary nebula ... more We performed a detailed spectroscopic analysis of the fullerene C 60-containing planetary nebula (PN) Lin49 in the Small Magellanic Cloud (SMC) using XSHOOTER at the European Southern Observatory Very Large Telescope and the Spitzer/Infrared Spectrograph instruments. We derived nebular abundances for nine elements. We used TLUSTY to derive photospheric parameters for the central star. Lin49 is C-rich and metal-deficient PN (Z ∼ 0.0006). The nebular abundances are in good agreement with asymptotic giant branch nucleosynthesis models for stars with initial mass 1.25 M and metallicity Z = 0.001. Using the TLUSTY synthetic spectrum of the central star to define the heating and ionizing source, we constructed the photoionization model with CLOUDY that matches the observed spectral energy distribution (SED) and the line fluxes in the UV to far-IR wavelength ranges simultaneously. We could not fit the ∼1-5 µm SED using a model with 0.005-0.1-µm-sized graphite grains and a constant hydrogen density shell owing to the prominent near-IR excess, while at other wavelengths the model fits the observed values reasonably well. We argue that the near-IR excess might indicate either (1) the presence of very small particles in the form of small carbon clusters, small graphite sheets, or fullerene precursors, or (2) the presence of a high-density structure surrounding the central star. We found that SMC C 60 PNe show a near-IR excess component to lesser or greater degree. This suggests that these C 60 PNe might maintain a structure nearby their central star.
Proceedings of the International Astronomical Union, 2016
We observed the Planetary Nebula NGC 6720 with the Gemini Telescope and the Gemini Multi-Object S... more We observed the Planetary Nebula NGC 6720 with the Gemini Telescope and the Gemini Multi-Object Spectrographs. We obtained spatial maps of 36 emission-lines in the wavelength range between 3600 Å and 9400 Å. We derived maps of c(Hβ), electronic densities, electronic temperatures, ionic and elemental abundances, and Ionization Correction Factors (ICFs) in the source and investigated the mass-loss history of the progenitor. The elemental abundance results indicate the need for ICFs based on three-dimensional photoionization models.
Planetary nebulae (PNe), the ejected envelopes of red giant stars, provide us with a history of t... more Planetary nebulae (PNe), the ejected envelopes of red giant stars, provide us with a history of the last, mass-losing phases of 90% of stars initially more massive than the Sun. Here, we analyse James Webb Space Telescope (JWST) Early Release Observation (ERO) images of the PN NGC 3132. A structured, extended H 2 halo surrounding an ionised central bubble is imprinted with spiral structures, likely shaped by a low-mass companion orbiting the central star at ∼40-60 AU. The images also reveal a mid-IR excess at the central star interpreted as a dusty disk, indicative of an interaction with another, closer companion. Including the previously known, A-type visual companion, the progenitor of the NGC 3132 PN must have been at least a stellar quartet. The JWST images allow us to generate a model of the illumination, ionisation and hydrodynamics of the molecular halo, demonstrating the power of JWST to investigate complex stellar outflows. Further, new measurements of the A-type visual companion allow us to derive the value for Springer Nature 2021 L A T E X template 6 JWST PN the mass of the progenitor of a central star to date with excellent precision: 2.86 ± 0.06 M. These results serve as pathfinders for future JWST observations of PNe providing unique insight into fundamental astrophysical processes including colliding winds, and binary star interactions, with implications for supernovae and gravitational wave systems.
The young and well-studied planetary nebula (PN) NGC 7027 harbors significant molecular gas that ... more The young and well-studied planetary nebula (PN) NGC 7027 harbors significant molecular gas that is irradiated by luminous, pointlike UV (central star) and diffuse (shocked nebular) X-ray emission. This nebula represents an excellent subject to investigate the molecular chemistry and physical conditions within photon- and X-ray-dominated regions (PDRs and XDRs). As yet, the exact formation routes of CO+ and HCO+ in PN environments remain uncertain. Here we present ∼2″ resolution maps of NGC 7027 in the irradiation tracers CO+ and HCO+ obtained with the IRAM NOEMA interferometer, along with SMA CO and HST 2.12 μm H2 data for context. The CO+ map constitutes the first interferometric map of this molecular ion in any PN. Comparison of CO+ and HCO+ maps reveals strikingly different emission morphologies, as well as a systematic spatial displacement between the two molecules; the regions of brightest HCO+, found along the central waist of the nebula, are radially offset by ∼1″ (∼900 au) ...
