Pierre Leisy - Academia.edu (original) (raw)

Papers by Pierre Leisy

Astronomy and Astrophysics, 2007

Astronomy and Astrophysics, 2006

Context. The Isaac Newton Telescope Photometric Hα Survey (IPHAS) is currently mapping the Northe... more Context. The Isaac Newton Telescope Photometric Hα Survey (IPHAS) is currently mapping the Northern Galactic plane reaching to r = 20 mag with typically 1 resolution. Hundreds of Planetary Nebulae (PNe), both point-like and resolved, are expected to be discovered. We report on the discovery of the first new PN from this survey: it is an unusual object located at a large galactocentric distance and has a very low oxygen abundance. Aims. Detecting and studying new PNe will lead to improved estimates of the population size, binary fraction and lifetimes, and yield new insights into the chemistry of the interstellar medium at large galactocentric distances. Methods. Compact nebulae are searched for in the IPHAS photometric catalogue, selecting those candidates with a strong Hα excess in the r − Hα vs. r − i colour-colour diagram. Searches for extended nebulae are by visual inspection of the mosaics of continuum-subtracted Hα images at a spatial sampling of 5 × 5 arcsec 2 . Follow-up spectroscopy enables confirmation of the PNe, and their physico-chemical study.

Comet Lee (C/1999 H1) was observed on June 6, 1999 when it was at r h = 0.98 AU and ∆ = 1.195 AU.... more Comet Lee (C/1999 H1) was observed on June 6, 1999 when it was at r h = 0.98 AU and ∆ = 1.195 AU. The spectrophotometric observations, between 0.6 and 1 µm, were aimed at the detection of the CI( 1 D) doublet λλ 9823/9850 Å. The non-detection of these lines, with a 3σ flux upper limit of the order of 4.6 × 10 −17 erg cm −2 s −1 , confirms the CO depletion already noted by other authors. Several CN and NH 2 emission bands lie in that spectral range, making it possible to derive production rates for both species as ∼3.1 × 10 26 s −1 and 1.2 × 10 27 s −1 , respectively. The oxygen forbidden line at 6300 Å was used to obtain Q H 2 O = (1.22 ± 0.7) × 10 29 s −1 . Assuming that CN and NH 2 are directly produced by HCN and NH 3 , Comet Lee has a HCN/H 2 O ≈ 0.25% and NH 3 /H 2 O ≈ 1% at r h = 0.98 AU, in reasonable agreement with what has been found in other long-period comets. The structural analysis carried out on cometary images acquired with broad band R Bessel filter clearly displays two pairs of ion rays likely produced by the H 2 O + doublet at 6198 and 6200 Å, wavelengths covered by the bandpass filter. Identical features are found in the images acquired with the Gunn i filter. The dust brightness profiles in the east-west direction do not deviate from a ρ −m law (with 0.7 < m ≤ 1.2) as expected for a steady state model coma with a constant dust production rate and expanding at constant velocity. The dust production rate, as obtained from the A f ρ parameter, is ∼500 cm, which compared with the gas production rate classifies this comet as a dust poor one with relatively high (6.5-11.7) gas-to-dust mass ratio. Analysis of the normalized reflectivity gradient (i.e. continuum color) as a function of ρ indicates a slight reddening of the solid component in the coma at large cometocentric distances, whereas the average dust color within an aperture of 20 000 km, centered at the nucleus, is ∼9% per 1000 Å. Mie scattering computations applied to an ensemble of particles indicate that the dust coma is characterised by a relative broad size distribution with a typical mean size of 1 µm. These grains might be composed of a mixture of silicates and icy material.

Proceedings of the International Astronomical Union, 2006

Page 1. The Census of Planetary Nebulae in the Local Group Romano LM Corradi1 and Laura Magrini2 ... more Page 1. The Census of Planetary Nebulae in the Local Group Romano LM Corradi1 and Laura Magrini2 ... 2 Imaging Searches for PNe in the LG The chase for extragalactic PNe started with the discovery by W. Baade [2] of five PNe in M31. ...