The young and well-studied planetary nebula NGC 7027 harbors significant molecular gas that is ir... more The young and well-studied planetary nebula NGC 7027 harbors significant molecular gas that is irradiated by luminous, point-like UV (central star) and diffuse (shocked nebular) X-ray emission. This nebula represents an excellent subject to investigate the molecular chemistry and physical conditions within photon-and X-ray-dominated regions (PDRs and XDRs). As yet, the exact formation routes of CO + and HCO + in PN environments remain uncertain. Here, we present ∼2 resolution maps of NGC 7027 in the irradiation tracers CO + and HCO + , obtained with the IRAM NOEMA interferometer, along with SMA CO and HST 2.12 µm H 2 data for context. The CO + map constitutes the first interferometric map of this molecular ion in any PN. Comparison of CO + and HCO + maps reveal strikingly different emission morphologies, as well as a systematic spatial displacement between the two molecules; the regions of brightest HCO + , found along the central waist of the nebula, are radially offset by ∼1 (∼900 au) outside the corresponding CO + emission peaks. The CO + emission furthermore precisely traces the inner boundaries of the nebula's PDR (as delineated by near-IR H 2 emission), suggesting that central star UV emission drives CO + formation. The displacement of HCO + radially outward with respect to CO + is indicative that dust-penetrating soft X-rays are responsible for enhancing the HCO + abundance in the surrounding molecular envelope, forming an XDR. These interferometric CO + and HCO + observations of NGC 7027 thus clearly establish the spatial distinction between the PDR and XDR formed (respectively) by intense UV and X-ray irradiation of molecular gas.
This workshop is the second of the WORKPLANS series, which we started in 2016. The main goal of W... more 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 emissio...
Monthly Notices of the Royal Astronomical Society, 2020
We present a new approach to study planetary nebulae using integral field spectroscopy. VLT@VIMOS... more We present a new approach to study planetary nebulae using integral field spectroscopy. VLT@VIMOS datacube of the planetary nebula Abell 14 is analysed in three different ways by extracting: (i) the integrated spectrum, (ii) one-dimensional simulated long-slit spectra for different position angles, and (iii) spaxel-by-spaxel spectra. These data are used to build emission-line diagnostic diagrams and explore the ionization structure and excitation mechanisms combining data from one- and three-dimensional photoionization models. The integrated and 1D simulated spectra are suitable for developing diagnostic diagrams, while the spaxel spectra can lead to misinterpretation of the observations. We find that the emission-line ratios of Abell 14 are consistent with UV photoionised emission; however, there are some pieces of evidence of an additional thermal mechanism. The chemical abundances confirm its previous classification as a Type I planetary nebula, without spatial variation. We find...
Proceedings of the International Astronomical Union
The excitation mechanism of the narrow line region (NLR) of AGNs is still an open question. Excit... more The excitation mechanism of the narrow line region (NLR) of AGNs is still an open question. Excitation by UV radiation from O and B stars, x-rays from the central black hole, shock from supernovae or jets, or a combination of these mechanisms have been suggested. In the present work, we use photoionization models to study the excitation mechanisms of the H_2 infrared emission lines in the NLR. In the literature, analyzes of the H_2 emission have been done assuming that the molecules is present only in neutral regions (photodissociation regions, x-ray-dominated regions, or shocks; Veilleux et al. 1997, Krabbe et al. 2000, Rigopoulou et al. 2002, Rodriguez-Ardila et al. 2004, 2005, and Davies et al. 2005). However, they are not conclusive. In previous work (Aleman & Gruenwald 2004, 2011), we show that the H_2 emission from the ionized region of PNe can be significant for planetary nebulae (PNe) with hot central stars (T* > 150000 K). Such stars produce copious amounts of high energ...
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Papers by Isabel Aleman