IAUC 7346 available at Central Bureau for Astronomical Telegrams.

We present preliminary results of VLT spectroscopy follow-up of Planetary Nebulae (PNe) and HII r... more We present preliminary results of VLT spectroscopy follow-up of Planetary Nebulae (PNe) and HII regions in the dwarf Irregular galaxy NGC 3109. In total we have observed 15 PNe (of a total of 18) and about 50 HII: at least for 10 PNe and 10 HII regions the very faint [O III]4363 line is observed allowing to derive accurate abundances.

We have analyzed the behaviour of various parameters of PNe in the Magellanic Clouds (MCs) and th... more We have analyzed the behaviour of various parameters of PNe in the Magellanic Clouds (MCs) and the Galaxy as a function of their morphology. The luminosity function of different morphological types has been built, finding that elliptical and round PNe dominate the bright cutoff both in the MCs and in the Galaxy. The dependence of the [OIII] absolute magnitude on

ESO ASTROPHYSICS SYMPOSIA European Southern Observatory, 2006

In the framework of the Local Group Census (LGC), an imaging programme to search for emission lin... more In the framework of the Local Group Census (LGC), an imaging programme to search for emission line objects in the Local Group, we present the detection of 13 new candidate planetary nebulae (PNe) and follow-up optical spectroscopic confirmation in the dwarf irregular galaxy NGC6822. This substantially increases the PNe sample of NGC6822 to 17. Our sample of PNe is complete within 3.5 mag below the brightest PN. Using the PN luminosity function (PNLF), we find a distance modulus of m-M = 23.32±0.45. The spectroscopic data help to discriminate between the different emission line objects (PNe, SNR, HII regions). The spectra with the highest S/N ratio allow us to determine abundances for 6 PNe and 4 HII regions. For the first time, we can compare the PN abundances of helium, nitrogen and oxygen in many LG galaxies. We find that the nitrogen is not enhanced in NGC6822 (nor in M33) as much as was expected from their respective metallicities. In contrast, the helium is largely enhanced in all the galaxies. The oxygen abundances in NGC6822 are high (close to those of the HII regions), which supports the idea that most PNe originated from relatively massive and young progenitors.

ESO ASTROPHYSICS SYMPOSIA European Southern Observatory, 2006

Sextans A and Sextans B are two dIr galaxies situated in the outskirts of the Local Group (LG), i... more Sextans A and Sextans B are two dIr galaxies situated in the outskirts of the Local Group (LG), in which both PNe and H II regions have been detected (Jacoby & Lesser [5], Magrini et al. [6], [7]). We present spectroscopic observations of PNe and HII regions in these two galaxies obtained with the VLT. Preliminary results on the PNe physico-chemical properties are presented.

Monthly Notices of the Royal Astronomical Society, 2008

The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is an imaging survey bei... more The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is an imaging survey being carried out in Hα, r ′ and i ′ filters, with the Wide Field Camera (WFC) on the 2.5-metre Isaac Newton Telescope (INT) to a depth of r ′ =20 (10σ). The survey is aimed at revealing the large scale organisation of the Milky Way and can be applied to identifying a range of stellar populations within it. Mapping emission line objects enables a particular focus on objects in the young and old stages of stellar evolution ranging from early T-Tauri stars to late planetary nebulae. In this paper we present the IPHAS Initial Data Release, primarily a photometric catalogue of about 200 million unique objects, coupled with associated image data covering about 1,600 square degrees in three passbands. We note how access to the primary data products has been implemented through use of standard virtual observatory publishing interfaces. Simple traditional web access is provided to the main IPHAS photometric catalogue, in addition to a number of common catalogues (such as 2MASS) which are of immediate relevance. Access through the AstroGrid VO Desktop opens up the full range of analysis options, and allows full integration with the wider range of data and services available through the Virtual Observatory. The IDR represents the largest dataset published primarily through VO interfaces to date, and so stands as an examplar of the future of survey data mining. Examples of data access are given, including a cross-matching of IPHAS photometry with sources in the UKIDSS Galactic Plane Survey that validates the existing calibration of the best data.

Astronomy and Astrophysics, 2007

Astronomy and Astrophysics, 2006

Context. The Isaac Newton Telescope Photometric Hα Survey (IPHAS) is currently mapping the Northe... more Context. The Isaac Newton Telescope Photometric Hα Survey (IPHAS) is currently mapping the Northern Galactic plane reaching to r = 20 mag with typically 1 resolution. Hundreds of Planetary Nebulae (PNe), both point-like and resolved, are expected to be discovered. We report on the discovery of the first new PN from this survey: it is an unusual object located at a large galactocentric distance and has a very low oxygen abundance. Aims. Detecting and studying new PNe will lead to improved estimates of the population size, binary fraction and lifetimes, and yield new insights into the chemistry of the interstellar medium at large galactocentric distances. Methods. Compact nebulae are searched for in the IPHAS photometric catalogue, selecting those candidates with a strong Hα excess in the r − Hα vs. r − i colour-colour diagram. Searches for extended nebulae are by visual inspection of the mosaics of continuum-subtracted Hα images at a spatial sampling of 5 × 5 arcsec 2 . Follow-up spectroscopy enables confirmation of the PNe, and their physico-chemical study.

Comet Lee (C/1999 H1) was observed on June 6, 1999 when it was at r h = 0.98 AU and ∆ = 1.195 AU.... more Comet Lee (C/1999 H1) was observed on June 6, 1999 when it was at r h = 0.98 AU and ∆ = 1.195 AU. The spectrophotometric observations, between 0.6 and 1 µm, were aimed at the detection of the CI( 1 D) doublet λλ 9823/9850 Å. The non-detection of these lines, with a 3σ flux upper limit of the order of 4.6 × 10 −17 erg cm −2 s −1 , confirms the CO depletion already noted by other authors. Several CN and NH 2 emission bands lie in that spectral range, making it possible to derive production rates for both species as ∼3.1 × 10 26 s −1 and 1.2 × 10 27 s −1 , respectively. The oxygen forbidden line at 6300 Å was used to obtain Q H 2 O = (1.22 ± 0.7) × 10 29 s −1 . Assuming that CN and NH 2 are directly produced by HCN and NH 3 , Comet Lee has a HCN/H 2 O ≈ 0.25% and NH 3 /H 2 O ≈ 1% at r h = 0.98 AU, in reasonable agreement with what has been found in other long-period comets. The structural analysis carried out on cometary images acquired with broad band R Bessel filter clearly displays two pairs of ion rays likely produced by the H 2 O + doublet at 6198 and 6200 Å, wavelengths covered by the bandpass filter. Identical features are found in the images acquired with the Gunn i filter. The dust brightness profiles in the east-west direction do not deviate from a ρ −m law (with 0.7 < m ≤ 1.2) as expected for a steady state model coma with a constant dust production rate and expanding at constant velocity. The dust production rate, as obtained from the A f ρ parameter, is ∼500 cm, which compared with the gas production rate classifies this comet as a dust poor one with relatively high (6.5-11.7) gas-to-dust mass ratio. Analysis of the normalized reflectivity gradient (i.e. continuum color) as a function of ρ indicates a slight reddening of the solid component in the coma at large cometocentric distances, whereas the average dust color within an aperture of 20 000 km, centered at the nucleus, is ∼9% per 1000 Å. Mie scattering computations applied to an ensemble of particles indicate that the dust coma is characterised by a relative broad size distribution with a typical mean size of 1 µm. These grains might be composed of a mixture of silicates and icy material.

Proceedings of the International Astronomical Union, 2006

Page 1. The Census of Planetary Nebulae in the Local Group Romano LM Corradi1 and Laura Magrini2 ... more Page 1. The Census of Planetary Nebulae in the Local Group Romano LM Corradi1 and Laura Magrini2 ... 2 Imaging Searches for PNe in the LG The chase for extragalactic PNe started with the discovery by W. Baade [2] of five PNe in M31. ...

IAUC 7346 available at Central Bureau for Astronomical Telegrams.

We present preliminary results of VLT spectroscopy follow-up of Planetary Nebulae (PNe) and HII r... more We present preliminary results of VLT spectroscopy follow-up of Planetary Nebulae (PNe) and HII regions in the dwarf Irregular galaxy NGC 3109. In total we have observed 15 PNe (of a total of 18) and about 50 HII: at least for 10 PNe and 10 HII regions the very faint [O III]4363 line is observed allowing to derive accurate abundances.

We have analyzed the behaviour of various parameters of PNe in the Magellanic Clouds (MCs) and th... more We have analyzed the behaviour of various parameters of PNe in the Magellanic Clouds (MCs) and the Galaxy as a function of their morphology. The luminosity function of different morphological types has been built, finding that elliptical and round PNe dominate the bright cutoff both in the MCs and in the Galaxy. The dependence of the [OIII] absolute magnitude on

ESO ASTROPHYSICS SYMPOSIA European Southern Observatory, 2006

In the framework of the Local Group Census (LGC), an imaging programme to search for emission lin... more In the framework of the Local Group Census (LGC), an imaging programme to search for emission line objects in the Local Group, we present the detection of 13 new candidate planetary nebulae (PNe) and follow-up optical spectroscopic confirmation in the dwarf irregular galaxy NGC6822. This substantially increases the PNe sample of NGC6822 to 17. Our sample of PNe is complete within 3.5 mag below the brightest PN. Using the PN luminosity function (PNLF), we find a distance modulus of m-M = 23.32±0.45. The spectroscopic data help to discriminate between the different emission line objects (PNe, SNR, HII regions). The spectra with the highest S/N ratio allow us to determine abundances for 6 PNe and 4 HII regions. For the first time, we can compare the PN abundances of helium, nitrogen and oxygen in many LG galaxies. We find that the nitrogen is not enhanced in NGC6822 (nor in M33) as much as was expected from their respective metallicities. In contrast, the helium is largely enhanced in all the galaxies. The oxygen abundances in NGC6822 are high (close to those of the HII regions), which supports the idea that most PNe originated from relatively massive and young progenitors.

ESO ASTROPHYSICS SYMPOSIA European Southern Observatory, 2006

Sextans A and Sextans B are two dIr galaxies situated in the outskirts of the Local Group (LG), i... more Sextans A and Sextans B are two dIr galaxies situated in the outskirts of the Local Group (LG), in which both PNe and H II regions have been detected (Jacoby & Lesser [5], Magrini et al. [6], [7]). We present spectroscopic observations of PNe and HII regions in these two galaxies obtained with the VLT. Preliminary results on the PNe physico-chemical properties are presented.

Monthly Notices of the Royal Astronomical Society, 2008

The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is an imaging survey bei... more The INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is an imaging survey being carried out in Hα, r ′ and i ′ filters, with the Wide Field Camera (WFC) on the 2.5-metre Isaac Newton Telescope (INT) to a depth of r ′ =20 (10σ). The survey is aimed at revealing the large scale organisation of the Milky Way and can be applied to identifying a range of stellar populations within it. Mapping emission line objects enables a particular focus on objects in the young and old stages of stellar evolution ranging from early T-Tauri stars to late planetary nebulae. In this paper we present the IPHAS Initial Data Release, primarily a photometric catalogue of about 200 million unique objects, coupled with associated image data covering about 1,600 square degrees in three passbands. We note how access to the primary data products has been implemented through use of standard virtual observatory publishing interfaces. Simple traditional web access is provided to the main IPHAS photometric catalogue, in addition to a number of common catalogues (such as 2MASS) which are of immediate relevance. Access through the AstroGrid VO Desktop opens up the full range of analysis options, and allows full integration with the wider range of data and services available through the Virtual Observatory. The IDR represents the largest dataset published primarily through VO interfaces to date, and so stands as an examplar of the future of survey data mining. Examples of data access are given, including a cross-matching of IPHAS photometry with sources in the UKIDSS Galactic Plane Survey that validates the existing calibration of the best data.